Surface treatment member and composite structure

Abstract

[Problem] To achieve excellent corrosion resistance even in soil having a depth of several cm from the soil surface. [Means for solving the problem] The surface-treated member of the present invention is composed of a surface-treated steel material having a steel material as a base material, a zinc-based plated layer on the surface of the steel material, and a chemical conversion treatment layer on the surface of the zinc-based plated layer, the chemical conversion treatment layer containing a compound containing phosphorus element P, and when an amount of the chemical conversion treatment layer corresponding to the size of 1 m 2 of the surface-treated steel material is immersed in ion-exchange water having a water temperature of 35 to 45°C for 60 minutes, the amount of P dissolved from the chemical conversion treatment layer into the ion-exchange water is 5 to 50 mg / m 2 .

Description

Technical Field

[0001] This invention relates to surface-treated components and composite structures. Background Technology

[0002] Zinc-plated steel, with various zinc-based coatings applied as surface treatment layers to the surface of the base steel, is a widely used raw material in construction, automotive, and other fields to improve the corrosion resistance of structural components. After being processed into various shapes, the zinc-plated steel raw material is joined together as needed using fasteners such as screws, bolts, and rivets, or various welding methods, to form a surface-treated component with the desired shape.

[0003] It is believed that surface-treated components, as described above, are exposed to various corrosive environments depending on their intended use. Therefore, various studies have been conducted previously regarding the corrosion resistance of surface-treated steel as raw material.

[0004] For example, Patent Document 1 discloses a polyolefin-coated heavy-duty corrosion-resistant steel, wherein, for a base steel or a chromate-coated steel with a chromate layer on its surface, an epoxy primer layer, a maleic anhydride-modified polyolefin layer, and a polyolefin layer are sequentially layered. The epoxy primer layer is composed of a phenolic curing agent with an oxygen permeability within a specific range and epoxy resin. Patent Document 1 states that this polyolefin-coated heavy-duty corrosion-resistant steel can be used even in extremely harsh corrosive environments such as soil, rivers, and oceans.

[0005] Furthermore, Patent Document 2 discloses a coated steel in which a phosphate chemical conversion coating and a paint coating are sequentially formed on the surface of a steel having a zinc-based plating. The phosphate chemical conversion coating contains at least one element selected from nickel, magnesium, or calcium, in addition to zinc and manganese. The paint coating contains a phosphate-based anti-rust pigment and an alkaline earth metal sulfate. Patent Document 2 describes that this coated steel can be used by embedding a portion of it in concrete or the ground.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2005-132105

[0009] Patent Document 2: Japanese Patent Application Publication No. 2007-262561 Summary of the Invention

[0010] The problem the invention aims to solve

[0011] As noted in Patent Documents 1 and 2 above, it is presumed that when surface-treated components are placed at desired locations, at least a portion thereof is usually buried in the soil. If the portion of the surface-treated component is exposed to the atmosphere, corrosion can be easily assessed visually. However, unlike in the atmosphere, corrosion is difficult to assess visually for the portion buried in the soil, and maintenance of the corroded portion is also challenging. Therefore, surface-treated components used in soil require high corrosion resistance.

[0012] The inventors conducted a study on the corrosion of zinc-plated steel in soil. The results showed that, as described below, the corrosion behavior of zinc-plated steel in soil at a depth of 1 meter or more from the soil surface differed significantly from that in soil at a depth of only a few centimeters. Therefore, the soil corrosion environment described in Patent Document 2 primarily corresponds to the corrosion behavior in soil at a depth of 1 meter or more from the soil surface. Based on this, it was found that even when using the surface-treated steel disclosed in Patent Documents 1 and 2 as raw material to manufacture surface-treated components in soil at a depth of only a few centimeters from the soil surface, there is room for improvement in their corrosion resistance.

[0013] Therefore, the present invention was made in view of the above-mentioned problems, and the object of the present invention is to provide a surface-treated component made of zinc-plated steel and a composite structure using the surface-treated component, which exhibits excellent corrosion resistance even in soil at a depth of about a few centimeters from the soil surface.

[0014] Solution for solving the problem

[0015] To address the aforementioned issues, the inventors conducted in-depth research and conceived of a method for modifying the state of the chemical conversion treatment layer applied to the surface of surface-treated steel with a zinc-based coating, used as a blank for a surface-treated component, depending on the exposed corrosive environment (e.g., in the atmosphere or in soil). Based on this concept, the inventors conducted further research and conceived of the surface-treated component described below.

[0016] The main idea of ​​the present invention, which is based on this concept, is as follows.

[0017] (1) A surface-treated component comprising surface-treated steel, the surface-treated steel having: a steel as a base material, a zinc-based plating layer on the surface of the steel, and a chemical conversion treatment layer on the surface of the zinc-based plating layer, the chemical conversion treatment layer containing a compound including phosphorus element P, which will react with the surface-treated steel 1m 2When the chemically converted treatment layer, corresponding to its size, is immersed in ion-exchange water at a temperature of 35-45°C for 60 minutes, the amount of P dissolved from the chemically converted treatment layer into the ion-exchange water is 5-50 mg / m³. 2 .

[0018] (2) The surface-treated component according to (1) is used by burying at least a portion of the surface-treated steel in the soil.

[0019] (3) The surface-treated component according to (1), wherein, in the P2p narrow spectrum obtained by analyzing the surface of the above-mentioned chemically converted layer using X-ray photoelectron spectroscopy (XPS), the ratio of the integrated intensity of the peak with a maximum value at 133.90±0.25eV to the integrated intensity of the peak with a maximum value at 132.80±0.25eV is 0.20 to 0.50.

[0020] (4) According to the surface treatment component of (1), in the depth distribution of P concentration obtained by performing line analysis of the chemical conversion treatment layer from the surface to the interface with the zinc coating by energy dispersive X-ray spectroscopy (EDS), the average concentration of P on the surface side of the chemical conversion treatment layer is 1 to 20 by mass.

[0021] (5) The surface treatment component according to (1), wherein the P concentration of the above chemical conversion treatment layer is 0.1 to 15.0 by mass when converted to P.

[0022] (6) The surface treatment component according to (1), wherein the thickness of the chemical conversion treatment layer is 30~5000 nm.

[0023] (7) The surface treatment component according to (1), wherein the chemical conversion treatment layer contains one or more selected from the group consisting of silane coupling agent, valve metal and organic resin.

[0024] (8) The surface-treated component according to any one of (1) to (7), wherein the zinc-based coating is a coating having the following chemical composition: containing Al: 0.10% or more and less than 40.00%, Mg: 0.10% or more and less than 15.00% by mass, with the balance being Zn and impurities.

[0025] (9) The surface treatment component according to (8), wherein the zinc coating contains Al: 0.10% or more and less than 40.00%, Mg: 0.10% or more and less than 15.00%, and Zn: 60.00% or more by mass%.

[0026] (10) The surface-treated component according to any one of (1) to (7), wherein the zinc-based coating is a coating having the following chemical composition: containing, by mass%, Al: 0.10% or more and less than 40.00%, Mg: 0.10% or more and less than 15.00%, and also containing one or more elements selected from the group consisting of the following element groups A, B, C, D, E and F, with the balance being Zn and impurities.

[0027] [Element Group A]: Select one or two elements from the group consisting of Si: less than 2.50% and Fe: less than 5.00%.

[0028] [Element Group B]: Select one or more elements from the group consisting of Sb: less than 0.50%, Pb: less than 0.50%, and Sr: less than 0.50%.

[0029] [Element Group C]: Selected from one or more elements in 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%.

[0030] [Element Group D]: Select one or more elements from the group consisting of Sn: less than 20.00%, Bi: less than 5.00%, and In: less than 2.00%.

[0031] [Element Group E]: Select one or more elements from the group consisting of Ca: less than 3.00%, La: less than 0.50%, Ce: less than 0.50%, and Y: less than 0.50%.

[0032] [Element group F]: B: less than 0.50%

[0033] (11) The surface-treated component according to (10) contains the above-mentioned element group A.

[0034] (12) The surface-treated component according to (10) contains the above-mentioned element group B.

[0035] (13) The surface-treated component according to (10) contains the above-mentioned element group C.

[0036] (14) The surface-treated component according to (10) contains the above-mentioned element group D.

[0037] (15) The surface-treated component according to (10) contains the above-mentioned element group E.

[0038] (16) The surface-treated component according to (10) contains the above-mentioned element group F.

[0039] (17) The surface treatment component according to (10), wherein the zinc coating contains at least 4.0% and less than 25.0% Al and 0.3% and less than 12.5% ​​Mg by mass%.

[0040] (18) A composite structure comprising a surface-treated component made of surface-treated steel and soil, wherein the surface-treated steel has a steel as a base material, a zinc-based coating on the surface of the steel, and a chemical conversion treatment layer on the surface of the zinc-based coating, wherein a P-Zn composite layer containing Zn and P exists between the chemical conversion treatment layer and the soil at least a portion of the interface between the surface-treated component and the soil.

[0041] (19) According to the composite structure described in (18), wherein the above-mentioned P-Zn composite layer is a layer having the following chemical composition: by mass%, containing Zn: more than 1.0% and less than 10.0%, P: more than 0.5% and less than 5.0%, with the balance being H, C, O, Si and impurities.

[0042] (20) According to the composite structure described in (19), wherein the chemical composition of the zinc-based coating further contains Al and Mg, and the chemical composition of the P-Zn composite layer further contains at least one of Al: 0% or more and 10.0% by mass or less, and Mg: 0% or more and 10.0% by mass or less to replace a portion of the balance of H, C, O, and Si.

[0043] The effects of the invention

[0044] As described above, according to the present invention, in the surface-treated component using zinc-plated steel and the composite structure using the surface-treated component, excellent corrosion resistance can be achieved even in soil at a depth of about a few centimeters from the soil surface. Attached Figure Description

[0045] Figure 1 This is a schematic diagram used to illustrate a structure placed on the soil surface.

[0046] Figure 2 This is a schematic diagram illustrating the structure of the surface treatment component for an embodiment of the present invention.

[0047] Figure 3 This is a schematic diagram illustrating the structure of a surface treatment component in the same embodiment.

[0048] Figure 4 This is an explanatory diagram illustrating a composite structure of a surface-treated component and soil in the same embodiment.

[0049] Figure 5 This is an explanatory diagram illustrating a composite structure of a surface-treated component and soil in the same embodiment. Detailed Implementation

[0050] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that in this specification and the accompanying drawings, constituent elements having substantially the same functional configuration are omitted from repeated description by using the same reference numerals.

[0051] (Corrosion behavior in soil at a depth of several centimeters from the soil surface)

[0052] Before describing the surface treatment components according to embodiments of the present invention, refer to Figure 1 The corrosion behavior in soil at a depth of about several centimeters from the soil surface, as discovered by the inventors, will be described. Figure 1 This is a schematic diagram used to illustrate a structure placed on the soil surface. Additionally, for convenience, the term "soil at a depth of several centimeters from the soil surface" will sometimes be referred to as the "soil surface layer".

[0053] like Figure 1 The diagram schematically illustrates various structures, such as pedestals supporting solar panels, road signs, guardrails, and traffic signals, installed on the soil surface. In order to more stably position these structures on the soil surface, such as... Figure 1 As shown, most of them will include a part of the structure (e.g., near the lower end of the support column, etc.) in Figure 1 The part enclosed by the dotted line is buried in the soil.

[0054] From the perspective of factors such as production costs, various types of steel are generally used as raw materials for various structures. However, when a structure using various types of steel as raw materials is buried in the soil, there are concerns about the corrosion of the steel used as raw materials.

[0055] The effects of soil on steel corrosion can be summarized by two main factors: moisture retention as a corrosion factor and inhibition of oxygen diffusion as another corrosion factor. Moisture retention increases the corrosion rate, while inhibition of oxygen diffusion decreases it. In soil, the environment remains moist for a longer period, such as after rainfall, compared to the atmosphere. On the other hand, due to the soil, the penetration and diffusion of oxygen from the atmosphere is inhibited, thus reducing the corrosion rate. For the actual corrosion rate in soil, these two factors, in a trade-off relationship, interact, resulting in a corrosion rate that remains relatively constant. Generally, the effect of inhibition of oxygen diffusion is greater than that of moisture retention; therefore, in soil, the corrosion rate is suppressed compared to the atmosphere.

[0056] On the other hand, the situation is quite different in the soil at a depth of several centimeters below the surface (the topsoil). Even in the topsoil, the soil makes it difficult for moisture to evaporate, thus keeping the steel in contact with moisture for a longer period compared to the atmosphere. Furthermore, the topsoil is closer to the atmosphere, allowing for earlier supply of oxygen, thus reducing the effect of oxygen diffusion inhibition caused by the soil. Therefore, combined with the effect of moisture retention, it can be considered that the corrosion inhibition effect from the soil is almost negligible in the topsoil. Thus, the topsoil, which the inventors focused on, represents an extremely harsh corrosive environment compared to soil at a depth of 1 meter or more below the surface.

