Tin-plated steel sheet and can

Abstract

Provided is a tin-plated steel sheet having superior yellowing resistance without conventional chromate treatment, wherein the steel sheet is used for containers and has a zirconium-containing film layer.　The tin-plated steel sheet comprises: a steel sheet; a tin-plating layer disposed on at least one surface of the steel sheet; and a film layer that is disposed on the tin-plating layer and contains zirconium oxide and tin sulfide, wherein the plating amount of the tin-plating layer is 0.1 g / m2 to 15 g / m2 in terms of metal Sn content, and in the film layer, the plating amount of zirconium oxide is 0.2 mg / m2 to 50 mg / m2 in terms of metal Zr content and the plating amount of tin sulfide is 0.1 mg / m2 to 5 mg / m2 in terms of sulfur content.

Description

Technical Field

[0001] The present invention relates to a tin-plated steel sheet and a can. This application claims priority based on Japanese Patent Application No. 2022-098082 filed in Japan on June 17, 2022, and incorporates its content herein.

Background Art

[0002] Tin-plated steel sheets are well-known as "tinplate" and are widely used for cans that contain beverages and foods, as well as for other food-related applications. This is because tin is safe for the human body and is a beautiful metal.

[0003] This tin-plated steel sheet is mainly manufactured by electroplating. This is because the electroplating method is more advantageous than the hot-dip plating method in controlling the amount of tin, which is a relatively expensive metal, to the minimum necessary amount. That is, the tin-plated steel sheet is manufactured by forming a tin-plated layer having a beautiful metallic luster on the surface of the steel sheet by performing an electroplating treatment, or an electroplating treatment and a heat melting treatment. Further, a chromate film is often applied on the tin-plated layer of the tin-plated steel sheet by performing a chromate treatment such as an electrolytic treatment or an immersion treatment using a solution of hexavalent chromate on the tin-plated steel sheet.

[0004] The effects of the chromate film include prevention of blackening of the tin plating layer due to sulfidation, prevention of yellowing of the tin plating layer, and prevention of deterioration of the coating adhesion. The blackening of the tin plating layer due to sulfidation is a phenomenon in which sulfur (S) in the contents of the can reacts with tin (Sn) and iron (Fe) contained in the tin plating layer to form black sulfides. By forming a chromate film, it is possible to prevent blackening due to sulfidation. Also, the yellowing of the tin plating layer is a phenomenon caused by the progress of oxidation on the surface of the tin plating layer, and by forming a chromate film, the yellowing of the tin plating layer is suppressed. Furthermore, the deterioration of the coating adhesion is a phenomenon that occurs due to the agglomeration and destruction of tin oxides when the tin plating layer is painted and used. By forming a chromate film between the tin plating layer and the coating film, deterioration of the coating adhesion can be prevented.

[0005] On the other hand, in recent years, due to the increasing awareness of environmental and safety issues, products that do not contain hexavalent chromium are required for final products, and furthermore, it is required not to perform chromate treatment itself. However, as described above, tin-plated steel sheets without a chromate film have reduced resistance to blackening due to sulfidation, yellowing of the appearance due to the growth of tin oxides, and reduced coating adhesion.

[0006] Therefore, several proposals have been made for tin-plated steel sheets with a film treatment to replace the chromate film.

[0007] For example, in Patent Document 1 below, a tin-plated steel sheet has been proposed in which a film containing P and Si is formed by treatment using a solution containing phosphate ions and a silane coupling agent.

[0008] Also, in Patent Document 2 below, a tin-plated steel sheet has been proposed in which a film containing a reaction product of aluminum phosphate, Al and P, at least one of Ni, Co, and Cu, and a silane coupling agent is formed by treatment using a solution containing aluminum phosphate.

[0009] Furthermore, Patent Document 3 proposes a method for manufacturing tin-plated steel sheets without a chromate coating, in which a Zn plating is applied to a tin-plated surface, followed by a heat treatment until the Zn-only plating layer disappears.

