Surface-treated steel sheet and method for producing same

Abstract

Provided is a surface-treated steel sheet which can be manufactured without using hexavalent chromium and which has excellent sulfur blackening resistance, coating secondary adhesion, and appearance at the same time. A surface-treated steel sheet which has, on at least one surface of a steel sheet, a Ni-containing layer and a coating layer that is disposed on the Ni-containing layer and contains at least one of a Zr oxide and a Ti oxide, and which has a water contact angle of 50 DEG or less and a total atomic ratio of K, Na, Mg, and Ca adsorbed on the surface of 5.0% or less relative to all the elements.

Description

Technical Field

[0001] The present invention relates to a surface-treated steel sheet, and particularly to a surface-treated steel sheet having excellent sulfide staining resistance in a painted state, adhesion to a coating film in a humid environment, and appearance. The surface-treated steel sheet of the present invention can be applied to containers such as cans. In addition, the present invention also relates to a method for manufacturing the above surface-treated steel sheet. Background Art

[0002] As a kind of surface-treated steel sheet, tin-plated steel sheet (tinplate) has excellent corrosion resistance, weldability, and workability, and has a bright and beautiful appearance and is also easy to manufacture. Therefore, it is widely used as a blank material for various metal cans such as beverage cans, food cans, barrel cans, 18-liter cans, and art cans.

[0003] For the surface-treated steel sheets used in these applications, excellent adhesion to the coating is required, and excellent resistance to discoloration (sulfide staining) caused by the reaction of sulfur from the contents of the can (especially protein) with Sn is also required. Therefore, in order to improve the coating adhesion and sulfide staining resistance, chromate treatment is usually required for tin-plated steel sheets.

[0004] Chromate treatment refers to a surface treatment using a treatment solution containing chromium compounds such as chromic acid and chromate. Typically, as the above chromate treatment, as described in Patent Documents 1 to 3, by performing cathodic electrolysis in an electrolytic solution containing a hexavalent chromium compound, a metal Cr layer and an oxidized Cr layer are formed on the surface of the steel sheet.

[0005] However, in recent years, due to the increased awareness of the environment, the world is moving towards restricting the use of hexavalent Cr. Therefore, even in the field of surface-treated steel sheets for containers and the like, it is required to establish a manufacturing method that does not use chromium.

[0006] For example, Patent Document 4 proposes a surface-treated steel sheet having a film containing a zirconium compound formed on the surface of a tin-plated steel sheet.

[0007] In addition, as another method for manufacturing a surface-treated steel sheet without using hexavalent chromium, a method using trivalent chromium has also been proposed. For example, Patent Document 5 proposes a method of forming a surface treatment layer composed of a metal Cr layer and an oxidized Cr layer on the surface of a tin-plated steel sheet by performing cathodic electrolysis treatment in an electrolytic solution containing trivalent chromium ions.

[0008] Prior Art Documents

[0009] Patent Documents

[0010] Patent Document 1: Japanese Patent Application Laid-Open No. 58-110695

[0011] Patent Document 2: Japanese Patent Application Laid-Open No. 55-134197

[0012] Patent Document 3: Japanese Patent Application Laid-Open No. 57-035699

[0013] Patent Document 4: Japanese Patent Application Laid-Open No. 2018-135569

[0014] Patent Document 5: Japanese Patent No. 7070823 SUMMARY OF THE INVENTION

[0015] However, the following problems exist in the above-mentioned conventional technologies.

[0016] For example, the surface-treated steel sheet proposed in Patent Document 4 can be formed without chromate treatment. In addition, according to Patent Document 4, the surface-treated steel sheet has excellent sulfur black resistance and coating adhesion.

[0017] However, in Patent Document 4, the coating adhesion was evaluated under conditions milder than the actual can environment. In fact, the surface-treated steel sheet proposed in Patent Document 4 has insufficient adhesion to the coating under more severe conditions, i.e., in a wet environment (hereinafter referred to as "coating secondary adhesion").

[0018] In addition, according to the method proposed in Patent Document 5, a surface treatment layer can be formed without using hexavalent chromium. According to Patent Document 5, the surface-treated steel sheet obtained by using the above method has excellent coating secondary adhesion and sulfur black resistance under strict conditions close to the actual can environment.

[0019] However, the original bright and beautiful metallic luster of the tinplate of the surface-treated steel sheet manufactured by the method proposed in Patent Document 5 is damaged, and the appearance is poor.

[0020] Therefore, in reality, a surface-treated steel sheet that can be manufactured without using hexavalent chromium and has excellent sulfur black resistance, coating secondary adhesion, and appearance has not been achieved.

[0021] The present invention has been made in view of the above actual situation, and an object thereof is to provide a surface-treated steel sheet that can be manufactured without using hexavalent chromium and has excellent sulfur black resistance, coating secondary adhesion, and appearance.

[0022] The inventors of the present invention conducted in-depth research to achieve the above object, and as a result, obtained the following insights (1) and (2).

[0023] (1) In a surface-treated steel sheet having a coating layer containing at least one of Zr oxide and Ti oxide on a Ni-containing layer, by controlling the water contact angle and the total atomic ratio of K, Na, Mg, and Ca adsorbed on the surface to all elements within specific ranges, respectively, a surface-treated steel sheet having excellent sulfur blackening resistance, secondary coating adhesion, and appearance can be obtained.

[0024] (2) The above surface-treated steel sheet can be manufactured by surface conditioning under specified conditions after film formation and then performing final water washing using water having a conductivity of a specified value or less.

[0025] The present invention has been completed based on the above insights. The gist of the present invention is as follows.

[0026] 1. A surface-treated steel sheet having a Ni-containing layer on at least one surface of the steel sheet and a coating layer containing at least one of Zr oxide and Ti oxide disposed on the above Ni-containing layer,

[0027] and the water contact angle is 50° or less,

[0028] and the total atomic ratio of K, Na, Mg, and Ca adsorbed on the surface to all elements is 5.0% or less.

[0029] 2. The surface-treated steel sheet according to the above 1, wherein the Ni adhesion amount of the above Ni-containing layer is 0.1 to 20.0 g / m on one side of the above steel sheet 2 .

[0030] 3. The surface-treated steel sheet according to the above 1 or 2, wherein the total adhesion amount of Zr oxide and Ti oxide in the above coating layer in terms of the amount of metallic Zr and metallic Ti is 0.3 to 50.0 mg / m on one side of the above steel sheet 2 .

[0031] 4. The surface-treated steel sheet according to any one of the above 1 to 3, wherein the above coating layer further contains P, and the P adhesion amount is 50.0 mg / m or less on one side of the above steel sheet 2 or less.

[0032] 5. The surface-treated steel sheet according to any one of the above 1 to 4, wherein the above coating layer further contains Mn, and the Mn adhesion amount is 50.0 mg / m or less on one side of the above steel sheet 2 or less.

[0033] 6. A method for manufacturing a surface-treated steel sheet, which is a method for manufacturing a surface-treated steel sheet having a Ni-containing layer on at least one surface of the steel sheet and a coating layer containing at least one of Zr oxide and Ti oxide disposed on the Ni-containing layer, the method comprising:

[0034] A film-forming step of treating the surface of a steel sheet having a Ni-containing layer on at least one surface with an aqueous solution containing at least one of Zr ions and Ti ions to form the coating layer on the Ni-containing layer,

[0035] A surface conditioning step of maintaining the aqueous solution in a state of being present in an amount exceeding 30.0 g / m 2 and being 60.0 g / m or less 2 for 0.1 to 20.0 seconds on the surface of the coating layer,

[0036] A water washing step of washing the steel sheet after the surface conditioning step at least once;

[0037] In the water washing step, water having a conductivity of 100 μS / m or less is used at least in the final water washing.