[0057] In order to study the corrosion behavior of steel in the surface layer of soil, the inventors conducted a study on the corrosion behavior of zinc-plated steel in the surface layer of soil, and found the following results.

[0058] In other words, zinc-coated steel exhibits high corrosion resistance due to the zinc coating covering its surface with zinc corrosion products in the atmosphere. However, it has been determined that the corrosion protection function of these zinc corrosion products is low in the surface layer of soil.

[0059] The inventors observed zinc-based corrosion products formed on zinc-based coatings in the surface layer of soil using a scanning electron microscope (SEM). The results showed that the zinc-based corrosion products formed in the soil surface layer were porous compared to those formed in the atmosphere. This is attributed to the fact that corrosion occurs more rapidly in the soil surface layer compared to the atmosphere.

[0060] Based on the above insights, the inventors have obtained the following insights: In order to improve the corrosion resistance of zinc-plated steel in the surface layer of soil, it is important to change the layer composed of corrosion products formed on the surface of the zinc-plated coating in the surface layer of soil into a dense state.

[0061] To achieve a dense corrosion product layer in the surface layer of the soil, the inventors conducted further research. They found that, in order to improve the corrosion resistance of zinc-plated steel in the surface layer of the soil, it is effective to have phosphorus (P) coexist in the zinc-based corrosion products during their formation. Based on this, the inventors conceived of using a chemical conversion treatment layer containing P as a source of P on the surface of the zinc-based coating.

[0062] Such a chemically converted coating exhibits adequate corrosion resistance in the atmosphere, and together with zinc-based coatings, it can contribute to improving the corrosion resistance of surface-treated components. In the atmosphere, the phosphorus (P) dissolved from the chemically converted coating (presumably in the form of P ions) is washed away by rain, etc., and rarely adheres to the surface of the chemically converted coating. On the other hand, in soil, as mentioned above, there is no water flow, so it is presumed that the dissolved P is adhered to the interface between the chemically converted coating and the soil.

[0063] Therefore, during the formation of zinc-based corrosion products, by dissolving phosphorus (P) from the chemically converted layer at a specific rate, a dense P-Zn composite oxide can be formed at the interface between the chemically converted layer and the soil as a corrosion product. By forming a corrosion product containing such a P-Zn composite oxide at the interface between the chemically converted layer and the soil, and utilizing this corrosion product layer, the chemically converted layer, and the zinc-based coating, the corrosion resistance of surface-treated components in the soil can be improved.

[0064] Furthermore, the inventors' research results show that when the zinc coating is an alloy coating containing Mg and Al in addition to Zn, Mg and Al ions dissolve in the soil in addition to Zn ions, thereby generating a P-Zn-Al-Mg composite oxide, which further improves corrosion resistance.

[0065] Based on the insights described above, the inventors conducted further research and came up with the surface treatment component of the present invention, which is described in detail below.

[0066] (Regarding surface-treated components)

[0067] The following is for reference Figure 2 and Figure 3 The surface treatment components according to embodiments of the present invention will be described in detail. Figure 2 and Figure 3This is a schematic diagram illustrating the structure of the surface treatment component in this embodiment. Additionally, in Figure 2 and Figure 3 For convenience, the coordinate axes shown in the figure are used for explanation.

[0068] As detailed below, the surface-treated component of this embodiment is constructed using surface-treated steel having a zinc-based coating and a chemical conversion treatment layer as a blank. Here, the specific structure of the surface-treated component of this embodiment is not particularly limited. The specific structure of the surface-treated component of this embodiment can be, for example, box-shaped, or plate-shaped using sheet steel, such as for roofs or walls of buildings. Furthermore, the specific structure of the surface-treated component of this embodiment can be, for example, a formed body or joint using various types of steel, such as a solar panel mounting platform; a formed body or joint using various H-beams or prisms, such as a structural skeleton; or a formed body or joint using various steel pipes, such as for various pillars, signs, signal lights, guardrails, etc. This surface-treated component is used, for example, by burying at least a portion of the surface-treated steel in the soil.

[0069] Figure 2 The diagram schematically illustrates a portion of the surface-treated member 1 of this embodiment when viewed from above (Z-axis direction in the figure). For example... Figure 2 As illustrated, the surface treatment component 1 of this embodiment, as described below, uses a surface-treated steel 10, on which a zinc-based plating layer 13 and a chemical conversion treatment layer 15 are provided on the surface of a steel 11 serving as the base material, as the blank.

[0070] Figure 3 Indicatively representing that Figure 2 The surface-treated component 1 shown is cut along the AA cutting line in the Z-axis direction. Figure 3 The cross-sectional view shown corresponds to the view obtained by cutting the surface treatment member 1 of this embodiment along the thickness direction of the surface treatment steel 10, which is the blank of the surface treatment member 1.

[0071] like Figure 3 As illustrated, the surface treatment component 1 of this embodiment is made of surface-treated steel 10, which has a steel 11 as a base material, a zinc-based plating layer 13 on the back surface of the steel 11, and a chemical conversion treatment layer 15 on the surface of the zinc-based plating layer 13.

[0072] The following is a detailed description of the steel 11, the zinc coating 13, and the chemical conversion treatment layer 15.

[0073] <About Steel 11>

[0074] The steel 11 used as the base material for the surface-treated component 1 in this embodiment is not particularly limited, and various steels can be used depending on the mechanical strength (e.g., tensile strength) required for the surface-treated component 1. Examples of such steels 11 include various Al-killed steels, ultra-low carbon steels containing Ti, Nb, etc., high-strength steels that also contain strengthening elements such as P, Si, Mn, etc. in ultra-low carbon steel, and various steels containing other components (Cr, N, Cu, B, Ni, Mg, Ca, V, Co, Zn, As, Y, Zr, Mo, Sn, Sb, Ta, W, Pb, Bi, REM, etc.).

[0075] Alternatively, a pre-plating layer can be applied before the zinc-based plating described later on the steel 11. Examples of metals that can be used in the pre-plating layer include Ni, Sn, or alloys combining these elements. Using pre-plated steel with these pre-plating layers eliminates unplated areas (areas where the plating metal is rejected by oxide films, etc.). This is presumably because when the pre-plated steel is immersed in a hot-dip galvanizing bath, the metal elements in the bath react with the pre-plating layer to form Ni(Sn)-Al-Fe-Zn. The average adhesion amount of the pre-plating layer on each side is preferably 0.2~2.0 g / m². 2 Within the range. By setting the adhesion amount of the pre-coating to 0.2 g / m 2 The above demonstrates a reliable inhibition effect against uncoated areas based on pre-coating, as described above. Furthermore, by setting the pre-coating adhesion amount to 2.0 g / m²... 2 The following method can prevent the leaching of Fe from being suppressed by the pre-plating layer, making it difficult to form Fe-Zn composite oxides, and can achieve the unplating suppression effect mentioned above.

[0076] In addition, there is no particular limitation on the thickness of the steel 11; it can be set appropriately according to the mechanical strength required by the surface-treated component 1.

[0077] <Regarding Zinc-Based Coatings 13>

[0078] The zinc-based coating 13 is formed on the entire surface of the back side of the steel 11 as described above. The zinc-based coating 13 is not particularly limited as long as it contains at least zinc (Zn), and various known zinc-based coatings can be used.

[0079] Examples of zinc-based coatings include hot-dip galvanizing, alloyed hot-dip galvanizing, zinc-nickel plating, zinc-iron plating, zinc-chromium plating, zinc-aluminum plating, zinc-titanium plating, zinc-magnesium plating, zinc-manganese plating, zinc-aluminum-magnesium plating, and zinc-aluminum-magnesium-silicon plating. Furthermore, zinc-based coatings can also be used that contain small amounts of dissimilar metal elements or impurities such as cobalt, molybdenum, tungsten, nickel, titanium, chromium, aluminum, manganese, iron, magnesium, lead, bismuth, antimony, tin, copper, cadmium, and arsenic, or that disperse inorganic substances such as silicon dioxide, aluminum oxide, and titanium dioxide. The plating method is not particularly limited; various known plating methods such as electroplating, hot-dip plating, vapor deposition, dispersion plating, and vacuum plating can be used.

[0080] Among the various zinc-based platings described above, the zinc-based plating layer 13 of this embodiment is more preferably a zinc-based plating layer having the chemical composition detailed below. As the zinc-based plating layer 13, by using a zinc-based plating layer having the chemical composition detailed below, various properties of the surface-treated component 1 of this embodiment, such as corrosion resistance, can be further improved. Hereinafter, a more preferred chemical composition of the zinc-based plating layer 13 described above will be explained in detail.

[0081] Chemical Composition of Zinc-Based Coating 13

[0082] According to a certain method, the zinc-based coating 13 of this embodiment has the following chemical composition: by mass%, it contains Al: 0.10% or more and less than 40.00%, Mg: 0.10% or more and less than 15.00%, and the balance is Zn and impurities.

[0083] Furthermore, in a certain chemical composition of the zinc-based coating 13 in this embodiment, the zinc-based coating 13 is more preferably a coating containing, by mass %: Al: 0.10% or more and less than 40.00%, Mg: 0.10% or more and less than 15.00%, and Zn: 60.00% or more.

[0084] In addition, according to another method, the zinc-based coating 13 of this embodiment has the following chemical composition: by mass%, it contains Al: 0.10% or more and less than 40.00%, Mg: 0.10% or more and less than 15.00%, and also contains one or more elements selected from the group consisting of element group A, element group B, element group C, element group D, element group E and element group F, with the balance being Zn and impurities.

[0085] [Element Group A]: Select one or two elements from the group consisting of Si: less than 2.50% and Fe: less than 5.00%.

[0086] [Element Group B]: Select one or more elements from the group consisting of Sb: less than 0.50%, Pb: less than 0.50%, and Sr: less than 0.50%.

[0087] [Element Group C]: Selected from one or more elements in 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%.

[0088] [Element Group D]: Select one or more elements from the group consisting of Sn: less than 20.00%, Bi: less than 5.00%, and In: less than 2.00%.

[0089] [Element Group E]: Select one or more elements from the group consisting of Ca: less than 3.00%, La: less than 0.50%, Ce: less than 0.50%, and Y: less than 0.50%.

[0090] [Element group F]: B: less than 0.50%

[0091] [Al: ≥0.10% by mass and <40.00% by mass]

[0092] In the preferred embodiment of the zinc-based coating 13, Al is an element required to form the main metallographic structure (Zn-Al-Mg metallographic structure). Therefore, to ensure the corrosion resistance of the coated steel, it is preferable to contain Al at a specified or higher content. If the Al content in the zinc-based coating 13 is less than 0.10% by mass, the aforementioned corrosion resistance may not be guaranteed. Therefore, in the zinc-based coating 13 of this embodiment, the Al content is preferably 0.10% by mass or more. The Al content is preferably 3.00% by mass or more, more preferably 4.00% by mass or more, and even more preferably 6.00% by mass or more. By keeping the Al content within the range described above, the corrosion resistance of the coated steel can be ensured.

[0093] On the other hand, when the Al content in the zinc-based coating 13 is 40.00% by mass or more, the excessive increase of the Al phase, which functions as a cathode, in a corrosive environment can easily lead to corrosion of the steel 11, potentially compromising the corrosion resistance of the coated steel. Therefore, in the zinc-based coating 13 of this embodiment, the Al content is preferably less than 40.00% by mass. The Al content is preferably less than 25.00% by mass, more preferably less than 25.00% by mass, and even more preferably less than 20.00% by mass.

[0094] [Mg: ≥0.10% by mass and <15.00% by mass]

[0095] In the preferred embodiment of the zinc-based coating 13, Mg is an element required to form the main metallographic structure (Zn-Al-Mg metallographic structure). Therefore, to ensure the corrosion resistance of the coated steel, it is preferable to contain Mg at a specified or higher content. If the Mg content in the zinc-based coating 13 is less than 0.10% by mass, the aforementioned corrosion resistance may not be guaranteed. Therefore, in the zinc-based coating 13 of this embodiment, the Mg content is preferably 0.10% by mass or more. The Mg content is preferably 0.30% by mass or more, and more preferably 3.00% by mass or more. By keeping the Mg content within the range described above, the corrosion resistance of the coated steel can be ensured.

[0096] On the other hand, when the Mg content in the zinc-based coating 13 is 15.00% by mass or more, anodic dissolution of the zinc-based coating can easily proceed under corrosive conditions, which may compromise the corrosion resistance of the coated steel. Therefore, in the zinc-based coating 13 of this embodiment, the Mg content is preferably less than 15.00% by mass. The Mg content is preferably less than 12.50% by mass, and more preferably less than 12.00% by mass. By keeping the Mg content within the range described above, corrosion resistance of the coated steel can be ensured.

