Surface-treated member

Abstract

[Problem] The present invention provides a surface-treated member which uses a steel material as a starting material and is capable of exhibiting excellent corrosion resistance even in soil at a depth of about several cm from the soil surface. [Solution] A surface-treated member according to the present invention comprises: a steel material that serves as a base material; and a protective layer that is positioned on the surface of the steel material. The protective layer has a Zn concentration of not less than 5.00 mass% but less than 30.00 mass%, an Si concentration of not less than 5.00 mass% but less than 25.00 mass%, and contains SiO2 and a Zn / Al-based carbonate type layered double hydroxide.

Description

Title of Invention: SURFACE-TREATED MEMBER TECHNICAL FIELD

[0001] The present invention relates to a surface-treated member. BACKGROUND ART

[0002] Steel material is widely used as a raw material for various structural objects. The steel material as a raw material is processed into various shapes and then, if necessary, they are joined to each other by joining processes using fastening members such as screws, bolts, or clinch, or various welding methods, or the like to form a member having a desired shape (for example, various steel structural objects).

[0003] It is considered that a member made of the steel material as a raw material (steel member) as described above is exposed to various environments depending on the application of the steel member, and stains or corrosion may occur on the surface. Therefore, various studies have been conventionally conducted regarding technologies for improving antifouling properties and corrosion resistance of the steel material.

[0004] For example, Patent Document 1 below discloses a technology for improving the antifouling properties (particularly, stain resistance against algae) of a coated steel material by providing, on the surface of various steel sheets, a coating layer that contains a pyrithione compound, at least one of a silicate-based compound and a cured product thereof, and hydrotalcites, and does not contain a resin paint.

[0005] Further, Patent Document 2 below discloses, as a repair method for improving the corrosion resistance of a steel structural object, a water-washing-less repair method including: a surface preparation step of performing a treatment of making a surface exposure area ratio of a corroded steel structural object 30% or more to obtain a surface-prepared surface; a corrosion inhibition step of applying a corrosion inhibitor containing hydrocalumite and / or hydrotalcite to the surface; a polishing / grinding step of performing a grinding treatment or a polishing treatment on the surface to which the corrosion inhibitor has been applied; a paint application step of applying a zinc powder-containing paint to the surface after the polishing / grinding treatment; and a painting step of further performing painting on the surface after applying the zinc powder-containing paint. PRIOR ART DOCUMENT PATENT DOCUMENT

[0006] Patent Document 1: Japanese Laid-open Patent Publication No. 2017-109417 Patent Document 2: Japanese Laid-open Patent Publication No. 2017-213557 SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] When installing various steel members made of the steel material as a raw material at desired locations, it is inferred that at least a part thereof is often embedded in soil. For a portion of each steel member that is exposed to the atmosphere, it is easy to investigate the corrosion state by visually observing the exposed portion. However, for a portion embedded in soil, unlike in the atmosphere, visual investigation of the corrosion state is difficult, and maintenance of the portion in a corroded state is also difficult. Therefore, high corrosion resistance is required for steel members used in soil.

[0008] The present inventors have studied the corrosion state of steel members in soil. As a result, as will be described later, it has been found that the corrosion behavior of a steel member in soil at a depth of 1 m or more from the soil surface is significantly different from the corrosion behavior of a steel member in soil at a depth of about several centimeters from the soil surface. Furthermore, it has been found that in soil where the depth from the soil surface is about several centimeters, there is room for improvement in corrosion resistance even if a steel member is manufactured by applying the technologies disclosed in Patent Document 1 and Patent Document 2.

[0009] Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to provide a surface-treated member made of a steel material as a raw material, which can exhibit excellent corrosion resistance even in soil at a depth of about several centimeters from a soil surface. MEANS FOR SOLVING THE PROBLEMS

[0010] As a result of intensive studies by the present inventors to solve the above problems, the inventors have conceived of providing a protective layer having a high barrier property mainly composed of SiO2 on the surface of a steel material as a base material, in order to suppress corrosion of a steel member in soil at a depth of about several centimeters from the soil surface. On the other hand, since SiO2, which is the main component of the protective layer, is a hard substance, there has been a concern that micro-level fine defects might occur in the protective layer when the steel material provided with the protective layer is processed into a desired shape or the like. If such micro-level defects exist in the protective layer, corrosion factors (particularly anions such as chloride ions (Cl-)) can reach the surface of the steel material through the defects, leading to local corrosion.

[0011] Based on the above findings, the present inventors have conceived of providing a protective layer containing SiO2 and a zinc-containing compound containing a zinc element having a sacrificial anticorrosive ability. Furthermore, the inventors have reached the idea of using a Zn / Al-based carbonate-type layered double hydroxide (i.e., Zn / Al-based hydrotalcites), which is a compound capable of trapping corrosion factors including anions, as the zinc-containing compound, in a specific content. The gist of the present invention completed based on the findings is as follows.

[0012] (1) A surface-treated member including: a steel material as a base material; and a protective layer located on a surface of the steel material; wherein the protective layer has a Zn concentration of 1.00 mass% or more and less than 30.00 mass% and an Si concentration of 1.00 mass% or more and less than 25.00 mass%, and contains SiO2 and a Zn / Al-based carbonate-type layered double hydroxide. (2) The surface-treated member according to (1), wherein a thickness of the protective layer is 0.1 pm or more and 50.0 pm or less. (3) The surface-treated member according to (1) or (2), wherein in a measurement result of the surface of the protective layer measured by an X-ray diffraction method (XRD), a peak intensity of a peak attributed to the Zn / Al-based carbonate-type layered double hydroxide is 1000 cps or more and 150000 cps or less. (4) The surface-treated member according to (1) or (2), wherein the protective layer has an Mg concentration of 0.10 mass% or more and 5.00 mass% or less, and further contains an Mg / Al-based carbonate-type layered double hydroxide. (5) The surface-treated member according to (4), wherein in a measurement result of the surface of the protective layer measured by an X-ray diffraction method (XRD), a peak intensity of a peak attributed to the Mg / Al-based carbonate-type layered double hydroxide is 1000 cps or more and 150000 cps or less. (6) The surface-treated member according to (1) or (2), wherein in a measurement result of the surface of the protective layer measured by an X-ray diffraction method (XRD), a peak intensity of a peak attributed to the SiO2 is 500 cps or more and 100000 cps or less. (7) The surface-treated member according to (1) or (2), wherein when a distribution state of the Si concentration in a thickness direction of the protective layer is observed, the Si concentration at a 1 / 2 thickness of the protective layer on a surface side is 1.3 times or more the Si concentration at a 1 / 2 thickness of the protective layer on a steel material side. (8) The surface-treated member according to (1) or (2), wherein the protective layer contains, as the SiO2, SiO2 particles having a particle size of 0.1 to 1.0 pm. (9) The surface-treated member according to (1) or (2), further including a second protective layer located on the protective layer, wherein the second protective layer contains SiO2 particles having a particle size of 1.0 to 30.0 pm. (10) The surface-treated member according to (9), wherein a thickness of the second protective layer is 1 pm or more and 100 pm or less. (11) The surface-treated member according to (1) or (2), further including a zinc-based coating layer between the steel material and the protective layer. (12) The surface-treated member according to (11), wherein the zinc-based coating layer has an Al concentration of 0.10 mass% or more and less than 40.00 mass%, and a Zn concentration of 60.00 mass% or more. (13) The surface-treated member according to (12), wherein the zinc-based coating layer has an Mg concentration of 0.10 mass% or more and less than 15.00 mass%. (14) The surface-treated member according to (11), wherein a thickness of the zinc-based coating layer is 1 pm or more and 200 pm or less. EFFECT OF THE INVENTION

[0013] As described above, according to the present invention, it is possible to provide a surface-treated member made of a steel material as a raw material, which can exhibit excellent corrosion resistance even in soil at a depth of about several centimeters from a soil surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIG. 1 is a schematic view for explaining a structural object installed on a soil surface. FIG. 2 is a schematic view for explaining a configuration of a surface-treated member according to an embodiment of the present invention. FIG. 3A is a schematic view for explaining an example of the configuration of the surface-treated member according to the same embodiment. FIG. 3B is a schematic view for explaining an example of the configuration of the surface-treated member according to the same embodiment. FIG. 4A is a schematic view for explaining another example of the configuration of the surface-treated member according to the same embodiment. FIG. 4B is a schematic view for explaining another example of the configuration of the surface-treated member according to the same embodiment. FIG. 5 is a schematic view for explaining a protective layer included in the surface-treated member according to the same embodiment. EMBODIMENTS FOR CARRYING OUT INVENTION

[0015] Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Note that in the present description and the drawings, components having substantially the same functional configurations are denoted by the same reference numerals, and redundant description thereof will be omitted.

[0016] (Corrosion behavior in soil at a depth of about several centimeters from a soil surface) Prior to describing a surface-treated member according to an embodiment of the present invention, the corrosion behavior in soil at a depth of about several centimeters from the soil surface, which has been found by the present inventors, will be described with reference to FIG. 1. FIG. 1 is a schematic view for describing a structural object installed on the soil surface. Further, in the following, "soil at a depth of about several centimeters from the soil surface" may be referred to as a "soil surface layer portion" for convenience.

[0017] As schematically illustrated in FIG. 1, various structural objects, including, for example, a rack on which solar power generation panels are placed, road signs, guardrails, traffic lights, and the like are installed on the soil surface. At this time, in order to more stably install the structural object on the soil surface, as illustrated in FIG. 1, a portion of the structural object (for example, a portion near a lower end portion of a support post, which is surrounded by a broken line in FIG. 1) is often embedded in soil.

[0018] Here, for various structural objects, various steel materials are often used as raw materials, for example, from the viewpoint of production costs. Here, when portions of the structural objects made of various steel materials as raw materials are embedded in soil, there is a concern regarding the corrosion of the steel materials, which are the raw materials.

[0019] Examples of influence of soil on the corrosion of the steel materials include two influences such as retention of moisture which is a corrosion factor, and suppression of diffusion of oxygen which is a corrosion factor. The retention of moisture is an influence that acts to increase the corrosion rate, whereas the suppression of diffusion of oxygen is an influence that acts to decrease the corrosion rate. In soil, a wet environment (i.e., moisture) is retained for a longer period of time after rainfall or the like than in the atmosphere. On the other hand, soil suppresses the penetration and diffusion of oxygen from the atmosphere, thus reducing the corrosion rate. Regarding the corrosion rate in actual soil, as a result of the mutual interaction between the aforementioned two influences that are in a trade-off relationship, the corrosion rate is determined to be in a certain state. Generally, since the influence of the suppression of oxygen diffusion is greater than the influence of the moisture retention, the corrosion rate in soil is suppressed compared to that in the atmosphere.

[0020] On the other hand, the situation is significantly different in soil at a depth of about several centimeters from the soil surface (soil surface layer portion). Even in the soil surface layer portion, moisture is unlikely to evaporate due to the soil, and therefore, the steel materials are kept in a state of being in contact with moisture for a longer period of time compared to those in the atmosphere. On the other hand, in the soil surface layer portion, since the distance from the atmosphere is short and the supply of oxygen from the atmosphere is rapid, the influence of the suppression of oxygen diffusion by the soil is small. Therefore, combined with the influence of the moisture retention, it is considered that a corrosion suppression effect by the soil is hardly obtained in the soil surface layer portion. As described above, it can be said that the soil surface layer portion focused on by the present inventors is in an extremely severe corrosive environment compared to that in soil where the depth from the soil surface is 1 m or more. Therefore, it can be said that extremely high corrosion resistance is required for steel materials installed in the soil surface layer portion.

[0021] In order to realize the extremely high corrosion resistance, the present inventors have conceived of providing a protective layer having a high barrier property mainly composed of SiO2 on the surface of a steel material as a base material. On the other hand, since SiO2, which is the main component of the protective layer, is a hard substance, there has been a concern that micro-level fine defects might occur in the protective layer when the steel material provided with the protective layer is processed into a desired shape or the like. If micro-level defects exist in the protective layer, corrosion factors (particularly anions such as chloride ions (Cl-)) can reach the surface of the steel material through the defects, leading to local corrosion.

[0022] Based on the above findings, the present inventors have conceived of providing a protective layer containing SiO2 and a zinc-containing compound containing a zinc element having a sacrificial anticorrosive ability. Since the protective layer having a high barrier property containing SiO2 further contains the zinc-containing compound having the sacrificial anticorrosive ability, further improvement in corrosion resistance is realized even if corrosion factors reach the inside of the protective layer.

[0023] Furthermore, the present inventors have reached the idea of using a Zn / Al-based carbonate-type layered double hydroxide (i.e., Zn / Al-based hydrotalcite), which is a compound capable of trapping corrosion factors including anions, as the zinc-containing compound, in a specific content. As inferred from the description "layered," the carbonate-type layered double hydroxide is a compound having a so-called layered structure in which plate-like structures are laminated at predetermined intervals, and can trap anions including Cl- ions between the layers. Thereby, in addition to the sacrificial anticorrosive ability exhibited by the zinc element, the carbonate-type layered double hydroxide itself can trap anions, which are corrosion factors. As a result, even if corrosion factors reach the inside of the protective layer, it is possible to further prevent the corrosion factors from reaching the steel material, and further improvement in corrosion resistance is realized.

[0024] As a result, even if a surface-treated member made of a steel material as a raw material is installed in the soil surface layer portion, it is possible to improve the corrosion resistance as the steel material.

[0025] Based on the findings described above, the present inventors have conducted further studies and, as a result, have arrived at a surface-treated member according to the embodiment of the present invention, which will be described in detail below.

[0026] (Regarding the surface-treated member) The surface-treated member according to the embodiment of the present invention will be described in detail below with reference to FIG. 2 to FIG. 4B. FIG. 2 to FIG. 4B are schematic views for explaining a configuration of the surface-treated member according to the present embodiment. In addition, in FIG. 2 to FIG. 4B, the explanation will be given using coordinate axes illustrated in the drawings for convenience.

[0027] The surface-treated member according to the present embodiment is configured using various steel materials as raw materials, as will be described in detail below. Here, the specific configuration of the surface-treated member according to the present embodiment is not particularly limited. The specific configuration of the surface-treated member according to the present embodiment may be, for example, a box-shaped one, or a plate-shaped one using a plate-shaped steel material such as a roof or a wall of a building. Further, the specific configuration of the surface-treated member according to the present embodiment may be, for example, a formed body or a joined body using various shaped steels such as a solar power generation panel rack, or a formed body or a joined body using various H-shaped steels or prisms such as a framework of a structural object, or a formed body or a joined body using various steel pipes such as various support posts, signs, traffic lights, guardrails, and the like. The surface-treated member is used, for example, by embedding at least a part of the surface-treated member in soil.

[0028] FIG. 2 schematically illustrates an appearance when a portion of a surface-treated member 1 according to the present embodiment is viewed in plan from above its surface (Z-axis direction in the drawing). As schematically illustrated in FIG. 2, the surface-treated member 1 according to the present embodiment is made from a surface-treated steel material 10, as a raw material, in which a protective layer 13 containing specific components is provided on a surface of a steel material 11 serving as a base material, as will be described later.

[0029] FIG. 3A to FIG. 4B schematically illustrate cross sections of the surface-treated member 1 illustrated in FIG. 2 when cut in the Z-axis direction along a cutting line of A-A. The cross-sectional views illustrated in FIG. 3A to FIG. 4B correspond to the surface-treated member 1 according to the present embodiment cut in the thickness direction of the surface-treated steel material 10, which is the raw material of the surface-treated member 1.

[0030] As schematically illustrated in FIG. 3A, the surface-treated member 1 according to the present embodiment is configured from a surface-treated steel material 10 having a steel material 11 as a base material and protective layers 13 located on front and back surfaces of the steel material 11. Further, as schematically illustrated in FIG. 3B, the surface-treated steel material 10 may further have a zinc-based coating layer 15 between the steel material 11 and the protective layer 13.

[0031] Hereinafter, first, the steel material 11, the protective layer 13, and the zinc-based coating layer 15 will be described in detail.

[0032] <Regarding the steel material 11> The steel material 11 used as a base material of the surface-treated steel material 10 according to the present embodiment is not particularly limited, and various steel materials can be used depending on the mechanical strength (for example, tensile strength) or the like required for the surface-treated member 1. Examples of the steel material 11 include various Al-killed steels, ultra-low carbon steels containing Ti, Nb, or the like, high-strength steels obtained by further adding strengthening elements such as P, Si, and Mn to ultra-low carbon steels, and various steels containing various other components (Cr, N, Cu, B, Ni, Mg, Ca, V, Co, Zn, As, Y, Zr, Mo, Sn, Sb, Ta, W, Pb, Bi, REM, etc.).

[0033] Further, as illustrated in FIG. 3B, a zinc-based coating layer 15 as described later may be located on the surface of the steel material 11, but a pre-coated layer may be provided on the surface of the steel material 11 before performing zinc-based coating for forming the zinc-based coating layer 15. Examples of metals usable for the pre-coated layer include Ni, Sn, or an alloy system combining these elements. When using a pre-coated steel material in which these coatings are pre-coated in advance, non-coating (locations where the coating metal is repelled by an oxide film or the like) can be eliminated. This is presumed to be because, when the pre-coated steel material is dipped in a hot-dip coating bath, the metal elements of the hot-dip coating bath and the pre-coated layer react to form Ni(Sn)-Al-Fe-Zn. The coating weight per side of the pre-coated layer is preferably within a range of 0.2 to 2.0 g / m2. By setting the coating weight of the pre-coated layer to 0.2 g / m2 or more, it becomes possible to reliably exhibit non-coating suppression effect by the pre-coating as described above. Further, by setting the coating weight of the pre-coated layer to 2.0 g / m2 or less, it is possible to achieve the non-coating suppression effect as described above while preventing the pre-coated layer from suppressing the elution of Fe and making it difficult to form an Fe-Zn-based composite oxide.

[0034] Besides, the thickness of the steel material 11 is not particularly limited, and may be appropriately set depending on the mechanical strength or the like required for the surface-treated member 1.

[0035] <Regarding the protective layer 13> The protective layer 13 is a layer located on the surface of the steel material 11 (FIG. 3A) or on the surface of the zinc-based coating layer 15 (FIG. 3B), has a Zn concentration of 5 mass% or more and less than 30 mass% and an Si concentration of 5 mass% or more and less than 25 mass%, and contains SiO2 and a Zn / Al-based carbonate-type layered double hydroxide. By having the protective layer 13 as described above, the surface-treated member 1 according to the present embodiment exhibits excellent corrosion resistance even when at least a part thereof is installed in the soil surface layer portion. The detailed configuration of the protective layer 13 will be described in detail again below.

[0037] <Regarding the zinc-based coating layer 15> The zinc-based coating layer 15 may be located between the steel material 11 and the protective layer 13 as illustrated in FIG. 3B. The zinc-based coating layer 15 is not particularly limited as long as it contains at least zinc (Zn), and various known zinc-based coatings can be applied.

[0038] Examples of the zinc-based coatings include zinc coatings represented by hot-dip galvanizing, alloyed hot-dip galvanizing, and the like, zinc-nickel coating, zinc-iron coating, zinc-chromium coating, zinc-aluminum coating, zinc-titanium coating, zinc-magnesium coating, zinc-manganese coating, zinc-aluminum-magnesium coating, and zinc-aluminum-magnesium-silicon coating. Further, as the zinc-based coatings, ones containing a small amount of a different metal element or impurity, such as cobalt, molybdenum, tungsten, nickel, titanium, chromium, aluminum, manganese, iron, magnesium, lead, bismuth, antimony, tin, copper, cadmium, arsenic, and the like, in the above-mentioned coatings, or ones in which inorganic substances such as silica, alumina, titania, and the like are dispersed may be used. A coating method is not particularly limited, and various known coating methods such as an electroplating method, a hot-dip coating method, a vapor deposition coating method, a dispersion coating method, a vacuum coating method, and the like may be used.

[0039] Among the various zinc-based coatings as described above, the zinc-based coating layer 15 according to the present embodiment is more preferably, for example, a zinc-based coating layer having chemical components as described in detail below. By using one having chemical components as described in detail below as the zinc-based coating layer 15, it is possible to further improve various properties including the corrosion resistance of the surface-treated member 1 according to the present embodiment. Hereinafter, first, a more preferable chemical composition of the zinc-based coating layer 15 as described above will be described in detail.

[0040] <<Regarding the chemical composition of the zinc-based coating layer 15>> According to one aspect, the chemical composition of the zinc-based coating layer 15 according to the present embodiment contains, by mass %, Al: 0.10% or more and less than 40.00%, with the balance consisting of 60.00 mass % or more of Zn and impurities.

[0041] Further, in the chemical composition in one aspect of the zinc-based coating layer 15 according to the present embodiment, the chemical composition of the zinc-based coating layer 15 more preferably contains Mg: 0.10% or more and less than 15.00% in place of a portion of Zn in the balance.

[0042] Further, according to another aspect, the chemical composition of the zinc-based coating layer 15 according to the present embodiment contains, by mass%, Al: 0.10% or more and less than 40.00% and Mg: 0.10% or more and less than 15.00%, and further contains one or two or more selected from the group consisting of the following element group A, element group B, element group C, element group D, element group E, and element group F, with the balance consisting of Zn and impurities.