[0038] According to the present invention, a surface-treated steel sheet that does not use hexavalent chromium and has excellent sulfur blackening resistance, secondary coating adhesion, and appearance can be provided. The surface-treated steel sheet of the present invention can be suitably used as a blank for containers and the like. Detailed Description of the Invention

[0039] Hereinafter, the method for implementing the present invention will be specifically described. It should be noted that the following description is an example showing a preferred embodiment of the present invention, and the present invention is not limited thereto.

[0040] A surface-treated steel sheet according to an embodiment of the present invention has a Ni-containing layer on at least one surface of the steel sheet and a coating layer disposed on the Ni-containing layer, and the coating layer contains at least one of Zr oxide and Ti oxide. In the present invention, it is important that the water contact angle of the surface-treated steel sheet is 50° or less, and the total atomic ratio of K, Na, Mg, and Ca adsorbed on the surface to all elements is 5.0% or less. Hereinafter, the constituent elements of the surface-treated steel sheet will be described separately.

[0041] [Steel Sheet]

[0042] As the above-mentioned steel plate, there is no particular limitation, and any steel plate can be used, but a steel plate for cans is preferably used. As the above-mentioned steel plate, for example, an extra-low carbon steel plate or a low-carbon steel plate can be used. There is also no particular limitation on the manufacturing method of the above-mentioned steel plate, and a steel plate manufactured by any method can be used, but generally a cold-rolled steel plate can be used. The above-mentioned cold-rolled steel plate can be manufactured, for example, by a general manufacturing process of hot rolling, pickling, cold rolling, annealing, and temper rolling.

[0043] The composition of the above-mentioned steel plate is not particularly limited, and the above-mentioned steel plate may also contain C, Mn, Cr, P, S, Si, Cu, Ni, Mo, Al, and inevitable impurities within the range that does not impair the effects of the scope of the present invention. At this time, as the above-mentioned steel plate, for example, a steel plate having a composition specified in ASTM A623M-09 can be preferably used.

[0044] In one embodiment of the present invention, a steel plate having a composition consisting of C: 0.0001 to 0.13% by mass, Si: 0 to 0.020%, Mn: 0.01 to 0.60%, P: 0 to 0.020%, S: 0 to 0.030%, Al: 0 to 0.20%, N: 0 to 0.040%, Cu: 0 to 0.20%, Ni: 0 to 0.15%, Cr: 0 to 0.10%, Mo: 0 to 0.05%, Ti: 0 to 0.020%, Nb: 0 to 0.020%, B: 0 to 0.020%, Ca: 0 to 0.020%, Sn: 0 to 0.020%, Sb: 0 to 0.020%, and the balance of Fe and inevitable impurities is preferably used. Among the above composition, Si, P, S, Al, and N are components with the lower content being better, and Cu, Ni, Cr, Mo, Ti, Nb, B, Ca, Sn, and Sb are components that can be added arbitrarily.

[0045] The lower limit of the plate thickness of the above-mentioned steel plate is not particularly limited, and the above plate thickness is preferably 0.10 mm or more. In addition, the upper limit of the above plate thickness is not particularly limited, and the above plate thickness is preferably 0.60 mm or less. It should be noted that "steel plate" is defined here to include "steel strip".

[0046] [Ni-containing layer]

[0047] The above Ni-containing layer only needs to be provided on at least one surface of the steel plate, and it can also be provided on both surfaces. The above Ni-containing layer only needs to cover at least a part of the steel plate, and it can also cover the entire surface on which the Ni-containing layer is provided. In addition, the above Ni-containing layer can be a continuous layer or a discontinuous layer. As the above discontinuous layer, for example, a layer having an island structure can be cited.

[0048] As the Ni-containing layer described above, any layer containing nickel can be used. For example, one or both of a Ni layer and a Ni alloy layer can be used. For example, the Ni alloy layer also includes a case where it becomes a Ni alloy layer through diffusion annealing treatment after Ni plating. In addition, as the above Ni alloy layer, for example, a Ni-Fe alloy layer can be cited.

[0049] The above Ni-containing layer is preferably a Ni-based plating layer. Here, the "Ni-based plating layer" is defined as a plating layer in which the Ni content is 50% by mass or more. In other words, the above Ni-based plating layer is a plating layer composed of a Ni plating layer or a Ni-based alloy.

[0050] The above Ni-based plating layer can also be a dispersion plating layer (composite plating layer) in which solid fine particles are dispersed in a matrix of Ni or a Ni-based alloy. As the above solid fine particles, there is no particular limitation, and fine particles of any material can be used. The above fine particles can be either inorganic fine particles or organic fine particles. As the above organic fine particles, for example, fine particles composed of resin can be cited. As the above resin, any resin can be used, but a fluororesin is preferably used, and polytetrafluoroethylene (PTFE) is more preferably used. As the above inorganic fine particles, there is no particular limitation, and fine particles composed of any inorganic material can be used. The above inorganic material can be, for example, a metal (including an alloy), a compound, or other monomers. Among them, fine particles composed of at least one selected from oxides, nitrides, and carbides are preferably used, and fine particles of metal oxides are preferably used. As the above metal oxides, for example, alumina, chromium oxide, titanium oxide, zinc oxide, etc. can be cited.

[0051] The particle size of the fine particles used in the above dispersion plating is not particularly limited, and particles of any size can be used. However, the diameter of the fine particles is preferably not more than the thickness of the dispersion plating layer as the Ni-containing layer. Typically, it is preferable to set the diameter of the above fine particles to 1 nm or more, more preferably 10 nm or more. In addition, it is preferable to set the diameter of the above fine particles to 50 μm or less, more preferably 1000 nm or less.

[0052] The Ni adhesion amount in the above Ni-containing layer is not particularly limited and can be set to any amount. However, from the viewpoint of further improving the appearance and corrosion resistance of the surface-treated steel sheet, the Ni adhesion amount is preferably 20.0 g / m on one side of the steel sheet 2 or less. From the same viewpoint, it is preferable to set the above Ni adhesion amount to 0.1 g / m 2 or more, more preferably 0.2 g / m 2 or more. In addition, from the viewpoint of further improving the workability, it is further preferable to set the above Ni adhesion amount to 1.0 g / m 2 or more.

[0053] The Ni adhesion amount of the Ni-containing layer described above is measured by a calibration curve method based on fluorescent X-rays. First, prepare multiple steel plates with known Ni adhesion amounts. For these steel plates, pre-measure the intensity of fluorescent X-rays from Ni, linearly approximate the relationship between the measured intensity of the fluorescent X-rays and the Ni adhesion amount to obtain a calibration curve. Then, the intensity of the fluorescent X-rays from Ni in the surface-treated steel plate can be measured, and the calibration curve described above can be used to obtain the Ni adhesion amount of the Ni-containing layer described above.

[0054] The method for forming the Ni-containing layer is not particularly limited. For example, any method such as electroplating can be used. When forming a Ni-Fe alloy layer as the Ni-containing layer, after forming a Ni layer on the surface of the steel plate by a method such as electroplating, a Ni-Fe alloy layer can be formed by annealing.