[0097] In the zinc-based coating 13 of this embodiment, the balance of Al and Mg is Zn and impurities.

[0098] In the preferred embodiment of the zinc-based coating 13, Zn is an element required to form the main metallographic structure (Zn-Al-Mg metallographic structure) and is an important element for improving the corrosion resistance of the coated steel. Furthermore, the zinc-based coating 13 contains Al and Mg within the aforementioned range, and also contains Zn, thereby ensuring the required corrosion resistance of the coated steel.

[0099] Next, in a preferred embodiment of the zinc-based coating 13, the chemical composition of the zinc-based coating 13 may include element groups A to F.

[0100] It should be noted that in another embodiment of the zinc-based coating 13, when it contains at least one of the elements belonging to element group A to element group F, it is preferable that it contains at least one of the elements belonging to element group A to element group F within the following content range and with a total content of 60.00% by mass or less.

[0101] By setting the total content of elements belonging to element groups A to F to 60.00% by mass or less, the effects resulting from the addition of each element, as detailed below, can be enjoyed without any mutual impairment. The total content of elements belonging to element groups A to F is preferably 50.00% by mass or less, and more preferably 40.00% by mass or less.

[0102] ◇Element Group A

[0103] In another embodiment of the zinc-based coating 13, the element group A that may be contained in the zinc-based coating 13 will be described. At least one element in element group A shown below is an element contained in the zinc-based coating 13 that can replace a portion of the balance Zn.

[0104] [Element Group A]: Select one or two elements from the group consisting of Si: less than 2.50% and Fe: less than 5.00%.

[0105] [Si: 0~2.50% by mass]

[0106] In another embodiment of the zinc-based coating 13, it is also possible to consider a case where Si is not present, and therefore its content is limited to 0% by mass. On the other hand, Si is an element that can suppress the excessive growth of Fe-Al metallographic structure formed at the interface between the zinc-based coating 13 and the steel 11, and further improve the adhesion between the zinc-based coating 13 and the steel 11. When the zinc-based coating 13 contains Si, in order to suppress the excessive growth of Fe-Al metallographic structure, the Si content is preferably 0.05% by mass or more, and more preferably 0.20% by mass or more. On the other hand, when the Si content exceeds 2.50% by mass, excessive Si may form high-melting-point intermetallic compounds with Mg, which may hinder the formation of Al-Mg oxides that have the effect of suppressing Zn evaporation during welding.

[0107] Furthermore, if the Si content in the plating bath used to manufacture the zinc-based coating 13 is too high, the viscosity of the plating bath increases beyond what is necessary, and the operability (hereinafter referred to as "plating operability") during the manufacture of the coated steel may decrease. Therefore, from the viewpoint of plating operability, the Si content in the plating bath is adjusted. The Si content in the zinc-based coating 13 is preferably 1.50% by mass or less, more preferably 1.00% by mass or less.

[0108] [Fe: 0~5.00% by mass]

[0109] In the zinc-based coating 13, elements constituting the steel are sometimes mixed in from the steel 11, which serves as the base material. Particularly in hot-dip galvanizing, due to the interdiffusion of elements caused by the solid-liquid reaction between the steel 11 and the zinc-based coating 13, elements constituting the steel 11 easily mix into the zinc-based coating 13. Through this mixing, the zinc-based coating 13 typically contains a specified amount of Fe, usually 0.01% by mass or more. Promoting this interdiffusion improves the adhesion between the steel 11 and the zinc-based coating 13. From the viewpoint of improving the adhesion between the steel 11 and the zinc-based coating 13, the Fe content in the zinc-based coating 13 is preferably 0.20% by mass or more.

[0110] Furthermore, Fe can be intentionally added to the plating bath used in manufacturing the zinc-based coating 13 without impairing the effects of the present invention. However, if the Fe content in the plating bath is increased, a high-melting-point intermetallic compound of Fe and Al will form in the plating bath. In this case, the high-melting-point intermetallic compound adheres to the zinc-based coating 13 as dross, which tends to significantly reduce the appearance quality and is therefore undesirable. From this point of view, the Fe content in the plating bath is adjusted. The Fe content in the zinc-based coating 13 is preferably 5.00% by mass or less. More preferably, the Fe content in the zinc-based coating 13 is 3.00% by mass or less, and even more preferably 2.00% by mass or less, 1.00% by mass or less, or 0.50% by mass or less.

[0111] ◇Element Group B

[0112] In another embodiment of the zinc-based coating 13, the element group B that may be contained in the zinc-based coating 13 will be described. At least one element in element group B shown below is an element contained in the zinc-based coating 13 that can replace a portion of the balance Zn.

[0113] [Element Group B]: Select one or more elements from the group consisting of Sb: less than 0.50%, Pb: less than 0.50%, and Sr: less than 0.50%.

[0114] [Sb: 0~0.50% by mass]

[0115] [Pb: 0~0.50% by mass]

[0116] [Sr: 0~0.50% by mass]

[0117] In another embodiment of the zinc-based coating 13, it is also possible to consider a case where Sb, Pb, and Sr are not present, and therefore the lower limit of the content of these elements is 0% by mass. On the other hand, if the zinc-based coating 13 contains at least one of Sb, Pb, and Sr, zinc flowers will form on the surface of the zinc-based coating 13, thereby improving the metallic luster. Therefore, from the viewpoint of further improving the designability of the coated steel, it is preferable that the zinc-based coating 13 contains at least one of Sb, Pb, and Sr. This improvement in designability is manifested when the content of at least one of Sb, Pb, and Sr is 0.05% by mass or more. Therefore, when the zinc-based coating 13 contains at least one of Sb, Pb, and Sr, the content of each of these elements is preferably set independently to 0.05% by mass or more.

[0118] On the other hand, when a zinc-based coating 13 is formed in which the content of any one of Sb, Pb, and Sr exceeds 0.50% by mass, the amount of dross generated in the plating bath used to form the zinc-based coating 13 increases, which may prevent the production of coated steel with good coating properties. Therefore, the content of Sb, Pb, and Sr in the zinc-based coating 13 is preferably 0.50% by mass or less, each independently. The content of Sb, Pb, and Sr is preferably 0.20% by mass or less, each independently.

[0119] ◇Element Group C

[0120] In another embodiment of the zinc-based coating 13, the element group C that may be contained in the zinc-based coating 13 will be described. At least one element in element group C shown below is an element contained in the zinc-based coating 13 that can replace a portion of the balance Zn.

[0121] [Element Group C]: Selected from one or more elements in 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%.

[0122] [Cu: ≥0.25% by mass]

[0123] [Ti: 0% by mass and less than 0.25% by mass]

[0124] [Cr: ≥0.25% by mass]

[0125] [Nb: ≥0.25% by mass]

[0126] [Ni: ≥0.25% by mass]

[0127] [Mn: ≥0% by mass and <0.25% by mass]

[0128] [Co: ≥0.25% by mass]

[0129] [V: 0% by mass and less than 0.25% by mass]

[0130] In another embodiment of the zinc-based coating 13, it is also possible to consider a case where Cu, Ti, Cr, Nb, Ni, Mn, Co, and V are not present, and therefore the lower limit of the content of these elements is 0% by mass. On the other hand, if the zinc-based coating 13 contains at least one of Cu, Ti, Cr, Nb, Ni, Mn, Co, and V, then when welding the coated steel, these elements are introduced into the Fe-Al metallographic structure formed by welding, which can further improve the corrosion resistance of the formed weld. This improvement in the corrosion resistance of the weld is manifested when the content of at least one of Cu, Ti, Cr, Nb, Ni, Mn, Co, and V in the zinc-based coating 13 is 0.05% by mass or more. Therefore, when the zinc-based coating 13 contains at least one of Cu, Ti, Cr, Nb, Ni, Mn, Co, and V, the content of each of these elements is preferably set to 0.05% by mass or more independently.

[0131] On the other hand, when a zinc-based coating 13 is formed in which the content of any one of Cu, Ti, Cr, Nb, Ni, Mn, Co, and V is 0.25% by mass or more, these elements form various intermetallic compounds in the plating bath used to form the zinc-based coating 13, leading to an increase in the viscosity of the plating bath, which may prevent the production of coated steel with good plating properties. Therefore, the content of Cu, Ti, Cr, Nb, Ni, Mn, Co, and V in the zinc-based coating 13 is preferably each independently set to less than 0.25% by mass. The content of Cu, Ti, Cr, Nb, Ni, Mn, Co, and V is preferably each independently set to 0.20% by mass or less.

[0132] ◇Element Group D

[0133] In another embodiment of the zinc-based coating 13, the element group D that may be contained in the zinc-based coating 13 will be described. At least one element in element group D shown below is an element contained in the zinc-based coating 13 that can replace a portion of the balance Zn.

[0134] [Element Group D]: Select one or more elements from the group consisting of Sn: less than 20.00%, Bi: less than 5.00%, and In: less than 2.00%.

[0135] [Sn: 0% or more by mass and less than 20.00% by mass]

[0136] [Bi: 0% by mass and less than 5.00% by mass]

[0137] [In: 0% by mass and less than 2.00% by mass]

[0138] In another embodiment of the zinc-based coating 13, it is also possible to exclude Sn, Bi, and In, thus the lower limit of the content of these elements is 0% by mass. On the other hand, Sn, Bi, and In form intermetallic compounds with Mg in the zinc-based coating 13, which can improve the weldability of the zinc-based coating 13. In addition, these intermetallic compounds all have high melting points, so they do not evaporate after welding when welding coated steel, and remain as intermetallic compounds. By having these elements present, corrosion resistance and corrosion protection can be improved, and the corrosion resistance of the welded part during welding can also be improved. This improvement in corrosion resistance is manifested when the content of at least any one of Sn, Bi, and In in the zinc-based coating 13 is 0.05% by mass or more. Therefore, when the zinc-based coating 13 contains at least any one of Sn, Bi, and In, the content of each of these elements is preferably set to 0.05% by mass or more independently.

[0139] On the other hand, excessive Sn addition increases the amount of intermetallic compounds formed, which may reduce the corrosion resistance of the zinc-based coating 13 after welding. Furthermore, excessive Bi and In addition may make the zinc-based coating 13 brittle and prone to peeling, and may also reduce its corrosion resistance after welding. These phenomena become significant when the Sn content exceeds 20.00% by mass, when the Bi content is 5.00% by mass or more, or when the In content is 2.00% by mass or more. Therefore, the Sn content is preferably 20.00% by mass or less, the Bi content is preferably less than 5.00% by mass, and the In content is preferably less than 2.00% by mass. The Sn content is more preferably 10.00% by mass or less, the Bi content is more preferably 3.00% by mass or less, and the In content is more preferably 1.00% by mass or less.

[0140] ◇Element Group E

[0141] In another embodiment of the zinc-based coating 13, the element group E that may be contained in the zinc-based coating 13 will be described. At least one element in element group E shown below is an element contained in the zinc-based coating 13 that can replace a portion of the balance Zn.

[0142] [Element Group E]: Select one or more elements from the group consisting of Ca: less than 3.00%, La: less than 0.50%, Ce: less than 0.50%, and Y: less than 0.50%.

[0143] [Ca: 0~3.00% by mass]

[0144] In another embodiment of the zinc-based coating 13, it is also possible to consider a case where it does not contain Ca, and therefore its content is limited to 0% by mass. On the other hand, if Ca is contained in the plating bath used to manufacture the zinc-based coating 13, the dross generated during the plating operation as the Mg concentration increases can be reduced, thereby improving the plating operability.

[0145] Furthermore, if the zinc-based coating 13 contains Ca, it forms intermetallic compounds with Al and Zn. Moreover, if the zinc-based coating 13 contains Si along with Ca, Ca forms intermetallic compounds with Si. These intermetallic compounds have high melting points and stable structures, thus suppressing liquid metal embrittlement (LME) during welding of plated steel. When the zinc-based coating 13 contains Ca, setting the Ca content to 0.01% by mass or more demonstrates both improved coating operability and suppression of LME during welding. More preferably, the Ca content in the zinc-based coating 13 is 0.05% by mass or more.

[0146] On the other hand, if the Ca content in the zinc-based coating 13 exceeds 3.00% by mass, the corrosion resistance of the coated steel may decrease. From this point of view, the Ca content in the zinc-based coating 13 is preferably 3.00% by mass or less. The Ca content in the zinc-based coating 13 is preferably 2.00% by mass or less, and more preferably 1.00% by mass or less.