[0043] [Element group A]: one or two selected from the group consisting of Si: 2.50% or less and Fe: 5.00% or less [Element group B]: one or two or more selected from the group consisting of Sb: less than 0.50%, Pb: less than 0.50%, and Sr: less than 0.50% [Element group C]: one or two or more selected from the group consisting of Cu: less than 0.25%, Ti: less than 0.25%, Cr: less than 0.25%, Nb: less than 0.25%, Ni: less than 0.25%, Mn: less than 0.25%, Co: less than 0.25%, and V: less than 0.25% [Element group D]: one or two or more selected from the group consisting of Sn: 2.00% or less, Bi: less than 0.50%, and In: less than 2.00% [Element group E]: one or two or more selected from the group consisting of Ca: 3.00% or less, La: less than 0.50%, Ce: less than 0.50%, and Y: 0.50% or less [Element group F]: B: less than 0.50%

[0044] [Al: 0.10 mass % or more and less than 40.00 mass %] Al is an element necessary for constituting a main metallographic structure (Zn-Al-based metallographic structure) in a preferable aspect of the zinc-based coating layer 15 according to the present embodiment. Therefore, Al is preferably contained in a content of a predetermined amount or more in order to ensure corrosion resistance as the coated steel material. If the Al content in the zinc-based coating layer 15 is less than 0.10 mass%, the above-mentioned corrosion resistance may not be ensured. Therefore, in the zinc-based coating layer 15 according to the present embodiment, the Al content is preferably 0.10 mass% or more. The Al content is preferably 3.00 mass% or more, more preferably 4.00 mass% or more, and still more preferably 6.00 mass% or more. When the Al content is within the above range, the corrosion resistance as the coated steel material can be ensured.

[0045] On the other hand, if the Al content in the zinc-based coating layer 15 is 40.00 mass% or more, an Al phase that functions as a cathode when placed in a corrosive environment excessively increases, and corrosion of the steel material 11 is more likely to progress, and therefore the corrosion resistance as the coated steel material may not be ensured. Therefore, in the zinc-based coating layer 15 according to the present embodiment, the Al content is preferably less than 40.00 mass%. The Al content is preferably 25.00 mass% or less, more preferably less than 25.00 mass%, and still more preferably 20.00 mass% or less.

[0046] In the zinc-based coating layer 15 according to the present embodiment, the balance of the above Al is Zn and impurities. Zn is an element necessary for constituting a main metallographic structure (Zn-Al-based metallographic structure) in a preferred aspect of the zinc-based coating layer 15 according to the present embodiment, and is an important element for improving corrosion resistance as the coated steel material. Further, when the zinc-based coating layer 15 contains the above Al within the above range and further contains Zn, it is possible to secure the corrosion resistance required for the coated steel material. [Mg: 0.10 mass % or more and less than 15.00 mass %] Mg is an element important for constituting the main metallographic structure (Zn-Al-Mg-based metallographic structure) in the preferable aspect of the zinc-based coating layer 15 according to the present embodiment. Therefore, Mg is preferably contained in a content of a predetermined amount or more in order to ensure corrosion resistance as the coated steel material. If the Mg content in the zinc-based coating layer 15 is less than 0.10 mass%, the above-mentioned corrosion resistance may not be ensured. Therefore, in the zinc-based coating layer 15 according to the present embodiment, the Mg content is preferably 0.10 mass% or more. The Mg content is preferably 0.30 mass% or more, and more preferably 3.00 mass% or more. When the Mg content is within the above range, the corrosion resistance as the coated steel material can be ensured.

[0048] On the other hand, if the Mg content in the zinc-based coating layer 15 is 15.00 mass% or more, anodic dissolution of the zinc-based coating layer is more likely to progress when placed in a corrosive environment, so that the corrosion resistance as the coated steel material may not be ensured. Therefore, in the zinc-based coating layer 15 according to the present embodiment, the Mg content is preferably less than 15.00 mass%. The Mg content is preferably less than 12.50 mass%, and more preferably 12.00 mass% or less. When the Mg content is within the above range, the corrosion resistance as the coated steel material can be ensured.

[0049] Subsequently, in a preferable specification of the zinc-based coating layer 15 according to another aspect of the present embodiment, the element group A to element group F, which the chemical composition of the zinc-based coating layer 15 may have, will be described in detail.

[0050] Note that in the zinc-based coating layer 15 according to another aspect of the present embodiment, when at least one of the elements belonging to the following element group A to element group F is contained, it is preferable to contain at least one of the elements belonging to the following element group A to element group F within the following content ranges and with a total content of 60.00 mass% or less.

[0051] By setting the total content of the elements belonging to the element group A to element group F to 60.00 mass% or less, it becomes possible to enjoy the effects exhibited by the addition of the elements, which will be described in detail below, without impairing each other. The total content of the elements belonging to the element group A to element group F is preferably 50.00 mass% or less, and more preferably 40.00 mass% or less.

[0052] O Element group A In another aspect of the zinc-based coating layer 15 according to the present embodiment, the element group A that can be contained in the zinc-based coating layer 15 will be described. At least one element in the element group A shown below is an element that can be contained in the zinc-based coating layer 15 in place of a portion of Zn in the balance. [Element group A]: one or two selected from the group consisting of Si: 2.50% or less and Fe: 5.00% or less

[0053] [Si: 0 to 2.50 mass %] In another aspect of the zinc-based coating layer 15 according to the present embodiment, a case where Si is not contained can be considered, and therefore the lower limit of the content thereof is 0 mass%. On the other hand, Si is an element capable of suppressing excessive growth of an Fe-Al-based metallographic structure formed at the interface between the zinc-based coating layer 15 and the steel material 11, and further improving the adhesion between the zinc-based coating layer 15 and the steel material 11. When Si is contained in the zinc-based coating layer 15, the Si content is preferably 0.05 mass% or more, and more preferably 0.20 mass% or more, in order to suppress the excessive growth of the Fe-Al-based metallographic structure. On the other hand, if the Si content exceeds 2.50 mass%, a high-melting-point intermetallic compound is excessively formed with Mg, which may inhibit the formation of Al-Mg oxides that have an effect of suppressing Zn evaporation during welding.

[0054] In addition, if the Si content in a coating bath for producing the zinc-based coating layer 15 is too high, the viscosity of the coating bath increases more than necessary, which may decrease operability during the production of the coated steel material (hereinafter referred to as "coating operability"). Therefore, the Si content in the coating bath is adjusted from the viewpoint of coating operability. The Si content in the zinc-based coating layer 15 is preferably 1.50 mass% or less, and more preferably 1.00 mass% or less.

[0055] [Fe: 0 to 5.00 mass %] From the steel material 11 which is a base material, elements constituting the steel material may be mixed into the zinc-based coating layer 15. Particularly, in the hot-dip coating method, elements constituting the steel material 11 are more likely to be mixed into the zinc-based coating layer 15 due to mutual diffusion of elements caused by a solid-liquid reaction between the steel material 11 and the zinc-based coating layer 15. Due to the mixing of elements, the zinc-based coating layer 15 often contains a predetermined amount of Fe, and the content thereof is often 0.01 mass% or more. If the mutual diffusion is promoted, the adhesion between the steel material 11 and the zinc-based coating layer 15 is improved. From the viewpoint of improving the adhesion between the steel material 11 and the zinc-based coating layer 15, the Fe content in the zinc-based coating layer 15 is preferably 0.20 mass% or more.

[0056] In addition, Fe may be intentionally added to the coating bath used in producing the zinc-based coating layer 15, within a range that does not impair the effects of the present invention. However, if the Fe content in the coating bath increases, a high-melting-point intermetallic compound of Fe and Al is formed in the coating bath. In this case, the high-melting-point intermetallic compound tends to adhere to the zinc-based coating layer 15 as dross, significantly deteriorating the appearance quality, which is undesirable. From the viewpoint, the Fe content in the coating bath is adjusted. The Fe content in the zinc-based coating layer 15 is preferably 5.00 mass% or less. The Fe content in the zinc-based coating layer 15 is more preferably 3.00 mass% or less, and still more preferably 2.00 mass% or less, 1.00 mass% or less, or 0.50 mass% or less.

[0057] O Element group B In another aspect of the zinc-based coating layer 15 according to the present embodiment, the element group B that can be contained in the zinc-based coating layer 15 will be described. At least one element in the element group B shown below is an element that can be contained in the zinc-based coating layer 15 in place of a portion of Zn in the balance. [Element group B]: one or two or more selected from the group consisting of Sb: less than 0.50%, Pb: less than 0.50%, and Sr: less than 0.50%

[0058] [Sb: 0 to 0.50 mass %] [Pb: 0 to 0.50 mass %] [Sr: 0 to 0.50 mass %] In another aspect of the zinc-based coating layer 15 according to the present embodiment, a case where Sb, Pb, and Sr are not contained can be considered, and therefore the lower limits of the contents of these elements are 0 mass%. On the other hand, when at least one of Sb, Pb, and Sr is contained in the zinc-based coating layer 15, spangles are formed on the surface of the zinc-based coating layer 13, making it possible to improve metallic luster. Therefore, from the viewpoint of further improving the designability of the coated steel material, at least one of Sb, Pb, and Sr is preferably contained in the zinc-based coating layer 15. The effect of improving designability is exhibited when the content of at least one of Sb, Pb, and Sr is 0.05 mass% or more. Therefore, when at least one of Sb, Pb, and Sr is contained in the zinc-based coating layer 15, the contents of these elements are each independently preferably set to 0.05 mass% or more.

[0059] On the other hand, when forming the zinc-based coating layer 15 in which any of the contents of Sb, Pb, and Sr exceeds 0.50 mass%, the amount of dross generated in the coating bath used for forming the zinc-based coating layer 15 increases, and there is a possibility that a coated steel material having good coating properties cannot be produced. Therefore, the contents of Sb, Pb, and Sr in the zinc-based coating layer 15 are each independently preferably 0.50 mass% or less. The contents of Sb, Pb, and Sr are each independently preferably 0.20 mass% or less.

[0060] O Element group C In another aspect of the zinc-based coating layer 15 according to the present embodiment, the element group C that can be contained in the zinc-based coating layer 15 will be described. At least one element in the element group C shown below is an element that can be contained in the zinc-based coating layer 15 in place of a portion of Zn in the balance. [Element group C]: one or two or more selected from the group consisting of Cu: less than 0.25%, Ti: less than 0.25%, Cr: less than 0.25%, Nb: less than 0.25%, Ni: less than 0.25%, Mn: less than 0.25%, Co: less than 0.25%, and V: less than 0.25%

[0061] [Cu: 0 mass % or more and less than 0.25 mass %] [Ti: 0 mass % or more and less than 0.25 mass %] [Cr: 0 mass % or more and less than 0.25 mass %] [Nb: 0 mass % or more and less than 0.25 mass %] [Ni: 0 mass % or more and less than 0.25 mass %] [Mn: 0 mass % or more and less than 0.25 mass %] [Co: 0 mass % or more and less than 0.25 mass %] [V: 0 mass % or more and less than 0.25 mass %] In another aspect of the zinc-based coating layer 15 according to the present embodiment, a case where Cu, Ti, Cr, Nb, Ni, Mn, Co, and V are not contained can be considered, and therefore the lower limits of the contents of these elements are 0 mass%. On the other hand, when at least one of Cu, Ti, Cr, Nb, Ni, Mn, Co, and V is contained in the zinc-based coating layer 15, these elements are incorporated into an Fe-Al-based metallographic structure generated by welding when the coated steel material is welded, and it becomes possible to further improve the corrosion resistance of a formed welded portion. The effect of improving the corrosion resistance of the welded portion is exhibited when the content of at least one of Cu, Ti, Cr, Nb, Ni, Mn, Co, and V in the zinc-based coating layer 13 is 0.05 mass% or more. Therefore, when at least one of Cu, Ti, Cr, Nb, Ni, Mn, Co, and V is contained in the zinc-based coating layer 15, the contents of these elements are each independently preferably set to 0.05 mass% or more.

[0062] On the other hand, when forming the zinc-based coating layer 15 in which any of the contents of Cu, Ti, Cr, Nb, Ni, Mn, Co, and V is 0.25 mass% or more, these elements form various intermetallic compounds in the coating bath for forming the zinc-based coating layer 15, leading to an increase in the viscosity of the coating bath, and there is a possibility that the coated steel material having good coating properties cannot be produced. Therefore, the contents of Cu, Ti, Cr, Nb, Ni, Mn, Co, and V in the zinc-based coating layer 15 are each independently preferably less than 0.25 mass%. The contents of Cu, Ti, Cr, Nb, Ni, Mn, Co, and V are each independently preferably 0.20 mass% or less.

[0063] O Element group D In another aspect of the zinc-based coating layer 15 according to the present embodiment, the element group D that can be contained in the zinc-based coating layer 13 will be described. At least one element in the element group D shown below is an element that can be contained in the zinc-based coating layer 13 in place of a portion of Zn in the balance. [Element group D]: one or two or more selected from the group consisting of Sn: 20.00% or less, Bi: less than 5.00%, and In: less than 2.00%

[0064] [Sn: 0 mass % or more and 2.00 mass %] [Bi: 0 mass % or more and less than 0.50 mass %] [In: 0 mass % or more and less than 2.00 mass %] In another aspect of the zinc-based coating layer 15 according to the present embodiment, a case where Sn, Bi, and In are not contained can be considered, and therefore the lower limits of the contents of these elements are 0 mass%. On the other hand, Sn, Bi, and In form intermetallic compounds with Mg in the zinc-based coating layer 15, making it possible to improve the weldability of the zinc-based coating layer 13. In addition, since all of these intermetallic compounds have high melting points, when the coated steel material is welded, they exist as intermetallic compounds without evaporating even after welding. The presence of these elements makes it possible to improve corrosion resistance and anticorrosion properties, and also makes it possible to improve the corrosion resistance of a welded portion during welding. The effect of improving corrosion resistance is exhibited when the content of at least one of Sn, Bi, and In in the zinc-based coating layer 15 is 0.05 mass% or more. Therefore, when at least one of Sn, Bi, and In is contained in the zinc-based coating layer 15, the contents of these elements are each independently preferably set to 0.05 mass% or more.

[0065] On the other hand, excessive addition of Sn may increase the amount of intermetallic compounds to be formed and decrease the corrosion resistance of the zinc-based coating layer 15 after welding. In addition, excessive addition of Bi and In may make the zinc-based coating layer 15 brittle and easy to peel off, and additionally may decrease the corrosion resistance of the zinc-based coating layer 15 after welding. These phenomena become remarkable when the Sn content exceeds 2.00 mass%, when the Bi content becomes 0.50 mass% or more, or when the In content becomes 2.00 mass% or more. Therefore, the Sn content is preferably 2.00 mass% or less, the Bi content is preferably less than 0.50 mass%, and the In content is preferably less than 2.00 mass%. The Sn content is more preferably 1.00 mass% or less, the Bi content is more preferably 0.30 mass% or less, and the In content is more preferably 1.00 mass% or less.

[0066] O Element group E In another aspect of the zinc-based coating layer 15 according to the present embodiment, the element group E that can be contained in the zinc-based coating layer 15 will be described. At least one element in the element group E shown below is an element that can be contained in the zinc-based coating layer 15 in place of a portion of Zn in the balance. [Element group E]: one or two or more selected from the group consisting of Ca: 3.00% or less, La: less than 0.50%, Ce: less than 0.50%, and Y: 0.50% or less

[0067] [Ca: 0 to 3.00 mass %] In another aspect of the zinc-based coating layer 15 according to the present embodiment, a case where Ca is not contained can be considered, and therefore the lower limit of the content thereof is 0 mass%. On the other hand, when Ca is contained in the coating bath for producing the zinc-based coating layer 15, dross to be generated with the increase of the Mg concentration during a coating operation can be reduced, and the coating operability can be improved.

[0068] In addition, when Ca is contained in the zinc-based coating layer 15, it forms intermetallic compounds with Al and Zn. Furthermore, when Si is contained together with Ca in the zinc-based coating layer 15, Ca forms an intermetallic compound with Si. Since these intermetallic compounds have high melting points and stable configurations, it becomes possible to suppress liquid metal embrittlement (LME) when the coated steel material is welded. When Ca is contained in the zinc-based coating layer 15, the effect of improving the coating operability and the effect of suppressing LME during welding are exhibited by setting the Ca content to 0.01 mass% or more. The Ca content in the zinc-based coating layer 15 is more preferably 0.05 mass% or more.

[0069] On the other hand, if the Ca content in the zinc-based coating layer 15 exceeds 3.00 mass%, the corrosion resistance as the coated steel material may decrease. From the viewpoint, the Ca content in the zinc-based coating layer 15 is preferably 3.00 mass% or less. The Ca content in the zinc-based coating layer 15 is preferably 2.00 mass% or less, and more preferably 1.00 mass% or less.

[0070] [La: 0 mass% or more and less than 0.50 mass%] [Ce: 0 mass% or more and less than 0.50 mass%] [Y: 0 mass% or more and 0.50 mass% or less] In another aspect of the zinc-based coating layer 15 according to the present embodiment, a case where La, Ce, and Y are not contained can be considered, and therefore the lower limits of the contents of these elements are 0 mass%. On the other hand, La, Ce, and Y are elements that exhibit almost the same effects as Ca. This is due to the fact that the atomic radius of each element is close to the atomic radius of Ca, and when these elements are contained in the zinc-based coating layer 15, they substitute at Ca sites.

[0071] The effect of improving the coating operability and the effect of suppressing LME during welding are exhibited by setting the contents of these elements each independently to 0.01 mass% or more. Therefore, when at least one of La, Ce, and Y is contained, the contents of these elements are each independently preferably set to 0.01 mass% or more. The contents of La, Ce, and Y in the zinc-based coating layer 15 are each independently more preferably 0.05 mass% or more.

[0072] On the other hand, in the coating bath for producing the zinc-based coating layer 15, if the contents of La, Ce, and Y are too high, the viscosity of the coating bath increases more than necessary, which may decrease coating operability. Therefore, the contents of La, Ce, and Y in the coating bath are adjusted from the viewpoint of the coating operability. The contents of La, Ce, and Y are independently preferably less than 0.50 mass%, less than 0.50 mass%, and 0.50 mass% or less, respectively. The contents of La, Ce, and Y are each independently preferably 0.10 mass% or less.

[0073] O Element group F In another aspect of the zinc-based coating layer 15 according to the present embodiment, the element group F that can be contained in the zinc-based coating layer 15 will be described. The element in the element group F shown below is an element that can be contained in the zinc-based coating layer 13 in place of a portion of Zn in the balance. [Element group F]: B: less than 0.50%

[0074] [B: 0 mass% or more and less than 0.50 mass%] In another aspect of the zinc-based coating layer 15 according to the present embodiment, a case where B is not contained can be considered, and therefore the lower limit of the content thereof is 0 mass%. On the other hand, when B is contained in the zinc-based coating layer 15, there is an effect of further suppressing LME. This is presumed to be because, when B is contained in the zinc-based coating layer 15, it combines with at least one of Zn, Al, Mg, and Ca to form various intermetallic compounds. In addition, it is considered that when B is present in the zinc-based coating layer 13, B diffuses from the zinc-based coating layer 15 into the steel material 11, thereby providing an effect of further suppressing LME of the steel material 11 through grain boundary strengthening. Furthermore, since the various intermetallic compounds formed regarding B have extremely high melting points, it is presumed that they also act to suppress Zn evaporation during welding. These improvement effects are exhibited by containing 0.05 mass% or more of B. Therefore, when B is contained, the content of B is preferably 0.05 mass% or more.

[0075] On the other hand, if B is excessively contained in the coating bath in order to contain B in the zinc-based coating layer 15, it causes a sharp rise in the coating melting point, leading to a decrease in coating operability, and there is a possibility that the coated steel material excellent in coating properties cannot be produced. Since the decrease in coating operability becomes remarkable when the content of B is 0.50 mass% or more, the content of B is preferably less than 0.50 mass%. The content of B is more preferably 0.10 mass% or less.

[0076] [Method for measuring chemical components] The chemical components of the above-mentioned zinc-based coating layer 15 can be measured using ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometry) or ICP-MS (Inductively Coupled Plasma Mass Spectrometry). Note that ICP-AES shall be used for the analysis of a chemical component down to units of 0.1 mass%, whereas ICP-MS shall be used for the analysis of a chemical component at a trace level of less than 0.1 mass%. The coated steel material is immersed in a 10% HCl aqueous solution with an inhibitor added for about 1 minute to peel off a zinc-based coating layer portion, thereby preparing a solution in which this zinc-based coating layer is dissolved. By analyzing the obtained solution by ICP-AES or ICP-MS, the chemical components as an overall average of the zinc-based coating layer can be obtained.

[0077] <<Regarding the thickness of the zinc-based coating layer 15>> The thickness (thickness dp in FIG. 3B) of the zinc-based coating layer 15 as described above is, for example, preferably 1 pm or more, and more preferably 3 pm or more. Further, the thickness of the zinc-based coating layer 15 is, for example, preferably 200 pm or less, and more preferably 50 pm or less. When the thickness of the zinc-based coating layer 15 is within the above range, the surface-treated member 1 according to the present embodiment can exhibit sufficient corrosion resistance.