[0010] Furthermore, Patent Documents 4 and 5 below propose steel sheets for containers having a chemical conversion coating containing zirconium, phosphoric acid, phenolic resin, etc. [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] Japanese Patent Publication No. 2004-60052 [Patent Document 2] Japanese Patent Publication No. 2011-174172 [Patent Document 3] Japanese Patent Application Publication No. 63-290292 [Patent Document 4] Japanese Patent Publication No. 2007-284789 [Patent Document 5] Japanese Patent Publication No. 2010-13728 [Overview of the project] [Problems that the invention aims to solve]

[0012] However, the tin-plated steel sheets and their manufacturing methods proposed in the above-mentioned Patent Documents 1 to 5 have problems in that they cannot sufficiently suppress the formation of black sulfides and the growth of tin oxides over time, resulting in poor resistance to sulfidation blackening and yellowing.

[0013] Therefore, the present invention has been made in view of the above problems, and the object of the present invention is to provide tin-plated steel sheets and cans that are even better in terms of resistance to sulfur blackening and yellowing without conventional chromate treatment. [Means for solving the problem]

[0014] To solve the above problems, the inventors conducted diligent research and found that by forming a film containing zirconium oxide and tin sulfide on the surface of a tin-plated steel sheet, it is possible to create a tin-plated steel sheet with even better resistance to yellowing without chromate treatment.

[0015] Based on the above findings, the gist of the present invention is as follows: (1) Steel plate and A tin-based plating layer located on at least one side of the steel plate, The coating layer is located on the tin-based plating layer and contains zirconium oxide and tin sulfide, The amount of the tin-based plating layer is 0.1 g / m² in terms of metallic Sn content. 2 More than 15g / m 2 The following: The amount of zirconium oxide deposited in the aforementioned coating layer is 0.2 mg / m² in terms of metallic Zr content. 2 More than 50mg / m 2 The following conditions apply, and the amount of tin sulfide adhering to the surface is 0.1 mg / m² in terms of sulfur content. 2 More than 5mg / m 2 A tin-plated steel sheet characterized by the following: (2) The tin-plated steel sheet according to (1), characterized in that the tin sulfide is SnS. (3) A can made of tin-plated steel sheet as described in (1) or (2) above.

[0016] It is preferable that the tin sulfide is present in a layered manner on the surface of the coating layer. Furthermore, it is preferable that the tin sulfide is dispersed within the coating layer. Furthermore, it is preferable that the tin sulfide is dispersed within the coating layer and present in a layered manner on the surface of the coating layer. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide tin-plated steel sheets and cans that are even more superior in resistance to sulfur blackening and yellowing without conventional chromate treatment. [Brief explanation of the drawing]

[0018] [Figure 1] Figure 1 is a schematic cross-sectional view of a tin-plated steel sheet according to an embodiment of the present invention, showing a case where zirconium oxide and tin sulfide are formed in layers. [Figure 2] Figure 2 is a schematic cross-sectional view of a tin-plated steel sheet according to an embodiment of the present invention, and is a schematic view of a case in which zirconium oxide and tin sulfide are mixed and formed. [Figure 3] Figure 3 is a schematic cross-sectional view of a tin-plated steel sheet according to an embodiment of the present invention, showing a case where zirconium oxide and tin sulfide are mixed and the tin sulfide is formed in layers. [Figure 4] Figure 4 is a perspective view showing an example of a can that is an embodiment of the present invention. [Modes for carrying out the invention]

[0019] Preferred embodiments of the present invention will be described in detail below.

[0020] The present invention, described below, relates to tin-plated steel sheets widely used for cans containing food, beverages, and other items. More specifically, it relates to tin-plated steel sheets and cans that offer superior resistance to sulfur blackening and yellowing without the need for conventional chromate treatment.

[0021] <1. Tin-plated steel sheet> As shown in Figures 1 to 3, the tin-plated steel sheet according to this embodiment is characterized by comprising a steel sheet, a tin-based plating layer provided on at least one surface of the steel sheet, and a film layer provided on the surface of the tin-based plating layer containing a predetermined amount of zirconium oxide and tin sulfide.