[0147] [La: 0% by mass and less than 0.50% by mass]

[0148] [Ce: 0% by mass and less than 0.50% by mass]

[0149] [Y: 0% or more by mass and less than 0.50% by mass]

[0150] In another embodiment of the zinc-based coating 13, it is also possible to consider a case where La, Ce, and Y are not present, and therefore the lower limit of the content of these elements is 0% by mass. On the other hand, La, Ce, and Y are elements that exhibit approximately the same effect as Ca. This is because the atomic radii of each element are close to the atomic radius of Ca, and if these elements are present in the zinc-based coating 13, they will displace Ca.

[0151] The improved plating operability and LME suppression during welding are achieved by independently setting the content of each of these elements to 0.01% by mass or more. Therefore, when at least one of La, Ce, and Y is contained, the content of each of these elements is preferably independently set to 0.01% by mass or more. The content of La, Ce, and Y in the zinc-based coating 13 is more preferably independently set to 0.05% by mass or more.

[0152] On the other hand, if the content of La, Ce, and Y in the plating bath used to manufacture the zinc-based coating 13 is too high, the viscosity of the plating bath increases beyond what is necessary, and the plating operability may decrease. Therefore, from the viewpoint of plating operability, the content of La, Ce, and Y in the plating bath is adjusted. The content of La, Ce, and Y is preferably each independently less than 0.50% by mass, less than 0.50% by mass, and less than 0.50% by mass. The content of La, Ce, and Y is preferably each independently less than 0.10% by mass.

[0153] ◇Element group F

[0154] In another embodiment of the zinc-based coating 13, the element group F that may be contained in the zinc-based coating 13 will be described. The elements in element group F shown below are elements contained in the zinc-based coating 13 that can replace a portion of the balance Zn.

[0155] [Element group F]: B: less than 0.50%

[0156] [B: 0% by mass or more and less than 0.50% by mass]

[0157] In another embodiment of the zinc-based coating 13, it is also possible to consider a case where B is not present, and therefore its content is limited to 0% by mass. On the other hand, if B is present in the zinc-based coating 13, it has a further effect of suppressing LME. This is presumably because if B is present in the zinc-based coating 13, it combines with at least one of Zn, Al, Mg, and Ca to form various intermetallic compounds. In addition, it is believed that by having B in the zinc-based coating 13, B diffuses from the zinc-based coating 13 to the steel 11, and through grain boundary strengthening, it has a further effect of suppressing LME of the steel 11. Furthermore, the various intermetallic compounds formed by B have extremely high melting points, so it is presumably also effective in suppressing Zn evaporation during welding. These improved effects are manifested by containing 0.05% by mass or more of B. Therefore, in the case where B is present, the content of B is preferably 0.05% by mass or more.

[0158] On the other hand, if the plating bath contains excessive amounts of B in order to include B in the zinc-based coating 13, it will cause a sharp increase in the plating melting point, reducing the plating operability and potentially making it impossible to produce coated steel with excellent plating properties. This reduction in plating operability becomes significant when the B content is 0.50% by mass or more, therefore the B content is preferably less than 0.50% by mass. The B content is more preferably 0.10% by mass or less.

[0159] Methods for measuring chemical composition

[0160] The chemical composition of the aforementioned zinc-based coating 13 can be measured using ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometry) or ICP-MS (Inductively Coupled Plasma Mass Spectrometry). It should be noted that ICP-AES is used for analysis of chemical composition down to 0.1% by mass, while ICP-MS is used for analysis of trace amounts of chemical composition less than 0.1% by mass. The coated steel is immersed in a 10% HCl aqueous solution containing an inhibitor for approximately 1 minute, and the zinc-based coating is peeled off to prepare a solution containing the dissolved zinc-based coating. Analysis of the obtained solution using ICP-AES or ICP-MS yields the overall average chemical composition of the zinc-based coating.

[0161] Regarding the adhesion amount of zinc-based coating 13

[0162] The zinc coating 13 described above preferably has an average adhesion amount of 10.0 g / m² on each side of the steel. 2 The above, more preferably 50.0 g / m 2 That's all. Furthermore, the amount of zinc-based coating 20 applied is preferably 200.0 g / m² on average per side of the steel. 2 The preferred value is 150.0 g / m³. 2 Therefore, by ensuring that the amount of zinc-based plating 13 adheres within the range described above, the surface-treated component 1 of this embodiment can exhibit sufficient corrosion resistance.

[0163] It should be noted that, regarding the adhesion amount of the zinc-based coating 13, a 30mm × 30mm sample is cut from the surface treatment component 1, and the mass of the sample is measured beforehand. Then, a protective tape that prevents moisture from passing through is attached to one side of the sample to prevent the zinc-based coating 13 on that side from dissolving in the next process. Based on this, the sample is immersed in a 10% HCl aqueous solution with added inhibitor, and the zinc-based coating 13 on the side without the protective tape is acid-washed and peeled off. The mass of the sample after acid washing is measured. Based on the change in sample mass before and after acid washing, the average adhesion amount of the zinc-based coating 13 on each side can be determined. It should be noted that, in this embodiment, the adhesion amount of the chemical conversion treatment layer 15 with the thickness detailed below is 1 g / m². 2 On the other hand, it is difficult to remove the chemical conversion treatment layer 15 by physical or chemical methods alone. Therefore, when determining the amount of zinc-based coating 13, the chemical conversion treatment layer 15 can be left unremoved from the sample.

[0164] <Regarding Chemical Conversion Treatment Layer 15>

[0165] In this embodiment, the chemical conversion treatment layer 15 is formed on the entire surface of the zinc-based plating layer 13 as described above. Here, the chemical conversion treatment layer 15 of this embodiment contains at least a compound containing phosphorus (P). At least a portion of this compound containing phosphorus (P) serves as a source of phosphorus (P) for generating the previously described P-Zn composite oxide.

[0166] Regarding the leaching amount of P from chemically converted layer 15

[0167] For the chemical conversion treatment layer 15 of this embodiment, it will be compared with the size 1m 2 When the surface-treated steel 10 is immersed in ion-exchange water at a temperature of 35-45°C for 60 minutes, the amount of P dissolved from the chemically converted steel layer 15 into the ion-exchange water is 5-50 mg / m² per single side. 2 Here, the water temperature of 35~45℃ mentioned above refers to the temperature of water under natural conditions. Furthermore, although the exact form of phosphorus P dissolved from the chemical conversion treatment layer 15 is unclear, it is presumed to be dissolved in the form of phosphate ions.

[0168] The dissolution rate of P mentioned above is less than 5 mg / m³. 2 In this case, the amount of P dissolved from the chemical conversion treatment layer 15 is too small to sufficiently generate the corrosion product layer composed of P-Zn composite oxides as described above, thus failing to improve the corrosion resistance of the surface-treated component 1. By making the P dissolution amount 5 mg / m³... 2The above process generates a corrosion product layer composed of P-Zn composite oxides, which improves the corrosion resistance of the surface-treated component 1. The preferred leaching amount of P is 10 mg / m³. 2 The above, more preferably 15 mg / m² 2 above.

[0169] On the other hand, in the surface treatment component 1 of this embodiment, it is important to consider not only the corrosion resistance of the surface treatment component 1 disposed in the soil, but also the corrosion resistance of the surface treatment component 1 in parts not present in the soil (e.g., parts present in the atmosphere). When the leaching amount of P exceeds 50 mg / m³... 2 In this case, the amount of P leached from the chemical conversion treatment layer 15 becomes excessive, resulting in the inability to ensure the corrosion resistance of the surface-treated component 1 not only in the soil but also in parts not present in the soil. By making the P leaching amount 50 mg / m³... 2 The following measures ensure the corrosion resistance of the portion not present in the soil and improve the corrosion resistance of the portion present in the soil. The preferred leaching amount of P is 45 mg / m³. 2 the following.

[0170] Here, when determining the amount of phosphorus (P) dissolved, ion-exchanged water of grade A1 or higher as specified in JIS K0557:1998 is prepared and preheated to a temperature of 35-45°C. Based on this, a sample measuring 40mm x 40mm (top view) is cut from the surface-treated component 1 of interest, and the cut sample is placed in a covered container with a diameter of 150mm and a volume of 3000mL. Then, 2000ml of the aforementioned ion-exchanged water at a temperature of 35-45°C is poured in, and the mixture is left to stand for 60 minutes while maintaining the temperature within the 35-45°C range. The ion-exchanged water is then collected from the container, and the amount of dissolved P is determined using ICP-MS. For example, an Agilent Technologies Agilent 8800 model can be used as the ICP-MS.

[0171] Integral Intensity of Peaks in X-ray Photoelectron Spectroscopy Results

[0172] As described above, in the surface-treated component 1 of this embodiment, the corrosion products containing P-Zn composite oxides on the surface of the surface-treated component 1 disposed in the soil have the effect of improving the corrosion resistance in the soil, and the properties of the P-Zn composite oxides affect the effect of improving corrosion resistance. From this perspective, repeated in-depth studies were conducted, and the results showed that, in the narrow P2p spectrum obtained by analyzing the surface of the chemical conversion treated layer 15 of this embodiment using X-ray photoelectron spectroscopy (XPS), when the ratio of the integrated intensity of the peak with a maximum value at 133.90 ± 0.25 eV to the integrated intensity of the peak with a maximum value at 132.80 ± 0.25 eV is in the range of 0.20 to 0.50, the corrosion resistance of the surface-treated component 1 in the soil is further improved compared to cases where this intensity ratio is not met. The reason for this is not yet clear, but it is speculated that it may be due to the change in the morphology of the dissolved P ions, which alters the morphology of the P-Zn composite oxides, thus improving the barrier properties.

[0173] By making the ratio of the integrated intensity 0.20 or higher, the surface-treated member 1 in the chemical conversion treatment layer 15 of this embodiment exhibits superior corrosion resistance in soil. The ratio of the integrated intensity is more preferably 0.25 or higher, and even more preferably 0.30 or higher.

[0174] On the other hand, by making the ratio of the aforementioned integral strength 0.50 or less, the surface-treated component 1 exhibits superior corrosion resistance in soil. More preferably, the ratio of the aforementioned integral strength is 0.45 or less, and even more preferably 0.40 or less.

[0175] Here, the ratio of the integral intensity described above can be determined as follows.

[0176] First, X-ray photoelectron spectroscopy was used to measure three arbitrary locations on the surface of the surface-treated component 1 of interest. It should be noted that if a portion of the surface-treated component 1 has a welded area, the area from the end of that welded area to 5 cm is excluded from the measurement. For example, an 800 μm × 300 μm area on the surface of surface-treated steel (the surface of the chemical conversion treatment layer 15) without pretreatment such as cleaning or sputtering was analyzed under the following conditions. The obtained P2p spectrum was separated into a peak with a maximum value at 133.90 ± 0.25 eV and a peak with a maximum value at 132.80 ± 0.25 eV. The integrated intensity of this peak was calculated, and the integrated intensity ratio was calculated based on this integrated intensity.

[0177] However, the narrow spectrum obtained through analysis sometimes shows a left-right shift in peak position depending on the measuring equipment and conditions. Therefore, firstly, the obtained spectrum is corrected so that the peak position (the position with the maximum value) of the C1s spectrum is 284.8 eV. Then, the P2p spectrum is separated into a peak with a maximum value at 133.90 ± 0.25 eV and a peak with a maximum value at 132.80 ± 0.25 eV.

[0178] During the measurement, the P2p spectrum was measured in the region of 130.00–135.00 eV. Peak separation was performed based on this 130.00–135.00 eV range, extended from this range according to the spectrum. Furthermore, the half-width at half-maximum (WWHM) of the peak with a maximum at 133.90 ± 0.25 eV was assumed to be 1.35 ± 0.20 eV, and the WWHM of the peak with a maximum at 132.80 ± 0.25 eV was assumed to be 1.15 ± 0.20 eV. Since no pretreatment was performed during the analysis, careful sample handling was necessary to minimize the adhering of oil, contaminants, etc.

[0179] It should be noted that the XPS measurement conditions are as follows.

[0180] (Measurement conditions)

[0181] X-ray source: monoAlKα (1486.6 eV)

[0182] X-ray output: 15kV 25W

[0183] X-ray diameter: 100μmφ

[0184] Vacuum level in the analysis chamber (before sample introduction): 2.2 × 10⁻⁶ -9 torr (It should be noted that 1 torr is approximately 133.32 Pa)

[0185] Detection angle: 45°

[0186] Neutralization: electron neutralization, ion neutralization

[0187] Data analysis software: MultiPak V.8.0 (Made by ULVAC-PHI)

[0188] On Depth Distribution in Energy-Dispersive X-ray Spectroscopy

[0189] Furthermore, in the chemical conversion layer 15 of this embodiment, when energy dispersive X-ray spectroscopy (EDS) is used to perform line analysis on the chemical conversion layer 15 from its surface to the interface with the zinc-based plating layer 13, the average concentration of P on the surface side of the chemical conversion layer 15 is preferably 1 to 20% by mass. Here, the surface side of the chemical conversion layer 15 refers to the range from half the thickness of the chemical conversion layer 15 to its surface.

