Surface-treated steel sheet, metal container, and method for manufacturing surface-treated steel sheet

Abstract

To provide a surface treated steel sheet excellent in surface appearance, sulfuration black discoloration resistance and alkali resistance and capable of showing high adhesion to a coating layer.SOLUTION: A surface treated steel sheet includes: a tin plated steel sheet obtained by subjecting a steel sheet to tin plating; a tin oxide layer formed on the tin plated steel sheet and including tin oxide as a main component; a composite oxide layer formed on the tin oxide layer and including phosphoric acid and aluminum as a main component; and an aluminum oxygen compound layer formed on the composite oxide layer and including an aluminum oxygen compound as a main component. The thickness of the tin oxide layer is 8-20 nm.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a surface-treated steel sheet, a metal container, and a method for producing the surface-treated steel sheet. [Background technology]

[0002] While chromate treatment is known for the surfaces of substrates used in fields such as metal containers, home appliances, building materials, vehicles, and aircraft, non-chromium surface treatments have also been developed as an alternative to such chromate treatments. For example, Patent Document 1 discloses a non-chromium surface treatment technique in which a plating layer containing Sn is formed on at least one side of a steel sheet, followed by immersion treatment or cathodic electrolysis in a chemical conversion treatment solution containing tetravalent tin ions and phosphate ions, and then immersion treatment or cathodic electrolysis in a chemical conversion treatment solution containing aluminum diphosphate, followed by drying. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-348360 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the conventional technology described in Patent Document 1, when a coating layer made of an organic material is formed on the obtained surface-treated steel sheet, the adhesion to the coating layer made of an organic material is insufficient, and therefore there is a problem that the steel sheet is not suitable for applications in which the steel sheet is used with a coating layer made of an organic material formed thereon, such as for food and beverage cans.

[0005] An object of the present invention is to provide a surface-treated steel sheet that has excellent resistance to sulfide blackening and alkali resistance while maintaining a good surface appearance and exhibits high adhesion to a coating layer. [Means for solving the problem]

[0006] As a result of intensive research into achieving the above-mentioned object, the present inventors have found that the above-mentioned object can be achieved by forming, in this order, a tin oxide layer containing tin oxide as a main component, a complex oxide layer containing phosphoric acid and aluminum as main components, and an aluminum oxygen compound layer containing an aluminum oxygen compound as a main component on a tin-plated steel sheet as a non-chromium surface treatment, and by setting the thickness of the tin oxide layer within a specific range, thereby completing the present invention.

[0007] That is, according to the present invention, there is provided a tin-plated steel sheet obtained by tin-plating a steel sheet, a tin oxide layer containing tin oxide as a main component formed on the tin-plated steel sheet; a composite oxide layer containing phosphoric acid and aluminum as main components formed on the tin oxide layer; an aluminum oxygen compound layer containing an aluminum oxygen compound as a main component, formed on the complex oxide layer; The surface-treated steel sheet has a thickness of the tin oxide layer of 8 to 20 nm.

[0008] In the surface-treated steel sheet of the present invention, when the diffraction pattern of the tin oxide layer is measured by nanobeam electron diffraction using a transmission electron microscope, the tin oxide layer preferably exhibits a diffraction pattern attributable to the crystal structure of stannic oxide (SnO). In the surface-treated steel sheet of the present invention, when the total proportion of Sn, P, Al, O, and Fe atoms in the tin oxide layer in atomic percentage is taken as 100 atomic %, it is preferable that the proportion of Sn atoms in the tin oxide layer is 30 atomic % or more but less than 50 atomic %, the proportion of P atoms is 2 to 14 atomic %, and the proportion of Al atoms is 3 to 15 atomic %. In the surface-treated steel sheet of the present invention, the atomic ratio P / Al of P atoms to Al atoms in the tin oxide layer is preferably 0.5 or more and less than 1.5. In the coated steel sheet of the present invention, the atomic ratio P / Al of P atoms to Al atoms in the aluminum oxygen compound layer is preferably 0.02 to 0.5. The surface-treated steel sheet of the present invention has a tin coating weight of 5.6 g / m 2 It is preferable that this is equal to or greater than this.

[0009] Furthermore, according to the present invention, there is provided a metal container made of the above-mentioned surface-treated steel sheet of the present invention.

[0010] Furthermore, according to the present invention, there is provided a method for manufacturing a tin-plated steel sheet, comprising: a first step of preparing a tin-plated steel sheet by plating a steel sheet with tin; The tin-plated steel sheet was electrolytically treated with a solution containing phosphate ions at 0.1 C / dm 2 Above, 1.0C / dm 2 A second step of performing electrolysis with the following amount of electricity: There is provided a method for producing a surface-treated steel sheet, which comprises a third step of subjecting the tin-plated steel sheet that has been subjected to the electrolytic treatment in the second step to a cathodic electrolytic treatment in an electrolytic treatment solution containing aluminum ions. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a surface-treated steel sheet that has excellent resistance to sulfide blackening and alkali resistance while maintaining a good surface appearance, and that exhibits high adhesion to a coating layer. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a cross-sectional view showing the configuration of a surface-treated steel sheet according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing a diffraction pattern of the tin oxide layer 20 of Example 7, measured by nanobeam electron diffraction using a transmission electron microscope. [Figure 3] FIG. 3(A) is a TEM photograph of the cross section of the surface-treated steel sheet of Comparative Example 4, and FIG. 3(B) is a TEM photograph of the cross section of the surface-treated steel sheet of Example 2. [Figure 4] 4(A) and 4(B) are diagrams showing an example of a metal container formed using a surface-treated steel sheet according to an embodiment of the present invention. [Figure 5]FIG. 5 is a diagram showing a diffraction pattern of the tin oxide layer 20 of Comparative Example 4, measured by nanobeam electron diffraction using a transmission electron microscope. DETAILED DESCRIPTION OF THE INVENTION

[0013] Fig. 1 is a cross-sectional view showing the configuration of a surface-treated steel sheet 1 according to an embodiment of the present invention. The surface-treated steel sheet 1 of this embodiment comprises a tin-plated steel sheet 10 formed by forming a tin-plated layer 12 on a steel sheet 11, and is provided with, in this order, a tin oxide layer 20 containing tin oxide as a main component, a complex oxide layer 30 containing phosphoric acid and aluminum as main components, and an aluminum oxygen compound layer 40 containing an aluminum oxygen compound as a main component. Note that while the example shown in Fig. 1 illustrates an embodiment in which the tin oxide layer 20, the complex oxide layer 30, and the aluminum oxygen compound layer 40 are formed on both surfaces of the tin-plated steel sheet 10, it is also acceptable to provide the tin oxide layer 20, the complex oxide layer 30, and the aluminum oxygen compound layer 40 on at least one surface of the tin-plated steel sheet 10.

[0014] The surface-treated steel sheet 1 of this embodiment can be used, for example, as a component for can containers, can lids, etc. When the surface-treated steel sheet 1 is used as a component for can containers, can lids, etc., the surface-treated steel sheet 1 may be used as is (unpainted with no coating layer formed on the surface) and molded into an unpainted can container or can lid, or a coating layer made of an organic material may be formed on the aluminum oxygen compound layer 40 and then molded into a can container, can lid, etc. The coating layer made of an organic material is usually formed on the surface that will become the inner surface of the can container or can lid (i.e., the surface that comes into contact with the contents).

[0015] <Tin-plated steel sheet 10> The tin-plated steel sheet 10 serving as the base material of the surface-treated steel sheet 1 of this embodiment is obtained by tin-plating a steel sheet 11 to form a tin-plated layer 12 on the steel sheet 11.

[0016] The thickness of the tin-plated steel sheet 10 is not particularly limited and may be appropriately selected depending on the intended use of the surface-treated steel sheet 1, but is preferably 0.07 to 0.4 mm.