[0078] Note that the thickness of the zinc-based coating layer 15 can be measured by direct observation from a cross section. Specifically, an arbitrary position of the surface-treated member 1 of interest is cut in the thickness direction of the surface-treated member 1 to obtain a cross-sectional sample including the zinc-based coating layer 15. Thereafter, the obtained cross-sectional sample is embedded in a room-temperature drying type epoxy resin so that the cross section can be observed, and the embedded surface is subjected to mechanical polishing and thereafter observed by SEM. In the SEM observation, those skilled in the art can easily distinguish the steel material 11, the zinc-based coating layer 15, and the protective layer 13 from their appearance. The thickness of the zinc-based coating layer 15 is measured at five arbitrary locations, and the average value of the obtained thicknesses at the five locations may be taken as the thickness of the zinc-based coating layer 15.

[0079] <Regarding the second protective layer 17> FIG. 4A and FIG. 4B schematically illustrate other examples of the configuration of the surface-treated member 1 according to the present embodiment. As schematically illustrated in FIG. 4A and FIG. 4B, the surface-treated member 1 according to the present embodiment may further have a second protective layer 17 on the protective layer 13.

[0080] Note that the detailed configuration of this second protective layer 17 will be described in detail again below.

[0081] <Regarding the detailed configuration of the protective layer 13> Next, the detailed configuration of the protective layer 13 included in the surface-treated member 1 according to the present embodiment will be described. As mentioned above, the protective layer 13 according to the present embodiment has a Zn concentration of 1 mass % or more and less than 30 mass % and an Si concentration of 1 mass % or more and less than 25 mass %, and contains SiO2 and a Zn / Al-based carbonate-type layered double hydroxide.

[0082] <<SiO2>> As mentioned above, the protective layer 13 according to the present embodiment contains SiO2, thereby exhibiting excellent barrier properties derived from SiO2, and making it possible to improve the corrosion resistance of the surface-treated member 1 according to the present embodiment.

[0083] The SiO2 is not particularly limited, and various known types of SiO2 can be used. Examples of the SiO2 include silica sand, colloidal silica, fumed silica, water-dispersed silica, precipitated silica, silica gel, and the like.

[0084] Here, whether or not the protective layer 13 of the surface-treated member 1 contains SiO2 can be determined by measuring the surface of the protective layer 13 by an X-ray diffraction (XRD) method checking whether or not a peak attributed to SiO2 exists in the obtained measurement results.

[0085] Here, as the peak attributed to SiO2, for example, a peak observed at 20 = 26.65 ± 0.50 can be exemplified. Here, the XRD measurement may be performed, for example, by the following method.

[0086] O Method for measuring an XRD pattern of the protective layer 13 First, a sample is cut out from the surface-treated member 1 having the protective layer 13. The dimensions of this sample are, for example, 20 mm x 20 mm when viewed from a direction perpendicular to the surface of the surface-treated member 1. Next, the XRD pattern of the sample is measured using an X-ray diffractometer (for example, RINT-TTR III manufactured by Rigaku Corporation or the like). Examples of XRD pattern measurement conditions at this time are listed below.

[0087] XRD pattern measurement conditions: X-ray output: 50 kV, 300 mA X-ray tube: Cu Measurement range: Start angle of 5°, end angle of 100° Scan speed: 2 deg / min Step width: 0.01 deg Scan axis: 2Theta / Theta Soller slit: 5° Divergence slit: 1 / 2° Divergence vertical limiting slit: 10 mm Scattering slit: Open (fully open) Receiving slit: Open (fully open) Goniometer radius: 285 mm Detector: One-dimensional detector D / tex Ultra-HE, with a monochromator placed in front of the detector

[0088] With respect to the measurement result data obtained under the above measurement conditions, the peak attributed to the SiO2 may be confirmed after removing the background using an application or the like implemented in the X-ray diffractometer (for example, PDXL2 manufactured by Rigaku Corporation or the like).

[0089] Further, in the protective layer 13 according to the present embodiment, the peak intensity of the peak attributed to SiO2 measured as described above is preferably 500 cps or more and 100000 cps or less. When the peak intensity is within the above range, it can be determined that the protective layer 13 contains a sufficient amount of SiO2 to exhibit a barrier effect against corrosion factors. The peak intensity of the peak attributed to SiO2 is more preferably 1000 cps or more.

[0090] Further, the protective layer 13 according to the present embodiment preferably contains, as the SiO2, SiO2 particles having a particle size of 0.10 to 1.00 pm. Further, the average particle size of the SiO2 particles is preferably 0.10 to 1.00 pm. Here, the SiO2 particles according to the present embodiment are particles that contain the element Si and the element O, in which the sum of the mass % of Si and the mass % of O is 95 mass % or more, and (number of moles of Si / sum of number of moles of Si and number of moles of O) is 0.25 or more and 0.50 or less. When the protective layer 13 contains SiO2 particles having the average particle size, the denseness of the protective layer 13 can be improved, and as a result, the barrier properties of the protective layer 13 can be further improved. The average particle size of the SiO2 particles is preferably 0.50 pm or less.

[0091] The ratio of the SiO2 particles having the above-mentioned particle size (0.10 to 1.00 pm) in all SiO2 particles is preferably 70 to 100% with respect to the total number of SiO2 particles contained in the protective layer 13 according to the present embodiment. By the SiO2 particles having the above-described particle size being contained in the above-described content, the denseness of the protective layer 13 and, in turn, the barrier properties of the protective layer 13 can be further improved. The ratio of the SiO2 particles having the above-mentioned particle size is more preferably 80% or more with respect to the total number of SiO2 particles contained in the protective layer 13.

[0092] Here, the particle size of the SiO2 particles as described above, and the ratio of the SiO2 particles having the above-described particle size (0.10 to 1.00 pm) to the total SiO2 particles, can be measured by direct observation from a cross section. Note that in the present embodiment, the particle size of the SiO2 particles identified by the cross-sectional observation is defined as the particle size of the SiO2 particles in the protective layer 13.

[0093] Specifically, the method for measuring the particle size of the SiO2 particles is as follows. First, an arbitrary position of the surface-treated member 1 of interest is cut in the thickness direction of the surface-treated member 1 (that is, a direction perpendicular to the surface of the surface-treated member 1) to obtain a cross-sectional sample of the protective layer 13. Thereafter, the obtained cross-sectional sample is embedded in a room-temperature drying type epoxy resin so that the cross section can be observed, and the embedded surface is subjected to mechanical polishing and thereafter observed by SEM. In the present embodiment, particles having a measured particle size of 0.05 pm or more are defined as "SiO2 particles." Particles having a measured particle size of less than 0.05 pm are not treated as "SiO2 particles" in the present embodiment because only the ends of the SiO2 particles may be observed, or the particles themselves may be too fine to have a significant influence on the exhibition of the barrier effect of the protective layer 13.

[0094] Note that the size of the field of view during SEM observation is 200 pm x 300 pm. In five arbitrary fields of view, the particle size and the number of particles of "all SiO2 particles having a particle size of 0.05 pm or more" existing in the fields of view are measured. Among them, the number of SiO2 particles having a particle size of 0.10 to 1.00 pm is calculated. This makes it possible to calculate "the number of SiO2 particles having a particle size of 0.10 to 1.00 pm" / "the number of SiO2 particles having a particle size of 0.05 pm or more."

[0095] Further, the average particle size of the SiO2 particles can be calculated by calculating the average value of the particle sizes of "all SiO2 particles having a particle size of 0.05 pm or more" existing in the fields of view (sum of particle sizes of all particles / number of all particles).

[0096] Note that those skilled in the art can easily recognize the SiO2 particles in the cross-sectional observation as described above. Further, even for a surface-treated member already embedded in soil, it is possible to perform the cross-sectional observation as described above by collecting a measurement sample from the embedded surface-treated member.

[0097] <<Zn / Al-based carbonate-type layered double hydroxide>> As mentioned above, the protective layer 13 according to the present embodiment contains the Zn / Al-based carbonate-type layered double hydroxide, thereby trapping anions as corrosion factors that have entered the protective layer 13. This makes it possible to improve the corrosion resistance of the surface-treated member 1 according to the present embodiment.

[0098] The Zn / Al-based layered double hydroxides (hydrotalcites) are compounds having a general formula as shown in (1) below. [Zn1-XA1X(OH)2]X+[An-X / n • mH2O]X- ...(1)

[0099] Here, in the above general formula (1), An- represents an n-valent anion such as OH-, F-, Cl-, Br-, NO2-, CO32-, SO42-, Fe(CN)33-, CH3COO-, oxalate ion, or salicylate ion. Further, X represents a value greater than 0 and 0.33 or less. Among the Zn / Al-based layered double hydroxides, those having a carbonate ion (CO32-) as An- are Zn / Al-based carbonate-type layered double hydroxides.

[0100] It is more preferable to use zinc aluminum hydroxide carbonate hydrate (Zn6Ah(OH)i6CO3MH2O), which is a particularly highly stable substance, among the Zn / Al-based carbonate-type layered double hydroxides as described above.

[0101] <<Mg / Al-based carbonate-type layered double hydroxide>> The protective layer 13 according to the present embodiment preferably further contains an Mg / Al-based carbonate-type layered double hydroxide in addition to the SiO2 and the Zn / Al-based carbonate-type layered double hydroxide. Similar to the Zn / Al-based carbonate-type layered double hydroxide, the Mg / Al-based carbonate-type layered double hydroxide is a compound having a layered structure and can trap anions between its layers. Here, since the interlayer distance of the Mg / Al-based carbonate-type layered double hydroxide is different from that of the Zn / Al-based carbonate-type layered double hydroxide, it can trap corrosion factors of a different type from those trapped by the Zn / Al-based carbonate-type layered double hydroxide. Therefore, by further containing the Mg / Al-based carbonate-type layered double hydroxide in addition to the Zn / Al-based carbonate-type layered double hydroxide, the protective layer 13 according to the present embodiment can further improve the corrosion resistance of the surface-treated member 1.

[0102] The Zn / Al-based layered double hydroxides (hydrotalcites) are compounds having a general formula as shown in (2) below. [Mg1-XAlX(OH)2]X+[An-X / n • mH2O]X- ...(1)

[0103] Here, in the above general formula (1), An- represents an n-valent anion such as OH-, F-, Cl-, Br-, NO2-, CO32-, SO42-, Fe(CN)33-, CH3COO-, oxalate ion, or salicylate ion. Further, X represents a value greater than 0 and 0.33 or less. Among the Mg / Al-based layered double hydroxides, those having a carbonate ion (CO32-) as An- are Mg / Al-based carbonate-type layered double hydroxides.

[0104] It is more preferable to use magnesium aluminum hydroxide carbonate hydrate (Mg6Ah(OH)16CO3MH2O), which is a particularly highly stable substance, among the Mg / Al-based carbonate-type layered double hydroxides as described above.

[0105] <<Method for confirming the carbonate-type layered double hydroxide>> Here, whether or not the protective layer 13 of the surface-treated member 1 contains the Zn / Al-based carbonate-type layered double hydroxide or the Mg / Al-based carbonate-type layered double hydroxide as described above can be determined based on whether or not a peak attributed to the Zn / Al-based carbonate-type layered double hydroxide or a peak attributed to the Mg / Al-based carbonate-type layered double hydroxide is present in the measurement results obtained by measuring the surface of the protective layer 13 by XRD.

[0106] Here, as the peak attributed to the Zn / Al-based carbonate-type layered double hydroxide, for example, a peak observed at 20 = 11.64 ± 0.50 can be exemplified.    Further, as the peak attributed to the Mg / Al-based carbonate-type layered double hydroxide, for example, a peak observed at 20 = 11.71 ± 0.50 can be exemplified. Since the XRD measurement conditions are the same as those described above, detailed description thereof is omitted below.

[0107] Further, in the protective layer 13 according to the present embodiment, the peak intensity of the peak attributed to the Zn / Al-based carbonate-type layered double hydroxide measured as described above is preferably 1000 cps or more and 150000 cps or less. When the peak intensity is within the above range, it can be determined that the protective layer 13 contains the Zn / Al-based carbonate-type layered double hydroxide at a level sufficient to trap anions, which are corrosion factors. The peak intensity of the peak attributed to the Zn / Al-based carbonate-type layered double hydroxide is more preferably 5000 cps or more.

[0108] Further, when the protective layer 13 according to the present embodiment contains the Mg / Al-based carbonate-type layered double hydroxide, the peak intensity of the peak attributed to the Mg / Al-based carbonate-type layered double hydroxide measured as described above is preferably 1000 cps or more and 150000 cps or less. When the peak intensity is within the above range, it can be determined that the protective layer 13 contains the Mg / Al-based carbonate-type layered double hydroxide at a level sufficient to effectively trap anions, which are corrosion factors. The peak intensity of the peak attributed to the Mg / Al-based carbonate-type layered double hydroxide is more preferably 5000 cps or more.

[0109] <<Regarding other components>> The protective layer 13 according to the present embodiment may contain various Si-containing compounds, Zn-containing compounds, Al-containing compounds, Mg-containing compounds, and the like, in addition to the components described above.

[0110] O Si-containing compounds Examples of the Si-containing compounds that can be contained in the protective layer 13 according to the present embodiment include various silicate-based compounds and cured products thereof. Examples of the silicate-based                      compounds                      include: 3-(2-aminoethyl)aminopropyltrimethoxysilane, 3-(2-aminoethyl)aminopropylmethyldimethoxysilane, 3-(2-aminoethyl)aminopropyltriethoxysilane, 3-(2-aminoethyl)aminopropylmethyldiethoxysilane, 3-(2-aminoethyl)aminopropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, N-2-(N-vinylbenzylaminoethyl)-3-aminopropyltrimethoxysilane, N-2-(N-vinylbenzylaminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(N-vinylbenzylaminoethyl)-3-aminopropyltriethoxysilane, N-2-(N-vinylbenzylaminoethyl)-3-aminopropylmethyldiethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldiethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane,                               vinyltriacetoxysilane, 3-chloropropyltrimethoxysilane, 3-chloropropylmethyldimethoxysilane, 3-chloropropyltriethoxysilane,          3-chloropropylmethyldiethoxysilane, 3-anilinopropyltrimethoxysilane, 3-anilinopropylmethyldimethoxysilane, 3-anilinopropyltriethoxysilane,         3-anilinopropylmethyldiethoxysilane, vinyltrimethoxysilane, vinylmethyldimethoxysilane, vinyltriethoxysilane, vinylmethyldiethoxysilane, octadecyldimethyl[3-(trimethoxysilyl)propyl]ammonium           chloride, octadecyldimethyl[3-(methyldimethoxysilyl)propyl]ammonium     chloride, octadecyldimethyl[3-(triethoxysilyl)propyl]ammonium             chloride, octadecyldimethyl[3-(methyldiethoxysilyl)propyl]ammonium       chloride, 3-chloropropylmethyldimethoxysilane, 3-mercaptopropylmethyldimethoxysilane,             methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, and the like.

[0111] O Zn-containing compounds Examples of the Zn-containing compounds that can be contained in the protective layer 13 according to the present embodiment include ZnO, Zn(OH)2, Zn5(OH)8CM2O, Zn5(CO3)2(OH)6, Zn2Al(OH>CM.8H2O, and the like.

[0112] O Al-containing compounds Examples of the Al-containing compounds that can be contained in the protective layer 13 according to the present embodiment include Al2O3, Al(OH)3, and the like.

[0113] O Mg-containing compounds Examples of the Mg-containing compounds that can be contained in the protective layer 13 according to the present embodiment include MgZn2, and the like.

[0114] O Organic resins Further, the protective layer 13 according to the present embodiment may contain various organic resins as a film-forming component. When the protective layer 13 according to the present embodiment further contains an organic resin, the corrosion resistance of the protective layer 13 can be further improved.

[0115] As the organic resin, for example, known organic resins such as polyester resins, polyurethane resins, epoxy resins, phenol resins, acrylic resins, polyolefin resins, and fluororesins can be used. Further, it is also possible to use film-forming resin components such as modified resins of these resins, which are crosslinked by a crosslinking agent component of a butylated melamine resin, a methylated melamine resin, a butyl-methyl mixed melamine resin, a urea resin, an isocyanate resin, or a mixed system of these resins. Further, an electron beam-curable resin, an ultraviolet-curable resin, or the like may be used as the organic resin. In order to further enhance the adhesion with the steel material 11 or the zinc-based coating layer 15, it is preferable to use at least one of resins (polyester resins, urethane resins, epoxy resins, acrylic resins, etc.) having a constrained site or a polar functional group in the molecular chain. These organic resins may be used alone or in combination of two or more types.

[0116] O Other components The protective layer 13 according to the present embodiment may contain a zirconium compound, a fluoride, a vanadium compound, tannin, tannic acid, or the like, in addition to the various components described above.

[0117] Further, the protective layer 13 according to the present embodiment may further contain various antirust pigments in addition to the various components described above. As the antirust pigment, any pigment can be used, such as, for example, calcium ion-exchanged silica (sometimes commonly referred to as calcium silicate), magnesium oxide, calcium molybdate, aluminum molybdate, barium molybdate, and the like.

[0118] Furthermore, the protective layer 13 according to the present embodiment may further contain extender pigments such as precipitated barium sulfate and clay, and coloring pigments such as titanium oxide, as necessary. Further, the protective layer 13 according to the present embodiment may contain additives such as a coloring agent, a viscosity modifier, a leveling agent, an antifoaming agent, and an ultraviolet absorber, as necessary, in addition to the anticorrosive pigments, the extender pigments, and the coloring pigments described above.

[0119] <<Regarding element concentration in the protective layer 13>> The protective layer 13 according to the present embodiment containing the components as described above has a Zn concentration of 5.00 mass% or more and less than 30.00 mass%, and an Si concentration of 5.00 mass% or more and less than 25.00 mass%. Further, the protective layer 13 according to the present embodiment preferably has an Al concentration of 0.01 mass% or more and 10.00 mass% or less.

[0120] [Zn: 1.00 mass% or more and less than 30.00 mass%] When the Zn concentration is less than 1.00 mass%, the content of the Zn / Al-based carbonate-type layered double hydroxide in the protective layer 13 according to the present embodiment is insufficient, and sufficient corrosion resistance cannot be obtained. When the Zn concentration is 1.00 mass% or more, even when the surface-treated member 1 is installed in the soil surface layer portion, it can exhibit sufficient corrosion resistance. In the protective layer 13 according to the present embodiment, the Zn concentration is preferably 10.00 mass% or more, and more preferably 15.00 mass% or more.

[0121] On the other hand, when the Zn concentration is 30.00 mass% or more, the content of the Zn / Al-based carbonate-type layered double hydroxide is too high in the protective layer 13 according to the present embodiment, and the content of SiO2 becomes insufficient. When the Zn concentration is less than 30.00 mass%, it is possible to exhibit sufficient corrosion resistance even when the surface-treated member 1 is installed in the soil surface layer portion while maintaining the content of SiO2. In the protective layer 13 according to the present embodiment, the Zn concentration is preferably 25.00 mass% or less, and more preferably 20.00 mass% or less.

[0122] [Si: 1.00 mass% or more and less than 25.00 mass%] When the Si concentration is less than 1.00 mass%, the content of SiO2 in the protective layer 13 according to the present embodiment is insufficient, and sufficient corrosion resistance cannot be obtained. When the Si concentration is 1.00 mass% or more, even when the surface-treated member 1 is installed in the soil surface layer portion, it can exhibit sufficient corrosion resistance. In the protective layer 13 according to the present embodiment, the Si concentration is preferably 10.00 mass% or more, and more preferably 15.00 mass% or more.

[0123] On the other hand, when the Si concentration is 25.00 mass% or more, the content of SiO2 is too high in the protective layer 13 according to the present embodiment, and the content of the Zn / Al-based carbonate-type layered double hydroxide becomes insufficient. When the Si concentration is less than 25.00 mass%, it is possible to exhibit sufficient corrosion resistance even when the surface-treated member 1 is installed in the soil surface layer portion while ensuring the content of the Zn / Al-based carbonate-type layered double hydroxide. In the protective layer 13 according to the present embodiment, the Si concentration is preferably 20.00 mass% or less, and more preferably 15.00 mass% or less.

[0124] [Mg: 0.10 mass% or more and 5.00 mass% or less] When the protective layer 13 according to the present embodiment contains an Mg-containing compound such as the Mg / Al-based carbonate-type layered double hydroxide, the Mg concentration of the protective layer 13 is preferably 0.10 mass% or more and 5.00 mass% or less.

[0125] When the Mg concentration in the protective layer 13 is 0.10 mass% or more, the protective layer 13 according to the present embodiment has the Mg / Al-based carbonate-type layered double hydroxide at a level sufficient to trap anions, which are corrosion factors, and exhibits more excellent corrosion resistance.   The Mg concentration in the protective layer 13 is more preferably 0.50 mass% or more, and further preferably 1.00 mass% or more.