[0190] By ensuring that the average concentration of P on the surface side of the chemical conversion treatment layer 15 is 1% by mass or more, the amount of P dissolved from the chemical conversion treatment layer 15 can be sufficiently ensured, and the surface-treated member 1 of this embodiment exhibits superior corrosion resistance. More preferably, the average concentration of P on the surface side is 2% by mass or more, and even more preferably 3% by mass or more.

[0191] On the other hand, by making the average concentration of P on the surface side of the chemical conversion treatment layer 15 5% by mass or less, the leaching of excessive P can be suppressed, and the amount of P leached from the chemical conversion treatment layer 15 is sufficiently ensured. Therefore, the surface-treated member 1 of this embodiment exhibits superior corrosion resistance. The average concentration of P on the surface side is more preferably 15% by mass or less, and even more preferably 10% by mass or less.

[0192] Here, the average concentration of P in the depth distribution described above can be determined as follows.

[0193] First, a cross-sectional sample of the chemical conversion treatment layer 15 is obtained by cutting along the thickness direction (perpendicular to the surface of the surface treatment component 1) at any position on the surface of the surface treatment component 1 of interest. Then, from any position on the surface of the chemical conversion treatment layer 15 in this cross-sectional sample, along the thickness direction (perpendicular to the surface of the chemical conversion treatment layer 15, for example, ...) Figure 3The analysis is performed along the Z-axis direction until it reaches the interface with the zinc-based coating 13. The analysis is then performed using an EDS analysis device on a scanning electron microscope (SEM, such as the JEOL JSM-7000F), and the results are mapped. Here, the elements of interest in the above analysis are at least P, Zn, Al, Mg, Si, Ti, Zr, C, and O; mapping analysis can be performed on all elements. Among the elements of interest, Zn, Al, and Mg are derived from the zinc-based coating, while Si, Ti, Zr, C, and O are derived from the chemical conversion treatment layer. The SEM-EDS observation conditions can be set, for example, to an accelerating voltage of 15 kV, an irradiation current of 4.9147 nA, 10 scans, and a magnification of 500x.

[0194] The extent of the chemical conversion treatment layer 15 can be easily determined by those skilled in the art from the SEM image. In this embodiment, within the depth distribution of each element obtained as described above, the region corresponding to the P concentration of 0.01% or higher is designated as the area of ​​the chemical conversion treatment layer 15. This allows the thickness of the chemical conversion treatment layer 15 within the obtained depth distribution to be determined. The location corresponding to half the thickness thus obtained is designated as the half-thickness location of the chemical conversion treatment layer 15.

[0195] Based on this, according to the depth distribution of P element obtained, the average concentration of P element from the position of 1 / 2 thickness as described above to the surface of the chemical conversion layer 15 (the surface on the opposite side of the interface between the zinc plating layer 13 and the chemical conversion layer 15) is calculated.

[0196] The same measurements as described above are performed at any 5 locations on the obtained cross-sectional sample. The average value of the average concentration of multiple P elements obtained at the number of measurement sites is taken as the "average concentration of P on the surface side of the chemical conversion treatment layer 15".

[0197] Regarding the P concentration in chemical conversion treatment layer 15

[0198] In the chemical conversion treatment layer 15 of this embodiment, the P concentration, converted to P, is preferably 0.1 to 15.0% by mass. By making the P concentration 0.1% by mass or more, the chemical conversion treatment layer 15 of this embodiment can ensure that it has a sufficient amount of P element required to achieve excellent corrosion resistance regardless of the presence of P in the soil, and the surface treatment component 1 of this embodiment exhibits superior corrosion resistance. The P concentration of the chemical conversion treatment layer 15 is more preferably 1.0% by mass or more, and even more preferably 2.0% by mass or more.

[0199] Here, the concentration of P mentioned above can be determined as follows.

[0200] First, a cross-sectional sample of the chemical conversion treatment layer 15 is obtained by cutting along the thickness direction of the surface-treated component 1 at any position in the cross-sectional sample. Then, from any position on the surface of the chemical conversion treatment layer 15 in this cross-sectional sample, along the thickness direction of the chemical conversion treatment layer 15 (the direction perpendicular to the surface of the chemical conversion treatment layer 15, for example, ...), ... Figure 3 The electron microscope (EDS) is used to analyze the surface along the Z-axis until it reaches the interface with the zinc-based coating 13. The analysis is performed using an EDS analyzer on a scanning electron microscope (SEM, such as the JEOL JSM-7000F). The results are then mapped. Here, the element of interest in the analysis is P. The SEM-EDS observation conditions can be set as follows: accelerating voltage: 15 kV, irradiation current: 4.9147 nA, number of scans: 10, and magnification: 500x.

[0201] The extent corresponding to the chemical conversion treatment layer 15 can be easily determined by those skilled in the art based on SEM images. However, in this embodiment, the extent corresponding to the chemical conversion treatment layer 15 is determined based on the measurement results of the P concentration in the range from the surface of the chemical conversion treatment layer 15 to the surface of the zinc-based plating layer 15. More specifically, in the depth distribution of each element obtained as described above, the portion corresponding to a P concentration of 0.01% or higher is defined as the region of the chemical conversion treatment layer 15. Based on this, the average concentration of P element in the region of the chemical conversion treatment layer 15 is calculated according to the obtained depth distribution of P element.

[0202] The same measurements as described above are performed at any 5 locations of the obtained cross-sectional sample. The average value of the average concentration of multiple P elements obtained at the number of measurement sites is used as the "P concentration converted to P in the chemical conversion treatment layer 15".

[0203] Specific examples of compounds containing phosphorus (P).

[0204] In the chemical conversion treatment layer 15 of this embodiment, various phosphates and their salts can be used as compounds containing phosphorus element P as described above.

[0205] Examples of phosphoric acids and their salts include orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid, hypophosphorous acid, phosphorous acid, hypophosphoric acid, triphosphoric acid, tetraphosphoric acid, and their salts; ammonium salts such as triammonium phosphate and diammonium hydrogen phosphate; phosphonic acids such as aminotris(methylenephosphonic acid), 1-hydroxyethylidene-1,1-diphosphonic acid, ethylenediaminetetra(methylenephosphonic acid), and diethylenetriaminepenta(methylenephosphonic acid); and organic phosphoric acids such as phytic acid and their salts. It should be noted that, as phosphates, salts other than ammonium salts include metal salts containing Na, Mg, Al, K, Ca, Mn, Ni, Zn, and Fe. Phosphoric acids and their salts can be used alone or in combination of two or more.

[0206] Furthermore, in the chemical conversion treatment layer 15 of this embodiment, among the various compounds described above, it is more preferable to use a compound that also functions as a so-called anti-rust pigment.

[0207] Regarding other components in chemical conversion treatment layer 15

[0208] In addition to the phosphorus-containing compound described above, the chemical conversion treatment layer 15 of this embodiment also contains one or more film-forming components selected from the group consisting of silane coupling agents, valve metals, and organic resins. By further containing such components, the chemical conversion treatment layer 15 of this embodiment can improve the film-forming properties after coating with the chemical conversion treatment solution, the barrier properties (density) of the coating against corrosive agents such as moisture and corrosive ions, and the adhesion of the coating to the plated surface, thereby contributing to improved corrosion resistance of the coating.

[0209] [Silane coupling agent]

[0210] Examples of silane coupling agents include 3-(2-aminoethyl)aminopropyltrimethoxysilane, 3-(2-aminoethyl)aminopropylmethyldimethoxysilane, 3-(2-aminoethyl)aminopropyltriethoxysilane, 3-(2-aminoethyl)aminopropylmethyldiethoxysilane, 3-(2-aminoethyl)aminopropylmethyldimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropylmethyldimethoxysilane, 3-methacryloyloxypropyltriethoxysilane, 3-methacryloyl... 3-Methyltriethoxysilane, 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-mercaptopropylmethyldimethoxysilane Dimethyldimethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, vinyltriacetoxysilane, 3-chloropropyltrimethoxysilane, 3-chloropropylmethyldimethoxysilane, 3-chloropropyltriethoxysilane, 3-chloropropylmethyldiethoxysilane, 3-anilinepropyltrimethoxysilane, 3-anilinepropylmethyldimethoxysilane, 3-anilinepropyltriethoxysilane, 3-anilinepropylmethyldiethoxysilane, vinyltrimethoxysilane, vinylmethyldimethoxysilane Silanes, vinyltriethoxysilanes, vinylmethyldiethoxysilanes, 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, etc.

[0211] [Valve Metal]

[0212] Valve metals are metals whose oxides exhibit high insulation resistance. Examples of valve metals include Ti, Zr, Hf, V, Mo, Nb, Ta, and W. The chemical conversion treatment layer 15 of this embodiment may contain one or more of these valve metals. It should be noted that the type of valve metal compound used is not particularly limited as long as it is soluble in water. Examples of valve metal compounds include ammonium salts, sodium salts, potassium salts, oxides, non-oxygen acid salts, oxygen acid salts, hydroxides, phosphates, nitrates, sulfates, and organic acid salts containing the aforementioned metals. Among these compounds, oxides, oxygen acid salts, and phosphates of the aforementioned metals are particularly preferred.

[0213] [Organic resin]

[0214] As organic resins, known organic resins such as polyester resins, polyurethane resins, epoxy resins, phenolic resins, acrylic resins, polyolefin resins, and fluororesins can be used. Alternatively, film-forming resin components such as modified resins of these resins can be crosslinked with crosslinking components of butylated melamine resins, methylated melamine resins, butylmethyl mixed melamine resins, urea-formaldehyde resins, isocyanate resins, or mixtures of these resins. Furthermore, electron beam curable resins and ultraviolet curable resins can also be used as organic resins. To further improve adhesion to the coating, at least one of resins (polyester resins, polyurethane resins, epoxy resins, acrylic resins, etc.) having polar sites and polar functional groups in their molecular chains is preferred. These organic resins can be used alone or in combination of two or more.

[0215] Here, the total content of silane coupling agent, valve metal, and organic resin in the solid components of the chemical conversion treatment solution is, for example, in the range of 30-80% by mass. When the total content is less than 30% by mass, the film-forming components are insufficient, making it difficult to uniformly coat the steel with the chemical conversion treatment layer. On the other hand, when the total content exceeds 80%, it is not possible to adequately contain phosphorus and other components, making it difficult to simultaneously achieve good corrosion resistance on the flat portion of the chemical conversion treatment layer, corrosion resistance on the processed portion, adhesion between the chemical conversion treatment layer and the steel, and resistance to blackening.

[0216] [Other ingredients]

[0217] In addition to the various components described above, the chemical conversion treatment layer 15 of this embodiment may also contain zirconium compounds, silicon dioxide, fluorides, vanadium compounds, tannins or tannic acid, etc.

[0218] In addition to the various components described above, the chemical conversion treatment layer 15 of this embodiment may further contain various rust-preventing pigments. As such rust-preventing pigments, for example, any rust-preventing pigments such as calcium ion-exchanged silica (also commonly known as calcium silicate), magnesium oxide, calcium molybdate, aluminum molybdate, barium molybdate, water-dispersible silica, and fumed silica can be used.

[0219] Furthermore, the chemical conversion treatment layer 15 of this embodiment may further contain extender pigments such as precipitating barium sulfate and clay, and coloring pigments such as titanium dioxide, as needed. Furthermore, in addition to containing the rust-preventive pigments, extender pigments, and coloring pigments as described above, the chemical conversion treatment layer 15 of this embodiment may also contain additives such as colorants, viscosity modifiers, leveling agents, defoamers, and ultraviolet absorbers, as needed.

[0220] Regarding the thickness of the chemical conversion treatment layer 15

[0221] The thickness of the chemical conversion treatment layer 15 described above ( Figure 3 The thickness d) is preferably in the range of 30~5000nm.

[0222] By making the thickness of the chemical conversion treatment layer 15 30 nm or more, the surface treatment member 1 of this embodiment can achieve superior corrosion resistance. The thickness of the chemical conversion treatment layer 15 is more preferably 100 nm or more, and even more preferably 200 nm or more.

[0223] On the other hand, by making the thickness of the chemical conversion treatment layer 15 5000 nm or less, the surface treatment member 1 of this embodiment can ensure the adhesion between the zinc-based plating layer 13 and the chemical conversion treatment layer 15, and achieve better corrosion resistance. The thickness of the chemical conversion treatment layer 15 is more preferably 3000 nm or less, and even more preferably 2000 nm or less.