[0055] On the surface side of the Ni-containing layer described above, Ni oxide may be contained, or it may not be contained at all. However, from the viewpoint of further improving the secondary adhesion of the coating and the resistance to sulfur black discoloration, it is preferable that the surface side of the Ni-containing layer does not contain Ni oxide. Ni oxide can also be formed by dissolved oxygen contained in the washing water after Ni plating, etc., but it is preferable to remove the Ni oxide contained in the Ni-containing layer described above by pre-treatment, etc. described later.

[0056] [Coating layer]

[0057] On the Ni-containing layer described above, there is a coating layer containing at least one of Zr oxide and Ti oxide. In order to obtain excellent resistance to sulfur black discoloration, secondary adhesion of the coating, and appearance, it is necessary that the coating layer contains at least one of Zr oxide and Ti oxide.

[0058] The lower limit of the total adhesion amount of Zr oxide and Ti oxide in the coating layer described above is not particularly limited. However, from the viewpoint of further improving the resistance to sulfur black discoloration, the total adhesion amount of Zr oxide and Ti oxide, in terms of the amount of metallic Zr and metallic Ti, is preferably 0.3 mg / m on one side of the steel plate 2 or more, more preferably 0.4 mg / m 2 or more, and still more preferably 0.5 mg / m 2 or more. On the other hand, the upper limit of the total adhesion amount of Zr oxide and Ti oxide in the coating layer is not particularly limited either. However, if the total adhesion amount of Zr oxide and Ti oxide is too large, the appearance may sometimes be impaired, and the secondary adhesion of the coating may sometimes be impaired due to the cohesive failure of the coating layer. Therefore, from the viewpoint of more stably ensuring the appearance and the secondary adhesion of the coating, the total adhesion amount of Zr oxide and Ti oxide, in terms of the amount of metallic Zr and metallic Ti, is preferably 50.0 mg / m on one side of the steel plate 2 or less, more preferably 45.0 mg / m 2Hereinafter, 40.0 mg / m is further preferably used. 2 Hereinafter, it should be noted that when calculating the total amount of the adhered Zr oxide and Ti oxide, as the amount of the adhered Zr oxide, the value converted to the amount of metallic Zr is used, and as the amount of the adhered Ti oxide, the value converted to the amount of metallic Ti is used.

[0059] The amount of the adhered Zr oxide in the above-mentioned coating layer is measured by the calibration curve method based on fluorescent X-ray. First, prepare a plurality of steel plates with known amounts of adhered metallic Zr, and for this steel plate, preliminarily measure the fluorescent X-ray intensity from Zr, linearly approximate the relationship between the measured fluorescent X-ray intensity and the amount of adhered metallic Zr to obtain a calibration curve. Then, the fluorescent X-ray intensity of Zr from the surface-treated steel plate can be measured, and the calibration curve described above is used to obtain the amount of the adhered Zr oxide in the above-mentioned coating layer in terms of metallic Zr conversion.

[0060] In addition, the amount of the adhered Ti oxide in the above-mentioned coating layer is measured by the calibration curve method based on fluorescent X-ray. First, prepare a plurality of steel plates with known amounts of adhered metallic Ti, and for this steel plate, preliminarily measure the fluorescent X-ray intensity from Ti, linearly approximate the relationship between the measured fluorescent X-ray intensity and the amount of adhered metallic Ti to obtain a calibration curve. Then, measure the fluorescent X-ray intensity of Ti from the surface-treated steel plate, and use the calibration curve described above to obtain the amount of the adhered Ti oxide in the above-mentioned coating layer in terms of metallic Ti conversion.

[0061] From the viewpoint of further improving the sulfide black resistance, the above-mentioned coating layer may contain P. The upper limit of the amount of adhered P contained in the coating layer is not particularly limited, but sometimes the secondary adhesion of the coating is damaged due to the coagulation failure of the coating layer. Therefore, it is preferably 50.0 mg / m on one side of the steel plate. 2 Hereinafter. The lower limit of the amount of adhered P contained in the coating layer is not particularly limited. For example, it may be 0.0 mg / m. 2 Or it may not contain it at all.

[0062] The amount of the adhered P in the above-mentioned coating layer can be measured by the calibration curve method based on fluorescent X-ray. First, prepare a plurality of steel plates with known amounts of adhered P, and for this steel plate, preliminarily measure the fluorescent X-ray intensity from P, linearly approximate the relationship between the measured fluorescent X-ray intensity and the amount of adhered P to obtain a calibration curve. Then, measure the fluorescent X-ray intensity of P from the surface-treated steel plate, and use the calibration curve described above to obtain the amount of the adhered P in the above-mentioned coating layer.

[0063] From the viewpoint of further improving the resistance to sulfur black discoloration, the above-mentioned film layer may contain Mn. The upper limit of the amount of Mn adhered in the film layer is not particularly limited, but sometimes the secondary adhesion of the coating is impaired due to the coagulation failure of the film layer. Therefore, it is preferably 50.0 mg / m 2 or less on one side of the steel sheet. The lower limit of the amount of Mn adhered in the film layer is not particularly limited. For example, it can be 0.0 mg / m 2 , or it may not contain any at all.

[0064] The amount of Mn adhered in the above-mentioned film layer can be measured by the calibration curve method based on fluorescent X-rays. First, prepare multiple steel sheets with known amounts of Mn adhered. For this steel sheet, pre-measure the intensity of fluorescent X-rays from Mn, linearly approximate the relationship between the measured intensity of fluorescent X-rays and the amount of Mn adhered to obtain a calibration curve. Then, the intensity of fluorescent X-rays from Mn in the surface-treated steel sheet can be measured, and the amount of Mn adhered in the above-mentioned film layer can be obtained using the above calibration curve.

[0065] The above-mentioned film layer may contain Ni. The upper limit of the Ni content in the film layer is not particularly limited. The film layer may not contain Ni and can be 0.0 mg / m 2 .

[0066] The above-mentioned film layer may contain C. The upper limit of the C content in the film layer is not particularly limited. The film layer may not contain C and can be 0.0 mg / m 2 .

[0067] Sometimes, elements other than Zr, Ti, O, Ni, Mn, P, C, and the following K, Na, Mg, and Ca are contained in the above-mentioned film layer. As elements other than the above-mentioned elements, metal impurities such as Cu, Zn, and Fe contained in the aqueous solution used in the following film formation process and elements such as S, N, F, Cl, Br, and Si can be cited. However, if elements other than Zr, Ti, O, Ni, Mn, P, C, K, Na, Mg, and Ca are excessively present, the resistance to sulfur black discoloration or adhesion may sometimes decrease. Therefore, the total content of elements other than Zr, Ti, O, Ni, Mn, P, C, K, Na, Mg, and Ca in the film layer is preferably 30% or less, more preferably 20% or less in atomic ratio. The film layer may not contain elements other than Zr, Ti, O, Ni, Mn, P, C, K, Na, Mg, and Ca, and can be 0% in atomic ratio. The content of the above-mentioned elements can be measured by XPS (X-ray photoelectron spectroscopy).

[0068] [Water contact angle]

[0069] In the present invention, it is important that the water contact angle of the surface-treated steel sheet is 50° or less. By making the water contact angle 50° or less, the surface of the surface-treated steel sheet is highly hydrophilized, whereby a strong hydrogen bond is formed between the resin contained in the coating and the surface-treated steel sheet. As a result, high adhesion can be obtained even in a humid environment. From the viewpoint of further improving the secondary adhesion of the coating, it is preferable to set the water contact angle to 48° or less, and more preferably 45° or less. From the viewpoint of improving adhesion, the lower the above water contact angle, the more preferable it is, and thus the lower limit is not particularly limited and may be 0°. However, from the viewpoint of ease of manufacturing, etc., it may be 5° or more, or may be 8° or more.