[0126] On the other hand, when the Mg concentration in the protective layer 13 is 5.00 mass% or less, the protective layer 13 according to the present embodiment can prevent the content of the Zn / Al-based carbonate-type layered double hydroxide from becoming insufficient, thereby allowing each of the Zn / Al-based and Mg / Al-based carbonate-type layered double hydroxides to trap various corrosion factors in a well-balanced manner, resulting in more excellent corrosion resistance. The Mg concentration in the protective layer 13 is more preferably 4.00 mass% or less, and further preferably 3.00 mass% or less.

[0127] Here, the above Zn concentration, Si concentration, and Mg concentration can be measured as follows. First, the surface-treated member 1 of interest is cut at an arbitrary position in the thickness direction of the surface-treated member 1 (that is, a direction perpendicular to the surface of the surface-treated member 1) to obtain a cross-sectional sample of the protective layer 13. From an arbitrary position on the surface of the protective layer 13 in the cross-sectional sample, along the thickness direction of the protective layer 13 (for example, the Z-axis direction in FIG. 3A) to the position of the interface with the zinc-based coating layer 15 or the position of the interface with the steel material 11, analysis is performed using an Energy Dispersive X-ray Spectroscopy (EDS) analyzer provided in a Scanning Electron Microscope (SEM, such as JSM-7000F manufactured by JEOL Ltd.), and the obtained analysis results are mapped. Here, the elements focused on in the above analysis are Zn, Si, Al, Mg, and C. The observation conditions of SEM-EDS at this time may be, for example, acceleration voltage: 15 kV, irradiation current: 4.91 nA, number of sweeps: 10 times, and observation magnification: 500 times.

[0128] The range corresponding to the protective layer 13 can be easily identified from an SEM image by those skilled in the art. However, in the present embodiment, in the depth profile of each element obtained as described above, a portion where the Zn concentration and the Si concentration fall within the above-mentioned ranges is regarded as the region of the protective layer 13. Then, the average concentrations of Zn, Si, and Mg elements in the region of the protective layer 13 are calculated from the obtained depth profiles of the Zn, Si, and Mg elements.

[0129] The above measurement is similarly performed at five arbitrary locations on the obtained cross-sectional sample, and the average values of the average concentrations obtained for the plurality of elements at the number of measured locations may be regarded as the Zn, Si, and Mg concentrations in the protective layer 13.

[0130] <<Regarding the distribution of an Si element in the protective layer 13>> Next, the distribution state of the Si element in the thickness direction of the protective layer 13 according to the present embodiment will be specifically described with reference to FIG. 5. FIG. 5 is an explanatory view for explaining the distribution state of the Si element in the protective layer 13 according to the present embodiment.

[0131] As schematically illustrated in FIG. 5, a region from the surface side of the protective layer 13 (the Z-axis positive direction side in FIG. 5) toward the steel material 11 side up to the center of the thickness of the protective layer 13 is referred to as a "region a" for convenience. Similarly, a region from the center of the thickness of the protective layer 13 toward the steel material 11 side up to the interface with the steel material 11 (the interface with the zinc-based coating layer 15 if the zinc-based coating layer 15 is present) is referred to as a "region b" for convenience.

[0132] In the same manner as the method for measuring the Si concentration described above, the depth profile for the region a and the depth profile for the region b are measured for the Si element, and the Si concentrations of the region a and the region b are calculated in the same manner as described above. The Si concentration of the region a obtained in this manner is expressed as [Si]a, and the Si concentration of the region b is expressed as [Si]b.

[0133] At this time, in the protective layer 13 according to the present embodiment, the Si concentration at a 1 / 2 thickness of the protective layer 13 on the surface side (that is, [Si]a) is preferably 1.3 times or more the Si concentration at a 1 / 2 thickness of the protective layer 13 on the steel material 11 side (that is, [Si]b) (that is, a relationship [Si]a > 1.3 x [Si]b is satisfied).

[0134] When the relationship [Si]a > 1.3 x [Si]b is satisfied, it means that the Si element in the protective layer 13 is localized more in the region a than in the region b. Corrosion factors are considered to penetrate from the surface side region of the protective layer 13 (that is, the region a) toward the steel material 11 side. Therefore, by the Si element being localized more on the region a side, it becomes possible to more effectively prevent the penetration of corrosion factors, making it possible to further improve the corrosion resistance of the protective layer 13.

[0135] The Si concentration [Si]a of the region a is more preferably 1.4 times or more, and further preferably 1.5 times or more, the Si concentration [Si]b of the region b. On the other hand, it is more preferable that this ratio ([Si]a / [Si]b) is as large as possible, and although its upper limit is not specified, the upper limit is substantially about 2.0 times.

[0136] <<Regarding the thickness of the protective layer 13>> The thickness (thickness d1 in FIG. 3A to FIG. 4B) of the protective layer 13 according to the present embodiment having the above configuration is preferably 0.1 pm or more and 50.0 pm or less. When the thickness dl of the protective layer 13 is 0.1 pm or more, the surface-treated member 1 according to the present embodiment exhibits more excellent corrosion resistance. The thickness d1 of the protective layer 13 is more preferably 1.0 pm or more.

[0137] On the other hand, when the thickness d1 of the protective layer 13 is 50.0 pm or less, the surface-treated member 1 exhibits more excellent corrosion resistance while ensuring the adhesion of the protective layer 13. The thickness d1 of the protective layer 13 is more preferably 30.0 pm or less.

[0138] Note that the thickness of the protective layer 13 can be measured by direct observation from a cross-section. Specifically, an arbitrary position of the surface-treated member 1 of interest is cut in the thickness direction of the surface-treated member 1 to obtain a cross-sectional sample including the protective layer 13. Thereafter, the obtained cross-sectional sample is embedded in a room-temperature drying type epoxy resin so that the cross-section can be observed, and the embedded surface is subjected to mechanical polishing and thereafter observed by SEM. In the SEM observation, those skilled in the art can easily distinguish the steel material 11, the zinc-based coating layer 15, and the protective layer 13 from their appearance. The thickness of the protective layer 13 is measured at five arbitrary locations, and the average value of the thicknesses obtained at the five locations may be taken as the thickness of the protective layer 13.

[0139] The detailed configuration of the protective layer 13 according to the present embodiment has been described above.

[0140] <Regarding a detailed configuration of the second protective layer 17> As schematically illustrated in FIG. 4A and FIG. 4B, in the surface-treated member 1 according to the present embodiment, the second protective layer 17 is preferably further positioned on the protective layer 13.

[0141] The second protective layer 17 contains SiO2 particles 19, as schematically illustrated in FIG. 4A and FIG. 4B. These SiO2 particles 19 have an average particle size of 1.00 to 30.00 gm. Since the average particle size of the SiO2 particles 19 contained in the second protective layer 17 is 1.00 to 30.00 gm, the second protective layer 17 becomes a layer having barrier properties, and the corrosion resistance as the surface-treated member 1 is further improved. Here, the average particle size of the SiO2 particles 19 is more preferably 10.00 gm or more. Further, the average particle size of the SiO2 particles 19 is more preferably 15.00 gm or less.

[0142] Note that the average particle size of the SiO2 particles 19 in the second protective layer 17 can be measured in the same manner as the average particle size of the SiO2 particles in the protective layer 13.

[0143] In the second protective layer 17 according to the present embodiment, the ratio of the SiO2 particles 19 having a particle size of 1.00 to 30.00 pm ("number of SiO2 particles having a particle size of 1.00 to 30.00 pm" / "number of SiO2 particles having a particle size of 0.05 pm or more") is preferably 10 to 80%. When the ratio of the SiO2 particles 19 having a particle size of 1.00 to 30.00 pm is 10% or more, the corrosion resistance of the surface-treated member 1 can be further improved. The ratio of the SiO2 particles 19 having a particle size of 1.00 to 30.00 pm is more preferably 30% or more.

[0144] On the other hand, when the ratio of the SiO2 particles 19 having a particle size of 1.00 to 30.00 pm is 80% or less, it is possible to further improve the corrosion resistance of the surface-treated member 1 while maintaining the adhesion of the second protective layer 19. The ratio of the SiO2 particles 19 is more preferably 70% or less.

[0145] Here, the particle size and number of the SiO2 particles in the second protective layer 17 can be measured in the same method as the method for measuring the content of SiO2 in the protective layer 13.

[0146] Further, the second protective layer 17 according to the present embodiment may contain, in addition to the SiO2 particles 19 as described above, various compounds containing elements such as Zn, Al, Mg, and C (for example, an oxides, a carbonate compound, or the like containing at least one of these elements).

[0147] The thickness (thickness d2 in FIG. 4A and FIG. 4B) of the second protective layer 19 according to the present embodiment is preferably 1.0 pm or more and 100.0 pm or less. When the thickness d2 of the second protective layer 19 is 1.0 pm or more, the surface-treated member 1 according to the present embodiment exhibits more excellent corrosion resistance. The thickness d2 of the second protective layer 19 is more preferably 10.0 pm or more.

[0148] On the other hand, when the thickness d2 of the second protective layer 19 is 100.0 pm or less, the surface-treated member 1 exhibits more excellent corrosion resistance while ensuring the adhesion of the second protective layer 19. The thickness d2 of the second protective layer 19 is more preferably 50.0 pm or less.

[0149] Note that the thickness d2 of the second protective layer 19 can be measured in the same manner as the thickness d1 of the protective layer 13 described above.

[0150] Here, the range corresponding to the protective layer 13 and the range corresponding to the second protective layer 19 can be easily identified from an SEM image by those skilled in the art. However, in the depth profile of each element by SEM-EDS described above, a region containing particles located in a further upper layer (the side opposite to the steel material 11 side) of the region identified as the region of the protective layer 13 is regarded as the region of the second protective layer 17.

[0151] The detailed configuration of the second protective layer 19 according to the present embodiment has been described above.

[0152] (Regarding a method for manufacturing the surface-treated member) An example of the method for manufacturing the surface-treated member 1 according to the present embodiment will be described below.

[0153] <Method for manufacturing the surface-treated steel material 10 as a raw material> The surface-treated steel material 10 as a raw material of the surface-treated member 1 according to the present embodiment is manufactured by using the steel material 11 as described above as a base material, forming the zinc-based coating layer 15 on the surface of the steel material 11, then applying a treatment agent for forming a protective layer to the surface of the zinc-based coating layer 15, and further storing the surface after applying the treatment agent in a specific atmosphere for a predetermined time.

[0154] <<Method for forming the zinc-based coating layer 15>> In addition to the hot-dip coating method, a thermal spraying method, a cold spray method, a sputtering method, a vapor deposition method, an electroplating method, or the like can be applied to form the zinc-based coating layer 15. However, the hot-dip coating method is most preferable in terms of cost.

[0155] An example of a manufacturing method for obtaining the zinc-based coating layer 15 according to the present embodiment using the hot-dip coating method will be described in detail below. In the manufacturing process of the zinc-based coating layer 15, first, a steel sheet as an example of the steel material 11 used as a base material is rolled to a desired sheet thickness by a Sendzimir method, then wound into a coil shape, and installed in a hot-dip coating line.

[0156] In the hot-dip coating line, the steel sheet is continuously passed while being fed from a coil. At this time, using an annealing facility provided on the line, the steel sheet is subjected to a heating reduction treatment at 800°C in an N2-5% H2 gas atmosphere, for example, under an environment with an oxygen concentration of 20 ppm or less where oxidation is unlikely to occur, and then air-cooled with N2 gas to around the bath temperature of the coating bath in the subsequent stage + 20°C, and immersed in the coating bath.

[0157] Here, a coating alloy in a molten state having the chemical components as described above is prepared in the coating bath. The bath temperature of the coating bath is set to be equal to or higher than the melting point of the coating alloy (for example, about 460 to 660°C).

[0158] When preparing the material for the coating alloy, it is preferable to use pure metals (purity of 99% or more) as alloy materials for preparation. First, predetermined amounts of alloy metals are mixed so as to achieve the composition of the coating layer as described above, and are completely melted into an alloy using a high-frequency induction furnace, an arc furnace, or the like in a vacuum or inert gas-substituted state. Furthermore, the alloy obtained by mixing predetermined components (the composition of the coating layer) is melted in the atmosphere, and the obtained melt is used as a coating bath.

[0159] Note that there is no particular restriction on using pure metals for preparing the coating alloy as described above, and existing Zn alloys, Mg alloys, and Al alloys may be melted and used. In this case, there is no problem as long as a predetermined composition alloy with few impurities is used.

[0160] After the steel sheet is immersed in the coating bath as described above, it is pulled up at a predetermined speed. At this time, the plating coating weight is controlled by, for example, N2 wiping gas so that the formed zinc-based coating layer has a desired thickness. Here, as for conditions other than the bath temperature, general coating operation conditions may be applied, and no special equipment or conditions are required.

[0161] Further, various heat treatments may be applied to the coating alloy in a molten state located on the steel sheet, as necessary.

[0162] <<Method for forming the protective layer 13 and the second protective layer 17>> The protective layer 13 and the second protective layer 17 in the surface-treated steel material 10 according to the present embodiment are formed by applying a treatment agent for forming a protective layer to the surface of the zinc-based coating layer 15 formed as described above, and further storing the surface after applying the treatment agent in a specific atmosphere for a predetermined time.

[0163] O Preparation of the treatment agent for forming the protective layer The treatment agent for forming the protective layer is prepared by mixing components to be contained in the protective layer (more specifically, the SiO2 component, and components of various carbonate-type layered double hydroxides such as Zn / Al-based and Mg / Al-based, and the like) into water as a solvent.

[0164] Here, as the SiO2 component to be contained in the treatment agent, various types of SiO2 as mentioned above are used. At this time, it is more preferable to use a mixture of SiO2 particles having a plurality of types of average particle sizes (hereinafter also simply referred to as "SiO2 mixture") as the SiO2.

[0165] For example, a treatment agent for forming the protective layer 13 can be obtained by using SiO2 particles having an average particle size of 0.1 to 1.0 pm as the SiO2 mixture. Here, the content of the SiO2 particles having an average particle size of 0.1 to 1.0 pm is preferably, for example, 50 to 75 mass% with respect to the total mass of the SiO2 mixture.

[0166] Similarly, a treatment agent for forming the second protective layer 17 can be obtained by using SiO2 particles having an average particle size of 1.0 to 30.0 gm as the SiO2 mixture. Here, the content of the S1O2 particles having an average particle size of 1.0 to 30.0 gm is preferably, for example, 10 to 20 mass% with respect to the total mass of the SiO2 mixture.

[0167] Here, the water content in each treatment agent (that is, the moisture content of the treatment agent) is preferably set so that the volume fraction of water is 50% or more and 80% or less with respect to pores of the SiO2 mixture. Here, the pores of the SiO2 mixture can be grasped in advance based on a pore ratio {1 - (B / A)} obtained from a specific gravity "A" of the SiO2 used and a bulk specific gravity "B" of the SiO2 mixture before adding water.

[0168] In addition, the pH of the water used as a solvent for each treatment agent is preferably within a range of 4 to 9. This makes it possible to bring the reactivity of the treatment agent into a more preferable state. Accordingly, coating components (particularly, components such as Zn) can be easily eluted from the zinc-based coating layer 15. As a result, in a storage step described later, the components of the already formed zinc-based coating layer 15 and the components of the treatment agent for forming the protective layer or the treatment agent for forming the second protective layer react appropriately, so that the protective layer 13 and the second protective layer 17 according to the present embodiment are formed.

[0169] O Application of the treatment agent The treatment agent for forming the protective layer prepared as described above may be applied to the surface of the zinc-based coating layer 15 so as to have a thickness of 0.5 mm or more and 3.0 mm or less. Here, the application of the treatment agent as described above can be performed by a generally known application method such as, for example, roll coating, curtain flow coating, air spraying, airless spraying, immersion, bar coating, brush coating, and the like.

[0170] O Storage of the steel material to which the treatment agent has been applied The steel material to which the treatment agent has been applied as described above (the steel material 11 having the zinc-based coating layer 15) is stored in an atmosphere at a temperature of 10 to 40°C and a relative humidity of 80% or more. Accordingly, the components of the already formed zinc-based coating layer 15 and the components of the treatment agent for forming the protective layer react appropriately, so that the protective layer 13 according to the present embodiment is formed.

[0171] Here, the storage time of the steel material as described above is preferably 240 hours or more. This makes it possible to form the protective layer 13 of the surface-treated steel material 10 according to the present embodiment. On the other hand, the upper limit of the storage time of the steel material is not particularly specified, but the upper limit is substantially about 1440 hours. In particular, by setting the storage time of the steel material to 360 hours or more and 720 hours or less, it becomes possible to form the protective layer 13 having a more preferable thickness.

[0172] When forming the second protective layer 17 as an upper layer of the protective layer 13 formed as described above, a part of the protective layer 13 formed as described above may be removed as necessary, and then the treatment agent for forming the second protective layer may be applied onto the protective layer 13 and stored in the same manner as described above.

[0173] Here, the application conditions and storage conditions of the treatment agent for forming the second protective layer are the same as those in the case of forming the protective layer, and therefore a detailed description thereof will be omitted below.

[0174] Note that the zinc-based coating layer 15 formed on the surface of the steel material 11 may disappear from the surface of the steel material 11 as a result of reacting completely with the components of the treatment agent through the storage step. Further, depending on the storage time, the zinc-based coating layer 15 may remain between the steel material 11 and the formed protective layer 13.

[0175] Further, in the treatment agent for forming the protective layer, by setting the pH of water used as a solvent to 4 to 5 to make it easier to elute the coating components, and by setting the temperature in the storage step to 30 to 40°C, it becomes possible to further concentrate the element Si on the surface side of the protective layer 13.

[0176] Through the steps as described above, the surface-treated steel material 10, which serves as a raw material of the surface-treated member 1 according to the present embodiment, can be manufactured. An example of the method for manufacturing the surface-treated steel material 10 according to the present embodiment has been specifically described above.

[0177] <Method for manufacturing the surface-treated member> The surface-treated member 1 according to the present embodiment is manufactured using the surface-treated steel material 10 obtained as described above as a raw material. Here, in obtaining parts for manufacturing the surface-treated member 1 from the surface-treated steel material 10, various shaping processes can be utilized, such as various forming processes, and joining processes by fastening members such as bolts or clinch, or by welding processes. By appropriately combining these processes, the surface-treated member 1 having a desired shape can be manufactured from the surface-treated steel material 10.

[0178] An example of the method for manufacturing the surface-treated member 1 according to the present embodiment has been briefly described above. EXAMPLES

[0179] The surface-treated member according to the present invention will be specifically described below while showing examples and comparative examples. Note that the examples described below are merely examples of the surface-treated member according to the present invention, and the surface-treated member according to the present invention is not limited to the following examples.

[0180] <Preparation of the coated steel material> In test examples described below, cold-rolled steel sheets and Ni-coated cold-rolled steel sheets (both manufactured by Nippon Steel Corporation) shown in Table 1 below were prepared as coating base sheets, 5 and cut into a size of 60 mm x 60 mm. Coating was performed using an in-house batch-type hot-dip coating test apparatus, and a plurality of coated steel materials having the coating layer compositions shown in Table 2 below were prepared for each level. Note that the coating thickness per side for each level is shown in Table 4 below. 10

[0181] [TABLE 1] TABLE 1 COATING BASE SHEET a COLD-ROLLED STEEL SHEET (JIS G 3141:2017) b Ni COLD-ROLLED STEEL SHEET (Ni COATING WEIGHT OF 0.5 g / m2) c Ni COLD-ROLLED STEEL SHEET (Ni COATING WEIGHT OF 2.0 g / m2) 15

[0182] [TABLE 2] TABLE 2 COATING COMPOSIITON (mass%) A Zn - 0.18%Al B Zn - 6.0%Al - 3.0%Mg C Zn - 11.0%Al - 3.0%Mg - 0.2%Si D Zn - 16.0%Al - 6.0%Mg - 0.2%Si E Zn - 19.0%Al - 6.0%Mg - 1.5%Sn - 0.5%Ca - 0.2%Si F Zn - 24.0%Al - 12.0%Mg - 0.5%Ca - 1.2%Si

[0183] <Preparation of the treatment agent for forming the protective layer> Using commercially available SiO2 having various average particle sizes (Silica Flour series manufactured by Masuoka Yo-gyo Raw Material Co., Ltd.), treatment agents for forming protective layers containing components as illustrated in each level of Table 4-1 to Table 4-6 below were prepared. Note that in preparing the treatment agents for forming protective layers, pH adjusters shown in Table 3 below were used as necessary.

[0184] [TABLE 3] TABLE 3 pH ADJUSTER 1 HYDROCHLORIC ACID 2 SULFURIC ACID 3 NITRIC ACID 4 PHOSPHORIC ACID 5 AMMONIA SOLUTION 6 1-AMINO-2-PROPANOL

[0185] The prepared treatment agents were applied to the surfaces of the coated steel materials, and a storage treatment was performed under the conditions shown in Table 4-1 to Table 4-6 below to form the protective layer and the second protective layer. Thereafter, SiO2 that did not contribute to the formation of the protective layer was removed by washing with water, followed by air drying to obtain a surface-treated steel material. Note that a plurality of the surface-treated steel materials were prepared for each level. For each of the surface-treated steel materials obtained in this manner, various measurements for the protective layer, the second protective layer, and the coating layer were performed in accordance with the above-described methods. The obtained results are collectively shown in Table 5-1 to Table 5-6 below.