[0224] Here, the thickness of the aforementioned chemical conversion layer 15 can be determined by direct observation from a cross-section. Specifically, the coated steel sheet 1 is embedded in room-temperature drying epoxy resin in a manner that allows observation of its cross-section. After mechanical grinding of the embedded surface, it is observed using SEM. In this SEM observation, those skilled in the art can easily distinguish the chemical conversion layer 15 and the zinc-based coating 13 by appearance. The thickness of the chemical conversion layer 15 is measured at any five points, and the average of the thicknesses obtained at the five points is taken as the thickness of the chemical conversion layer 15.

[0225] The surface treatment component 1 of this embodiment has been described in detail above.

[0226] (Regarding composite structures)

[0227] Next, refer to Figure 4 and Figure 5 The surface treatment component 1 and the composite structure 5 of soil in this embodiment described above will be explained. Figure 4 and Figure 5 This is an explanatory diagram used to illustrate the composite structure of this embodiment.

[0228] like Figure 4 As illustrated, the composite structure 5 of this embodiment is a structure formed by combining the surface-treated component 1 of this embodiment described above with soil. As described above, a chemical conversion treatment layer 15 is formed on the surface of the surface-treated steel 10 constituting the surface-treated component 1. In the composite structure 5 of this embodiment, at least a portion of the chemical conversion treatment layer 15 is in contact with the soil, thus forming a state in which the surface-treated component 1 is combined with the soil.

[0229] Figure 5 Indicatively representing that Figure 4 The cross-section of the composite structure 5 shown is cut along the AA cutting line in the X-axis direction. Figure 5 The cross-sectional view shown corresponds to the view obtained by cutting the portion of the composite structure 5 in this embodiment that is in contact with the soil along the thickness direction of the surface-treated steel 10, which is the blank of the surface-treated member 1.

[0230] like Figure 5 As illustrated, in the composite structure 5 of this embodiment, the portion in contact with the soil is composed of surface-treated steel 10 and soil. The surface-treated steel 10 has a steel 11, a zinc-based plating 13 on the surface of the steel 11, and a chemical conversion treatment layer 15. Additionally, as... Figure 5 As illustrated, an oxide layer 21 is formed at the interface between the chemically transformed treatment layer 15 and the soil, which is an example of a P-Zn composite layer containing Zn and P.

[0231] Here, the steel 11 in the composite structure 5 of this embodiment has the same structure as the steel 11 in the surface treatment member 1 described above, and exhibits the same effect, so the description is omitted below.

[0232] Furthermore, regarding the zinc plating layer 13 and the chemical conversion treatment layer 15 in the composite structure 5 of this embodiment, since they have the same structure as the zinc plating layer 13 and the chemical conversion treatment layer 15 in the surface treatment member 1 described above, the description is omitted below.

[0233] It should be noted that, in the interface portion of the composite structure 5 that is in contact with the soil, due to the interdiffusion of components with the soil, the chemical composition of the interface portion of the chemical conversion treatment layer 15 is also considered to change compared to the chemical composition of the chemical conversion treatment layer 15 in the portion not in contact with the soil. However, the overall average composition of the chemical conversion treatment layer 15 is presumed to be the same as that of the chemical conversion treatment layer 15 in the surface treatment component 1 described above.

[0234] As an example of a P-Zn-based composite layer containing Zn and P, the oxide layer 21 is a layer composed of P-Zn-based composite oxides, which are generated by the reaction of P derived from the chemical conversion treatment layer 15 and Zn derived from the zinc-based plating layer 13. Here, it is presumed that in the soil, compounds containing P contained in the chemical conversion treatment layer 15 also dissolve from the chemical conversion treatment layer 15 in the form of phosphate ions. The P-Zn-based composite compound generated through such a reaction has a dense structure. Therefore, by having an oxide layer 21 composed of this P-Zn-based composite oxide at at least a portion of the interface between the chemical conversion treatment layer 15 and the soil, the composite structure 5 of this embodiment exhibits excellent corrosion resistance in soil.

[0235] Such an oxide layer 21 is preferably a layer having the following chemical composition: by mass%, it contains Zn: 1.0% or more and 10.0% or less, P: 0.5% or more and 5.0% or less, with the balance being H, C, O, Si, and impurities. The oxide layer 21 is composed of a P-Zn-based composite compound having the chemical composition described above, thereby the composite structure 5 of this embodiment exhibits superior corrosion resistance in soil.

[0236] Furthermore, when the zinc-based coating 13 contains Al and Mg in its chemical composition, the oxide layer 21 preferably contains at least one of Al: 0% or more and 10.0% by mass or less, and Mg: 0% or more and 10.0% by mass or less, to replace a portion of the balance of H, C, O, and Si as described above. The oxide layer 21 is composed of a P-Zn-Al-Mg composite compound having the chemical composition described above, thereby the composite structure 5 of this embodiment exhibits superior corrosion resistance in soil.

[0237] It should be noted that the chemical composition of the oxide layer 21 described above can be determined in the same way as the chemical composition of the zinc-based coating 13 described previously.

[0238] Above, refer to Figure 4 and Figure 5 The composite structure 5 of this embodiment has been described.

[0239] (Regarding the manufacturing method of surface-treated components)

[0240] Hereinafter, an example of the manufacturing method of the surface treatment component 1 of this embodiment will be described.

[0241] <Manufacturing method of surface-treated steel 10 as billet>

[0242] The surface-treated steel 10, which serves as the blank for the surface-treated component 1 in this embodiment, is manufactured by forming a zinc-based plating layer 13 and a chemical conversion treatment layer 15 on the surface of the steel 11, using the steel 11 as described above as the base material.

[0243] Method for forming zinc-based coating 13

[0244] In the formation of the zinc-based coating 13, in addition to hot-dip galvanizing, spraying, cold spraying, sputtering, vapor deposition, electroplating, etc., can also be used. However, hot-dip galvanizing is the most cost-effective method.

[0245] Hereinafter, an example of a manufacturing method for obtaining the zinc-based coating 13 of this embodiment using hot-dip galvanizing will be described in detail.

[0246] In the manufacturing process of the zinc-based coating 13, firstly, a steel plate, which is used as a base material, is rolled to the desired thickness using the Sendzimir method, then rolled into a coil and placed on the hot-dip galvanizing production line.

[0247] In a hot-dip galvanizing production line, steel sheets are continuously passed through while being drawn from coils. At this time, the steel sheets are subjected to a reduction treatment at 800°C in an annealing device installed on the production line, for example, in an environment where oxidation is unlikely to occur (oxygen concentration below 20 ppm) and an atmosphere of N2-5% H2 gas. Afterward, the steel sheets are air-cooled with N2 gas to approximately +20°C the temperature of the subsequent plating bath, and then immersed in the plating bath.

[0248] Here, in the plating bath, a plating alloy having the chemical composition described above is prepared in advance in a molten state. The bath temperature is set in advance above the melting point of the plating alloy (for example, around 460~660°C).

[0249] When preparing the material for the plating alloy, it is preferable to use a pure metal (purity of 99% or higher) as the alloying material. First, a specified amount of alloy metal is mixed in such a way that it becomes the composition of the coating as described above. The mixture is then completely melted in a high-frequency induction furnace, electric arc furnace, or similar apparatus under vacuum or inactive gas purging conditions to form the alloy. Next, the alloy, mixed with the specified composition (the composition of the coating described above), is dissolved in the atmosphere, and the resulting melt is used as the plating bath.

[0250] It should be noted that the above-described plating alloys are not restricted to using pure metals; existing Zn alloys, Mg alloys, and Al alloys can also be melted and used. In this case, as long as a specified composition alloy with few impurities is used, there will be no problem.

[0251] The steel sheet is immersed in the plating bath as described above, and then lifted out at a specified speed. At this time, the amount of plating is controlled, for example, by using N2 wiping gas, to ensure that the formed zinc-based coating reaches the desired thickness. Regarding conditions other than the bath temperature, general plating operation conditions can be applied; no special equipment or conditions are required.

[0252] In addition, various heat treatments can be applied to the molten alloy plating on the steel plate as needed.

[0253] Method for forming chemical conversion treatment layer 15

[0254] The chemical conversion treatment layer 15 of this embodiment can be formed as follows: after coating the surface of the zinc-based plating layer 13 formed as described above with a chemical conversion agent containing the components constituting the chemical conversion treatment layer 15 as described above, it is baked at a specified temperature to cure and dry, thereby forming the layer. Thus, when applied to surface-treated steel 1m... 2 When the chemical conversion treatment layer of a certain size is immersed in ion-exchange water at a temperature of 35~45℃ for 60 minutes, the amount of P dissolved from the chemical conversion treatment layer into the ion-exchange water is within the desired range.

[0255] Furthermore, by forming the chemical conversion treatment layer 15 using the heating process detailed below, the formed chemical conversion treatment layer 15 satisfies the previously explained relationship of the integral intensity of the peaks in XPS, enabling the amount of P dissolved from the aforementioned chemical conversion treatment layer into the ion-exchanged water to be within a more preferred range.

[0256] The conditions for this heating direction will be explained in detail below.

[0257] <Heating Method>

[0258] In the heating process of heating the chemical conversion agent coated on the zinc-based coating, the heating method for the chemical conversion agent is a method that heats the chemical conversion agent from the steel side. By heating the chemical conversion agent from the steel side, in the narrow P2p spectrum obtained by analyzing the outermost surface of the chemical conversion layer 15 using XPS, the ratio of the integrated intensity of the peak with a maximum value at 133.90 ± 0.25 eV to the integrated intensity of the peak with a maximum value at 132.80 ± 0.25 eV is greater than 0.20.

[0259] As a specific heating method, an example is an induction heating device (IH). When heating steel coated with a chemical conversion agent (i.e., steel with a zinc-based coating) using an IH, the IH can directly heat the steel. Therefore, the chemical conversion agent is heated through heat transfer from the steel, thus the chemical conversion agent is heated from the steel side.

[0260] The mechanism by which the integrated intensity of the peak with a maximum value at 133.90 ± 0.25 eV is greater than that of the peak with a maximum value at 132.80 ± 0.25 eV in the narrow P2p spectrum obtained by analyzing the outermost surface of the chemically converted layer 15 using XPS after heating the chemical conversion agent from the steel side is not yet clear. However, the inventors speculate that the reason is as follows.

[0261] Phosphorus (P) exists in the chemical conversion agent as a water-soluble anion. When the water, acting as a solvent, is evaporated by heating the chemical conversion agent, a precipitation reaction occurs between P in the chemical conversion agent and positively charged metal ions. At this time, P, as an anion, reacts with the positively charged metal ions to form an insoluble compound.

[0262] It is believed that the precipitation reaction of P in the chemical conversion treatment agent with positively charged metal ions, and the formation of insoluble compounds accompanying this precipitation reaction, occur due to the concentration increase caused by the evaporation of water as a solvent. When the chemical conversion treatment agent is heated from the steel side, the formation of insoluble compounds preferentially occurs near the steel. That is, by heating the chemical conversion treatment agent from the steel side, metal ions are preferentially consumed near the steel. Then, P that does not form insoluble compounds with positively charged metal ions precipitates as soluble P on the surface side of the chemical conversion layer. As a result, in the narrow P2p spectrum obtained by analyzing the outermost surface of the chemical conversion layer 15 using XPS, the ratio of the integrated intensity of the peak with a maximum value at 133.90 ± 0.25 eV to the integrated intensity of the peak with a maximum value at 132.80 ± 0.25 eV is greater than 0.20.

[0263] <Maximum temperature reached by steel during the heating process>

[0264] In the heating process described above, the steel coated with the chemical conversion treatment agent is heated to dry and bake. The maximum temperature reached by the steel in the heating process is preferably 50°C or higher and 100°C or lower, more preferably 50°C or higher and 80°C or lower, and even more preferably 50°C or higher and 70°C or lower. When the maximum temperature reaches less than 50°C, the solvent of the chemical conversion treatment agent will not completely evaporate, which is therefore undesirable. On the other hand, when the maximum temperature reaches more than 100°C, in the narrow P2p spectrum obtained by analyzing the outermost surface of the chemical conversion treatment layer 15 using XPS, the ratio of the integrated intensity of the peak with a maximum value at 133.90 ± 0.25 eV to the integrated intensity of the peak with a maximum value at 132.80 ± 0.25 eV is less than 0.20. The reason for this is not yet clear, but it is presumed to be because the chemical bonding state of P changes with thermal input.