[0070] Furthermore, the surface state of the surface of the surface-treated steel sheet in the present invention, that is, the surface of the film layer containing at least one of Zr oxide and Ti oxide, is stable with respect to heat. For example, even after heat treatment equivalent to coating baking, the water contact angle does not change significantly. It is presumed that this thermal stability of the surface state also contributes to improving the adhesion to the coating. Therefore, the water contact angle of the surface-treated steel sheet after heat treatment equivalent to coating is also preferably 50° or less, more preferably 48° or less, and further preferably 45° or less. In addition, the lower limit of the water contact angle of the surface-treated steel sheet after heat treatment equivalent to coating is not particularly limited and may be 0°, and the above water contact angle may be 5° or more, or may be 8° or more. It should be noted that in the conditions of the heat treatment equivalent to coating, the maximum temperature is set to 200°C, and the holding time at the above maximum temperature is set to 10 minutes.

[0071] The mechanism of hydrophilization of the surface of the surface-treated steel sheet is not yet clear, but it is considered that the minute roughness of the surface is adjusted in the surface conditioning process described later, and high hydrophilicity is imparted. Without going through the surface conditioning process as described later, even if the surface of the surface-treated steel sheet is hydrophilized just after manufacturing, it cannot be fixed in the hydrophilized state, and the water contact angle exceeds 50°.

[0072] It should be noted that the above water contact angle can be measured by the θ / 2 method. In the above measurement, the temperature of the surface-treated steel sheet to be measured is set to 20°C, and distilled water at a temperature of 20°C is dropped onto the surface of the surface-treated steel sheet. The contact angle after 1 second from the start of dropping is calculated by the θ / 2 method. More specifically, the measurement can be carried out by the method described in the examples. Here, rust preventive oils such as CSO (Cottonseed Oil), DOS (Dioctyl Sebacate), and ATBC (Acetyl Tributyl Citrate) may be applied to the surface of the surface-treated steel sheet. In the case where the surface-treated steel sheet is oiled, the above-mentioned heat treatment equivalent to painting is carried out to vaporize the oil on the oiled surface, and then the water contact angle measured by the method described in the examples is used as the water contact angle of the surface-treated steel sheet after oiling. As described above, the surface-treated steel sheet of the present invention is stable with respect to heat treatment. Therefore, if the water contact angle measured after the above heat treatment and the atomic ratio of the adsorbed elements described below satisfy the conditions of the present invention, it is considered that the effects of the present invention are also achieved for the surface-treated steel sheet before the above heat treatment. It should be noted that additive components such as rust preventive agents contained in the oil on the oiled surface may remain on the surface of the surface-treated steel sheet even after the heat treatment equivalent to painting, but since the amount is small, it has no influence on the above water contact angle and the atomic ratio of the adsorbed elements.

[0073] It should be noted that in the surface-treated steel sheets produced using the conventional hexavalent chromium baths proposed in Patent Documents 1 to 3, the composition of the hydrated chromium oxide layer present in the surface layer has a great influence on the adhesion of coatings or films in a humid environment. In a humid environment, the water that penetrates into the coating film or film hinders the adhesion at the interface between the coating film or film and the hydrated chromium oxide layer. Therefore, when there are a large number of hydrophilic OH groups in the hydrated chromium oxide layer, the spreading and wetting of water at the interface are promoted, and the adhesion force decreases. Therefore, in the conventional surface-treated steel sheets, the OH groups are reduced by the oxidation of the hydrated chromium oxide, that is, the hydrophobicity of the surface is increased to improve the adhesion to coatings or films in a humid environment.

[0074] In contrast, the present invention is based on a technical idea completely different from the above prior art, that is, it exhibits high hydrophilicity through the action of fine irregularities on the surface of the film layer formed in the surface conditioning step described below. As a result, the coating enters the fine irregularities, and a strong mechanical bond based on the anchoring effect is formed at the interface between the coating film and the surface-treated steel sheet, thereby maintaining high adhesion even in a humid environment.

[0075] [Atomic ratio of adsorbed elements]

[0076] As described above, the surface-treated steel sheet of the present invention has a high hydrophilicity with a water contact angle of 50° or less, and the surface has chemical activity. Therefore, cations of elements such as K, Na, Mg, and Ca are easily adsorbed on the surface of the above-described surface-treated steel sheet. The inventors found that simply setting the water contact angle to 50° or less cannot exhibit the original adhesion due to the influence of the adsorbed cations. In the present invention, by reducing the amount of the above-described cations adsorbed on the surface of the surface-treated steel sheet, the adhesion to the resin can be improved, excellent secondary adhesion of the coating can be achieved, and a stable barrier property against the penetration of sulfur can be exhibited. Therefore, excellent sulfur blackening resistance can be achieved.

[0077] Specifically, the total atomic ratio of K, Na, Mg, and Ca adsorbed on the surface of the surface-treated steel sheet to all elements is set to 5.0% or less, preferably 3.0% or less, and more preferably 1.0% or less. Since the lower the total of the above atomic ratios, the better, the lower limit is not particularly limited and can be 0.0%. The total of the above atomic ratios can be measured by XPS. In the above measurement, the atomic ratios of K, Na, Mg, and Ca to all elements can be obtained by the relative sensitivity factor method based on the integrated intensities of the narrow spectra of K2p, Na1s, Ca2p, and Mg1s on the outermost surface of the surface-treated steel sheet. More specifically, the measurement can be performed by the method described in the examples. It should be noted that when the surface-treated steel sheet is oiled, the above-described heat treatment equivalent to coating is performed to vaporize the oiled gas, and then the atomic ratio measured by the method described in the examples is used as the atomic ratio of the adsorbed elements of the surface-treated steel sheet after oiling.

[0078] [Manufacturing method]

[0079] In the manufacturing method of the surface-treated steel sheet according to an embodiment of the present invention, a surface-treated steel sheet having the above characteristics can be manufactured using the method described below.

[0080] A manufacturing method of a surface-treated steel sheet according to an embodiment of the present invention is a manufacturing method of a surface-treated steel sheet having a Ni-containing layer on at least one surface of a steel sheet and a coating layer disposed on the Ni-containing layer, and includes the following steps (1) to (3).

[0081] (1) Coating formation step

[0082] (2) Surface conditioning step

[0083] (3) Water washing step

[0084] Hereinafter, each step will be described.

[0085] [Coating formation step]

[0086] In the above-described film-forming step, the surface of a steel sheet having a Ni-containing layer on at least one surface is treated with an aqueous solution containing at least one of Zr ions and Ti ions, and a film layer is formed on the Ni-containing layer. The formed film layer is a film layer containing at least one of Zr oxide and Ti oxide.

[0087] The treatment using the above aqueous solution is not particularly limited and can be carried out by any method. For example, the treatment can be carried out by electrolysis. When the treatment is carried out by electrolysis, it is preferable to subject the steel sheet having a Ni-containing layer to cathodic electrolysis treatment in the above aqueous solution. In the above cathodic electrolysis treatment, existing equipment for chromate treatment or the like can be directly used. Therefore, from the viewpoint of reducing equipment costs, it is preferable to form a film layer by cathodic electrolysis treatment.