[0017] <Tin oxide layer 20> The tin oxide layer 20 is formed on the tin plated layer 12 of the tin plated steel sheet 10 and is a layer containing tin oxide as a main component.

[0018] The tin oxide layer 20 may be any layer containing tin oxide as a main component, but in this embodiment, a layer in which the proportion of Sn atoms is 30 atomic % or more and the proportion of O atoms is 30 atomic % or more but less than 50 atomic % may be used as the tin oxide layer 20. The proportions of Sn atoms and O atoms can be determined by subjecting the tin oxide layer 20 to energy dispersive X-ray analysis (EDS) using a transmission electron microscope, and calculating the proportions of Sn atoms and O atoms from the results of the energy dispersive X-ray analysis, where the total proportion, in atomic percentage, of the Sn, P, Al, O, and Fe atoms contained in the tin oxide layer 20 is taken as 100 atomic %.

[0019] The thickness of the tin oxide layer 20 is 8 to 20 nm, preferably 8 to 14 nm, and more preferably 10 to 14 nm. According to this embodiment, the surface-treated steel sheet 1 is formed by forming the tin oxide layer 20, the composite oxide layer 30, and the aluminum oxygen compound layer 40 in this order on the tin-plated steel sheet 10. By setting the thickness of the tin oxide layer 20 within the above range, the surface-treated steel sheet 1 itself has a good appearance, and the surface-treated steel sheet 1 has excellent resistance to sulfide blackening and alkali resistance and exhibits high adhesion to a coating layer. If the thickness of the tin oxide layer 20 is too thin, the surface-treated steel sheet 1 will have poor resistance to sulfide blackening and will have poor product properties. On the other hand, if the thickness of the tin oxide layer 20 is too thick, the tin oxide layer will undergo cohesive failure, resulting in reduced adhesion to a coating layer.

[0020] Furthermore, when the diffraction pattern of the tin oxide layer 20 is measured by nanobeam electron diffraction using a transmission electron microscope, the tin oxide layer 20 preferably exhibits a diffraction pattern attributable to the crystalline structure of stannic oxide (SnO). That is, the tin oxide layer 20 preferably has a crystalline structure of stannic oxide (SnO). FIG. 2 shows the diffraction pattern of the tin oxide layer 20 of Example 7, which will be described later, measured by nanobeam electron diffraction using a transmission electron microscope. As shown in FIG. 2, the tin oxide layer 20 of Example 7 exhibits reflections attributable to the (110), (020), (111), (120), and (121) crystal planes attributable to the crystalline structure of stannic oxide (SnO). In this embodiment, a method for determining whether or not a diffraction pattern resulting from the crystal structure of stannic oxide (SnO2) can be performed, for example, by measuring a diffraction pattern by nanobeam electron diffraction using a transmission electron microscope, and analyzing the obtained diffraction pattern using an analysis program (product name "ReciPro", supervised by Kobe University). If three or more crystal planes resulting from the crystal structure of stannic oxide (SnO2) are detected, the pattern can be determined to be a diffraction pattern resulting from the crystal structure of stannic oxide (SnO2).

[0021] In this embodiment, the tin oxide layer 20 is subjected to energy dispersive X-ray analysis (EDS) using a transmission electron microscope. The results of the EDS analysis indicate that, when the total atomic percentage of the Sn, P, Al, O, and Fe atoms contained in the tin oxide layer 20 is taken as 100 atomic %, the percentages of Sn atoms, P atoms, and Al atoms are preferably within the ranges shown below. That is, the percentage of Sn atoms is preferably 30 atomic % or more but less than 50 atomic %, more preferably 30 to 49 atomic %, and even more preferably 40 to 47 atomic %. The percentage of P atoms is preferably 2 to 14 atomic %, more preferably 2 to 11 atomic %, and the percentage of Al atoms is preferably 3 to 15 atomic %, and more preferably 3 to 12 atomic %. By setting the percentages of Sn atoms, P atoms, and Al atoms within the above ranges, it is possible to further improve resistance to sulfide blackening, alkali resistance, and adhesion to a coating layer. In this embodiment, it is preferable that the proportions of Sn atoms, P atoms, and Al atoms are within the above ranges throughout the tin oxide layer 20. However, from the viewpoint of highly effective improvements in resistance to sulfide blackening, alkali resistance, and adhesion to coating layers, it is more preferable that the proportions of Sn atoms, P atoms, and Al atoms are within the above ranges within an area of ​​8 nm or less from the tin plating layer 12 side.

[0022] The atomic ratio P / Al of P atoms to Al atoms in the tin oxide layer 20 is not particularly limited, but is preferably 0.5 or more and less than 1.5, and more preferably 0.6 to 1.4. By setting the atomic ratio P / Al of P atoms to Al atoms within the above range, it is possible to further improve resistance to sulfide blackening, alkali resistance, and adhesion to a coating layer. The atomic ratio P / Al of P atoms to Al atoms can be calculated using the ratio of P atoms and the ratio of Al atoms measured according to the above method.

[0023] <Complex oxide layer 30> The complex oxide layer 30 is formed on the tin oxide layer 20 and contains phosphoric acid and aluminum as main components. The complex oxide layer 30 may be formed directly on the tin oxide layer 20, or may be formed via a diffusion layer formed by mutual diffusion of the complex oxide layer 30 and the tin oxide layer 20.

[0024] The complex oxide layer 30 may be a layer containing phosphoric acid and aluminum as main components. In this embodiment, the tin plating amount is 5.6 to 11.2 g / m 2 In this case, the composite oxide layer 30 may be a layer in which the proportion of Sn atoms is 10 atomic % or more, the proportion of P atoms is 7 atomic % or more, the proportion of Al atoms is less than 24 atomic %, and the proportion of O atoms is 48 atomic % or more. 2 More than 5.6g / m 2 When the ratio is less than 100 atomic %, a layer having a ratio of Sn atoms of 9 atomic % or more, a ratio of P atoms of 4 atomic % or more, a ratio of Al atoms of 22 atomic % or more, and a ratio of O atoms of 40 atomic % or more may be used as the complex oxide layer 30. The ratios of P atoms, Al atoms, and O atoms can be determined by subjecting the complex oxide layer 30 to energy dispersive X-ray analysis (EDS) using a transmission electron microscope, and from the results of the energy dispersive X-ray analysis, in atomic percentages, where the total ratio of the Sn, P, Al, O, and Fe atoms contained in the tin oxide layer 20 is taken as 100 atomic %.

[0025] The thickness of the complex oxide layer 30 is preferably 1 to 10 nm, more preferably 3 to 5 nm. By setting the thickness of the complex oxide layer 30 within the above range, it is possible to further improve resistance to sulfide blackening, alkali resistance, and adhesion to a coating layer.

[0026] In this embodiment, the Sn atom percentage, P atom percentage, and Al atom percentage of the complex oxide layer 30, measured in the same manner as the tin oxide layer 20, are preferably within the following ranges. That is, the Sn atom percentage is preferably less than 30 atomic %, and more preferably 20 atomic % or less. The P atom percentage is preferably 25 atomic % or less, and more preferably 21 atomic % or less, and the Al atom percentage is preferably 10 atomic % or more, and more preferably 12 atomic % or more. By setting the Sn atom percentage, P atom percentage, and Al atom percentage within the above ranges, it is possible to further improve resistance to sulfide blackening, alkali resistance, and adhesion to a coating layer.