[0186] 5   [TABLE 4-1]

[0187] [TABLE 4-2] No. CLASSIFI CATION BASE SHEET COAT ING COATING THICK NESS (pm) FORMATION OF PROTECTIVE FILM FORMATION OF SECOND PROTECTIVE FILM TREATMENT AGENT STORAGE CONDITIONS TREATMENT AGENT STORAGE CONDITIONS SIO2 AVERAGE PARTICLE SIZE (pm) MOISTURE CONTENT (%) pH pH ADJUST ER APPLI CATION THICK NESS (mm) TEMPERA TURE (°C) RELATIVE HUMIDITY TIME (h) SIO2 AVERAGE PARTICLE SIZE (pm) MOISTURE CONTENT (%) pH pH ADJUST ER APPLI CATION THICK NESS (mm) TEMPERA TURE (°C) RELATIVE HUMIDITY TIME (h) 1 EXAMPLE a A 5 0.48 50 4.0 1 0.5 10 90 540 2 EXAMPLE a A 10 0.69 60 4.5 2 1.0 15 90 540 3 EXAMPLE b A 15 0.33 65 5.0 3 1.5 20 90 540 4 EXAMPLE a A 20 0.12 70 6.0 4 2.5 25 90 540 5 EXAMPLE a A 30 0.58 75 8.0 5 3.0 30 90 360 6 EXAMPLE a A 50 0.38 80 9.0 6 0.5 35 90 540 7 EXAMPLE a B 5 0.49 60 9.0 5 1.0 40 90 540 8 EXAMPLE a B 10 0.26 65 4.0 2 1.5 40 90 540 9 EXAMPLE a B 15 0.88 70 4.5 3 2.5 35 90 540 10 EXAMPLE a B 20 0.22 75 5.0 4 3.0 30 90 540 11 EXAMPLE a B 30 0.31 80 6.0 1 0.5 25 90 1080 12 EXAMPLE a B 50 0.43 50 8.0 6 1.0 20 90 540 13 EXAMPLE a C 5 0.54 65 8.0 5 1.5 15 90 540 14 EXAMPLE c C 10 0.57 70 9.0 6 2.5 10 90 540 15 EXAMPLE a C 15 0.85 75 4.0 3 3.0 10 90 540 16 EXAMPLE a C 20 0.20 80 4.5 4 0.5 15 90 540 17 EXAMPLE a C 30 0.34 50 5.0 1 1.0 20 90 540 18 EXAMPLE a C 50 0.13 60 6.0 2 1.5 25 90 1440 19 EXAMPLE a D 5 0.15 70 6.0 3 2.5 30 90 540 20 EXAMPLE a D 10 0.27 75 8.0 6 3.0 35 90 540 21 EXAMPLE b D 15 0.56 80 9.0 5 0.5 40 90 540 22 EXAMPLE a D 20 0.85 50 4.0 4 1.0 40 90 720 23 EXAMPLE a D 30 0.66 60 4.5 1 1.5 35 90 540 24 EXAMPLE a D 50 0.64 65 5.0 2 2.5 30 90 540 25 EXAMPLE a E 5 0.11 75 5.0 3 3.0 25 90 540 26 EXAMPLE a E 10 0.60 80 6.0 4 0.5 20 90 540 27 EXAMPLE a E 15 0.87 50 8.0 5 1.0 15 90 540 28 EXAMPLE c E 20 0.45 60 9.0 6 1.5 10 90 540 29 EXAMPLE a E 30 0.67 65 4.0 1 2.5 10 90 540 30 EXAMPLE a E 50 0.24 70 4.5 2 3.0 15 90 540

[0188] [TABLE 4-3] No. CLASSIFI CATION BASE SHEET COAT ING COATING THICK NESS (pm) FORMATION OF PROTECTIVE FILM FORMATION OF SECOND PROTECTIVE FILM TREATMENT AGENT STORAGE CONDITIONS TREATMENT AGENT STORAGE CONDITIONS SiO2 AVERAGE PARTICLE SIZE (um) MOISTURE CONTENT (%) pH pH ADJUST ER APPLI CATION THICK NESS (mm) TEMPERA TURE (°C) RELATIVE HUMIDITY TIME (h) SiO2 AVERAGE PARTICLE SIZE (um) MOISTURE CONTENT (%) pH pH ADJUST ER APPLI CATION THICK NESS (mm) TEMPERA TURE (°C) RELATIVE HUMIDITY TIME (h) 31 EXAMPLE a F 5 0.12 80 4.5 3 0.5 20 90 540 32 EXAMPLE a F 10 0.37 50 5.0 4 1.0 25 90 540 33 EXAMPLE a F 15 0.27 60 6.0 1 1.5 30 90 540 34 EXAMPLE a F 20 0.84 65 8.0 6 2.5 35 90 540 35 EXAMPLE a F 30 0.45 70 9.0 5 3.0 40 90 1440 36 EXAMPLE a F 50 0.17 75 4.0 2 0.5 40 90 540 37 EXAMPLE a A 5 2.88 50 4.0 1 0.5 10 90 540 38 EXAMPLE a A 10 2.28 60 4.5 2 1.0 15 90 540 39 EXAMPLE b A 15 1.42 65 5.0 3 1.5 20 90 540 40 EXAMPLE a B 20 2.68 70 6.0 4 2.5 25 90 540 41 EXAMPLE a B 30 1.26 75 8.0 5 3.0 30 90 540 42 EXAMPLE a B 50 1.92 80 9.0 6 0.5 35 90 540 43 EXAMPLE a C 5 2.28 60 9.0 5 1.0 40 90 540 44 EXAMPLE a C 10 5.48 65 4.0 2 1.5 40 90 540 45 EXAMPLE a C 15 3.67 70 4.5 3 2.5 35 90 540 46 EXAMPLE a D 20 4.10 75 5.0 4 3.0 30 90 540 47 EXAMPLE a D 30 4.63 80 6.0 1 0.5 25 90 540 48 EXAMPLE a D 50 3.13 50 8.0 6 1.0 20 90 540 49 EXAMPLE a E 5 4.96 65 8.0 5 1.5 15 90 540 50 EXAMPLE c E 10 2.10 70 9.0 6 2.5 10 90 540 51 EXAMPLE a E 15 4.73 75 4.0 3 3.0 10 90 540 52 EXAMPLE a F 20 5.16 80 4.5 4 0.5 15 90 540 53 EXAMPLE a F 30 4.76 50 5.0 1 1.0 20 90 540 54 EXAMPLE a F 50 1.34 60 6.0 2 1.5 25 90 540 55 EXAMPLE a A 5 0.44 50 4.0 1 1.0 10 90 360 9.53 70 8.0 6 1.0 35 95 540 56 EXAMPLE a A 10 0.76 60 4.5 2 1.5 15 90 360 17.90 75 9.0 5 1.5 40 95 540 57 EXAMPLE a A 15 0.57 65 5.0 3 2.5 20 90 360 14.99 80 4.0 4 2.5 40 95 540 58 EXAMPLE a A 20 0.65 70 6.0 4 3.0 25 90 360 24.95 60 4.5 1 3.0 10 95 540 59 EXAMPLE b A 30 0.16 75 8.0 5 0.5 30 90 360 11.92 65 5.0 2 0.5 15 95 540 60 EXAMPLE a A 50 0.75 80 9.0 6 1.0 35 90 360 13.58 70 5.0 3 1.0 20 95 540

[0189] No. CLASSIFI CATION BASE SHEET COAT ING COATING THICK NESS (pm) FORMATION OF PROTECTIVE FILM FORMATION OF SECOND PROTECTIVE FILM TREATMENT AGENT STORAGE CONDITIONS TREATMENT AGENT STORAGE CONDITIONS SIO2 AVERAGE PARTICLE SIZE (um) MOISTURE CONTENT (%) pH pH ADJUST ER APPLI CATION THICK NESS (mm) TEMPERA TURE (°C) RELATIVE HUMIDITY TIME (h) SiO2 AVERAGE PARTICLE SIZE (um) MOISTURE CONTENT (%) pH pH ADJUST ER APPLI CATION THICK NESS (mm) TEMPERA TURE (°C) RELATIVE HUMIDITY TIME (h) 61 EXAMPLE a B 5 0.90 60 9.0 5 1.5 40 90 360 17.35 75 6.0 4 1.5 25 95 540 62 EXAMPLE a B 10 0.86 65 4.0 2 2.5 40 90 360 4.04 80 8.0 5 2.5 30 95 540 63 EXAMPLE b B 15 0.77 70 4.5 3 3.0 35 90 360 4.28 50 9.0 6 3.0 35 95 540 64 EXAMPLE a B 20 0.60 75 5.0 4 0.5 30 90 360 7.39 65 4.0 1 0.5 40 95 540 65 EXAMPLE a B 30 0.49 80 6.0 1 1.0 25 90 360 26.80 70 4.5 2 1.0 40 95 540 66 EXAMPLE a B 50 0.69 50 8.0 6 1.5 20 90 360 3.48 75 4.5 3 1.5 35 95 540 67 EXAMPLE a C 5 0.88 65 8.0 5 2.5 15 90 360 5.41 80 5.0 4 2.5 30 95 540 68 EXAMPLE c C 10 0.61 70 9.0 6 3.0 10 90 360 16.06 50 6.0 1 3.0 25 95 540 69 EXAMPLE c C 15 0.82 75 4.0 3 0.5 10 90 360 15.26 60 8.0 6 0.5 20 95 540 70 EXAMPLE a C 20 0.80 80 4.5 4 1.0 15 90 360 22.21 70 9.0 5 1.0 15 95 540 71 EXAMPLE a C 30 0.11 50 5.0 1 1.5 20 90 360 8.46 75 4.0 2 1.5 10 95 540 72 EXAMPLE a C 50 0.30 60 6.0 2 2.5 25 90 360 13.54 80 4.0 1 2.5 10 95 540 73 EXAMPLE a D 5 0.43 70 6.0 3 3.0 30 90 360 23.54 50 4.5 2 3.0 15 95 540 74 EXAMPLE a D 10 0.69 75 8.0 6 0.5 35 90 360 19.74 60 5.0 3 0.5 20 95 540 75 EXAMPLE a D 15 0.49 80 9.0 5 1.0 40 90 360 28.04 65 6.0 4 1.0 25 95 540 76 EXAMPLE a D 20 0.74 50 4.0 4 1.5 40 90 360 12.15 75 8.0 5 1.5 30 95 540 77 EXAMPLE a D 30 0.22 60 4.5 1 2.5 35 90 360 21.93 80 9.0 6 2.5 35 95 540 78 EXAMPLE a D 50 0.56 65 5.0 2 3.0 30 90 360 18.91 50 9.0 5 3.0 40 95 540 79 EXAMPLE a E 5 0.25 75 5.0 3 0.5 25 90 360 15.78 60 4.0 2 0.5 40 95 540 80 EXAMPLE a E 10 0.41 80 6.0 4 1.0 20 90 360 20.70 65 4.5 3 1.0 35 95 540 81 EXAMPLE a E 15 0.34 50 8.0 5 1.5 15 90 360 28.12 70 5.0 4 1.5 30 95 540 82 EXAMPLE a E 20 0.83 60 9.0 6 2.5 10 90 360 18.29 80 6.0 1 2.5 25 95 540 83 EXAMPLE a E 30 0.28 65 4.0 1 3.0 10 90 360 3.52 50 8.0 6 3.0 20 95 540 84 EXAMPLE a E 50 0.44 70 4.5 2 0.5 15 90 360 24.85 60 8.0 5 0.5 15 95 540 85 EXAMPLE b F 5 0.74 80 4.5 3 1.0 20 90 360 4.11 65 9.0 6 1.0 10 95 540 86 EXAMPLE a F 10 0.30 50 5.0 4 1.5 25 90 360 6.52 70 4.0 3 1.5 10 95 540 87 EXAMPLE a F 15 0.79 60 6.0 1 2.5 30 90 360 5.74 75 4.5 4 2.5 15 95 540 88 EXAMPLE a F 20 0.51 65 8.0 6 3.0 35 90 360 25.84 50 5.0 1 3.0 20 95 540 89 EXAMPLE c F 30 0.62 70 9.0 5 0.5 40 90 360 16.85 60 6.0 2 0.5 25 95 540 90 EXAMPLE a F 50 0.26 75 4.0 2 1.0 40 90 360 5.38 65 6.0 3 1.0 30 95 540

[0190] [TABLE 4-5] TABLE 4-4 No. CLASSIFI CATION BASE SHEET COAT ING COATING THICK NESS (pm) FORMATION OF PROTECTIVE FILM! FORMATION OF SECOND PROTECTIVE FILM! TREATMENT AGENT STORAGE CONDITIONS TREATMENT AGENT STORAGE CONDITIONS S1O2 AVERAGE PARTICLE SIZE (pm) MOISTURE CONTENT (%) pH pH ADJUST ER APPLI CATION THICK NESS (mm) TEMPERA TURE CC) RELATIVE HUM1IDITY TIME (h) S1O2 AVERAGE PARTICLE SIZE (pm) MOISTURE CONTENT (%) pH pH ADJUST ER APPLI CATION THICK NESS (mm) TEMPERA TURE CC) RELATIVE HJM1IDITY TIME (h) 91 COMPARATIVE EXAMPLE a A 50 92 COMPARATIVE EXAMPLE b A 50 93 COMPARATIVE EXAMPLE c A 50 94 COMPARATIVE EXAMPLE a B 50 95 COMPARATIVE EXAMPLE b B 50 96 COMPARATIVE EXAMPLE c B 50 97 COMPARATIVE EXAMPLE a C 50 98 COMPARATIVE EXAMPLE b C 50 99 COMPARATIVE EXAMPLE c C 50 100 COMPARATIVE EXAMPLE a D 50 101 COMPARATIVE EXAMPLE b D 50 102 COMPARATIVE EXAMPLE c D 50 103 COMPARATIVE EXAMPLE a E 50 104 COMPARATIVE EXAMPLE b E 50 105 COMPARATIVE EXAMPLE c E 50 106 COMPARATIVE EXAMPLE a F 50 107 COMPARATIVE EXAMPLE b F 50 108 COMPARATIVE EXAMPLE c F 50 109 COMPARATIVE EXAMPLE a A 50 0.12 50 4.0 1 0.5 10 90 24 110 COMPARATIVE EXAMPLE b A 50 0.62 60 4.5 2 1.0 15 90 48 111 COMPARATIVE EXAMPLE c A 50 0.71 65 5.0 3 1.5 20 90 72 112 COMPARATIVE EXAMPLE a B 50 0.86 70 6.0 4 2.5 25 90 48 113 COMPARATIVE EXAMPLE b B 50 0.37 75 8.0 5 3.0 30 90 72 114 COMPARATIVE EXAMPLE c B 50 0.73 80 9.0 6 0.5 35 90 24 115 COMPARATIVE EXAMPLE a C 50 0.89 60 9.0 5 1.0 40 90 72 116 COMPARATIVE EXAMPLE b C 50 0.36 65 4.0 2 1.5 40 90 24 117 COMPARATIVE EXAMPLE c C 50 0.43 70 4.5 3 2.5 35 90 48 118 COMPARATIVE EXAMPLE a D 50 0.85 75 5.0 4 3.0 30 90 24 119 COMPARATIVE EXAMPLE b D 50 0.28 80 6.0 1 0.5 25 90 48 120 COMPARATIVE EXAMPLE c D 50 0.78 50 8.0 6 1.0 20 90 72 [TABLE 4-4] [TABLE 4-6] TABLE 4-5 No. CLASSIFI CATION BASE SHEET COAT ING COATING THICK NESS (pm) FORMATION OF PROTECTIVE FILM FORMATION OF SECOND PROTECTIVE FILM TREATMENT AGENT STORAGE CONDITIONS TREATMENT AGENT STORAGE CONDITIONS S1O2 AVERAGE PARTICLE SIZE (pm) MOISTURE CONTENT (%) PH pH ADJUST ER APPLI CATION THICK NESS (mm) TEMPERA TURE CC) RELATIVE HUMIDITY TIME (h) S1O2 AVERAGE PARTICLE SIZE (pm) MOISTURE CONTENT (%) pH PH ADJUST ER APPLI CATION THICK NESS (mm) TEMPERA TURE CC) RELATIVE HUMIDITY TIME (h) 121 COMPARATIVE EXAMPLE a E 50 0.32 65 8.0 5 1.5 15 90 48 122 COMPARATIVE EXAMPLE b E 50 0.45 70 9.0 6 2.5 10 90 72 123 COMPARATIVE EXAMPLE c E 50 0.61 75 4.0 3 3.0 10 90 24 124 COMPARATIVE EXAMPLE a F 50 0.28 80 4.5 4 0.5 15 90 72 125 COMPARATIVE EXAMPLE b F 50 0.81 50 5.0 1 1.0 20 90 24 126 COMPARATIVE EXAMPLE c F 50 0.47 60 6.0 2 1.5 25 90 48 127 COMPARATIVE EXAMPLE a A 50 0.90 50 4.0 1 0.5 10 50 540 128 COMPARATIVE EXAMPLE b A 50 0.32 60 4.5 2 1.0 15 40 540 129 COMPARATIVE EXAMPLE c A 50 0.36 65 5.0 3 1.5 20 60 540 130 COMPARATIVE EXAMPLE a B 50 0.75 70 6.0 4 2.5 25 40 540 131 COMPARATIVE EXAMPLE b B 50 0.47 75 8.0 5 3.0 30 50 540 132 COMPARATIVE EXAMPLE c B 50 0.87 80 9.0 6 0.5 35 60 540 133 COMPARATIVE EXAMPLE a C 50 0.66 60 9.0 5 1.0 40 60 540 134 COMPARATIVE EXAMPLE b C 50 0.73 65 4.0 2 1.5 40 50 540 135 COMPARATIVE EXAMPLE c C 50 0.42 70 4.5 3 2.5 35 40 540 136 COMPARATIVE EXAMPLE a D 50 0.73 75 5.0 4 3.0 30 50 540 137 COMPARATIVE EXAMPLE b D 50 0.85 80 6.0 1 0.5 25 40 540 138 COMPARATIVE EXAMPLE c D 50 0.48 50 8.0 6 1.0 20 60 540 139 COMPARATIVE EXAMPLE a E 50 0.22 65 8.0 5 1.5 15 40 540 140 COMPARATIVE EXAMPLE b E 50 0.41 70 9.0 6 2.5 10 50 540 141 COMPARATIVE EXAMPLE c E 50 0.33 75 4.0 3 3.0 10 60 540 142 COMPARATIVE EXAMPLE a F 50 0.83 80 4.5 4 0.5 15 60 540 143 COMPARATIVE EXAMPLE b F 50 0.27 50 5.0 1 1.0 20 50 540 144 COMPARATIVE EXAMPLE c F 50 0.52 60 6.0 2 1.5 25 40 540 145 COMPARATIVE EXAMPLE a A 50 0.27 50 4.0 1 10.0 10 90 1440 146 COMPARATIVE EXAMPLE a A 50 0.80 60 4.5 2 20.0 15 90 1440 147 COMPARATIVE EXAMPLE b A 50 0.48 65 5.0 3 15.0 20 90 1440 148 COMPARATIVE EXAMPLE a B 50 0.14 70 6.0 4 10.0 25 90 1440 149 COMPARATIVE EXAMPLE a B 50 0.39 75 8.0 5 20.0 30 90 1440 150 COMPARATIVE EXAMPLE c B 50 0.64 80 9.0 6 15.0 35 90 1440 [TABLE 5-1] No. CLASSIFI CATION BASE SHEET COAT ING COATING THICK NESS (pm) FORMATION OF PROTECTIVE FILM FORMATION OF SECOND PROTECTIVE FILM TREATMENT AGENT STORAGE CONDITIONS TREATMENT AGENT STORAGE CONDITIONS S1O2 AVERAGE PARTICLE SIZE (pm) MOISTURE CONTENT (%) pH pH ADJUST ER APPLI CATION THICK NESS (mm) TEMPERA TURE CC) RELATIVE HUMIDITY TIME (h) S1O2 AVERAGE PARTICLE SIZE (pm) MOISTURE CONTENT (%) pH PH ADJUST ER APPLI CATION THICK NESS (mm) TEMPERA TURE (°C) RELATIVE HJMIDITY TIME (h) 151 COMPARATIVE EXAMPLE a C 50 0.64 60 9.0 5 10.0 40 90 1440 152 COMPARATIVE EXAMPLE a C 50 0.88 65 4.0 2 20.0 40 90 1440 153 COMPARATIVE EXAMPLE b C 50 0.51 70 4.5 3 15.0 35 90 1440 154 COMPARATIVE EXAMPLE a D 50 0.35 75 5.0 4 10.0 30 90 1440 155 COMPARATIVE EXAMPLE a D 50 0.41 80 6.0 1 20.0 25 90 1440 156 COMPARATIVE EXAMPLE c D 50 0.17 50 8.0 6 15.0 20 90 1440 157 COMPARATIVE EXAMPLE a E 50 0.30 65 8.0 5 10.0 15 90 1440 158 COMPARATIVE EXAMPLE a E 50 0.75 70 9.0 6 20.0 10 90 1440 159 COMPARATIVE EXAMPLE b E 50 0.47 75 4.0 3 15.0 10 90 1440 160 COMPARATIVE EXAMPLE a F 50 0.40 80 4.5 4 10.0 15 90 1440 161 COMPARATIVE EXAMPLE a F 50 0.45 50 5.0 1 20.0 20 90 1440 162 COMPARATIVE EXAMPLE c F 50 0.20 60 6.0 2 15.0 25 90 1440 163 COMPARATIVE EXAMPLE a A 50 0.57 60 9.0 5 1.0 40 90 3600 164 COMPARATIVE EXAMPLE a A 50 0.47 65 4.0 2 1.5 40 90 3600 165 COMPARATIVE EXAMPLE b A 50 0.51 70 4.5 3 2.5 35 90 3600 166 COMPARATIVE EXAMPLE a B 50 0.60 75 5.0 4 3.0 30 90 3600 167 COMPARATIVE EXAMPLE a B 50 0.44 80 6.0 1 0.5 25 90 3600 168 COMPARATIVE EXAMPLE c B 50 0.78 50 8.0 6 1.0 20 90 3600 169 COMPARATIVE EXAMPLE a C 50 0.81 65 8.0 5 1.5 15 90 3600 170 COMPARATIVE EXAMPLE a C 50 0.62 70 9.0 6 2.5 10 90 3600 171 COMPARATIVE EXAMPLE b C 50 0.15 75 4.0 3 3.0 10 90 3600 172 COMPARATIVE EXAMPLE a D 50 0.58 80 4.5 4 0.5 15 90 3600 173 COMPARATIVE EXAMPLE a D 50 0.17 50 5.0 1 1.0 20 90 3600 174 COMPARATIVE EXAMPLE c D 50 0.28 60 6.0 2 1.5 25 90 3600 175 COMPARATIVE EXAMPLE a E 50 0.85 70 6.0 3 2.5 30 90 3600 176 COMPARATIVE EXAMPLE a E 50 0.11 75 8.0 6 3.0 35 90 3600 177 COMPARATIVE EXAMPLE b E 50 0.82 80 9.0 5 0.5 40 90 3600 178 COMPARATIVE EXAMPLE a F 50 0.12 50 4.0 4 1.0 40 90 3600 179 COMPARATIVE EXAMPLE a F 50 0.73 60 4.5 1 1.5 35 90 3600 180 COMPARATIVE EXAMPLE c F 50 0.30 65 5.0 2 2.5 30 90 3600