[0088] The method for preparing the above aqueous solution is not particularly limited. For example, it can be prepared by dissolving one or both of a Zr compound as a Zr ion source and a Ti compound as a Ti ion source in water. As the above water, distilled water or deionized water can be used, but it is not limited thereto, and any water can be used.

[0089] As the above Zr compound and Ti compound, any compound capable of supplying Zr ions and Ti ions can be used respectively. As the above Zr compound, for example, Zr salts such as ZrF 4 etc. or H 2 ZrF 6 、K 2 ZrF 6 etc. Zr complexes can be used. Zr ions become Zr oxide as the pH of the cathode surface increases and form a film. As the above Ti compound, for example, Ti salts such as TiF 4 etc. or H 2 TiF 6 、K 2 TiF 6 etc. Ti complexes can be used. Ti ions become Ti oxide as the pH of the cathode surface increases and form a film.

[0090] In the above aqueous solution, at least one selected from fluoride ions, nitrate ions, ammonium ions, phosphate ions, Mn ions, and sulfate ions can be further contained. When both nitrate ions and ammonium ions are contained in the above aqueous solution, the treatment can be carried out in a short time of about several seconds to several tens of seconds, which is extremely advantageous industrially. Therefore, in addition to at least one of Zr ions and Ti ions, it is preferable that both nitrate ions and ammonium ions are contained in the above aqueous solution. Hereinafter, unless otherwise specified, the unit "ppm" of ion concentration refers to parts per million by mass.

[0091] When the above aqueous solution contains Zr ions, the lower limit of the concentration of Zr ions is not particularly limited, and is preferably 100 ppm or more. In addition, the upper limit of the concentration of Zr ions is not particularly limited, and is preferably 4000 ppm or less. Similarly, when the above aqueous solution contains Ti ions, the lower limit of the concentration of Ti ions is not particularly limited, and is preferably 100 ppm or more. In addition, the upper limit of the concentration of Ti ions is not particularly limited, and is preferably 4000 ppm or less.

[0092] In addition, when the above aqueous solution contains fluoride ions, the lower limit of the concentration of fluoride ions is not particularly limited, and is preferably 120 ppm or more. In addition, the upper limit of the concentration of fluoride ions is not particularly limited, and is preferably 4000 ppm or less. When the above aqueous solution contains phosphate ions, the lower limit of the concentration of phosphate ions is not particularly limited, and is preferably 50 ppm or more. In addition, the upper limit of the concentration of phosphate ions is not particularly limited, and is preferably 5000 ppm or less. When the above aqueous solution contains Mn ions, the lower limit of the concentration of Mn ions is not particularly limited, and is preferably 50 ppm or more. In addition, the upper limit of the concentration of Mn ions is not particularly limited, and is preferably 5000 ppm or less. When the above aqueous solution contains ammonium ions, the lower limit of the concentration of ammonium ions is not particularly limited and can be 0 ppm. In addition, the upper limit of the concentration of ammonium ions is not particularly limited, and is preferably 20000 ppm or less. When the above aqueous solution contains nitrate ions, the lower limit of the concentration of nitrate ions is not particularly limited and can be 0 ppm. In addition, the upper limit of the concentration of nitrate ions is not particularly limited, and is preferably 20000 ppm or less. When the above aqueous solution contains sulfate ions, the lower limit of the concentration of sulfate ions is not particularly limited and can be 0 ppm. In addition, the upper limit of the concentration of sulfate ions is not particularly limited, and is preferably 20000 ppm or less.

[0093] The upper limit of the temperature of the above aqueous solution during cathodic electrolysis treatment is not particularly limited, and is preferably 50 °C or less, for example. By performing cathodic electrolysis at 50 °C or less, a dense and uniform film structure composed of very fine particles can be formed. In addition, by setting the temperature of the above aqueous solution to 50 °C or less, the generation of defects, cracks, microcracks, etc. in the formed film layer can be suppressed, and the film adhesion can be further improved. In addition, the lower limit of the temperature of the above aqueous solution during cathodic electrolysis treatment is not particularly limited, and is preferably 10 °C or more, for example. By setting the temperature of the above aqueous solution to 10 °C or more, the film formation efficiency can be improved. In addition, if the temperature of the above aqueous solution is set to 10 °C or more, it is not necessary to cool the aqueous solution even in the case of high external temperatures such as in summer, so it is economical.

[0094] The lower limit of the pH of the above aqueous solution is not particularly limited, and is preferably 3 or more. If the pH is 3 or more, the production efficiency of Zr oxide or Ti oxide can be further improved. In addition, the upper limit of the pH of the above aqueous solution is not particularly limited, and is preferably 5 or less. If the pH is 5 or less, a large amount of precipitation in the above aqueous solution can be prevented, and the continuous productivity can be improved.

[0095] It should be noted that, in order to adjust the pH and improve the electrolysis efficiency, for example, nitric acid, ammonia water, etc. can be added to the above aqueous solution.

[0096] The lower limit of the current density during cathodic electrolysis is not particularly limited. For example, it is preferably 0.05 A / dm 2 or more, more preferably 1 A / dm 2 or more. If the current density is 0.05 A / dm 2 or more, the production efficiency of Zr oxide or Ti oxide is improved. As a result, a film layer containing more stable Zr oxide or Ti oxide can be formed, and the sulfur black resistance and anti-yellowing property can be further improved. In addition, the upper limit of the current density during cathodic electrolysis is not particularly limited. For example, it is preferably 50 A / dm 2 or less, more preferably 10 A / dm 2 or less. If the current density is 50 A / dm 2 or less, the production efficiency of Zr oxide or Ti oxide can be made moderate, and the formation of thick and poorly adherent Zr oxide or Ti oxide can be suppressed.

[0097] It should be noted that the electrolysis time in the above cathodic electrolysis treatment is not particularly limited, and can be appropriately adjusted according to the current density to obtain the above Zr adhesion amount and Ti adhesion amount.

[0098] The energization mode in the above cathodic electrolysis treatment can be continuous energization or intermittent energization. In addition, the relationship between the aqueous solution and the steel plate during the above cathodic electrolysis is not particularly limited, and they can be relatively stationary or movable. However, from the viewpoints of promoting the reaction and improving the uniformity, it is preferable to perform cathodic electrolysis while relatively moving the steel plate and the aqueous solution. For example, by continuously performing cathodic electrolysis while passing the steel plate through a treatment tank containing an aqueous solution containing at least one of Zr ions or Ti ions, the steel plate and the aqueous solution can be relatively moved.

[0099] In the case of performing cathodic electrolysis while relatively moving a steel sheet and an aqueous solution on one side, the relative flow rate of the aqueous solution and the steel sheet is preferably 50 m / min or more. If the relative flow rate is 50 m / min or more, the pH of the surface of the steel sheet where hydrogen is generated with energization becomes more uniform, and generation of coarse Zr oxide or Ti oxide can be effectively suppressed. It should be noted that the upper limit of the relative flow rate is not particularly limited.

[0100] [Surface conditioning step]

[0101] Next, the coating layer obtained in the above coating formation step is surface-conditioned. Specifically, the aqueous solution is present on the surface of the above coating layer in an amount exceeding 30.0 g / m 2 and 60.0 g / m 2 or less and maintained for 0.1 to 20.0 seconds. By performing surface conditioning under the above conditions, the above coating layer can be fixed in a highly hydrophilic state.