[0027] The atomic ratio P / Al of P atoms to Al atoms in the composite oxide layer 30 is not particularly limited, but the tin plating amount is preferably 5.6 to 11.2 g / m 2 In this case, the tin plating amount is preferably 0.30 to 1.4, more preferably 0.38 to 1.35, and even more preferably 0.41 to 1.28. 2 More than 5.6g / m 2 When the atomic ratio of P atoms to Al atoms is less than 0.10, the atomic ratio P / Al is preferably 0.10 to 0.40, more preferably 0.16 to 0.37, and even more preferably 0.20 to 0.30. By setting the atomic ratio P / Al of P atoms to Al atoms within the above range, it is possible to further improve resistance to sulfide blackening, alkali resistance, and adhesion to the coating layer. The atomic ratio P / Al of P atoms to Al atoms can be calculated using the ratio of P atoms and the ratio of Al atoms measured according to the above method.

[0028] <Aluminum oxygen compound layer 40> The aluminum oxygen compound layer 40 is formed on the complex oxide layer 30 and contains an aluminum oxygen compound as a main component. The aluminum oxygen compound layer 40 may be formed directly on the complex oxide layer 30, or may be formed via a diffusion layer formed by mutual diffusion of the aluminum oxygen compound layer 40 and the complex oxide layer 30. The aluminum oxygen compound contained as a main component in the aluminum oxygen compound layer 40 is not particularly limited, but examples thereof include Al2O3 and Al(OH)3.

[0029] The aluminum oxygen compound layer 40 may be any layer containing an aluminum oxygen compound as a main component. In this embodiment, the tin plating amount is 5.6 to 11.2 g / m 2 In this case, a layer in which the ratio of P atoms is less than 7 atomic %, the ratio of Al atoms is 24 atomic % or more, and the ratio of O atoms is 49 atomic % or more may be used as the aluminum oxygen compound layer 40. In addition, when the tin plating amount is 1.3 g / m 2 More than 5.6g / m 2 When the ratio is less than 100 atomic %, a layer in which the ratio of P atoms is less than 4 atomic %, the ratio of Al atoms is less than 22 atomic %, and the ratio of O atoms is 57 atomic % or more may be used as the aluminum oxygen compound layer 40. The ratios of Al atoms and O atoms can be determined by subjecting the complex oxide layer 30 to energy dispersive X-ray analysis (EDS) using a transmission electron microscope, and from the results of the energy dispersive X-ray analysis, as atomic ratios where the total ratio, in atomic percentage, of the Sn, P, Al, O, and Fe atoms contained in the tin oxide layer 20 is taken as 100 atomic %.

[0030] The thickness of the aluminum oxygen compound layer 40 is preferably 2 to 5 nm, more preferably 3 to 4 nm. By setting the thickness of the aluminum oxygen compound layer 40 within the above range, it is possible to further improve resistance to sulfide blackening, alkali resistance, and adhesion to a coating layer.

[0031] In this embodiment, the aluminum oxygen compound layer 40 preferably has the following ranges for the proportions of Sn atoms, P atoms, and Al atoms measured in the same manner as the tin oxide layer 20. That is, the proportion of Sn atoms is preferably 3 to 20 atomic %. The proportion of P atoms is preferably 1 atomic % or more, and the proportion of Al atoms is preferably 10 atomic % or more, and more preferably 16 atomic % or more. The aluminum oxygen compound layer 40 has a lower proportion of P atoms than the composite oxide layer 30. By setting the proportions of Sn atoms, P atoms, and Al atoms within the above ranges, it is possible to further improve resistance to sulfide blackening, alkali resistance, and adhesion to a coating layer.

[0032] The atomic ratio P / Al of P atoms to Al atoms in the aluminum oxygen compound layer 40 is not particularly limited, but is preferably 0.02 to 0.5, and the tin plating amount is 5.6 to 11.2 g / m 2 In this case, the tin plating amount is preferably 0.04 to 0.40, more preferably 0.05 to 0.29, and even more preferably 0.05 to 0.25. 2 More than 5.6g / m 2 When the atomic ratio P / Al of P atoms to Al atoms is less than 0.02, the atomic ratio P / Al of P atoms to Al atoms is preferably 0.02 to 0.20, more preferably 0.04 to 0.18, and even more preferably 0.05 to 0.15. By setting the atomic ratio P / Al of P atoms to Al atoms within the above range, it is possible to further improve resistance to sulfide blackening, alkali resistance, and adhesion to a coating layer. The atomic ratio P / Al of P atoms to Al atoms can be calculated using the proportion of P atoms and the proportion of Al atoms measured according to the above method. Note that the atomic ratio P / Al of P atoms to Al atoms in the aluminum oxygen compound layer 40 is preferably within the above range, but usually the atomic ratio P / Al of the aluminum oxygen compound layer 40 is lower than the atomic ratio P / Al of the complex oxide layer 30.

[0033] In addition, the surface-treated steel sheet 1 of this embodiment preferably has a coating amount of tin (Sn) (when the tin plating layer 12, the tin oxide layer 20, the composite oxide layer 30, and the aluminum oxygen compound layer 40 are formed on both sides, the coating amount on only one side) of 1.3 g / m 2 or more, more preferably 2.8 to 11.2 g / m 2 , and more preferably 5.6 to 11.2 g / m 2 The tin coating weight is 5.6g / m 2 By doing so, the adhesion to the coating layer can be further improved by adjusting the electrolytic treatment conditions in the electrolytic treatment solution containing phosphate ions. The amount of tin deposited can be adjusted, for example, by controlling the amount of tin plating when tin-plating the steel sheet 11 to form the tin-plated steel sheet 10.

[0034] By subjecting the tin-plated steel sheet to a reflow treatment, a tin-iron alloy layer is formed between the steel sheet 11 and the tin-plated layer 12. The amount of tin deposited is 5.6 g / m 2 When the tin coating weight is less than 5.6 g / m, the amount of tin in the tin plating layer present on the tin-iron alloy layer after reflow treatment is small, so the tin-iron alloy layer is thought to be closer to the tin oxide layer. 2 If the thickness is less than 5.6g / m, there will be minute irregularities in the tin oxide layer, tin plating layer, and tin-iron alloy layer after reflow treatment, and it is thought that there will be very thin areas in the tin oxide layer. If electrolytic treatment is carried out in the second and third steps described below in this state, it is thought that the flow of electricity in the outermost layer will not be uniform (there will be areas where the flow is concentrated). In contrast, if the tin deposition amount is 5.6g / m, 2 In the above cases, the amount of tin present under the tin oxide layer after reflow treatment is large, so the tin-iron alloy layer is thought to be located farther from the tin oxide layer. In addition, the tin oxide layer, tin plating layer, and tin-iron alloy layer after reflow treatment are 5.6 g / m 2It is believed that there are fewer irregularities than when the surface is less than 100%. When electrolytic treatment is performed in the second and third steps described below in this state, the flow of electricity in the outermost layer is uniform. It is believed that the difference in surface condition due to the amount of tin attached affects the deposition of the complex oxide phosphate treatment layer formed in the second step and the distribution of P and Al in the aluminum oxygen compound layer film formed in the third step.

[0035] <Method of manufacturing surface-treated steel sheet 1> The method for producing the surface-treated steel sheet 1 of this embodiment is not particularly limited, but for example, A first step of preparing a tin-plated steel sheet 10 by tin-plating a steel sheet 11; The tin-plated steel sheet 10 is electrolytically treated with a solution containing phosphate ions at 0.1 C / dm 2 Above, 1.0C / dm 2 A second step of performing electrolysis with the following amount of electricity: The tin-plated steel sheet 10 can be produced by a method for producing a surface-treated steel sheet, which includes a third step of subjecting the tin-plated steel sheet 10 that has been subjected to electrolytic treatment in the second step to cathodic electrolytic treatment in an electrolytic treatment solution containing aluminum ions.