[0193] [TABLE 5-2] No. CLASSIFI CATION PROTECTIVE LAYER SECOND PROTECTIVE FILM ZINC-BASED COATING LAYER THICK LESS (pm) Zn CONCENT RATION (maa%) Si CONCENT RATION (maa%) Mg CONCENT RATION (maa%) Si CONCENT RATION RATIO SiO2 Zh / AI-BASED CARBONATE-TYPE LAYERED DOUBLE HYDROXIDE Mg / AI-BASED CARBONATE-TYPE LAYERED DOUBLE HYDROXIDE THICK NESS (pm) SiO2 PRESENCE OR ABSENCE THICK NESS (pm) Al CONCENT RATION (maa%) Mg CONCENT RATION (maa%) PRESENCE OR ABSENCE PEAK bITEN STY (ops) AVERAGE PARTICLE SIZE (pm) RATIO (%) PRESENCE OR ABSENCE PEAK bITEN STY (ops) PRESENCE OR ABSENCE PEAK bITEN STY (ops) PRESENCE OR ABSENCE AVERAGE PARTICLE SIZE (pm) RATIO (%) 1 EXAMPLE 6.0 16.28 13.24 0.92 PRESENT 11419 0.53 73.10 PRESENT 314 ABSENT ABSENT ABSENT 0.0 2 EXAMPLE 10.9 18.77 18.65 1.05 PRESENT 20748 0.72 95.81 PRESENT 570 ABSENT ABSENT ABSENT 0.0 3 EXAMPLE 14.3 3.13 18.31 0.95 PRESENT 27199 0.40 95.33 PRESENT 747 ABSENT ABSENT PRESENT 0.7 0.20 0.00 4 EXAMPLE 11.7 9.41 11.39 1.06 PRESENT 22234 0.20 92.52 PRESENT 611 ABSENT ABSENT PRESENT 8.3 0.20 0.00 5 EXAMPLE 12.9 7.36 22.65 1.06 PRESENT 24625 0.62 89.87 PRESENT 677 ABSENT ABSENT PRESENT 17.1 0.20 0.00 6 EXAMPLE 16.3 4.41 19.23 0.94 PRESENT 31042 0.44 95.69 PRESENT 853 ABSENT ABSENT PRESENT 33.7 0.20 0.00 7 EXAMPLE 5.8 14.45 24.66 1.12 1.00 PRESENT 11006 0.54 73.11 PRESENT 10079 PRESENT 3255 ABSENT ABSENT 0.0 8 EXAMPLE 11.0 7.44 20.82 1.13 1.46 PRESENT 20921 0.34 78.53 PRESENT 19159 PRESENT 3295 ABSENT ABSENT 0.0 9 EXAMPLE 15.3 11.99 15.51 1.15 1.36 PRESENT 29166 0.89 91.61 PRESENT 26710 PRESENT 3329 ABSENT ABSENT 0.0 10 EXAMPLE 18.2 10.54 13.13 1.04 1.34 PRESENT 34632 0.30 94.14 PRESENT 31716 PRESENT 3031 ABSENT PRESENT 1.8 5.70 3.00 11 EXAMPLE 16.7 10.30 17.57 1.00 1.02 PRESENT 31747 0.38 89.67 PRESENT 29074 PRESENT 2905 ABSENT PRESENT 13.3 6.40 3.00 12 EXAMPLE 11.8 2.64 16.20 1.14 0.91 PRESENT 22403 0.48 97.30 PRESENT 20516 PRESENT 3319 ABSENT PRESENT 38.2 5.60 3.30 13 EXAMPLE 5.5 16.93 12.69 1.05 0.91 PRESENT 10537 0.58 79.29 PRESENT 17692 PRESENT 3047 ABSENT ABSENT 0.0 14 EXAMPLE 7.6 16.94 10.88 1.03 0.90 PRESENT 14518 0.61 71.40 PRESENT 24374 PRESENT 2988 ABSENT PRESENT 2.4 10.00 2.70 15 EXAMPLE 9.2 14.17 15.61 1.01 1.10 PRESENT 17444 0.87 94.44 PRESENT 29288 PRESENT 2929 ABSENT PRESENT 5.8 10.10 2.90 16 EXAMPLE 12.0 4.49 12.94 1.07 1.06 PRESENT 22779 0.28 92.50 PRESENT 38244 PRESENT 3117 ABSENT PRESENT 8.0 10.10 3.30 17 EXAMPLE 15.3 9.28 24.23 0.95 1.05 PRESENT 29209 0.41 90.14 PRESENT 49041 PRESENT 2765 ABSENT PRESENT 14.7 11.70 2.80 18 EXAMPLE 19.1 5.34 21.89 0.98 0.94 PRESENT 36355 0.22 80.06 PRESENT 61039 PRESENT 2852 ABSENT PRESENT 30.9 11.60 3.00 19 EXAMPLE 5.6 9.02 12.56 2.11 1.07 PRESENT 10629 0.24 92.20 PRESENT 25957 PRESENT 6121 ABSENT ABSENT 0.0 20 EXAMPLE 10.6 1.94 22.47 2.19 1.06 PRESENT 20213 0.35 98.71 PRESENT 49363 PRESENT 6349 ABSENT ABSENT 0.0 21 EXAMPLE 15.3 2.97 11.70 2.14 1.04 PRESENT 29140 0.60 77.68 PRESENT 71162 PRESENT 6212 ABSENT ABSENT 0.0 22 EXAMPLE 20.8 4.34 20.26 2.29 1.50 PRESENT 39618 0.86 82.19 PRESENT 96750 PRESENT 6661 ABSENT ABSENT 0.0 23 EXAMPLE 19.4 14.48 18.91 1.95 1.50 PRESENT 36882 0.70 80.37 PRESENT 90069 PRESENT 5657 ABSENT PRESENT 10.6 15.80 6.20 24 EXAMPLE 19.6 16.72 24.46 2.30 1.47 PRESENT 37325 0.68 75.46 PRESENT 91152 PRESENT 6690 ABSENT PRESENT 30.4 16.50 5.80 25 EXAMPLE 5.3 2.16 20.12 2.30 1.10 PRESENT 10104 0.20 71.63 PRESENT 29302 PRESENT 6674 ABSENT ABSENT 0.0 26 EXAMPLE 11.0 12.30 19.11 2.12 0.97 PRESENT 20861 0.64 82.72 PRESENT 60497 PRESENT 6171 ABSENT ABSENT 0.0 27 EXAMPLE 10.0 5.88 24.56 2.09 1.00 PRESENT 19101 0.88 87.21 PRESENT 55393 PRESENT 6075 ABSENT PRESENT 5.0 20.60 5.80 28 EXAMPLE 8.5 7.10 10.60 2.01 0.99 PRESENT 16245 0.50 72.80 PRESENT 47110 PRESENT 5828 ABSENT PRESENT 11.5 20.50 5.90 29 EXAMPLE 9.4 6.52 23.84 1.94 1.03 PRESENT 17968 0.70 72.41 PRESENT 52106 PRESENT 5648 ABSENT PRESENT 20.6 18.00 5.50 30 EXAMPLE 11.3 8.04 21.76 2.01 1.04 PRESENT 21594 0.32 83.11 PRESENT 62623 PRESENT 5836 ABSENT PRESENT 38.7 20.50 6.60

[0194] No. CLy\SSIFI CATION PROTECTIVE LAYER SECOND PROTECTIVE FILM ZINC-BASED COATING LAYER THICK NESS (pm) Zn CONCENT RATION (maa%) Si CONCENT RATION (maa%) Mg CONCENT RATION (maa%) Si CONCENT RATION RATIO SiO2 Zn / AI-BASED CARBONATE-TYPE LAYERED DOUBLE HYDROXIDE Mg / AI-BASED CARBONATE-TYPE LAYERED DOUBLE HYDROXIDE THICK NESS (pm) SiO2 PRESENCE OR ABSENCE THICK NESS (pm) Al CONCENT RATION (maa%) Mg CONCENT RATION (maa%) PRESENCE OR ABSENCE PEAK INTEN STY (ops) AVERAGE PARTICLE SIZE (pm) RATIO (%) PRESENCE OR ABSENCE PEAK INTEN STY (ops) PRESENCE OR ABSENCE PEAK NTEN SITY (ops) PRESENCE OR ABSENCE AVERAGE PARTICLE SIZE (pm) RATIO (%) 31 EXAMPLE 5.6 4.02 19.37 4.00 1.01 PRESENT 10638 0.21 77.52 PRESENT 38968 PRESENT 11614 ABSENT ABSENT 0.0 32 EXAMPLE 10.2 10.60 19.46 4.51 0.99 PRESENT 19372 0.44 77.40 PRESENT 70961 PRESENT 13110 ABSENT ABSENT 0.0 33 EXAMPLE 15.2 4.34 22.47 4.27 0.96 PRESENT 28975 0.35 73.66 PRESENT 106139 PRESENT 12395 ABSENT ABSENT 0.0 34 EXAMPLE 17.9 7.20 14.59 4.39 0.99 PRESENT 34032 0.85 78.18 PRESENT 124664 PRESENT 12759 ABSENT PRESENT 2.1 23.40 12.80 35 EXAMPLE 25.4 8.07 11.57 3.79 1.05 PRESENT 48445 0.51 98.37 PRESENT 177463 PRESENT 11015 ABSENT PRESENT 4.6 22.10 11.30 36 EXAMPLE 18.2 3.31 17.66 4.02 1.39 PRESENT 34698 0.26 87.54 PRESENT 127103 PRESENT 11672 ABSENT PRESENT 31.8 25.10 12.70 37 EXAMPLE 5.3 10.51 12.13 0.97 PRESENT 10106 2.69 93.68 PRESENT 278 ABSENT ABSENT ABSENT 0.0 38 EXAMPLE 10.4 7.12 14.37 0.96 PRESENT 19895 2.15 99.56 PRESENT 547 ABSENT ABSENT ABSENT 0.0 39 EXAMPLE 13.1 7.63 21.76 0.95 PRESENT 24897 1.38 96.82 PRESENT 684 ABSENT ABSENT PRESENT 1.9 0.20 0.00 40 EXAMPLE 13.5 15.87 17.72 0.92 PRESENT 25683 2.52 77.46 PRESENT 23521 ABSENT ABSENT PRESENT 6.5 6.30 0.00 41 EXAMPLE 16.2 17.62 19.10 0.93 PRESENT 30916 1.23 89.44 PRESENT 28313 ABSENT ABSENT PRESENT 13.8 5.90 0.00 42 EXAMPLE 16.0 5.21 23.39 1.07 PRESENT 30403 1.83 84.14 PRESENT 27843 ABSENT ABSENT PRESENT 34.0 5.50 0.00 43 EXAMPLE 5.6 5.48 11.54 1.00 0.95 PRESENT 10744 2.15 75.57 PRESENT 18039 PRESENT 2905 ABSENT ABSENT 0.0 44 EXAMPLE 11.0 3.03 24.87 1.09 1.38 PRESENT 20921 5.03 90.42 PRESENT 35125 PRESENT 3160 ABSENT ABSENT 0.0 45 EXAMPLE 15.5 18.51 21.40 1.02 1.34 PRESENT 29482 3.40 73.17 PRESENT 49499 PRESENT 2953 ABSENT ABSENT 0.0 46 EXAMPLE 20.7 7.15 21.20 0.96 1.48 PRESENT 39333 3.79 80.20 PRESENT 96056 PRESENT 2784 ABSENT ABSENT 0.0 47 EXAMPLE 12.8 6.56 16.29 1.14 1.08 PRESENT 24318 4.27 71.31 PRESENT 59386 PRESENT 3321 ABSENT PRESENT 17.2 16.50 3.20 48 EXAMPLE 11.2 7.88 19.34 1.02 1.07 PRESENT 21257 2.92 98.90 PRESENT 51911 PRESENT 2961 ABSENT PRESENT 38.8 15.50 3.20 49 EXAMPLE 5.0 5.73 20.22 0.99 1.10 PRESENT 9543 4.57 77.13 PRESENT 27675 PRESENT 2867 ABSENT ABSENT 0.0 50 EXAMPLE 8.6 2.11 24.34 1.02 0.91 PRESENT 16319 1.99 71.15 PRESENT 47324 PRESENT 2976 ABSENT PRESENT 1.4 20.60 3.00 51 EXAMPLE 11.5 14.57 12.11 1.11 0.95 PRESENT 21898 4.36 99.93 PRESENT 63503 PRESENT 3239 ABSENT PRESENT 3.5 19.20 2.90 52 EXAMPLE 9.1 9.69 12.33 1.04 1.03 PRESENT 17308 4.74 99.72 PRESENT 63402 PRESENT 3008 ABSENT PRESENT 10.9 22.70 2.90 53 EXAMPLE 14.2 8.27 17.65 1.15 1.08 PRESENT 26944 4.38 73.14 PRESENT 98702 PRESENT 3346 ABSENT PRESENT 15.8 23.30 2.90 54 EXAMPLE 12.2 5.14 20.09 1.06 1.08 PRESENT 23168 1.31 76.24 PRESENT 84869 PRESENT 3072 ABSENT PRESENT 37.8 24.30 2.80 55 EXAMPLE 5.5 8.62 17.48 0.91 PRESENT 10554 0.50 72.31 PRESENT 290 PRESENT 46.5 PRESENT 8.58 70.79 ABSENT 0.0 56 EXAMPLE 9.6 17.71 13.20 0.96 PRESENT 18237 0.78 99.13 PRESENT 501 PRESENT 46.5 PRESENT 16.11 52.53 PRESENT 0.4 0.20 0.00 57 EXAMPLE 12.9 4.24 14.80 1.06 PRESENT 24599 0.61 71.30 PRESENT 676 PRESENT 56.5 PRESENT 13.49 80.29 PRESENT 2.1 0.20 0.00 58 EXAMPLE 8.6 14.69 19.34 1.02 PRESENT 16448 0.69 86.25 PRESENT 452 PRESENT 27.4 PRESENT 22.45 47.61 PRESENT 11.4 0.20 0.00 59 EXAMPLE 14.8 18.28 14.83 0.93 PRESENT 28218 0.25 80.16 PRESENT 775 PRESENT 27.6 PRESENT 10.73 80.24 PRESENT 15.2 0.20 0.00 60 EXAMPLE 14.9 12.73 11.32 0.98 PRESENT 28311 0.78 71.31 PRESENT 778 PRESENT 38.0 PRESENT 12.22 62.93 PRESENT 35.1 0.20 0.00 TABLE 5-3 No. CLASSIFI CATION PROTECTIVE LAYER SECOND PROTECTIVE FILM ZbIC-BASED COATING LAYER THICK NESS (pm) Zn CONCENT RATION (maa%) Si CONCENT RATION (maa%) Mg CONCENT RATION (maa%) Si CONCENT RATION RATIO SiO2 Zn / AI-BASED CARBONATE-TYPE LAYERED DOUBLE HYDROXIDE Mg / AI-BASED CARBONATE-TYPE LAYERED DOUBLE HYDROXIDE THICK FESS (pm) SiO2 PRESENCE OR ABSENCE THICK FESS (pm) Al CONCENT RATION (maa%) Mg CONCENT RATION (maa%) PRESENCE OR ABSENCE PEAK bITEN STY (ops) AVERAGE PARTICLE SIZE (pm) RATIO (%) PRESENCE OR ABSENCE PEAK bITEN STY (ops) PRESENCE OR ABSENCE PEAK bITEN STY (ops) PRESENCE OR ABSENCE AVERAGE PARTICLE SIZE (pm) RATIO (%) 61 EXAMPLE 5.6 3.42 17.86 1.04 0.93 PRESENT 10632 0.91 75.62 PRESENT 9737 PRESENT 3018 31.5 PRESENT 15.61 71.04 ABSENT 0.0 62 EXAMPLE 11.0 14.81 16.87 1.08 1.31 PRESENT 20918 0.88 87.96 PRESENT 19156 PRESENT 3151 46.7 PRESENT 3.63 77.84 ABSENT 0.0 63 EXAMPLE 15.5 16.50 17.03 0.98 1.40 PRESENT 29529 0.80 85.84 PRESENT 27043 PRESENT 2841 46.7 PRESENT 3.86 56.12 ABSENT 0.0 64 EXAMPLE 17.3 5.07 13.99 0.99 1.31 PRESENT 32917 0.64 99.58 PRESENT 30145 PRESENT 2890 56.3 PRESENT 6.66 81.39 PRESENT 2.7 6.30 3.10 65 EXAMPLE 10.0 10.09 17.25 1.12 0.95 PRESENT 19109 0.54 78.79 PRESENT 17500 PRESENT 3243 55.2 PRESENT 24.12 82.71 PRESENT 20.0 5.50 2.80 66 EXAMPLE 9.4 20.04 24.74 0.98 0.99 PRESENT 17901 0.72 74.20 PRESENT 16393 PRESENT 2858 55.4 PRESENT 3.13 55.90 PRESENT 40.6 6.20 2.90 67 EXAMPLE 5.3 15.44 17.94 0.97 0.93 PRESENT 10066 0.90 96.57 PRESENT 16901 PRESENT 2807 55.3 PRESENT 4.87 52.89 ABSENT 0.0 68 EXAMPLE 7.8 11.10 19.51 1.11 1.01 PRESENT 14853 0.65 86.54 PRESENT 24937 PRESENT 3212 32.1 PRESENT 14.46 59.44 PRESENT 2.2 11.60 2.80 69 EXAMPLE 8.8 5.35 12.73 1.08 0.91 PRESENT 16729 0.83 89.89 PRESENT 28087 PRESENT 3134 33.7 PRESENT 13.73 72.18 PRESENT 6.2 10.90 3.20 70 EXAMPLE 9.8 7.78 20.49 1.04 1.05 PRESENT 18660 0.82 99.02 PRESENT 31330 PRESENT 3018 23.3 PRESENT 19.99 63.12 PRESENT 10.2 11.20 3.10 71 EXAMPLE 11.0 2.73 23.96 0.95 0.91 PRESENT 20913 0.20 91.39 PRESENT 35112 PRESENT 2768 29.7 PRESENT 7.61 87.13 PRESENT 19.0 11.00 2.70 72 EXAMPLE 11.4 3.83 21.69 0.97 0.97 PRESENT 21789 0.37 84.79 PRESENT 36583 PRESENT 2829 29.5 PRESENT 12.19 59.92 PRESENT 38.6 10.30 2.80 73 EXAMPLE 5.8 10.32 11.88 1.95 0.90 PRESENT 11109 0.48 72.51 PRESENT 27130 PRESENT 5674 27.4 PRESENT 21.18 58.93 ABSENT 0.0 74 EXAMPLE 10.3 10.98 24.68 1.92 1.02 PRESENT 19574 0.73 97.10 PRESENT 47801 PRESENT 5578 39.9 PRESENT 17.77 84.19 ABSENT 0.0 75 EXAMPLE 14.5 10.07 15.79 2.26 1.03 PRESENT 27592 0.54 85.23 PRESENT 67382 PRESENT 6570 33.2 PRESENT 25.24 57.01 PRESENT 0.5 16.00 6.20 76 EXAMPLE 17.7 12.37 19.56 2.11 1.44 PRESENT 33628 0.77 79.42 PRESENT 82123 PRESENT 6119 45.3 PRESENT 10.94 57.64 PRESENT 2.3 16.40 5.60 77 EXAMPLE 15.0 15.63 15.37 2.24 1.37 PRESENT 28529 0.30 75.92 PRESENT 69671 PRESENT 6499 46.1 PRESENT 19.73 53.02 PRESENT 15.0 14.50 6.50 78 EXAMPLE 15.5 4.90 12.87 2.13 1.38 PRESENT 29502 0.61 83.85 PRESENT 72047 PRESENT 6192 45.5 PRESENT 17.02 81.25 PRESENT 34.5 16.20 6.00 79 EXAMPLE 5.7 5.72 21.42 2.17 0.94 PRESENT 10815 0.33 71.04 PRESENT 31362 PRESENT 6294 55.2 PRESENT 14.20 82.52 ABSENT 0.0 80 EXAMPLE 9.8 12.68 19.94 2.25 1.05 PRESENT 18662 0.47 81.77 PRESENT 54120 PRESENT 6539 54.7 PRESENT 18.63 81.18 PRESENT 0.2 17.80 6.40 81 EXAMPLE 7.4 8.86 23.03 1.96 0.97 PRESENT 14037 0.41 74.06 PRESENT 40708 PRESENT 5696 54.2 PRESENT 25.31 86.59 PRESENT 7.6 18.90 5.80 82 EXAMPLE 8.2 3.06 17.63 2.15 1.00 PRESENT 15654 0.85 86.53 PRESENT 45398 PRESENT 6254 31.7 PRESENT 16.46 59.46 PRESENT 11.8 20.30 6.60 83 EXAMPLE 8.7 2.64 17.94 2.22 1.02 PRESENT 16483 0.35 92.44 PRESENT 47800 PRESENT 6447 32.5 PRESENT 3.17 73.60 PRESENT 21.3 19.40 5.90 84 EXAMPLE 7.5 10.06 16.17 2.14 1.07 PRESENT 14338 0.49 99.17 PRESENT 41580 PRESENT 6213 22.7 PRESENT 22.37 52.20 PRESENT 42.5 17.30 5.70 85 EXAMPLE 5.3 3.90 22.43 4.40 1.00 PRESENT 10104 0.76 88.04 PRESENT 37013 PRESENT 12792 22.5 PRESENT 3.70 78.03 ABSENT 0.0 86 EXAMPLE 11.0 3.16 20.30 4.40 0.99 PRESENT 20928 0.37 88.36 PRESENT 76664 PRESENT 12776 29.3 PRESENT 5.87 74.77 ABSENT 0.0 87 EXAMPLE 14.9 11.72 24.37 4.49 0.97 PRESENT 28375 0.81 78.81 PRESENT 103944 PRESENT 13039 29.4 PRESENT 5.17 60.34 PRESENT 0.1 23.60 12.30 88 EXAMPLE 13.5 3.64 20.80 4.59 1.05 PRESENT 25651 0.55 78.32 PRESENT 93964 PRESENT 13336 40.2 PRESENT 23.25 61.33 PRESENT 6.5 22.80 11.40 89 EXAMPLE 15.0 14.21 23.49 3.99 0.98 PRESENT 28555 0.66 75.25 PRESENT 104602 PRESENT 11591 32.4 PRESENT 15.17 67.18 PRESENT 15.0 25.70 12.90 90 EXAMPLE 17.3 3.22 20.93 4.05 1.37 PRESENT 32953 0.34 95.31 PRESENT 120712 PRESENT 11775 46.0 PRESENT 4.84 73.19 PRESENT 32.7 25.90 12.20 [TABLE 5-3]