[0102] The mechanism by which the above coating layer can be fixed in a highly hydrophilic state through the above surface conditioning step is not yet clear, but it is considered as follows. That is, by bringing the above coating layer into contact with the above aqueous solution, the surface of the coating layer is slightly etched, and fine irregularities are formed on the surface of the coating layer. By the action of the fine irregularities, high hydrophilicity is exhibited. This hydrophilicity is different from the hydrophilicity caused by the presence of hydrophilic functional groups such as OH groups, and is caused by the physical structure of the surface roughness, and thus is also excellent in thermal stability.

[0103] It should be noted that the state of existence of the above aqueous solution on the surface of the above coating layer is not particularly limited, and a liquid film state is preferred from the viewpoint of uniform etching.

[0104] · Amount of aqueous solution: exceeding 30.0 g / m 2 and 60.0 g / m 2 or less

[0105] If the amount of the aqueous solution during surface conditioning is 30.0 g / m 2 or less, etching cannot be sufficiently performed, and as a result, the water contact angle is greater than 50°. Therefore, the amount of the above aqueous solution exceeds 30.0 g / m 2 , preferably 32.0 g / m 2 or more, more preferably 35.0 g / m 2 or more. On the other hand, if the amount of the aqueous solution exceeds 60.0 g / m 2, etching does not progress, and the desired hydrophilicity cannot be obtained. It is considered that the progress of the above etching depends on the amount of dissolved oxygen present near the interface between the film layer and the aqueous solution. That is, if the amount of the aqueous solution is too large, the thickness of the layer formed by the aqueous solution increases, so that sufficient oxygen cannot be supplied to the above interface. As a result, the etching is not sufficiently carried out. Therefore, the amount of the aqueous solution is set to 60.0 g / m 2 Hereinafter, it is preferably 58.0 g / m 2 Hereinafter, it is more preferably 55.0 g / m 2 Hereinafter.

[0106] · Holding time: 0.1 to 20.0 seconds

[0107] In addition, in the above surface conditioning, if the holding time is less than 0.1 second, the etching cannot be sufficiently carried out, and as a result, the water contact angle is greater than 50°. Therefore, the holding time is set to 0.1 second or more, preferably 0.2 second or more, and more preferably 0.3 second or more. On the other hand, if the holding time exceeds 20.0 seconds, the water contact angle is also greater than 50°. It is considered that this is because the etching is carried out excessively and deviates from the surface state suitable for presenting hydrophilicity. Therefore, the holding time is set to 20.0 seconds or less, preferably 18.0 seconds or less, and more preferably 15.0 seconds or less.

[0108] It should be noted that the amount of the aqueous solution can be measured using a moisture meter based on the filter-type infrared absorption method. Specifically, the absorbance of the surface is measured by a moisture meter based on the filter-type infrared absorption method, and the amount of the aqueous solution is obtained from the absorbance using a calibration curve obtained in advance. It should be noted that the above calibration curve can be prepared according to the following steps. First, a steel plate having the above film layer is placed on an electronic balance. An aqueous solution is dropped onto the steel plate having the above film layer using a pipette to form a liquid film on the entire surface of the steel plate having the above film layer. According to the weight of the steel plate having the above film layer before dropping the aqueous solution and the weight of the steel plate having the above film layer after dropping the aqueous solution, the weight of the aqueous solution present on the steel plate having the above film layer is obtained. The weight of the obtained aqueous solution is divided by the area of the steel plate having the above film layer, whereby the amount of the aqueous solution per unit area is obtained. At the same time, the absorbance of the surface of the steel plate having the above film layer is measured by a moisture meter based on the filter-type infrared absorption method. The above measurements are carried out multiple times while changing the amount of the aqueous solution to prepare a calibration curve showing the correlation between the amount of the aqueous solution and the absorbance. As the above calibration curve, a curve obtained by linearly approximating the correlation between the amount of the aqueous solution and the absorbance can be used.

[0109] The method for adjusting the amount of the aqueous solution present on the surface of the above-described film layer is not particularly limited, and any method can be used. For example, the amount of the aqueous solution on the surface of the above-described steel plate can be adjusted by a method of squeezing the solution with a water squeezing roller, wiping, or the like.

[0110] It should be noted that before the above-described film forming step, the steel plate having a Ni-containing layer can be arbitrarily subjected to a pretreatment. By performing the pretreatment, for example, the natural oxide film present on the surface of the Ni-containing layer can be removed. By removing the natural oxide film, the amount of Ni oxide can be adjusted, and in addition, the surface can be activated.

[0111] The method of the above-described pretreatment is not particularly limited, and any method can be used. As the above-described pretreatment, for example, pickling can be performed. The above-described pickling is not particularly limited, and any method can be used for performing it. The type of the pickling treatment liquid used for the above-described pickling is not particularly limited, and a sulfuric acid aqueous solution such as dilute sulfuric acid is preferably used. Here, the sulfuric acid aqueous solution refers to an aqueous solution of sulfuric acid, and also includes cases where components other than sulfuric acid are contained. The lower limit of the concentration of the sulfate ion contained in the sulfuric acid aqueous solution is not particularly limited, and is preferably 3 g / L or more, more preferably 5 g / L or more. The upper limit of the concentration of the sulfate ion contained in the sulfuric acid aqueous solution is not particularly limited, and is preferably 200 g / L or less, more preferably 150 g / L or less. The lower limit of the temperature of the sulfuric acid aqueous solution is not particularly limited, and is preferably 10°C or more, more preferably 15°C or more. The upper limit of the temperature of the sulfuric acid aqueous solution is not particularly limited, and is preferably 70°C or less, more preferably 60°C or less.

[0112] After performing the above-described pretreatment, from the viewpoint of removing the pretreatment liquid adhering to the surface, it is preferable to perform water washing.

[0113] In addition, when forming a Ni-containing layer on the surface of the base steel plate, it is preferable to perform a pretreatment on the base steel plate. As the above-described pretreatment, any treatment can be performed, but at least one of degreasing, pickling, and water washing is preferably performed.

[0114] By performing degreasing, rolling oil, rust preventive oil, etc. adhering to the steel plate can be removed. The above-described degreasing is not particularly limited, and any method can be used for performing it. After degreasing, in order to remove the degreasing treatment liquid adhering to the surface of the steel plate, it is preferable to perform water washing.

[0115] In addition, by performing pickling, the natural oxide film present on the surface of the steel plate is removed, and the surface can be activated. The above-described pickling is not particularly limited, and any method can be used for performing it. After pickling, in order to remove the pickling treatment liquid adhering to the surface of the steel plate, it is preferable to perform water washing.

[0116] [Water washing step]

[0117] Next, the steel sheet after the above surface adjustment process is washed with water at least once. By performing the water washing, the aqueous solution remaining on the surface of the steel sheet can be removed. The above water washing is not particularly limited, and any method can be used. For example, a water washing tank can be provided downstream of the tank for film formation, and the steel sheet after the film formation process can be continuously immersed in water. Alternatively, water washing can be performed by spraying water on the steel sheet after the film formation process with a sprayer.

[0118] The number of times of water washing is not particularly limited, and it can be once or two or more times. However, in order to avoid excessive increase in the number of water washing tanks, the number of times of water washing is preferably 5 times or less. In addition, when performing two or more water washing treatments, each water washing can be performed by the same method or by different methods.

[0119] What is important in the present invention is to use water having a conductivity of 100 μS / m or less in at least the last water washing in the above water washing treatment process. Thereby, the amounts of K, Na, Mg, and Ca adsorbed on the surface of the surface-treated steel sheet are reduced, and as a result, the adhesion can be improved. Water having a conductivity of 100 μS / m or less can be produced by any method. The water having a conductivity of 100 μS / m or less can be, for example, reverse osmosis water, ion-exchanged water, or distilled water. The conductivity of the water used in the water washing can be measured using a conductivity meter.