[0036] <1st process> In the above manufacturing method, the first step is a step of preparing a tin-plated steel sheet 10 by plating a steel sheet 11 with tin.

[0037] The steel sheet 11 to be tin-plated may be any steel sheet having excellent workability in drawing, drawing and ironing, and drawing and bending back (DTR). Examples of suitable steel sheets include hot-rolled steel sheets based on aluminum-killed continuous cast steel or cold-rolled steel sheets obtained by cold-rolling such hot-rolled steel sheets. Alternatively, the steel sheet 11 to be tin-plated may be a nickel-plated steel sheet obtained by forming a nickel-plated layer on the above-mentioned steel sheet and then heating the nickel-plated layer for thermal diffusion to form a nickel-iron alloy layer between the steel sheet and the nickel-plated layer, thereby improving corrosion resistance. Furthermore, if the nickel-plated layer is formed into a granular shape, the anchor effect can enhance the adhesion of the organic coating layer formed on the aluminum oxygen compound layer 40.

[0038] The method for tin-plating the steel sheet 11 is not particularly limited, and examples include methods using known plating baths such as a ferrostane bath, a halogen bath, and a sulfate bath. The method for nickel-plating is also not particularly limited, and a known Watts bath containing nickel sulfate and nickel chloride can be used. However, when forming a granular nickel plating layer, a bath composition containing nickel sulfate and ammonium sulfate is preferably used. Furthermore, in this embodiment, the tin-plated steel sheet 10 obtained by tin-plating in this manner may be subjected to a reflow treatment in which the tin-plated steel sheet 10 is heated to a temperature above the melting point of tin and then rapidly cooled to form a tin-iron alloy layer between the steel sheet 11 and the tin plating layer 12. In this embodiment, by performing such a reflow treatment, the resulting tin-plated steel sheet 10 has a tin-iron alloy layer and a tin plating layer 12 formed in this order on the steel sheet 11, thereby improving corrosion resistance. When a nickel plating layer is present as an underlying layer, such a reflow treatment may also form a tin-nickel alloy or a tin-nickel-iron alloy between the steel sheet 11 and the tin plating layer 12.

[0039] Furthermore, a tin oxide layer 20a containing tin oxide as a main component is usually formed on the surface of the tin-plated steel sheet 10. The tin oxide layer 20a formed at this time has a crystalline structure of stannic oxide (SnO2) (exhibits a diffraction pattern resulting from the crystalline structure of stannic oxide (SnO2)). According to this embodiment, the formation of such a tin oxide layer 20a can be promoted by performing the reflow treatment described above. Usually, before post-treatment after the reflow treatment, a "cleaning treatment" is carried out to remove the tin oxide layer 20a formed on the tin-plated surface. This treatment involves cathodic electrolysis, anodic electrolysis, or a combination of cathodic and anodic electrolysis using an acid or alkali, but this treatment may or may not be carried out.

[0040] <Second process> In the second step of the above manufacturing method, the tin-plated steel sheet 10 prepared in the first step is electrolytically treated in a solution containing phosphate ions at a concentration of 0.1 C / dm 2 Above, 1.0C / dm 2 This is a process of performing electrolysis with the following amount of electricity.

[0041] The phosphate compound contained in the electrolytic treatment solution containing phosphate ions is not particularly limited, but in addition to phosphoric acid (H3PO4), phosphate salts such as sodium dihydrogen phosphate (NaH2PO4), disodium hydrogen phosphate (Na2HPO4), phosphorous acid (H3PO3), etc. These phosphoric acids and phosphate salts may be used alone or in combination, and among these, a mixture of phosphoric acid and sodium dihydrogen phosphate is preferred.

[0042] The content of phosphate ions in the electrolytic treatment solution is not particularly limited, but is preferably 5 to 15 g / L, more preferably 10 to 13 g / L in terms of phosphorus. The pH of the electrolytic treatment solution is not particularly limited, but is preferably 1 to 7, more preferably 2 to 4.

[0043] When electrolytic treatment is performed, the amount of electricity used is 0.1 C / dm 2 Above, 1.0C / dm2 or less, preferably 0.3 to 0.7 C / dm 2 If the quantity of electricity in the electrolysis treatment is too low, the formation of the complex oxide layer 30 will be insufficient, resulting in poor resistance to sulfide blackening, alkali resistance, and adhesion to the coating layer. On the other hand, if the quantity of electricity in the electrolysis treatment is too high, the surface of the metal tin layer will dissolve (Sn → Sn) during anodic electrolysis. 2+ + 2e - ) takes priority, and the smoothness of the surface formed by the reflow treatment is lost due to the dissolution of tin. As a result, the glossy appearance characteristic of tinplate is significantly deteriorated. The amount of electricity used in the electrolytic treatment can be controlled by adjusting the current density and treatment time during the electrolytic treatment, but the current density is preferably 0.1 to 1.5 A / dm 2 The processing time may be selected from the range of 0.1 to 2.0 seconds.

[0044] When electrolysis is performed, either cathodic electrolysis or anodic electrolysis may be used, but a method of performing cathodic electrolysis followed by anodic electrolysis, or a method of performing anodic electrolysis followed by cathodic electrolysis, is preferred, and a method of performing cathodic electrolysis followed by anodic electrolysis is particularly preferred. In this case, the quantity of electricity in the cathodic electrolysis is 0.05 C / dm 2 Above, 0.5C / dm 2 or less, preferably 0.1 to 0.4 C / dm 2 The amount of electricity used in the anodic electrolysis treatment is 0.05 C / dm 2 Above, 0.5C / dm 2 or less, preferably 0.1 to 0.4 C / dm 2 The ratio of the amount of electricity in the cathodic electrolysis treatment to the amount of electricity in the anodic electrolysis treatment is not particularly limited, but it is preferable that the amount of electricity in the cathodic electrolysis treatment: the amount of electricity in the anodic electrolysis treatment = 1:2 to 2:1, and it is more preferable that the amount of electricity in the cathodic electrolysis treatment and the amount of electricity in the anodic electrolysis treatment are substantially the same.

[0045] Furthermore, when cathodic electrolytic treatment is performed on the tin-plated steel sheet 10, any counter electrode plate may be placed on the tin-plated steel sheet 10 as long as it does not dissolve in the electrolytic treatment solution while the electrolytic treatment is being performed. However, a titanium plate coated with iridium oxide or a titanium plate coated with platinum is preferred because they are less likely to dissolve in the electrolytic treatment solution.

[0046] In this embodiment, tin ions (Sn) generated from the tin-plated steel sheet 10 by electrolysis using an electrolysis solution containing phosphate ions are 2+ During the electrolytic treatment, tin receives electrons and precipitates on the surface as the main component of the coating. 2+ However, the phosphate ion PO4 in the electrolytic treatment solution 3- reacts with Sn3(PO4) 2 The tin ions Sn generated from the tin-plated steel sheet 10 are precipitated on the tin-plated steel sheet 10 as tin phosphate. 2+ is tin oxide (SnO x ) is also deposited on the tin-plated steel sheet 10.

[0047] <3rd process> The third step in the above manufacturing method is a step of subjecting the tin-plated steel sheet 10 that has been subjected to the electrolytic treatment in the second step to cathodic electrolytic treatment in an electrolytic treatment solution containing aluminum ions.

[0048] The content of aluminum ions contained in the electrolytic treatment solution containing aluminum ions is preferably 0.5 to 10 g / L, more preferably 1 to 5 g / L, in terms of the mass concentration of Al atoms. By setting the content of aluminum ions in the electrolytic treatment solution within this range, the stability of the electrolytic treatment solution can be improved, and the precipitation efficiency of aluminum oxygen compounds can be improved.