[0196] [TABLE 5-5] TABLE 5-4 No. CLASSIFI CATION PROTECTIVE LAYER SECOND PROTECTIVE FILM ZINC-BASED COATING LAYER THICK NESS (pm) CONCENT RATION (maa%) Si CONCENT RATION (maa%) Mg CONCENT RATION (maa%) Si CONCENT SiOs Zh / AI-BASED CARBONATE-TYPE LAYERED DOUBLE HYDROXIDE Mg / AI-BASED CARBONATE-TYPE LAYERED DOUBLE HYDROXIDE THICK SiOs PRESENCE OR ABSENCE THICK NESS (pm) CONCENT RATION (maa%) Mg CONCENT RATION (maa%) RATION RATIO PRESENCE OR ABSENCE PEAK NTEN STY (ops) AVERAGE PARTICLE SIZE (pm) RATIO (%) PRESENCE OR ABSENCE PEAK NTEN STY (ops) PRESENCE OR ABSENCE PEAK NTEN STY (ops) (pm) PRESENCE OR ABSENCE AVERAGE PARTICLE SIZE (pm) RATIO (%) 91 COMPARATIVE EXAMPLE 0.0 ABSENT ABSENT ABSENT ABSENT PRESENT 50.0 0.18 0.00 92 COMPARATIVE EXAMPLE 0.0 ABSENT ABSENT ABSENT ABSENT PRESENT 50.0 0.18 0.00 93 COMPARATIVE EXAMPLE 0.0 ABSENT ABSENT ABSENT ABSENT PRESENT 50.0 0.18 0.00 94 COMPARATIVE EXAMPLE 0.0 ABSENT ABSENT ABSENT ABSENT PRESENT 50.0 6.00 3.00 95 COMPARATIVE EXAMPLE 0.0 ABSENT ABSENT ABSENT ABSENT PRESENT 50.0 6.00 3.00 96 COMPARATIVE EXAMPLE 0.0 ABSENT ABSENT ABSENT ABSENT PRESENT 50.0 6.00 3.00 97 COMPARATIVE EXAMPLE 0.0 ABSENT ABSENT ABSENT ABSENT PRESENT 50.0 11.00 3.00 98 COMPARATIVE EXAMPLE 0.0 ABSENT ABSENT ABSENT ABSENT PRESENT 50.0 11.00 3.00 99 COMPARATIVE EXAMPLE 0.0 ABSENT ABSENT ABSENT ABSENT PRESENT 50.0 11.00 3.00 100 COMPARATIVE EXAMPLE 0.0 ABSENT ABSENT ABSENT ABSENT PRESENT 50.0 16.00 6.00 101 COMPARATIVE EXAMPLE 0.0 ABSENT ABSENT ABSENT ABSENT PRESENT 50.0 16.00 6.00 102 COMPARATIVE EXAMPLE 0.0 ABSENT ABSENT ABSENT ABSENT PRESENT 50.0 16.00 6.00 103 COMPARATIVE EXAMPLE 0.0 ABSENT ABSENT ABSENT ABSENT PRESENT 50.0 19.00 6.00 104 COMPARATIVE EXAMPLE 0.0 ABSENT ABSENT ABSENT ABSENT PRESENT 50.0 19.00 6.00 105 COMPARATIVE EXAMPLE 0.0 ABSENT ABSENT ABSENT ABSENT PRESENT 50.0 19.00 6.00 106 COMPARATIVE EXAMPLE 0.0 ABSENT ABSENT ABSENT ABSENT PRESENT 50.0 24.00 12.00 107 COMPARATIVE EXAMPLE 0.0 ABSENT ABSENT ABSENT ABSENT PRESENT 50.0 24.00 12.00 108 COMPARATIVE EXAMPLE 0.0 ABSENT ABSENT ABSENT ABSENT PRESENT 50.0 24.00 12.00 109 COMPARATIVE EXAMPLE 0.0 3.25 13.79 0.94 ABSENT ABSENT ABSENT ABSENT PRESENT 50.0 0.20 0.00 110 COMPARATIVE EXAMPLE 0.0 9.01 11.41 1.06 ABSENT ABSENT ABSENT ABSENT PRESENT 50.0 0.20 0.00 111 COMPARATIVE EXAMPLE 0.1 7.59 17.52 1.07 ABSENT ABSENT ABSENT ABSENT PRESENT 49.9 0.20 0.00 112 COMPARATIVE EXAMPLE 0.0 18.24 23.15 1.12 1.01 ABSENT ABSENT ABSENT ABSENT PRESENT 50.0 6.10 3.10 113 COMPARATIVE EXAMPLE 0.0 3.49 11.91 0.98 1.10 ABSENT ABSENT ABSENT ABSENT PRESENT 50.0 5.90 2.80 114 COMPARATIVE EXAMPLE 0.0 8.18 22.44 1.08 0.98 ABSENT ABSENT ABSENT ABSENT PRESENT 50.0 6.00 2.90 115 COMPARATIVE EXAMPLE 0.0 2.59 13.59 1.11 1.01 ABSENT ABSENT ABSENT ABSENT PRESENT 50.0 11.70 3.00 116 COMPARATIVE EXAMPLE 0.0 4.37 21.06 1.13 1.40 ABSENT ABSENT ABSENT ABSENT PRESENT 50.0 10.10 3.20 117 COMPARATIVE EXAMPLE 0.0 15.39 23.91 1.13 1.40 ABSENT ABSENT ABSENT ABSENT PRESENT 50.0 12.10 3.00 118 COMPARATIVE EXAMPLE 0.0 13.46 15.76 1.94 1.41 ABSENT ABSENT ABSENT ABSENT PRESENT 50.0 17.30 6.00 119 COMPARATIVE EXAMPLE 0.0 15.04 22.91 2.30 1.08 ABSENT ABSENT ABSENT ABSENT PRESENT 50.0 16.80 5.70 120 COMPARATIVE EXAMPLE 0.1 17.14 24.45 2.23 0.94 ABSENT ABSENT ABSENT ABSENT PRESENT 49.9 15.50 5.80

[0195] [TABLE 5-4]

[0197] [TABLE 5-6] TABLE 5-5 No. CLASSIFI CATION PROTECTIVE LAYER SECOND PROTECTIVE FILM ZINC-BASED COATING LAYER THICK NESS (Pm) Zn CONCENT Si CONCENT Mg CONCENT Si CONCENT SiO2 Zn / AJ-BASED CARBONATE-TYPE LAYERED DOUBLE HYDROXIDE Mg / AI-BASED CARBONATE-TYPE LAYERED DOUBLE HYDROXIDE THICK SiO2 PRESENCE OR ABSENCE THICK NESS (pm) CONCENT RATION (maa%) Mg CONCENT RATION (maa%) RATION (maa%) RATION (maa%) RATION (maa%) RATION RATIO PRESENCE OR ABSENCE PEAK INTEN SITY (cps) AVERAGE PARTICLE SIZE (pm) RATIO (%) PRESENCE OR ABSENCE PEAK NTEN SITY (CPS) PRESENCE OR ABSENCE PEAK INTEN SITY (cps) (pm) PRESENCE OR ABSENCE AVERAGE PARTICLE SIZE (pm) RATIO (%) 121 COMPARATIVE EXAMPLE 0.0 16.35 18.50 1.89 1.06 ABSENT ABSENT ABSENT ABSENT PRESENT 50.0 20.20 6.30 122 COMPARATIVE EXAMPLE 0.1 10.62 24.47 2.07 1.05 ABSENT ABSENT ABSENT ABSENT PRESENT 49.9 19.60 6.00 123 COMPARATIVE EXAMPLE 0.0 1.79 11.61 2.13 0.90 ABSENT ABSENT ABSENT ABSENT PRESENT 50.0 20.40 6.10 124 COMPARATIVE EXAMPLE 0.0 7.52 11.87 4.00 1.06 ABSENT ABSENT ABSENT ABSENT PRESENT 50.0 22.10 12.10 125 COMPARATIVE EXAMPLE 0.0 1.86 15.66 4.58 1.04 ABSENT ABSENT ABSENT ABSENT PRESENT 50.0 23.40 11.80 126 COMPARATIVE EXAMPLE 0.0 12.33 20.89 4.46 1.00 ABSENT ABSENT ABSENT ABSENT PRESENT 50.0 22.00 11.20 127 COMPARATIVE EXAMPLE 0.3 7.95 11.90 0.92 ABSENT ABSENT ABSENT ABSENT PRESENT 49.7 0.20 0.00 128 COMPARATIVE EXAMPLE 0.4 11.70 21.15 0.98 ABSENT ABSENT ABSENT ABSENT PRESENT 49.6 0.20 0.00 129 COMPARATIVE EXAMPLE 0.1 20.40 21.76 0.98 ABSENT ABSENT ABSENT ABSENT PRESENT 49.9 0.20 0.00 130 COMPARATIVE EXAMPLE 0.1 8.67 19.90 0.95 0.97 ABSENT ABSENT ABSENT ABSENT PRESENT 49.9 6.50 2.90 131 COMPARATIVE EXAMPLE 0.1 11.99 22.08 1.13 0.99 ABSENT ABSENT ABSENT ABSENT PRESENT 49.9 6.20 3.10 132 COMPARATIVE EXAMPLE 0.5 9.62 20.69 1.06 0.93 ABSENT ABSENT ABSENT ABSENT PRESENT 49.5 6.30 2.90 133 COMPARATIVE EXAMPLE 0.3 15.12 24.41 1.09 1.09 ABSENT ABSENT ABSENT ABSENT PRESENT 49.7 11.80 2.90 134 COMPARATIVE EXAMPLE 0.1 5.67 23.11 0.96 1.38 ABSENT ABSENT ABSENT ABSENT PRESENT 49.9 10.10 3.10 135 COMPARATIVE EXAMPLE 0.2 12.49 20.14 1.06 1.31 ABSENT ABSENT ABSENT ABSENT PRESENT 49.8 12.10 3.00 136 COMPARATIVE EXAMPLE 0.2 9.39 10.88 2.07 1.34 ABSENT ABSENT ABSENT ABSENT PRESENT 49.8 17.30 6.30 137 COMPARATIVE EXAMPLE 0.0 7.62 19.21 2.02 1.09 ABSENT ABSENT ABSENT ABSENT PRESENT 50.0 14.70 5.90 138 COMPARATIVE EXAMPLE 0.4 2.25 12.65 2.01 0.91 ABSENT ABSENT ABSENT ABSENT PRESENT 49.6 17.60 6.20 139 COMPARATIVE EXAMPLE 0.2 8.26 16.37 2.10 0.95 ABSENT ABSENT ABSENT ABSENT PRESENT 49.8 20.60 6.00 140 COMPARATIVE EXAMPLE 0.1 1.90 12.19 2.24 0.91 ABSENT ABSENT ABSENT ABSENT PRESENT 49.9 18.80 6.40 141 COMPARATIVE EXAMPLE 0.5 7.66 24.98 2.29 0.95 ABSENT ABSENT ABSENT ABSENT PRESENT 49.5 17.60 6.30 142 COMPARATIVE EXAMPLE 0.0 14.01 15.96 4.39 0.94 ABSENT ABSENT ABSENT ABSENT PRESENT 50.0 24.70 12.00 143 COMPARATIVE EXAMPLE 0.1 4.61 13.83 4.22 1.09 ABSENT ABSENT ABSENT ABSENT PRESENT 49.9 23.80 12.50 144 COMPARATIVE EXAMPLE 0.0 4.92 17.57 4.14 1.08 ABSENT ABSENT ABSENT ABSENT PRESENT 50.0 23.10 10.90 145 COMPARATIVE EXAMPLE 16.6 4.45 18.42 1.04 PRESENT 31687 0.35 98.72 ABSENT ABSENT ABSENT PRESENT 33.4 0.20 0.00 146 COMPARATIVE EXAMPLE 16.3 3.65 18.39 0.91 PRESENT 31023 0.82 76.09 ABSENT ABSENT ABSENT PRESENT 33.7 0.20 0.00 147 COMPARATIVE EXAMPLE 22.6 15.40 19.62 0.96 PRESENT 43069 0.53 98.37 ABSENT ABSENT ABSENT PRESENT 27.4 0.20 0.00 148 COMPARATIVE EXAMPLE 19.1 14.13 21.70 0.98 0.99 PRESENT 36373 0.22 73.69 ABSENT ABSENT ABSENT PRESENT 30.9 5.50 2.80 149 COMPARATIVE EXAMPLE 26.1 7.10 15.43 1.02 1.01 PRESENT 49664 0.45 95.94 ABSENT ABSENT ABSENT PRESENT 23.9 5.70 2.80 150 COMPARATIVE EXAMPLE 25.7 10.32 18.66 1.12 0.98 PRESENT 48932 0.68 71.71 ABSENT ABSENT ABSENT PRESENT 24.3 6.40 2.80