[0120] It should be noted that when performing two or more water washings in the above water washing treatment process, if water having a conductivity of 100 μS / m or less is used in the last water washing, the above effects can be obtained. Therefore, for water washings other than the last water washing, any water can be used. Water washings other than the last water washing can also use water having a conductivity of 100 μS / m or less. However, from the viewpoint of cost reduction, it is preferable to use water having a conductivity of 100 μS / m or less only in the last water washing, and to use ordinary water such as tap water or industrial water in water washings other than the last water washing.

[0121] From the viewpoint of further reducing the amounts of K, Na, Mg, and Ca adsorbed on the surface of the surface-treated steel sheet, the conductivity of the water used in the last water washing is preferably 50 μS / m or less, more preferably 30 μS / m or less. On the other hand, the lower limit of the above conductivity is not particularly limited and can be 0 μS / m. However, from the viewpoint of cost reduction, the above conductivity is preferably 1 μS / m or more.

[0122] The temperature of the water used in the water washing treatment is not particularly limited and can be any temperature. However, if the temperature is too high, an excessive burden is imposed on the water washing equipment. Therefore, the temperature of the water used in the water washing is preferably 95°C or less. On the other hand, the lower limit of the temperature of the water used in the water washing is also not particularly limited, but it is preferably 0°C or more. The temperature of the water used in the above water washing can also be room temperature.

[0123] The water washing time for each water washing treatment is not particularly limited, but from the viewpoint of improving the effect of the water washing treatment, it is preferably 0.1 second or more, and more preferably 0.2 second or more. In addition, the upper limit of the water washing time for each water washing treatment is not particularly limited, but when manufacturing on a continuous production line, for the reason that a decrease in the line speed will reduce the productivity, it is preferably 10 seconds or less, and more preferably 8 seconds or less.

[0124] Drying can be arbitrarily performed after the above water washing treatment step. The drying method is not particularly limited. For example, a usual dryer or an electric furnace drying method can be applied. As the temperature during the drying treatment, it is preferably 100°C or less. If within the above range, deterioration of the surface treatment film can be suppressed. It should be noted that the lower limit is not particularly limited and is usually around room temperature.

[0125] The use of the surface-treated steel sheet of the present invention is not particularly limited, but it is particularly suitable for use as a surface-treated steel sheet for containers used in the manufacture of various containers such as food cans, beverage cans, barrel cans, 18-liter cans, etc.

[0126] Examples

[0127] In order to confirm the effects of the present invention, a surface-treated steel sheet was manufactured according to the steps described below, and its properties were evaluated. It should be noted that the present invention is not limited to these.

[0128] (Formation of Ni-containing layer)

[0129] First, electrolytic degreasing, water washing, pickling by immersion in dilute sulfuric acid, and water washing were successively performed on the steel sheet. Then, electroplating Ni was performed on the above steel sheet to obtain a Ni-plated steel sheet having Ni-plated layers as Ni-containing layers on both sides of the above steel sheet. At this time, the Ni adhesion amount of the above Ni-containing layer was set to the values shown in Tables 2 and 3 by changing the energization time. The Ni adhesion amount of the above Ni-containing layer was measured by the calibration curve method based on the above fluorescent X-ray. It should be noted that in some of the examples, a Ni-Fe alloy layer was formed as the Ni-containing layer. That is, after forming the Ni-plated layer by the above method, a Ni-Fe alloy layer was formed by annealing.

[0130] As the above steel sheet, a can-making steel sheet (T4 base plate) with a thickness of 0.17 mm was used.

[0131] (Pretreatment of the steel sheet formed with the Ni-containing layer)

[0132] Then, pickling by immersion in dilute sulfuric acid and water washing shown in Tables 2 and 3 were successively performed on the obtained steel sheet formed with the Ni-containing layer. It should be noted that for comparison, in some of the examples, no pretreatment was performed.

[0133] (Film formation step)

[0134] Next, the surface of the steel sheet on which the above Ni-containing layer and the pre-treated steel sheet are formed is treated with an aqueous solution to form a coating layer on the above Ni-containing layer. Specifically, as the above aqueous solution, an aqueous solution having the composition shown in Table 1 is used, and cathodic electrolysis treatment is performed in this aqueous solution to thereby form a coating layer. The temperature of the above aqueous solution is adjusted to 35 °C, and the pH is adjusted to 3 to 5. The Zr adhesion amount and the Ti adhesion amount are controlled by adjusting the charge density. It should be noted that as the Zr-containing compound, zirconium fluoride (ZrF 4 ) is used, and as the Ti-containing compound, titanium fluoride (TiF 4 ) is used. Further, by using compounds other than the Zr-containing compound and the Ti-containing compound to adjust the concentration of each ion so that the above aqueous solution has the composition shown in Table 1, an aqueous solution is prepared.

[0135] (Surface conditioning process)

[0136] After the above coating formation process, surface conditioning is performed under the conditions shown in Tables 2 and 3. Specifically, by squeezing the steel sheet in a state where the aqueous solution adheres to the surface at the end of the coating formation process with a squeeze roll, the amount of the aqueous solution present on the surface of the coating layer is adjusted to the amount described in Tables 2 and 3. The amount of the above aqueous solution is measured using a moisture meter based on the filter type infrared absorption method as described above. Then, it is held during the holding time shown in Tables 2 and 3. That is, the aqueous solution used in the surface conditioning process is the same as the aqueous solution used in the above coating formation process.

[0137] (Water washing process)

[0138] Next, a water washing treatment is performed on the steel sheet after the above surface conditioning process. The above water washing treatment is performed 1 to 5 times under the conditions shown in Tables 2 and 3. The method of each water washing and the conductivity of the water used are shown in Tables 2 and 3. It should be noted that when the method of water washing is "immersion", the steel sheet is immersed in water for water washing. On the other hand, when the method of water washing is "spraying", water washing is performed by spraying water on the steel sheet with a sprayer. In addition, the conductivity is measured using a conductivity meter.

[0139] The adhesion amount of Zr oxide, the adhesion amount of Ti oxide, the P adhesion amount, and the Mn adhesion amount in the coating layer are respectively measured for the obtained surface-treated steel sheet. The above measurement is performed by the above calibration curve method based on fluorescent X-rays. The measurement results are shown in Tables 4 and 5. It should be noted that in Tables 4 and 5, the adhesion amounts of Zr oxide and Ti oxide are respectively described as the amount of metallic Zr and the amount of metallic Ti.

[0140] The water contact angle and the atomic ratio of adsorbed elements are respectively measured for the obtained surface-treated steel sheet according to the following steps. The measurement results are shown in Tables 4 and 5.

[0141] (Water contact angle)

[0142] The water contact angle was measured using an automatic contact angle meter CA-VP type manufactured by Kyowa Interface Science Co., Ltd. The surface temperature of the surface-treated steel sheet was 20°C ± 1°C, and distilled water at 20 ± 1°C was used. The distilled water was dropped onto the surface of the surface-treated steel sheet in a droplet volume of 2 μl, and after 1 second, the contact angle was measured by the θ / 2 method. The arithmetic mean of the contact angles of 5 droplets was taken as the water contact angle.