[0049] According to this embodiment, in the second step described above, electrolysis is performed in an electrolyte containing phosphate ions at a relatively low specific amount of electricity, thereby converting the tin oxide layer 20a formed on the surface of the tin-plated steel sheet 10 into an amorphous phosphorus-treated layer 20b containing tin and phosphorus as main components and having an O atomic content of 10 atomic % or less. Then, according to this embodiment, in the third step, cathodic electrolysis is performed using an electrolytic treatment solution containing aluminum ions. This cathodic electrolysis causes a chemical change in the phosphate-treated layer 20b formed in the second step, thereby converting the tin oxide layer 20 into a tin oxide layer containing tin oxide as a main component, and further forming a composite oxide layer 30 and an aluminum oxygen compound layer 40 thereon. Furthermore, according to the third step, the tin oxide layer 20 formed from the amorphous phosphorus-treated layer 20b can have a stannic oxide (SnO) crystal structure (exhibiting a diffraction pattern due to the stannic oxide (SnO) crystal structure). Fig. 3(A) shows a TEM photograph of the cross section of the surface-treated steel sheet of Comparative Example 4, and Fig. 3(B) shows a TEM photograph of the cross section of the surface-treated steel sheet of Example 2. Fig. 3(A) corresponds to a TEM photograph of the cross section after the second step (Comparative Example 4 is an example in which the third step was not carried out after the second step), and Fig. 3(B) is a TEM photograph of the cross section after the third step.

[0050] Nitrate ions may be added to the aluminum ion-containing electrolytic treatment solution used in the third step. When nitrate ions are added to the aluminum ion-containing electrolytic treatment solution, the content of nitrate ions in the electrolytic treatment solution is preferably 11,500 to 25,000 ppm by weight. By setting the content of nitrate ions within the above range, the conductivity of the electrolytic treatment solution can be adjusted to an appropriate range.

[0051] The aluminum ion-containing electrolytic solution used in the third step may contain at least one additive selected from the group consisting of organic acids (citric acid, lactic acid, tartaric acid, glycolic acid, etc.), polyacrylic acid, polyitaconic acid, phenolic resin, etc. By adding these additives to the electrolytic solution alone or in combination, the organic material can be contained in the aluminum oxygen compound layer 40 that is formed. This allows the adhesion of a coating layer made of an organic material to be further improved when the coating layer is formed on the aluminum oxygen compound layer 40.

[0052] When performing cathodic electrolysis in the third step, the amount of electricity in the cathodic electrolysis is preferably 3 to 10 C / dm 2 , more preferably 5 to 8 C / dm 2 By setting the quantity of electricity in the cathodic electrolysis treatment within the above range, it is possible to further improve resistance to sulfide blackening, adhesion to the coating layer, and corrosion resistance. When performing cathodic electrolysis in the third step, an intermittent electrolysis method in which cycles of energizing and stopping the energization may be used.

[0053] Then, in the third step, cathodic electrolysis is carried out, and then washing with water or the like is carried out as necessary, whereby the surface-treated steel sheet 1 can be obtained.

[0054] <Metal container> The surface-treated steel sheet 1 of this embodiment can be used as a component such as a can container or a can lid, although there is no particular limitation thereto. When the surface-treated steel sheet 1 is used as a component such as a can container or a can lid, the surface-treated steel sheet 1 may be used as is (unpainted, with no coating layer formed on the surface) and molded into an unpainted can container or can lid, or a coating layer made of an organic material may be formed on the aluminum oxygen compound layer 40 of the surface-treated steel sheet 1 and then molded into a can container, a can lid, or the like. The organic material constituting the coating layer is not particularly limited and may be appropriately selected depending on the application of the surface-treated steel sheet 1 (for example, the application of a can container to be filled with a specific content), and both a thermoplastic resin and a thermosetting resin can be used.

[0055] Examples of thermoplastic resins that can be used include olefin resin films such as polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic ester copolymer, and ionomer; polyester films such as polyethylene terephthalate and polybutylene terephthalate; unstretched or biaxially stretched films such as polyvinyl chloride and polyvinylidene chloride; and polyamide films such as nylon 6, nylon 6,6, nylon 11, and nylon 12. Among these, non-oriented polyethylene terephthalate copolymerized with isophthalic acid is particularly preferred. The organic material for forming such a coating layer may be used alone or in combination with a blend of different organic materials. As the thermosetting resin, an epoxy-phenol resin, a polyester resin, or the like can be used.

[0056] When a thermoplastic resin is used as the coating layer, it may be a single resin layer or a multi-layer resin layer formed by co-extrusion, etc. When a multi-layer polyester resin layer is used, it is advantageous to select a polyester resin with a composition that has excellent adhesive properties for the base layer, i.e., the surface-treated steel sheet 1 side, and a polyester resin with a composition that has excellent resistance to contents, i.e., excellent resistance to extraction and non-adsorption of flavor components, for the surface layer. Examples of multilayer polyester resin layers, expressed as surface layer / lower layer, include polyethylene terephthalate / polyethylene terephthalate isophthalate, polyethylene terephthalate / polyethylene cyclohexylene dimethylene terephthalate, polyethylene terephthalate isophthalate with a low isophthalate content / polyethylene terephthalate isophthalate with a high isophthalate content, and polyethylene terephthalate isophthalate / [a blend of polyethylene terephthalate isophthalate and polybutylene terephthalate adipate], but are not limited to the above examples. The thickness ratio of the surface layer to the lower layer is preferably in the range of 5:95 to 95:5.

[0057] The coating layer may contain known resin compounding agents, such as antiblocking agents such as amorphous silica, inorganic fillers, various antistatic agents, lubricants, antioxidants (e.g., tocopherol), ultraviolet absorbers, etc., in accordance with known formulations.

[0058] The thickness of the coating layer is preferably in the range of 3 to 50 μm, more preferably 5 to 40 μm, in the case of a thermoplastic resin coating, and in the case of a paint film, the thickness after baking is preferably in the range of 1 to 50 μm, more preferably 3 to 30 μm. By setting the thickness of the coating layer within this range, excellent corrosion resistance can be achieved while maintaining sufficient processability.

[0059] The coating layer can be formed on the surface-treated steel sheet 1 by any means. For example, in the case of a thermoplastic resin coating, it can be formed by extrusion coating, cast film thermal bonding, biaxially stretched film thermal bonding, etc.

[0060] The polyester resin is thermally bonded to the surface-treated steel sheet 1 by the heat quantity of the molten resin layer and the heat quantity of the surface-treated steel sheet 1. The heating temperature of the surface-treated steel sheet 1 is preferably 90°C to 290°C, more preferably 100°C to 230°C, while the temperature of the laminating roll is preferably 10°C to 150°C.

[0061] The coating layer formed on the surface-treated steel sheet 1 can also be formed by thermally bonding a polyester resin film, which has been formed in advance by the T-die method or the inflation film forming method, to the surface-treated steel sheet 1. As the film, an unstretched film formed by a cast molding method in which an extruded film is quenched can be used, or a biaxially stretched film produced by sequentially or simultaneously biaxially stretching this film at a stretching temperature and heat-setting the stretched film can also be used.

[0062] The surface-treated steel sheet 1 of this embodiment can be formed into a can by, for example, forming a coating layer on the surface to obtain an organic material-coated steel sheet, and then processing the obtained can. Examples of the can include, but are not limited to, a seamless can 5 (two-piece can) shown in FIG. 4(A) and a three-piece can 5a (welded can) shown in FIG. 4(B). The body 51 and top lid 52 of the seamless can 5, and the body 51a, top lid 52a, and bottom lid 53 of the three-piece can 5a, are all formed using organic material-coated steel sheets obtained by forming a coating layer on the surface-treated steel sheet 1 of this embodiment. In FIGS. 4(A) and 4(B), the cross-sectional views of the seamless can 5 and the three-piece can 5a are rotated 90° so that the coating layer faces the inner surface of the can. The cans 5, 5a shown in Figures 4(A) and 4(B) can be produced by conventionally known means such as drawing, drawing and re-drawing, bending and stretching by drawing and re-drawing (stretching), bending and stretching by drawing and re-drawing and ironing, or drawing and ironing, so that the coating layer faces the inner surface of the can.