[0198] Further, for each of the surface-treated steel materials obtained in this manner, the corrosion resistance in soil was evaluated in accordance with a method described below. TABLE 5-6 No. CLASSIFI CATION PROTECTIVE LAYER SECOND PROTECTIVE FILM ZINC-BASED COATING LAYER THICK NESS (pm) Zn CONCENT Si CONCENT Mg CONCENT Si CONCENT SiOj Zn / AJ-BASED CARBONATE-TYPE LAYERED DOUBLE HYDROXIDE Mg / AI-BASED CARBONATE-TYPE LAYERED DOUBLE HYDROXIDE THICK SiOj PRESENCE OR ABSENCE THICK NESS (pm) CONCENT RATION (maa%) Mg CONCENT RATION (maa%) RATION (maa%) RATION (maa%) RATION (maa%) RATION RATIO PRESENCE OR ABSENCE PEAK INTEN SITY (ops) AVERAGE PARTICLE SIZE (pm) RATIO (%) PRESENCE OR ABSENCE PEAK NTEN SITY (ops) PRESENCE OR ABSENCE PEAK INTEN SITY (ops) (pm) PRESENCE OR ABSENCE AVERAGE PARTICLE SIZE (pm) RATIO (%) 151 COMPARATIVE EXAMPLE 26.2 15.56 12.50 0.96 1.05 PRESENT 49849 0.68 76.76 / >BSENT ABSENT ABSENT PRESENT 23.8 10.20 3.20 152 COMPARATIVE EXAMPLE 31.9 18.39 19.64 1.09 1.37 PRESENT 60639 0.89 97.39 / >BSENT ABSENT ABSENT PRESENT 18.1 10.20 2.90 153 COMPARATIVE EXAMPLE 29.5 4.99 22.09 1.10 1.33 PRESENT 56208 0.56 80.56 / >BSENT ABSENT ABSENT PRESENT 20.5 11.10 3.00 154 COMPARATIVE EXAMPLE 29.8 10.62 20.87 2.12 1.41 PRESENT 56711 0.41 82.13 / >BSENT ABSENT ABSENT PRESENT 20.2 17.00 6.40 155 COMPARATIVE EXAMPLE 19.0 6.35 20.15 2.19 0.91 PRESENT 36122 0.47 91.16 / >BSENT ABSENT ABSENT PRESENT 31.0 17.30 5.40 156 COMPARATIVE EXAMPLE 18.3 5.33 15.38 2.18 0.92 PRESENT 34830 0.26 90.39 / >BSENT ABSENT ABSENT PRESENT 31.7 15.60 5.90 157 COMPARATIVE EXAMPLE 14.8 7.43 18.60 2.11 0.94 PRESENT 28256 0.37 98.31 / >BSENT ABSENT ABSENT PRESENT 35.2 19.60 6.20 158 COMPARATIVE EXAMPLE 14.6 15.57 24.22 1.97 1.08 PRESENT 27 7 57 0.77 94.71 / >BSENT ABSENT ABSENT PRESENT 35.4 17.20 6.00 159 COMPARATIVE EXAMPLE 15.2 12.84 10.33 2.08 1.08 PRESENT 28982 0.52 90.71 / >BSENT ABSENT ABSENT PRESENT 34.8 17.90 5.90 160 COMPARATIVE EXAMPLE 15.6 13.21 24.20 4.29 1.07 PRESENT 29757 0.46 94.33 / >BSENT ABSENT ABSENT PRESENT 34.4 23.10 12.20 161 COMPARATIVE EXAMPLE 23.0 13.14 10.47 4.47 1.03 PRESENT 43769 0.50 87.20 / >BSENT ABSENT ABSENT PRESENT 27.0 22.50 12.10 162 COMPARATIVE EXAMPLE 17.5 10.39 17.13 4.43 1.00 PRESENT 33265 0.28 84.84 / >BSENT ABSENT ABSENT PRESENT 32.5 24.20 13.10 163 COMPARATIVE EXAMPLE 40.9 0.37 28.69 1.07 PRESENT 77791 0.62 71.48 PRESENT 2137 ABSENT ABSENT PRESENT 9.1 0.20 0.00 164 COMPARATIVE EXAMPLE 47.4 0.38 29.85 1.45 PRESENT 90195 0.52 78.47 PRESENT 2478 ABSENT ABSENT PRESENT 2.6 0.20 0.00 165 COMPARATIVE EXAMPLE 48.0 0.78 32.67 1.34 PRESENT 91476 0.56 75.36 PRESENT 2513 ABSENT ABSENT PRESENT 2.0 0.20 0.00 166 COMPARATIVE EXAMPLE 46.5 0.15 36.94 0.06 1.41 PRESENT 885 75 0.64 89.41 PRESENT 81116 ABSENT 168 ABSENT PRESENT 3.5 5.70 3.10 167 COMPARATIVE EXAMPLE 30.0 0.98 34.81 0.09 0.93 PRESENT 57057 0.49 72.27 PRESENT 52252 ABSENT 252 ABSENT PRESENT 20.0 6.10 3.30 168 COMPARATIVE EXAMPLE 28.1 0.04 35.91 0.07 1.08 PRESENT 53523 0.80 98.07 PRESENT 49016 ABSENT 198 ABSENT PRESENT 21.9 5.50 2.90 169 COMPARATIVE EXAMPLE 22.3 0.03 38.19 0.00 1.10 PRESENT 42546 0.82 95.60 PRESENT 71433 ABSENT 4 ABSENT PRESENT 27.7 11.80 2.80 170 COMPARATIVE EXAMPLE 20.5 0.04 25.69 0.03 0.98 PRESENT 38997 0.66 93.25 PRESENT 65474 ABSENT 97 ABSENT PRESENT 29.5 11.00 3.10 171 COMPARATIVE EXAMPLE 24.3 0.99 30.46 0.01 0.93 PRESENT 46303 0.24 93.43 PRESENT 77740 ABSENT 34 ABSENT PRESENT 25.7 11.50 3.20 172 COMPARATIVE EXAMPLE 25.9 0.53 35.79 0.09 0.96 PRESENT 49383 0.62 81.92 PRESENT 120599 ABSENT 263 ABSENT PRESENT 24.1 14.80 6.40 173 COMPARATIVE EXAMPLE 32.8 0.38 31.45 0.00 0.93 PRESENT 62474 0.25 96.07 PRESENT 152568 ABSENT 4 ABSENT PRESENT 17.2 14.50 6.00 174 COMPARATIVE EXAMPLE 28.5 0.10 25.98 0.05 0.99 PRESENT 54167 0.35 99.92 PRESENT 132282 ABSENT 155 ABSENT PRESENT 21.5 14.40 5.50 175 COMPARATIVE EXAMPLE 41.6 0.75 26.45 0.10 1.07 PRESENT 79104 0.87 99.64 PRESENT 229401 ABSENT 290 ABSENT PRESENT 8.4 18.20 5.60 176 COMPARATIVE EXAMPLE 39.1 0.52 34.48 0.07 0.97 PRESENT 74531 0.20 87.11 PRESENT 216139 ABSENT 212 ABSENT PRESENT 10.9 20.00 5.50 177 COMPARATIVE EXAMPLE 39.7 0.23 34.38 0.03 1.09 PRESENT 756 1 5 0.84 76.96 PRESENT 219285 ABSENT 89 ABSENT PRESENT 10.3 17.80 6.20 178 COMPARATIVE EXAMPLE 48.6 0.21 29.37 0.10 1.30 PRESENT 92606 0.21 87.65 PRESENT 339229 ABSENT 284 ABSENT PRESENT 1.4 25.00 12.80 179 COMPARATIVE EXAMPLE 47.4 0.75 28.55 0.09 1.40 PRESENT 90254 0.75 75.18 PRESENT 330614 ABSENT 258 ABSENT PRESENT 2.6 21.90 11.80 180 COMPARATIVE EXAMPLE 47.1 0.08 30.30 0.08 1.37 PRESENT 89592 0.37 83.41 PRESENT 328189 ABSENT 245 ABSENT PRESENT 2.9 22.30 12.10 <Corrosion resistance evaluation method> The obtained surface-treated steel material of each level was embedded in soil simulating the soil surface layer portion, and the corrosion resistance was evaluated. As the soil, silica sand having an average particle size of 200 gm (Flattery 40H manufactured by Yamakawa Sangyo Co., Ltd.) was used. The cover thickness of each surface-treated steel material was 50 mm. After embedding each surface-treated steel material in this manner, ion-exchanged water containing 0.3 mass% of NaCl and 0.1 mass% of Na2SO4 was dropped onto the soil to adjust the moisture content to 100%. Thereafter, the following drying step and wetting step were repeated. Those with the number of repetitions set to 20 times, 40 times, and 100 times were prepared and evaluated, respectively. Drying step: Stored at 30°C and stored for 7 days Wetting step: Ion-exchanged water was dropped to adjust the moisture content to 100%

[0200] The surface-treated steel material after the above test was pickled with hydrochloric acid to remove the second protective layer, the protective layer, the coating layer existing under the protective layer, and corrosion products of the steel material. Thereafter, the mass of the steel material was measured and compared with the mass of a test material (before coating) to measure the corrosion weight loss. The evaluation criteria are as follows, and grades "A", "B", and "C" were evaluated as acceptable. The obtained results are collectively shown in Table 6-1 to Table 6-6 below. <Evaluation criteria> Grade A: Corrosion weight loss of 1 g / m2 or less B: Corrosion weight loss of more than 1 g / m2 and 5 g / m2 or less C: Corrosion weight loss of more than 5 g / m2 and 15 g / m2 or less 5                 D: Corrosion weight loss of 15 g / m2 and 200 g / m2 or less E: Corrosion weight loss of more than 200 g / m2

[0201] [TABLE 6-1] 10 TABLE 6-1 No. CLASSIFI CATION CORROSION RESISTANCE EVALUATION 20 CYCLES 40 CYCLES 100 CYCLES 1 EXAMPLE A A B 2 EXAMPLE A A B 3 EXAMPLE A A B 4 EXAMPLE A A A 5 EXAMPLE A A A 6 EXAMPLE A A A 7 EXAMPLE A A A 8 EXAMPLE A A A 9 EXAMPLE A A A 10 EXAMPLE A A A 11 EXAMPLE A A A 12 EXAMPLE A A A 13 EXAMPLE A A A 14 EXAMPLE A A A 15 EXAMPLE A A A 16 EXAMPLE A A A 17 EXAMPLE A A A 18 EXAMPLE A A A 19 EXAMPLE A A A 20 EXAMPLE A A A 21 EXAMPLE A A A 22 EXAMPLE A A A 23 EXAMPLE A A A 24 EXAMPLE A A A 25 EXAMPLE A A A 26 EXAMPLE A A A 27 EXAMPLE A A A 28 EXAMPLE A A A 29 EXAMPLE A A A 30 EXAMPLE A A A

[0202] [TABLE 6-2] TABLE 6-2 No. CLASSIFI CATION CORROSION RESISTANCE EVALUATION 20 CYCLES 40 CYCLES 100 CYCLES 31 EXAMPLE A A A 32 EXAMPLE A A A 33 EXAMPLE A A A 34 EXAMPLE A A A 35 EXAMPLE A A A 36 EXAMPLE A A A 37 EXAMPLE C C D 38 EXAMPLE C C D 39 EXAMPLE B B C 40 EXAMPLE A B C 41 EXAMPLE A B C 42 EXAMPLE A B C 43 EXAMPLE A B C 44 EXAMPLE A A B 45 EXAMPLE A A B 46 EXAMPLE A A B 47 EXAMPLE A A A 48 EXAMPLE A A A 49 EXAMPLE A B C 50 EXAMPLE A A A 51 EXAMPLE A A A 52 EXAMPLE A A A 53 EXAMPLE A A A 54 EXAMPLE A A A 55 EXAMPLE A A A 56 EXAMPLE A A A 57 EXAMPLE A A A 58 EXAMPLE A A A 59 EXAMPLE A A A 60 EXAMPLE A A A

[0203] [TABLE 6-3] TABLE 6-3 No. CLASSIFI CATION CORROSION RESISTANCE EVALUATION 20 CYCLES 40 CYCLES 100 CYCLES 61 EXAMPLE A A A 62 EXAMPLE A A A 63 EXAMPLE A A A 64 EXAMPLE A A A 65 EXAMPLE A A A 66 EXAMPLE A A A 67 EXAMPLE A A A 68 EXAMPLE A A A 69 EXAMPLE A A A 70 EXAMPLE A A A 71 EXAMPLE A A A 72 EXAMPLE A A A 73 EXAMPLE A A A 74 EXAMPLE A A A 75 EXAMPLE A A A 76 EXAMPLE A A A 77 EXAMPLE A A A 78 EXAMPLE A A A 79 EXAMPLE A A A 80 EXAMPLE A A A 81 EXAMPLE A A A 82 EXAMPLE A A A 83 EXAMPLE A A A 84 EXAMPLE A A A 85 EXAMPLE A A A 86 EXAMPLE A A A 87 EXAMPLE A A A 88 EXAMPLE A A A 89 EXAMPLE A A A 90 EXAMPLE A A A

[0204] [TABLE 6-4] TABLE 6-4 No. CLASS IFI CATION CORROSION RESISTANCE EVALUATION 20 CYCLES 40 CYCLES 100 CYCLES 91 COMPARATIVE EXAMPLE E E E 92 COMPARATIVE EXAMPLE E E E 93 COMPARATIVE EXAMPLE E E E 94 COMPARATIVE EXAMPLE E E E 95 COMPARATIVE EXAMPLE E E E 96 COMPARATIVE EXAMPLE E E E 97 COMPARATIVE EXAMPLE E E E 98 COMPARATIVE EXAMPLE E E E 99 COMPARATIVE EXAMPLE E E E 100 COMPARATIVE EXAMPLE E E E 101 COMPARATIVE EXAMPLE E E E 102 COMPARATIVE EXAMPLE E E E 103 COMPARATIVE EXAMPLE E E E 104 COMPARATIVE EXAMPLE E E E 105 COMPARATIVE EXAMPLE E E E 106 COMPARATIVE EXAMPLE E E E 107 COMPARATIVE EXAMPLE E E E 108 COMPARATIVE EXAMPLE E E E 109 COMPARATIVE EXAMPLE E E E 110 COMPARATIVE EXAMPLE E E E 111 COMPARATIVE EXAMPLE E E E 112 COMPARATIVE EXAMPLE E E E 113 COMPARATIVE EXAMPLE E E E 114 COMPARATIVE EXAMPLE E E E 115 COMPARATIVE EXAMPLE E E E 116 COMPARATIVE EXAMPLE E E E 117 COMPARATIVE EXAMPLE E E E 118 COMPARATIVE EXAMPLE E E E 119 COMPARATIVE EXAMPLE E E E 120 COMPARATIVE EXAMPLE E E E

[0205] TABLE 6-5 No. CLASS IFI CATON CORROSION RESISTANCE EVALUATION 20 CYCLES 40 CYCLES 100 CYCLES 121 COMPARATIVE EXAMPLE E E E 122 COMPARATIVE EXAMPLE E E E 123 COMPARATIVE EXAMPLE E E E 124 COMPARATIVE EXAMPLE E E E 125 COMPARATIVE EXAMPLE E E E 126 COMPARATIVE EXAMPLE E E E 127 COMPARATIVE EXAMPLE E E E 128 COMPARATIVE EXAMPLE E E E 129 COMPARATIVE EXAMPLE E E E 130 COMPARATIVE EXAMPLE E E E 131 COMPARATIVE EXAMPLE E E E 132 COMPARATIVE EXAMPLE E E E 133 COMPARATIVE EXAMPLE E E E 134 COMPARATIVE EXAMPLE D E E 135 COMPARATIVE EXAMPLE D E E 136 COMPARATIVE EXAMPLE D E E 137 COMPARATIVE EXAMPLE E E E 138 COMPARATIVE EXAMPLE E E E 139 COMPARATIVE EXAMPLE E E E 140 COMPARATIVE EXAMPLE E E E 141 COMPARATIVE EXAMPLE E E E 142 COMPARATIVE EXAMPLE E E E 143 COMPARATIVE EXAMPLE E E E 144 COMPARATIVE EXAMPLE E E E 145 COMPARATIVE EXAMPLE D D E 146 COMPARATIVE EXAMPLE D D E 147 COMPARATIVE EXAMPLE D D E 148 COMPARATIVE EXAMPLE D D E 149 COMPARATIVE EXAMPLE D D E 150 COMPARATIVE EXAMPLE D D E

[0206] TABLE 6-6 No. CLASS IFI CATION CORROSION RESISTANCE EVALUATION 20 CYCLES 40 CYCLES 100 CYCLES 151 COMPARATIVE EXAMPLE D D E 152 COMPARATIVE EXAMPLE D D E 153 COMPARATIVE EXAMPLE D D E 154 COMPARATIVE EXAMPLE D D E 155 COMPARATIVE EXAMPLE D D E 156 COMPARATIVE EXAMPLE D D E 157 COMPARATIVE EXAMPLE D D E 158 COMPARATIVE EXAMPLE D D E 159 COMPARATIVE EXAMPLE D D E 160 COMPARATIVE EXAMPLE D D E 161 COMPARATIVE EXAMPLE D D E 162 COMPARATIVE EXAMPLE D D E 163 COMPARATIVE EXAMPLE D D E 164 COMPARATIVE EXAMPLE D D E 165 COMPARATIVE EXAMPLE D D E 166 COMPARATIVE EXAMPLE D D D 167 COMPARATIVE EXAMPLE D D E 168 COMPARATIVE EXAMPLE D D E 169 COMPARATIVE EXAMPLE D D E 170 COMPARATIVE EXAMPLE D D E 171 COMPARATIVE EXAMPLE D D E 172 COMPARATIVE EXAMPLE D D E 173 COMPARATIVE EXAMPLE D D E 174 COMPARATIVE EXAMPLE D D E 175 COMPARATIVE EXAMPLE D D E 176 COMPARATIVE EXAMPLE D D E 177 COMPARATIVE EXAMPLE D D E 178 COMPARATIVE EXAMPLE D D E 179 COMPARATIVE EXAMPLE D D E 180 COMPARATIVE EXAMPLE D D E

[0207] As is clear from Table 4-1 to Table 6-6 above, it is understood that 5 those corresponding to the examples of the present invention exhibit excellent corrosion resistance, while those corresponding to the comparative examples of the present invention exhibit insufficient corrosion resistance.

[0208] While preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention belongs could conceive of various modifications or variations within the scope of the technical idea described in the claims, and it is understood that these also naturally fall within the technical scope of the present invention.

[0209] The embodiments disclosed herein are illustrative in all respects and not restrictive. Various omissions, substitutions, and modifications in various forms may be made without departing from the scope of the appended claims, the configurations belonging to the technical scope of the present invention as described below, and the gist thereof. For example, the constituent elements of the above-described embodiments can be optionally combined within a range that does not impair the effects thereof. Further, from the optional combinations, functions and effects of the respective constituent elements relating to the combinations can be naturally obtained, and other functions and effects obvious to those skilled in the art from the description herein can also be obtained.

[0210] Besides, the effects described herein are merely explanatory or illustrative in all respects and not restrictive. In other words, the technique relating to the present invention can offer other effects apparent to those skilled in the art from the description herein in addition to or in place of the above effects.

[0211] Note that the following configurations also belong to the technical scope of the present invention. (1) A surface-treated member including: a steel material as a base material; and a protective layer located on a surface of the steel material; wherein the protective layer has a Zn concentration of 1.00 mass% or more and less than 30.00 mass% and an Si concentration of 1.00 mass% or more and less than 25.00 mass%, and contains SiO2 and a Zn / Al-based carbonate-type layered double hydroxide. (2) The surface-treated member according to (1), wherein a thickness of the protective layer is 0.1 pm or more and 50.0 pm or less. (3) The surface-treated member according to (1) or (2), wherein in a measurement result of the surface of the protective layer measured by an X-ray diffraction method (XRD), a peak intensity of a peak attributed to the Zn / Al-based carbonate-type layered double hydroxide is 1000 cps or more and 150000 cps or less. (4) The surface-treated member according to any one of (1) to (3), wherein the protective layer has an Mg concentration of 0.10 mass% or more and 5.00 mass% or less, and further contains an Mg / Al-based carbonate-type layered double hydroxide. (5) The surface-treated member according to (4), wherein in a measurement result of the surface of the protective layer measured by an X-ray diffraction method (XRD), a peak intensity of a peak attributed to the Mg / Al-based carbonate-type layered double hydroxide is 1000 cps or more and 150000 cps or less. (6) The surface-treated member according to any one of (1) to (5), wherein in a measurement result of the surface of the protective layer measured by an X-ray diffraction method (XRD), a peak intensity of a peak attributed to the SiO2 is 500 cps or more and 100000 cps or less. (7) The surface-treated member according to any one of (1) to (6), wherein when a distribution state of the Si concentration in a thickness direction of the protective layer is observed, the Si concentration at a 1 / 2 thickness of the protective layer on a surface side is 1.3 times or more the Si concentration at a 1 / 2 thickness of the protective layer on a steel material side. (8) The surface-treated member according to any one of (1) to (7), wherein the protective layer contains, as the SiO2, SiO2 particles having a particle size of 0.1 to 1.0 pm. (9) The surface-treated member according to any one of (1) to (8), further including a second protective layer located on the protective layer, wherein the second protective layer contains SiO2 particles having a particle size of 1.0 to 30.0 pm. (10) The surface-treated member according to (9), wherein a thickness of the second protective layer is 1 pm or more and 100 pm or less. (11) The surface-treated member according to any one of (1) to (10), further including a zinc-based coating layer between the steel material and the protective layer. (12) The surface-treated member according to (11), wherein the zinc-based coating layer has an Al concentration of 0.10 mass% or more and less than 40.00 mass%, and a Zn concentration of 60.00 mass% or more. (13) The surface-treated member according to (11) or (12), wherein the zinc-based coating layer has an Mg concentration of 0.10 mass% or more and less than 15.00 mass%. (14) The surface-treated member according to any one of (11) to (13), wherein a thickness of the zinc-based coating layer is 1 pm or more and 200 pm or less. EXPLANATION OF CODES

[0212] 1     surface-treated member 10     surface-treated steel material 5   11 steel material 13     protective layer 15     zinc-based coating layer 17     second protective layer 19     SiO2 particle 10

Claims

1. A surface-treated member comprising:a steel material as a base material; anda protective layer located on a surface of the steel material;wherein the protective layer has a Zn concentration of 1.00 mass% or more and less than 30.00 mass% and an Si concentration of 1.00 mass% or more and less than 25.00 mass%, and contains SiO2 and a Zn / Al-based carbonate-type layered double hydroxide.

2. The surface-treated member according to claim 1,wherein a thickness of the protective layer is 0.1 pm or more and 50.0 pm or less.

3. The surface-treated member according to claim 1 or 2,wherein in a measurement result of the surface of the protective layer measured by an X-ray diffraction method (XRD), a peak intensity of a peak attributed to the Zn / Al-based carbonate-type layered double hydroxide is 1000 cps or more and 150000 cps or less.

4. The surface-treated member according to claim 1 or 2,wherein the protective layer has an Mg concentration of 0.10 mass% or more and 5.00 mass% or less, and further contains an Mg / Al-based carbonate-type layered double hydroxide.

5. The surface-treated member according to claim 4,wherein in a measurement result of the surface of the protective layer measured by an X-ray diffraction method (XRD), a peak intensity of a peak attributed to the Mg / Al-based carbonate-type layered double hydroxide is 1000 cps or more and 150000 cps or less.

6. The surface-treated member according to claim 1 or 2,wherein in a measurement result of the surface of the protective layer measured by an X-ray diffraction method (XRD), a peak intensity of a peak attributed to the SiO2 is 500 cps or more and 100000 cps or less.

7. The surface-treated member according to claim 1 or 2,wherein when a distribution state of the Si concentration in a thickness direction of the protective layer is observed, the Si concentration at a 1 / 2 thickness of the protective layer on a surface side is 1.3 times or more the Si concentration at a 1 / 2 thickness of the protective layer on a steel material side.

8. The surface-treated member according to claim 1 or 2,wherein the protective layer contains, as the SiO2, SiO2 particles having a particle size of 0.1 to 1.0 pm.

9. The surface-treated member according to claim 1 or 2, further comprisinga second protective layer located on the protective layer,wherein the second protective layer contains SiO2 particles having a particle size of 1.0 to 30.0 pm.

10. The surface-treated member according to claim 9,wherein a thickness of the second protective layer is 1 pm or more and 100 pm or less.

11. The surface-treated member according to claim 1 or 2, further comprisinga zinc-based coating layer between the steel material and the protective layer.

12. The surface-treated member according to claim 11,wherein the zinc-based coating layer has an Al concentration of 0.10 mass% or more and less than 40.00 mass%, and a Zn concentration of 60.00 mass% or more.

13. The surface-treated member according to claim 12,wherein the zinc-based coating layer has an Mg concentration of 0.10 mass% or more and less than 15.00 mass%.

14. The surface-treated member according to claim 11,wherein a thickness of the zinc-based coating layer is 1 pm or more and 200 pm or less.

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