[0143] It should be noted that in order to confirm the change in the contact angle due to heat, the contact angle of the surface-treated steel sheet after heat treatment at 200°C for 10 minutes was also measured. The measurement conditions were the same as above. As a result, in the surface-treated steel sheets that satisfy the conditions of the present invention, the contact angle values before and after heat treatment are substantially the same. In contrast, in the surface-treated steel sheets that do not satisfy the conditions of the present invention, the contact angle values sometimes change significantly due to heat treatment.

[0144] (Atomic ratio of adsorbed elements)

[0145] The total atomic ratio of K, Na, Mg, and Ca adsorbed on the surface of the surface-treated steel sheet relative to all elements was measured by XPS. During the measurement, sputtering was not performed. Based on the integrated intensities of the narrow spectra of K2p, Na1s, Ca2p, and Mg1s on the outermost surface of the sample, the atomic ratios relative to all detected elements were quantified by the relative sensitivity factor method, and (K atomic ratio + Na atomic ratio + Ca atomic ratio + Mg atomic ratio) was calculated. The XPS measurement was performed using a scanning type X-ray photoelectron spectroscopy apparatus PHI X-tool manufactured by ULVAC-PHI Inc. The X-ray source was monochromatic AlKα rays, the voltage was 15 kV, the beam diameter was 100 μmφ, and the take-off angle was 45°.

[0146] Furthermore, the surface-treated steel sheets obtained were evaluated for sulfur black resistance, secondary coating adhesion, and appearance according to the following methods. The evaluation results are shown in Tables 4 and 5.

[0147] (Sulfur black resistance)

[0148] A commercially available epoxy resin coating for cans was applied at a dry mass of 60 mg / dm 2After coating on the surface of the surface-treated steel sheet produced by the above method, it is baked at a temperature of 200 °C for 10 minutes, and then left at room temperature for 24 hours. Then, the obtained steel sheet is cut into a specified size. Prepare an aqueous solution containing disodium hydrogen phosphate anhydrous: 7.1 g / L, sodium dihydrogen phosphate anhydrous: 3.0 g / L, and L-cysteine hydrochloride: 6.0 g / L. After boiling for 1 hour, the volume reduced due to evaporation is replenished with pure water. The obtained aqueous solution is poured into a pressure-resistant and heat-resistant container made of TEFLON (registered trademark), and the steel sheet cut into a specified size is immersed in the above aqueous solution, and the lid of the container is closed and sealed. The sealed container is subjected to a steaming treatment at a temperature of 131 °C for 60 minutes.

[0149] The sulfide black resistance is evaluated based on the appearance of the steel sheet after the above steaming treatment. If the appearance remains completely unchanged before and after the test, it is "1"; if blackening of 10% or less of the area occurs, it is "2"; if blackening of more than 10% and 20% or less of the area occurs, it is "3"; if blackening of more than 20% of the area occurs, it is "4". The cases evaluated as 1 to 3 are regarded as qualified, and the sulfide black resistance is excellent in practical use.

[0150] (Coating secondary adhesion)

[0151] Epoxy phenol-based coating is applied to the surface of the obtained surface-treated steel sheet and baked at 210 °C for 10 minutes to produce a coated steel sheet. The coating adhesion amount is 50 mg / dm 2 .

[0152] Two coated steel sheets produced under the same conditions are laminated with a nylon adhesive film with the coated surfaces facing each other, and then bonded under the bonding conditions of a pressure of 2.94×10 5 Pa, a temperature of 190 °C, and a bonding time of 30 seconds. Then, it is cut into test pieces with a width of 5 mm. The cut test pieces are immersed in a test solution at 55 °C composed of a mixed aqueous solution containing 1.5% by mass of citric acid and 1.5% by mass of sodium chloride for 168 hours. After immersion, they are washed and dried, and then the steel sheets of the two cut test pieces are torn off using a tensile testing machine, and the tensile strength at the time of tearing is measured. The average value of 3 test pieces is evaluated according to the following 4 criteria. In practical use, if the result is 1 to 3, it can be evaluated that the coating secondary adhesion is excellent.

[0153] 1: 2.5 kgf or more

[0154] 2: More than 2.0 kgf and less than 2.5 kgf

[0155] 3: More than 1.5 kgf and less than 2.0 kgf

[0156] 4: Less than 1.5 kgf

[0157] (Appearance)

[0158] Measure the L value of the surface-treated steel sheet produced by the above method and the steel sheet before the film-forming process. The L value is measured using a spectro-colorimeter SQ-2000 manufactured by Nippon Denshoku Industries Co., Ltd., with a measurement diameter of 30 mmφ, and the value of SCI (Specular Component Include) is adopted. Moreover, calculate the difference ΔL of the L value using the formula (L value of the steel sheet before the film-forming process) - (L value of the obtained surface-treated steel sheet). The L value represents color brightness, and the larger ΔL is, the more damaged the appearance is. Evaluate ΔL according to the following 4 criteria. If the result is 1 to 3, it can be evaluated as having excellent appearance in practical use.

[0159] 1: Less than 1.0

[0160] 2: 1.0 or more and less than 3.0

[0161] 3: 3.0 or more and less than 5.0

[0162] 4: 5.0 or more

[0163] From the results shown in Tables 4 and 5, it can be seen that although the surface-treated steel sheets satisfying the conditions of the present invention are all manufactured without using hexavalent chromium, they have excellent sulfur blackening resistance, secondary coating adhesion, and appearance.

[0164] Table 1

[0165]

[0166]

[0167]

[0168]

[0169]

Claims

1. A surface-treated steel sheet, having on at least one surface of the steel sheet: a Ni-containing layer, and a coating layer containing at least one of Zr oxide and Ti oxide disposed on the Ni-containing layer; and having a water contact angle of 50° or less, wherein the total atomic ratio of K, Na, Mg, and Ca adsorbed on the surface to all elements is 5.0% or less.

2. The surface-treated steel sheet according to claim 1, wherein, The Ni adhesion amount of the Ni-containing layer is 0.1 to 20.0 g / m on one side of the steel sheet 2 .

3. The surface-treated steel sheet according to claim 1 or 2, wherein, In terms of the amounts of metallic Zr and metallic Ti, the total amount of the adhered Zr oxide and Ti oxide in the coating layer is 0.3 to 50.0 mg / m on one side of the steel sheet 2 .

4. The surface-treated steel sheet according to any one of claims 1 to 3, wherein, The coating layer further contains P, and the attached amount of P is 50.0 mg / m on one side of the steel plate 2 or less.

5. The surface-treated steel sheet according to any one of claims 1 to 4, wherein, The coating layer further contains Mn, and the amount of Mn adhered is 50.0 mg / m on one side of the steel plate 2 or less.

6. A method for manufacturing a surface-treated steel sheet, which is a method for manufacturing a surface-treated steel sheet having a Ni-containing layer on at least one surface of the steel sheet and a coating layer containing at least one of Zr oxide and Ti oxide disposed on the Ni-containing layer, and includes the following steps: a film formation step of treating the surface of the steel sheet having a Ni-containing layer on at least one surface with an aqueous solution containing at least one of Zr ions and Ti ions to form the coating layer on the Ni-containing layer, Surface conditioning step, wherein the aqueous solution is present on the surface of the coating layer in an amount exceeding 30.0 g / m 2 and not exceeding 60.0 g / m 2 and maintained in this state for 0.1 to 20.0 seconds, a water washing step of washing the steel sheet after the surface conditioning step at least once; and in the water washing step, using water having a conductivity of 100 μS / m or less at least in the final water washing.

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