[0063] Furthermore, in seamless cans 5 that are subjected to advanced processes such as bending and stretching by drawing and re-drawing (stretching), and bending and stretching by drawing and re-drawing and ironing, it is preferable that the coating layer be made of a thermoplastic resin coating formed by extrusion coating. That is, such organic material-coated steel sheets have excellent adhesion during processing, and therefore can provide seamless cans that have excellent coating adhesion and excellent corrosion resistance even when subjected to severe processing.

[0064] The surface-treated steel sheet 1 of this embodiment can also be used to produce can lids by forming a coating layer on the surface to obtain an organic material-coated steel sheet as described above, and then processing the steel sheet. The can lids are not particularly limited, but include flat lids, stay-on-tab type easy-open can lids, and full-open type easy-open can lids. [Example]

[0065] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The evaluation methods for each property are as follows.

[0066] <Analysis of electrolytic treatment solution> The electrolytically treated solution was measured for phosphorus ion concentration and aluminum ion concentration using an ICP emission spectrometer (Shimadzu Corporation, ICPE-9000), and for nitrate ion concentration using an ion chromatograph (Dionex Corporation, DX-500). The pH of the electrolytically treated solution was also measured using a pH meter (Horiba, Ltd.).

[0067] <Proportions of atoms in the tin oxide layer 20, the composite oxide layer 30, and the aluminum oxygen compound layer 40> The tin oxide layer 20, the composite oxide layer 30, and the aluminum oxygen compound layer 40 constituting the surface-treated steel sheet were subjected to carbon vapor deposition. Then, approximately 1 μm of carbon was deposited in a FIB system. Samples were cut out by microsampling and fixed on a copper support. Cross-sectional TEM samples were then prepared by FIB processing. Quantitative analysis was performed using TEM observation and energy dispersive X-ray analysis (EDS) with a transmission electron microscope. Specifically, the atomic percentages of each of the Sn, P, Al, O, and Fe atoms in the tin oxide layer 20, the composite oxide layer 30, and the aluminum oxygen compound layer 40 were calculated, assuming the sum of the atomic percentages of Sn, P, Al, O, and Fe atoms is 100 atomic %. The proportion of each atom in the tin oxide layer 20 was measured at a position 5 nm from the surface of the tin plating layer 12, the proportion of each atom in the complex oxide layer 30 was measured at a depth of 7 nm from the outermost surface of the surface-treated steel sheet, and the proportion of each atom in the aluminum oxygen compound layer 40 was measured at a depth of 2 nm from the outermost surface of the surface-treated steel sheet. Note that in both the present example and the comparative example, the amount of Fe was small, at 1 to 10 atomic %, and therefore the amount of O atoms was taken as the remainder of the proportion of Sn atoms, the proportion of P atoms, and the proportion of Al atoms, taking into account the presence of such a small amount of Fe. FIB: Hitachi FB-2000C focused ion beam device, accelerating voltage 40 kV TEM: JEOL JEM-2010F field emission transmission electron microscope, accelerating voltage 200 kV EDS: Nolan UTW type Si(Li) semiconductor detector, analysis area 1nm

[0068] <Thickness of tin oxide layer 20> Similar to the measurement of the proportions of each atom described above, a cross-sectional TEM sample was prepared, and the prepared cross-sectional TEM sample was subjected to TEM observation using a transmission electron microscope and energy dispersive X-ray analysis (EDS) to sequentially perform quantitative analysis from the formation position of the tin plating layer 12 toward the surface side to determine the thickness of the tin oxide layer 20. Specifically, the range where the proportion of Sn atoms was 30 atomic % or more and the proportion of O atoms was 30 atomic % or more was defined as the tin oxide layer 20, and its thickness was defined as the thickness of the tin oxide layer 20.

[0069] <Crystal structure of stannic oxide (SnO2) in the tin oxide layer 20> Cross-sectional TEM samples were prepared in the same manner as in the measurement of the proportions of each atom described above. The diffraction patterns of the prepared cross-sectional TEM samples were measured by nanobeam electron diffraction using a transmission electron microscope (JEOL JEM-2010F field emission transmission electron microscope, accelerating voltage 200 kV). The obtained diffraction patterns were then analyzed using an analysis program (product name "ReciPro," supervised by Kobe University) to determine whether or not the crystalline structure of stannic oxide (SnO2) was present. Specifically, samples with three or more crystal planes derived from the crystalline structure of stannic oxide (SnO2) were considered to contain the crystalline structure of stannic oxide (SnO2).

[0070] <Surface appearance evaluation> The surface of the surface-treated steel sheet 1 was visually observed, and the surface appearance was evaluated according to the following criteria. The better the surface appearance, the better and more desirable the product. In the surface appearance evaluation, when the evaluation was ○ or ◎ according to the following criteria, it was determined that the surface appearance was sufficient for various products. ◎: As a result of visual inspection, there is no difference in appearance compared to the conventional example (Comparative Example 3) ○: As a result of visual inspection, the gloss is slightly inferior to that of the conventional example (Comparative Example 3). ×: As a result of visual inspection, the gloss is inferior to that of the conventional example (Comparative Example 3), and the tin crystal grain pattern is clearly visible.

[0071] <Alkali resistance evaluation> The surface-treated steel sheet 1 was immersed in a 4 wt % aqueous solution of NaOH as an alkaline aqueous solution at 40°C for 15 seconds. After immersion, the surface of the surface-treated steel sheet 1 was visually observed, and the alkali resistance was evaluated according to the following criteria. Specifically, the residual P rate was calculated as a weight percent from the Sn and P film amounts measured before and after immersion using an X-ray fluorescence analyzer (ZSX100e, manufactured by Rigaku Corporation). Since Al dissolves within a few seconds when immersed in an alkaline aqueous solution, it was difficult to use the Al amount as a criterion for evaluation. Therefore, only the P amount was used as the evaluation criteria in this study. If the alkali resistance is poor, when a coating layer is formed on the surface of the surface-treated steel sheet 1, the coating layer will easily dissolve. In the alkali resistance evaluation, a rating of 3 or higher according to the following criteria was considered to be sufficient for the surface-treated steel sheet 1 when used in food and beverage cans. 5 points: The residual P rate is calculated to be more than 40% by weight. 4 points: The calculated residual P rate is greater than 30% by weight and less than 40% by weight. 3 points: The calculated residual P rate is greater than 20% by weight and less than 30% by weight. 2 points: The calculated residual P rate is greater than 0% by weight and less than 20% by weight, and the amount of Sn has also decreased. 1 point: The calculated residual P rate is 0% and the amount of Sn has also decreased.

[0072] <Paint adhesion evaluation> The organic material-coated steel sheet, which was obtained by forming a coating layer on the surface-treated steel sheet 1, was subjected to retort treatment at a temperature of 125°C for 30 minutes, and then a grid was made at 5 mm intervals to a depth reaching the steel sheet 11, which was peeled off with tape, and the degree of peeling was visually observed and evaluated according to the following criteria. In the paint adhesion evaluation, if the surface-treated steel sheet 1 was evaluated as having sufficient adhesion of the coating layer when used for food and beverage cans, a score of 3 or more according to the following criteria was used. 5 points: No peeling of paint was observed by visual inspection. 4 points: Visual inspection revealed that paint peeling was observed over an area of ​​20% or less. 3 points: Visual inspection revealed that the paint had peeled off over an area of ​​more than 20% and less than 50%. 2 points: Visual inspection revealed that the paint had peeled off over an area of ​​more than 50% and less than 80%. 1 point: Visual inspection revealed that the paint had peeled off over an area of ​​more than 80%.