[0265] Relative humidity inside the heating furnace

[0266] In the heating process described above, the relative humidity inside the heating furnace is preferably set to 85% or higher and 98% or lower. By heating in an environment with such relative humidity, in the P2p narrow spectrum obtained by analyzing the outermost surface of the chemical conversion treatment layer 15 using XPS, the ratio of the integrated intensity of the peak with a maximum value at 133.90 ± 0.25 eV to the integrated intensity of the peak with a maximum value at 132.80 ± 0.25 eV is 0.20 or higher and 0.50 or lower.

[0267] When the relative humidity is less than 85%, it is impossible to achieve a ratio of the integrated intensity of the peak with a maximum value at 133.90 ± 0.25 eV to the integrated intensity of the peak with a maximum value at 132.80 ± 0.25 eV greater than 0.20. The reason for this is unclear, but it is presumed to be based on the following: When the relative humidity is less than 85%, even when using a method that heats the chemical conversion agent from the steel side, solvent evaporation occurs at the outermost layer of the chemical conversion agent. At this time, P in the chemical conversion agent forms an insoluble compound with positively charged metal ions. As a result, it is impossible to achieve an integrated intensity ratio of 0.20 or greater as described above.

[0268] On the other hand, when the relative humidity exceeds 98%, it is impossible to achieve a ratio of the integrated intensity of the peak with a maximum value at 133.90 ± 0.25 eV to the integrated intensity of the peak with a maximum value at 132.80 ± 0.25 eV below 0.50. The reason for this is unclear, but it is speculated to be based on the following: When the relative humidity exceeds 98%, solvent evaporation is suppressed. As a result, even after heating the chemical conversion treatment agent, water, acting as a solvent, remains in the coating. Due to the influence of this water, P readily exists as a soluble compound, thus preventing the ratio of the integrated intensity from falling below 0.50.

[0269] <Heating rate of steel during the heating process>

[0270] In the heating process described above, the heating rate of the steel is preferably set to 1°C / second or higher and 15°C / second or lower. When the heating rate is 15°C / second or lower, a method is used to heat the chemical conversion agent from the steel side, and the phosphorus (P) concentration of the chemical conversion agent is set to 0.1-15% by mass, thereby setting the average P concentration on the surface side of the chemical conversion layer to 1-20% by mass. It should be noted that when the heating rate is 1°C / second or lower, the productivity is poor.

[0271] It should be noted that the mechanism by which the average concentration of P on the surface side of the chemical conversion treatment layer is set to 1-20% by mass by heating the chemical conversion agent from the steel side, setting the P concentration of the chemical conversion agent to 0.1-15% by mass, and setting the heating rate of the steel in the heating process to less than 15°C / second, is not yet clear. However, the inventors speculate that the reason is as follows.

[0272] When using a method that heats the chemical conversion agent from the steel side, the solvent readily evaporates on the steel side during the formation of the chemical conversion layer, increasing the phosphorus (P) concentration near the steel. Therefore, due to this concentration difference, P migrates towards the surface side where the concentration is lower. Furthermore, when the heating rate is below 15°C / second, the formation of the chemical conversion layer, accompanied by solvent evaporation, takes longer compared to rates exceeding 15°C / second. Therefore, it is considered that the longer P can migrate in the solvent during the formation of the chemical conversion layer, the greater the amount of P that migrates towards the surface side of the chemical conversion layer, and the more easily P accumulates on the surface side. Therefore, by setting the P concentration of the chemical conversion agent to 0.1–15% by mass, the average P concentration on the surface side of the chemical conversion layer can be set to 1–20% by mass.

[0273] <Cooling process after heating>

[0274] The cooling process after heating is set to a method other than water cooling. Air cooling is a specific example of such a cooling method. When water cooling is used, the water-soluble P contained in the chemical conversion treatment layer 15 dissolves in the cooling water, resulting in insufficient P dissolution.

[0275] <Cooling rate after heating>

[0276] The cooling rate after heating is preferably 3°C / s or more and 50°C / s or less, more preferably 15°C / s or more and 40°C / s or less, and even more preferably 20°C / s or more and 40°C / s or less. When the cooling rate is 3°C / s or less, in the narrow P2p spectrum obtained by analyzing the outermost surface of the chemical conversion treatment layer 15 using XPS, the ratio of the integrated intensity of the peak with a maximum value at 133.90 ± 0.25 eV to the integrated intensity of the peak with a maximum value at 132.80 ± 0.25 eV cannot be 0.20 or more. The reason for this is not yet clear, but it is presumed that the chemical conversion treatment agent is also heated during the cooling process, causing a change in the chemical bonding state of P. On the other hand, a cooling rate exceeding 50°C / s is uneconomical and therefore not preferred.

[0277] Here, the coating of the chemical conversion treatment agent as described above can be carried out by commonly known coating methods such as roller coating, curtain flow coating, air spraying, airless spraying, dipping, bar coating, brush coating, etc.

[0278] Through the processes described above, it is possible to manufacture the surface-treated steel 10, which serves as the blank for the surface-treated component 1 of this embodiment. An example of the manufacturing method for the surface-treated steel 10 of this embodiment has been specifically described above.

[0279] <Manufacturing Method of Surface-Treated Components>

[0280] Using the surface-treated steel 10 obtained as described above as a blank, the surface-treated component 1 of this embodiment is manufactured. Here, when obtaining the component for manufacturing the surface-treated component 1 from the surface-treated steel 10, various forming processes, joint processes based on fastening components such as bolts and rivets, and welding processes can be used. By appropriately combining these processes, the surface-treated component 1 with the desired shape can be manufactured from the surface-treated steel 10.

[0281] The above provides a brief description of an example of the manufacturing method of the surface treatment component 1 according to this embodiment.

[0282] Example

[0283] Hereinafter, the surface treatment component of the present invention will be specifically described with reference to embodiments and comparative examples. It should be noted that the embodiments shown below are merely examples of the surface treatment component of the present invention, and the surface treatment component of the present invention is not limited to the examples described below.

[0284] <Preparation of coated steel>

[0285] In the test examples shown below, the plated base material shown in Table 1 was cut into 100mm × 200mm pieces. Then, plating was carried out using an intermittent hot-dip galvanizing test apparatus manufactured by our company, and multiple plated steel pieces with the coating composition shown in Table 2 were produced for each level.

[0286] [Table 1]

[0287]

[0288] [Table 2]

[0289]

[0290] <Preparation of Chemical Conversion Agents>

[0291] Prepare chemical conversion treatment agents for forming chemical conversion treatment layers using the commercially available compounds shown in Tables 3 to 7 below.

[0292] Table 3 lists the compounds used as phosphorus-containing compounds, Table 4 lists the silane coupling agents used, and Table 5 lists the valve metals used. These compounds are all general reagents. Additionally, Table 6 lists the organic resins used, and Table 7 lists other compounds used. It should be noted that, in Table 7, all compounds except silica sol are general reagents.

[0293] [Table 3]

[0294]

[0295] [Table 4]

[0296]

[0297] [Table 5]

[0298]

[0299] [Table 6]

[0300]

[0301] [Table 7]

[0302]

[0303] Using the various compounds described above, prepare the chemical conversion treatment agents as shown in Tables 10-1 to 10-8 below.

[0304] <Formation of the Chemical Conversion Treatment Layer>

[0305] The chemical conversion treatment agent prepared as described above is applied to the surface of the previously described plated steel using a bar coater to form a chemical conversion treatment layer. The conditions for forming the chemical conversion treatment layer are shown in Tables 8 to 11-8 below. Thus, multiple surface-treated steel samples were prepared as test materials for each level.

[0306] [Table 8]

[0307]

[0308] [Table 9]

[0309]

[0310] For each surface-treated steel obtained, the concentrations of various phosphorus (P) and the XPS intensity ratio in the chemical conversion treatment layer were measured, and the thickness of the chemical conversion treatment layer was also measured. Furthermore, leaching tests were performed to determine the amount of P leached into ion-exchanged water, following the previously described method. The results are summarized in Tables 11-1 to 11-8 below.

[0311] Furthermore, for each of the obtained surface-treated steels, their corrosion resistance in soil was evaluated using the following two test methods, and it was confirmed whether an oxide layer, as an example of a P-Zn composite layer, was formed upon burial in the soil. Furthermore, for each of the obtained surface-treated steels,

[0312] (Test Method 1: Evaluation of Corrosion Resistance in Ordinary Soil)

[0313] The surface-treated steel obtained as described above was buried in soil to evaluate its corrosion resistance. Silica sand with an average particle size of 300 μm was used as the soil. The cover thickness (distance from the surface of the chemically converted treatment layer to the soil surface) was set to 20 mm. After burial, to simulate ordinary soil, ion-exchanged water containing 0.03% by mass NaCl was added dropwise to adjust the moisture content to 100%. Here, the NaCl added to the ion-exchanged water simulates the electrolytes present in the soil. The drying and wetting processes described below were then repeated 50 times.

[0314] Drying process: Store at 30℃ for 7 days.

[0315] Humidification process: Add ion-exchanged water dropwise to adjust the moisture content to 100%.

[0316] For the surface-treated steel after the above-described tests, the method described earlier was used to confirm whether an oxide layer formed between the chemical conversion treatment layer and the soil. Additionally, the surface treatment agent after the tests was pickled with hydrochloric acid to remove the coating, chemical conversion treatment layer, and corrosion products. Then, the corrosion status of the steel was investigated using a shape measuring machine (KEYENCE, VR-5000). The evaluation criteria are as follows. Scores A, B, and C were set as acceptable. The results are summarized in Tables 12-1 to 12-8 below.

[0317] Rating A: No pits were formed in the steel.

[0318] B: The steel has formed pits with a depth of less than 10 μm.

[0319] C: The steel has formed pits with a depth of more than 10μm and less than 50μm.

[0320] D: The steel has formed pits with a depth of more than 50μm and less than 100μm.

[0321] E: The steel has formed pits with a depth of more than 100μm.

[0322] (Test Method 2: Evaluation of Corrosion Resistance in Acidic Soils)

[0323] The surface-treated steel obtained as described above was buried in soil to evaluate its corrosion resistance. Silica sand with an average particle size of 100 μm was used as the soil. The covering thickness was set to 50 mm. After burial, to simulate acidic soil, an HCl aqueous solution prepared by adding HCl to ion-exchange water to adjust the pH to 4 was dripped into the soil to adjust the moisture content to 100%. Then, the drying and wetting processes described below were repeated 50 times.

[0324] Drying process: Store at 30℃ for 7 days.

[0325] Humidification process: Add ion-exchanged water dropwise to adjust the moisture content to 100%.

[0326] For the surface-treated steel after the above tests, the method described above was used to confirm whether an oxide layer formed between the chemical conversion treatment layer and the soil. Additionally, the surface treatment agent after the tests was pickled with hydrochloric acid to remove the coating and corrosion products. Then, the corrosion status of the steel was investigated using a shape measuring machine (KEYENCE, VR-5000). The evaluation criteria are as follows. Scores A, B, and C were set as acceptable. The results are summarized in Tables 12-1 to 12-8 below.

[0327] Rating A: No pits were formed in the steel.

[0328] B: The steel has formed pits with a depth of less than 10 μm.

[0329] C: The steel has formed pits with a depth of more than 10μm and less than 50μm.

[0330] D: The steel has formed pits with a depth of more than 50μm and less than 100μm.

[0331] E: The steel has formed pits with a depth of more than 100μm.

[0332] (Test Method 3: Evaluation of Corrosion Resistance under Atmospheric Conditions)

[0333] The surface-treated steel obtained as described above was cut into 50×100mm pieces. The back side of the test surface and the cut ends were protected with sealing tape (Nitto Denko Co., Ltd. Polyester-based Adhesive Tape for Electrical Insulation No. 31C). Then, a composite cyclic corrosion test as specified in JISG 0594:2019 was performed. This test consists of a cyclic corrosion test of 1 hour of salt spray, 4 hours of drying, and 3 hours of humid environment. Such a test was performed for 120 hours (15 cycles).

[0334] Visually observe the corrosion status of the surface-treated steel after the above tests, and investigate the area ratio of white rust formation. The evaluation criteria are as follows. Scores A, B, and C are set as qualified. The results are summarized in Tables 12-1 to 12-8 below.

[0335] Rating A: White rust formation area is less than 5%.

[0336] B: The area affected by white rust exceeds 5% but is less than 10%.

[0337] C: The area affected by white rust exceeds 10% but is less than 20%.

[0338] D: The area affected by white rust exceeds 20% but is less than 50%.

[0339] E: White rust formation area exceeds 50%.