[0073] <Evaluation of sulfur blackening resistance (model liquid)> An organic material-coated steel sheet obtained by forming a coating layer on the surface-treated steel sheet 1 was cut into 40 mm squares, and the cut surfaces were protected with 3 mm wide tape to prepare test pieces. The prepared test pieces were then lined up and placed in a stainless steel container, which was filled with the following model liquid so that the entire test piece was immersed, and then retort-treated at 125°C for 4 hours. Model solution: A pH 7.0 aqueous solution containing sodium dihydrogen phosphate (NaH2PO4) 3.0 g / L, disodium hydrogen phosphate (Na2HPO4) 7.1 g / L, and L-cysteine ​​hydrochloride monohydrate 6 g / L. Thereafter, the test piece was taken out, and the degree of sulfide blackening was visually observed and evaluated according to the following criteria: In the evaluation of sulfide blackening resistance (model solution), if the evaluation score was 3 or more according to the following criteria, the surface-treated steel sheet 1 was judged to have sufficient resistance to sulfide blackening when used for food and beverage cans. 5 points: No sulfide blackening was observed by visual inspection. 4 points: Upon visual inspection, sulfide blackening was observed in an area ratio of 20% or less. 3 points: Upon visual inspection, sulfide blackening was observed in an area ratio of more than 20% and less than 50%. 2 points: Upon visual inspection, sulfide blackening was observed in an area ratio of more than 50% and less than 80%. 1 point: Upon visual inspection, sulfide blackening was observed over an area ratio of more than 80%.

[0074] Example 1 First, a low carbon cold rolled steel sheet (thickness: 0.225 mm) was prepared as the steel sheet 11 .

[0075] Next, the prepared steel sheet 11 was degreased by cathodic electrolysis at 60°C for 10 seconds using an aqueous solution of an alkaline degreasing agent (Formula 618-TK2, manufactured by Japan Quaker Chemical Co., Ltd.). The degreased steel sheet was then rinsed with tap water, and then pickled by immersing it in a pickling agent (a 5% by volume aqueous solution of sulfuric acid) at room temperature for 5 seconds. After that, it was rinsed with tap water, and the steel sheet was tin-plated using a known ferrostane bath under the following conditions, so that the tin amount on both sides of the steel sheet (the tin amount on one side) was 8.4 g / m. 2 The tin-plated layer 12 was then formed on the steel sheet on which the tin-plated layer 12 had been formed. Thereafter, the steel sheet on which the tin-plated layer 12 had been formed was washed with water, and subjected to a reflow treatment in which the steel sheet was heated to above the melting point of tin by passing a direct current through it, and then rapidly cooled by pouring tap water over it, thereby producing a tin-plated steel sheet 10. Bath temperature: 40℃ Current density: 10A / dm 2 Anode material: Commercially available 99.999% metallic tin Total power-on time: 16

[0076] The obtained tin-plated steel sheet 10 was then immersed in an electrolytic treatment solution containing phosphate ions under the following conditions, and while stirring the electrolytic treatment solution, cathodic electrolysis was performed using an iridium oxide-coated titanium sheet positioned at an electrode distance of 17 mm as the anode, and then the direction of current flow was reversed and anodic electrolysis was performed. Composition of electrolytic treatment solution: Aqueous solution containing 10g / L of phosphoric acid and 30g / L of disodium hydrogen phosphate pH of electrolytic treatment solution: 2.5 Electrolytic treatment solution temperature: 40℃ Electrical charge for cathodic electrolysis: 0.15C / dm 2 Amount of electricity for anodic electrolysis: 0.15C / dm 2

[0077] Next, the tin-plated steel sheet 10 that had been subjected to cathodic electrolysis and anodic electrolysis in an electrolytic treatment solution containing phosphate ions was rinsed with water and then immersed in an electrolytic treatment solution containing aluminum ions under the following conditions. While stirring the electrolytic treatment solution, cathodic electrolysis was performed using an iridium oxide-coated titanium sheet positioned at an electrode distance of 17 mm as the anode. Immediately thereafter, the sheet was rinsed with running water and dried to obtain a surface-treated steel sheet 1 in which a tin oxide layer 20, a complex oxide layer 30, and an aluminum oxygen compound layer 40 were formed in this order on the tin-plated steel sheet 10. The tin oxide layer 20, the complex oxide layer 30, and the aluminum oxygen compound layer 40 formed on this tin-plated steel sheet 10 are layers that substantially do not contain chromium. Composition of electrolytic treatment solution: Aqueous solution obtained by dissolving aluminum nitrate as an aluminum compound, with an aluminum ion concentration of 1,500 ppm by weight, a nitrate ion concentration of 15,000 ppm by weight, and a fluoride ion concentration of 0 ppm by weight pH of electrolytic treatment solution: 3.0 Electrolytic treatment solution temperature: 40℃ Electricity consumption for electrolysis: 7.5C / dm 2

[0078] The obtained surface-treated steel sheet 1 was then measured and evaluated according to the above-mentioned methods for the proportion of each atom in the tin oxide layer 20, the composite oxide layer 30, and the aluminum oxygen compound layer 40, the thickness of the tin oxide layer 20, the crystal structure of stannic oxide (SnO) in the tin oxide layer 20, surface appearance evaluation, and alkali resistance evaluation. The results are shown in Table 1.

[0079] Next, the surface-treated steel sheet 1 was subjected to a heat treatment at a temperature of 190°C for 10 minutes, and then the coating thickness after baking and drying was 70 mg / dm 2After applying an epoxy phenol-based paint so that the coating was as shown in Table 1, the paint was baked at 200°C for 10 minutes to form a coating layer on the surface-treated steel sheet 1, thereby obtaining an organic material-coated steel sheet. Next, the obtained organic material-coated steel sheet was evaluated for paint adhesion and resistance to sulfur blackening (model liquid) according to the methods described above. The results are shown in Table 1.

[0080] Example 2 The amount of electricity in electrolysis using an electrolytic treatment solution containing phosphate ions is 0.25 C / dm 2 Anode electrolysis electricity amount: 0.25C / dm 2 Except for this, a surface-treated steel sheet 1 and an organic material-coated steel sheet were obtained and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0081] Example 3 The amount of electricity in electrolysis using an electrolytic treatment solution containing phosphate ions is 0.35 C / dm 2 Anode electrolysis electricity amount: 0.35C / dm 2 Except for this, a surface-treated steel sheet 1 and an organic material-coated steel sheet were obtained and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0082] Example 4 The amount of electricity in electrolysis using an electrolytic treatment solution containing phosphate ions is 0.5 C / dm 2 Anode electrolysis electricity amount: 0.5C / dm 2 Except for this, a surface-treated steel sheet 1 and an organic material-coated steel sheet were obtained and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0083] Comparative Example 1 The amount of electricity in electrolysis using an electrolytic treatment solution containing phosphate ions is 0.75 C / dm 2 Anode electrolysis electricity amount: 0.75C / dm 2 The quantity of electricity for the cathodic electrolysis treatment using an electrolytic treatment solution containing aluminum ions is set to 6.2 C / dm 2Except for this, surface-treated steel sheets and organic material-coated steel sheets were obtained and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0084] Comparative Example 2 The amount of electricity in electrolysis using an electrolytic treatment solution containing phosphate ions is 0.9 C / dm 2 Anode electrolysis electricity amount: 0.9C / dm 2 The quantity of electricity for the cathodic electrolysis treatment using an electrolytic treatment solution containing aluminum ions is set to 6.0 C / dm 2 Except for this, surface-treated steel sheets and organic material-coated steel sheets were obtained and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0085] Comparative Example 3 Except for not carrying out the electrolysis treatment with an electrolysis solution containing phosphate ions and the cathodic electrolysis treatment with an electrolysis solution containing aluminum ions, surface-treated steel sheets and organic material-coated steel sheets were obtained and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0086] Comparative Example 4 Except for not carrying out the cathodic electrolysis treatment using an electrolytic treatment solution containing aluminum ions, surface-treated steel sheets and organic material-coated steel sheets were obtained and evaluated in the same manner as in Example 2. The results are shown in Table 1.

[0087] [Table 1]

[0088] Example 5 By changing the current density and the total current application time when tin plating is performed on the steel sheet 11, the tin amount of the tin plating layer 12 (the tin amount on one side) can be increased to 2.8 g / m 2 The amount of electricity in the electrolytic treatment using an electrolytic treatment solution containing phosphate ions was set to 0.05 C / dm 2 Anode electrolysis electricity amount: 0.05C / dm 2Except for this, a surface-treated steel sheet 1 and an organic material-coated steel sheet were obtained and evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0089] Example 6 The amount of electricity in electrolysis using an electrolytic treatment solution containing phosphate ions is 0.15 C / dm 2 Anode electrolysis electricity amount: 0.15C / dm 2 Except for this, a surface-treated steel sheet 1 and an organic material-coated steel sheet were obtained and evaluated in the same manner as in Example 5. The results are shown in Table 2.

[0090] Example 7 The amount of electricity in electrolysis using an electrolytic treatment solution containing phosphate ions is 0.25 C / dm 2 Anode electrolysis electricity amount: 0.25C / dm 2 Except for this, a surface-treated steel sheet 1 and an organic material-coated steel sheet were obtained and evaluated in the same manner as in Example 5. The results are shown in Table 2.

[0091] Example 8 The amount of electricity in electrolysis using an electrolytic treatment solution containing phosphate ions is 0.35 C / dm 2 Anode electrolysis electricity amount: 0.35C / dm 2 Except for this, a surface-treated steel sheet 1 and an organic material-coated steel sheet were obtained and evaluated in the same manner as in Example 5. The results are shown in Table 2.

[0092] Example 9 The amount of electricity in electrolysis using an electrolytic treatment solution containing phosphate ions is 0.5 C / dm 2 Anode electrolysis electricity amount: 0.5C / dm 2 Except for this, a surface-treated steel sheet 1 and an organic material-coated steel sheet were obtained and evaluated in the same manner as in Example 5. The results are shown in Table 2.

[0093] Comparative Example 5 The amount of electricity in electrolysis using an electrolytic treatment solution containing phosphate ions is 0.75 C / dm 2 Anode electrolysis electricity amount: 0.75C / dm 2 The quantity of electricity for the cathodic electrolysis treatment using an electrolytic treatment solution containing aluminum ions is set to 6.2 C / dm 2 Except for this, surface-treated steel sheets and organic material-coated steel sheets were obtained and evaluated in the same manner as in Example 5. The results are shown in Table 2.

[0094] Comparative Example 6 The amount of electricity in electrolysis using an electrolytic treatment solution containing phosphate ions is 0.9 C / dm 2 Anode electrolysis electricity amount: 0.9C / dm 2 The quantity of electricity for the cathodic electrolysis treatment using an electrolytic treatment solution containing aluminum ions is set to 6.0 C / dm 2 Except for this, surface-treated steel sheets and organic material-coated steel sheets were obtained and evaluated in the same manner as in Example 5. The results are shown in Table 2.

[0095] Comparative Example 7 Except for not carrying out the electrolysis using an electrolysis solution containing phosphate ions and the cathodic electrolysis using an electrolysis solution containing aluminum ions, surface-treated steel sheets and organic material-coated steel sheets were obtained and evaluated in the same manner as in Example 5. The results are shown in Table 2.

[0096] Comparative Example 8 Except for not carrying out the cathodic electrolysis treatment using an electrolytic treatment solution containing aluminum ions, surface-treated steel sheets and organic material-coated steel sheets were obtained and evaluated in the same manner as in Example 7. The results are shown in Table 2.

[0097] [Table 2]

[0098] As shown in Tables 1 and 2, the surface-treated steel sheets 1 of Examples 1 to 9, which had a tin oxide layer 20, a composite oxide layer 30, and an aluminum oxygen compound layer 40 formed in this order on a tin-plated steel sheet 10, and in which the tin oxide layer 20 had a thickness of 8 to 20 nm, exhibited good surface appearance, excellent resistance to sulfide blackening and alkali resistance, and high adhesion to coating layers. Furthermore, when the diffraction patterns of the tin oxide layers 20 of all of the surface-treated steel sheets 1 of Examples 1 to 9 were measured by nanobeam electron diffraction using a transmission electron microscope, the tin oxide layers 20 exhibited diffraction patterns attributable to the crystalline structure of stannic oxide (SnO). That is, the tin oxide layers 20 contained the crystalline structure of stannic oxide (SnO). Note that FIG. 2 shows the diffraction pattern of the tin oxide layer 20 of Example 7 measured by nanobeam electron diffraction using a transmission electron microscope.

[0099] On the other hand, Comparative Examples 1, 2, 5, and 6, in which the thickness of the tin oxide layer 20 was less than 8 nm, were inferior in surface appearance. 2 Comparative Examples 1 and 2, in which the amount was increased, were inferior in surface appearance and also in alkali resistance. In addition, Comparative Examples 3, 4, 7, and 8, in which the surface-treated steel sheet did not have a configuration including the tin oxide layer 20, the composite oxide layer 30, and the aluminum oxygen compound layer 40, were inferior in resistance to sulfide blackening and also had poor adhesion to the coating layer. Furthermore, in Comparative Examples 4 and 8, the results of component analysis (EDS analysis) showed that the main component of the coating was Sn, and therefore the tin ions Sn generated from the tin-plated steel sheet 10 2+ It is thought that tin ions (Sn) received electrons during electrolysis and precipitated on the surface as tin. This is because the dissolved tin ions (Sn) were precipitated on the surface as tin during electrolysis using an electrolytic treatment solution containing phosphate ions. 2+ It is thought that this precipitated on the surface as shown in Figure 3(A), incorporating the P in the treatment bath. In all of Comparative Examples 1 to 3 and 5 to 7, when the diffraction pattern of the tin oxide layer 20 was measured by nanobeam electron diffraction using a transmission electron microscope, the tin oxide layer 20 did not exhibit a diffraction pattern due to the crystal structure of stannic oxide (SnO2). Figure 5 shows the diffraction pattern of the tin oxide layer 20 of Comparative Example 4 measured by nanobeam electron diffraction using a transmission electron microscope. [Explanation of symbols]

[0100] 1...Surface-treated steel sheet 10...Tin-plated steel sheet 11...Steel plate 12...Tin plating layer 20...Tin oxide layer 30...Complex oxide layer 40...Aluminum oxygen compound layer

Claims

[Claim 1] A first step of preparing a tin-plated steel sheet by plating a steel sheet with tin; The tin-plated steel sheet was electrolytically treated in an electrolytic treatment solution containing phosphate ions at 0.1 C / dm ２ Above, 0.7C / dm ２ A second step of performing electrolysis with the following amount of electricity: a third step of subjecting the tin-plated steel sheet that has been subjected to the electrolytic treatment in the second step to a cathodic electrolytic treatment in an electrolytic treatment solution containing aluminum ions; In the second step, when the electrolytic treatment is performed, cathodic electrolytic treatment is performed first, and then anodic electrolytic treatment is performed.

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