[0340] [Table 10-1]

[0341]

[0342] [Table 10-2]

[0343]

[0344] [Table 10-3]

[0345]

[0346] [Table 10-4]

[0347]

[0348] [Table 10-5]

[0349]

[0350] [Table 10-6]

[0351]

[0352] [Table 10-7]

[0353]

[0354] [Table 10-8]

[0355]

[0356] [Table 11-1]

[0357]

[0358] [Table 11-2]

[0359]

[0360] [Table 11-3]

[0361]

[0362] [Table 11-4]

[0363]

[0364] [Table 11-5]

[0365]

[0366] [Table 11-6]

[0367]

[0368] [Table 11-7]

[0369]

[0370] [Table 11-8]

[0371]

[0372] [Table 12-1]

[0373]

[0374] [Table 12-2]

[0375]

[0376] [Table 12-3]

[0377]

[0378] [Table 12-4]

[0379]

[0380] [Table 12-5]

[0381]

[0382] [Table 12-6]

[0383]

[0384] [Table 12-7]

[0385]

[0386] [Table 12-8]

[0387]

[0388] As can be seen from Tables 10-1 to 12-8 above, the surface-treated components corresponding to the embodiments of the present invention exhibit excellent corrosion resistance even in soil. On the other hand, the surface-treated components corresponding to the comparative examples of the present invention cannot achieve sufficient corrosion resistance.

[0389] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to these examples. Various modifications and alterations will be readily apparent to anyone skilled in the art to which this invention pertains, within the scope of the technical concept set forth in the claims, and these are, of course, also understood to fall within the technical scope of this invention.

[0390] The embodiments disclosed herein are illustrative and not restrictive in all respects. The above embodiments can be omitted, substituted, or modified in various ways without departing from the appended claims, the technical scope and spirit of the invention as described below. For example, the constituent elements of the above embodiments can be arbitrarily combined without impairing their effects. Furthermore, based on such arbitrary combinations, the functions and effects of each constituent element involved in the combination can naturally be obtained, and according to the description herein, other functions and effects that can be understood by those skilled in the art can be obtained.

[0391] Furthermore, the effects described in this specification are merely illustrative or exemplary and not limiting. That is, in addition to the effects described above, the technology involved in this invention may also achieve other effects that are obvious to those skilled in the art based on the description in this specification, thus replacing the effects described above.

[0392] It should be noted that the following configurations also fall within the technical scope of this invention. (1)

[0394] A surface-treated component is made of surface-treated steel, wherein the surface-treated steel has the following characteristics:

[0395] Steel as the base material,

[0396] The zinc coating on the surface of the aforementioned steel, and

[0397] The chemical conversion treatment layer located on the surface of the aforementioned zinc-based coating,

[0398] The aforementioned chemical conversion treatment layer contains compounds containing phosphorus (P).

[0399] 1m of the surface-treated steel mentioned above 2 When the chemically converted treatment layer, corresponding to its size, is immersed in ion-exchange water at a temperature of 35-45°C for 60 minutes, the amount of P dissolved from the chemically converted treatment layer into the ion-exchange water is 5-50 mg / m³. 2 . (2)

[0401] The surface-treated component according to (1) is used by burying at least a portion of the surface-treated steel in the soil. (3)

[0403] According to the surface-treated component described in (1) or (2), in the narrow P2p spectrum obtained by analyzing the surface of the above-mentioned chemical conversion treated layer using X-ray photoelectron spectroscopy (XPS),

[0404] The ratio of the integrated intensity of the peak with a maximum value at 133.90±0.25 eV to the integrated intensity of the peak with a maximum value at 132.80±0.25 eV is 0.20 to 0.50. (4)

[0406] According to any one of (1) to (3), in the surface-treated component, the depth distribution of P concentration obtained by performing energy dispersive X-ray spectroscopy (EDS) line analysis on the chemical conversion treatment layer from the surface to the interface with the zinc-based coating,

[0407] The average concentration of P on the surface side of the above chemical conversion treatment layer is 1~20 by mass. (5)

[0409] The surface-treated component according to any one of (1) to (4), wherein the P concentration of the above-mentioned chemical conversion treatment layer is 0.1 to 15.0 by mass when converted to P. (6)

[0411] The surface treatment component according to any one of (1) to (5), wherein the thickness of the above chemical conversion treatment layer is 30 to 5000 nm. (7)

[0413] The surface treatment component according to any one of (1) to (6) wherein the chemical conversion treatment layer contains one or more of the following selected from the group consisting of silane coupling agent, valve metal and organic resin. (8)

[0415] The surface-treated component according to any one of (1) to (7), wherein the zinc-based coating is a coating having the following chemical composition: containing, by mass%,

[0416] Al: ≥0.10% and <40.00%

[0417] Mg: ≥0.10% and <15.00%,

[0418] The balance consists of Zn and impurities. (9)

[0420] According to the surface-treated component described in (8), wherein the zinc-based coating contains, by mass%, a percentage of the zinc content in the zinc-based coating.

[0421] Al: ≥0.10% and <40.00%

[0422] Mg: ≥0.10% and <15.00%

[0423] Zn: 60.00% or more of the coating. (10)

[0425] The surface-treated component according to any one of (1) to (7), wherein the zinc-based coating is a coating having the following chemical composition: containing, by mass%,

[0426] Al: ≥0.10% and <40.00%

[0427] Mg: ≥0.10% and <15.00%,

[0428] It also contains one or more elements selected from the following groups: A, B, C, D, E, and F, with the balance being Zn and impurities.

[0429] [Element Group A]: Select one or two elements from the group consisting of Si: less than 2.50% and Fe: less than 5.00%.

[0430] [Element Group B]: Select one or more elements from the group consisting of Sb: less than 0.50%, Pb: less than 0.50%, and Sr: less than 0.50%.

[0431] [Element Group C]: Selected from one or more elements in 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%.

[0432] [Element Group D]: Select one or more elements from the group consisting of Sn: less than 20.00%, Bi: less than 5.00%, and In: less than 2.00%.

[0433] [Element Group E]: Select one or more elements from the group consisting of Ca: less than 3.00%, La: less than 0.50%, Ce: less than 0.50%, and Y: less than 0.50%.

[0434] [Element group F]: B: less than 0.50% (11)

[0436] The surface-treated component according to (10) contains the above-mentioned element group A. (12)

[0438] The surface-treated component according to (10) contains the above-mentioned element group B. (13)

[0440] The surface-treated component according to (10) contains the above-mentioned element group C. (14)

[0442] The surface-treated component according to (10) contains the above-mentioned element group D. (15)

[0444] The surface-treated component according to (10) contains the above-mentioned element group E. (16)

[0446] The surface-treated component according to (10) contains the above-mentioned element group F. (17)

[0448] According to the surface treatment component described in (10), wherein the zinc-based coating contains at least [amount] by mass%.

[0449] Al: 4.0% or more but less than 25.0%

[0450] Mg: Coating with a content of 0.3% or more but less than 12.5%. (18)

[0452] A composite structure is a composite structure of a surface-treated component made of surface-treated steel and soil, wherein the surface-treated steel has a base steel material, a zinc-based coating on the surface of the steel material, and a chemical conversion treatment layer on the surface of the zinc-based coating.

[0453] Specifically, for at least a portion of the interface between the surface-treated component and the soil, a P-Zn composite layer containing Zn and P exists between the chemically converted treatment layer and the soil. (19)

[0455] According to the composite structure described in (18), the above-mentioned P-Zn composite layer is a layer having the following chemical composition: containing, by mass%,

[0456] Zn: 1.0% or more but less than 10.0%

[0457] P: Above 0.5% and below 5.0%,

[0458] The balance consists of H, C, O, Si, and impurities. (20)

[0460] According to the composite structure described in (19), wherein,

[0461] The chemical composition of the aforementioned zinc-based coatings also contains Al and Mg.

[0462] The chemical composition of the above-mentioned P-Zn composite layer also contains

[0463] Al: 0% or more and less than 10.0% by mass

[0464] Mg: at least one of the following, which is more than 0% and less than 10.0% by mass, is used to replace a portion of the balance of H, C, O, and Si.

[0465] Explanation of reference numerals in the attached figures

[0466] 1 Surface-treated components

[0467] 5. Composite Structure

[0468] 10 Surface-treated steel

[0469] 11. Steel

[0470] 13 Zinc-based coatings

[0471] 15 Chemical conversion treatment layer

[0472] 21 Oxide layer

Claims

1. A surface-treated component comprising surface-treated steel, said surface-treated steel having: Steel as the base material, The zinc coating on the surface of the steel, and A chemical conversion treatment layer located on the surface of the zinc-based coating, The chemical conversion treatment layer contains compounds containing phosphorus (P). 1m of the surface-treated steel 2 When the chemically converted treatment layer, corresponding to its size, is immersed in ion-exchange water at a temperature of 35-45°C for 60 minutes, the amount of P dissolved from the chemically converted treatment layer into the ion-exchange water is 5-50 mg / m³. 2 .

2. The surface-treated component according to claim 1, wherein it is used by burying at least a portion of the surface-treated steel in the soil.

3. The surface-treated component according to claim 1, wherein, In the narrow P2p spectrum obtained by analyzing the surface of the chemically converted layer using X-ray photoelectron spectroscopy (XPS), The ratio of the integrated intensity of the peak with a maximum value at 133.90±0.25 eV to the integrated intensity of the peak with a maximum value at 132.80±0.25 eV is 0.20 to 0.

50.

4. The surface-treated component according to claim 1, wherein, The depth distribution of P concentration obtained when performing line analysis of the chemical conversion treated layer from the surface to the interface with the zinc-based coating using energy-dispersive X-ray spectroscopy (EDS) The average concentration of P on the surface side of the chemical conversion treatment layer is 1~20 by mass.

5. The surface-treated component according to claim 1, wherein, The P concentration of the chemical conversion treatment layer is 0.1 to 15.0 by mass, calculated as P.

6. The surface-treated component according to claim 1, wherein, The thickness of the chemical conversion treatment layer is 30~5000nm.

7. The surface-treated component according to claim 1, wherein, The chemical conversion treatment layer contains one or more of the following: selected from the group consisting of silane coupling agents, valve metals, and organic resins.

8. The surface-treated component according to any one of claims 1 to 7, wherein, The zinc-based coating has the following chemical composition: (by mass%), it contains... Al: ≥0.10% and <40.00% Mg: ≥0.10% and <15.00%, The balance consists of Zn and impurities.

9. The surface-treated component according to claim 8, wherein, The zinc-based coating contains, by weight % Al: ≥0.10% and <40.00% Mg: ≥0.10% and <15.00% Zn: 60.00% or more of the coating.

10. The surface-treated component according to any one of claims 1 to 7, wherein, The zinc-based coating has the following chemical composition: (by mass%), containing... Al: ≥0.10% and <40.00% Mg: ≥0.10% and <15.00%, It also contains one or more elements selected from the following groups: A, B, C, D, E, and F, with the balance being Zn and impurities. Element group A: Selected from one or two elements in the group consisting of Si: less than 2.50% and Fe: less than 5.00%; Element group B: Select one or more elements from the group consisting of Sb: less than 0.50%, Pb: less than 0.50%, and Sr: less than 0.50%; Element group C: selected from one or more of the following groups: 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: Selected from one or more elements in the group consisting of Sn: less than 20.00%, Bi: less than 5.00%, and In: less than 2.00%; Element group E: selected from one or more elements in the group consisting of Ca: less than 3.00%, La: less than 0.50%, Ce: less than 0.50%, and Y: less than 0.50%; Element group F:B: less than 0.50%.

11. The surface-treated component according to claim 10, comprising the element group A.

12. The surface-treated component according to claim 10, comprising the element group B.

13. The surface-treated component according to claim 10, comprising the element group C.

14. The surface-treated component according to claim 10, comprising the element group D.

15. The surface-treated component according to claim 10, comprising the element group E.

16. The surface-treated component according to claim 10, comprising the element group F.

17. The surface-treated component according to claim 10, wherein, The zinc-based coating contains at least [amount]% by mass. Al: 4.0% or more but less than 25.0% Mg: Coating with a content of 0.3% or more but less than 12.5%.

18. A composite structure comprising a surface-treated component made of surface-treated steel and soil, said surface-treated steel having a base steel, a zinc-based coating on the surface of said steel, and a chemical conversion treatment layer on the surface of said zinc-based coating. in, For at least a portion of the interface between the surface-treated component and the soil, a P-Zn composite layer containing Zn and P exists between the chemically converted treatment layer and the soil.

19. The composite structure according to claim 18, wherein, The P-Zn composite layer is a layer having the following chemical composition: (by mass%), it contains... Zn: 1.0% or more but less than 10.0% P: Above 0.5% and below 5.0%, The balance consists of H, C, O, Si, and impurities.

20. The composite structure according to claim 19, wherein, The zinc-based coating also contains Al and Mg in its chemical composition. The chemical composition of the P-Zn composite layer also contains Al: 0% or more and less than 10.0% by mass Mg: at least one of the following, which is more than 0% and less than 10.0% by mass, is used to replace a portion of the balance of H, C, O, and Si.

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