[0022] (1.1 steel plate) The steel sheet used as the base material for the tin-plated steel sheet according to this embodiment is not particularly limited, and any steel sheet used for tin-plated steel sheets for general containers can be used. Examples of such steel sheets include low-carbon steel sheets and ultra-low-carbon steel sheets.

[0023] (1.2 Tin-based plating layer) A tin-based plating layer is formed on at least one or both sides of the steel sheet described above. This tin-based plating layer improves the corrosion resistance of the steel sheet. In this specification, "tin-based plating layer" includes not only a plating layer made of metallic tin, but also metallic tin mixed with impurities or metallic tin containing trace elements.

[0024] In other words, the tin-based plating layer contains 90.0% by mass or more of tin (Sn) and the remainder being impurities. Alternatively, the tin-based plating layer may consist of 90.0% by mass or more of tin (Sn) and the remainder being impurities. In this case, the tin content in the tin-based plating layer may be 95.0% by mass or more, 98.0% or more, 99.0% by mass or more, 99.5% by mass or more, or 99.9% by mass or more. Furthermore, in addition to tin and impurities, trace amounts of alloying elements may also be included.

[0025] Furthermore, the tin-based plating layer may contain more than 50.0% by mass of tin (Sn), 0 to 20% by mass of Fe, and the remainder being impurities. Alternatively, the tin-based plating layer may consist of more than 50.0% by mass of tin (Sn), 0 to 20% by mass of Fe, and the remainder being impurities. In addition, trace amounts of alloying elements may be included in addition to tin, Fe, and impurities. Thus, a tin-based plating layer containing tin and Fe is composed of an Fe-tin alloy. Furthermore, the tin-based plating layer may have a single-layer structure of Fe-tin alloy layers, or a two-layer structure of Fe-tin alloy layers and a tin layer laminated on top of the Fe-tin alloy layer. In this case, the ratio of the thickness of the tin layer to the iron-tin alloy layer is not particularly limited.

[0026] As described above, the tin-based plating layer can take various forms, but as long as the deposition amount as the amount of metallic tin described below is ensured throughout the tin-based plating layer, the limitation of the chemical composition of the tin-based plating layer is not essential in the present invention.

[0027] In the tin-based plating layer according to the present embodiment, the deposition amount of the tin-based plating layer per side is not particularly limited. For example, as the amount of metallic tin, it is 0.1 g / m 2 or more and 15 g / m 2 or less, preferably 1.0 g / m 2 or more and 10 g / m 2 or less. When the deposition amount of the tin-based plating layer per side is 0.1 g / m 2 or more in terms of tin conversion amount, the corrosion resistance can be made sufficiently excellent. Further, when the deposition amount of the tin-based plating layer per side is 15 g / m 2 or less in terms of tin conversion amount, while suppressing the decrease in adhesion and the increase in cost, the effect of improving the corrosion resistance by tin can be sufficiently obtained. The lower limit of the deposition amount of the tin-based plating layer per side is preferably 1.0 g / m 2 or more, more preferably 2.0 g / m 2 or more, and even more preferably 2.5 g / m 2 or more as the amount of metallic tin. The upper limit of the deposition amount of the tin-based plating layer per side is preferably 10 g / m 2 or less, more preferably 5.0 g / m 2 or less, 4.0 g / m 2 or less, 3.5 g / m 2 or less, and even more preferably 3.0 g / m 2 or less.

[0028] Here, the amount of tin deposited on one side is the value measured by, for example, the electrolytic stripping method or X-ray fluorescence analysis method described in JIS G 3303:2017. When measuring by X-ray fluorescence analysis, the primary line of fluorescent X-rays used for measurement is SnαK (wavelength 0.0492 nm). The target of the X-ray tube is Rh, and the tube voltage and tube current are set to appropriate values ​​in the range of 30-40 kV and 80-100 mA, respectively. The slit width, spectroscopic crystal, and detector are selected to have conditions suitable for the resolution and tin deposit range for the fluorescent X-rays to be measured. A calibration curve is created using the fluorescent X-ray intensity from test pieces with known tin deposit amounts. Then, the tin-based plating layer to be measured is irradiated with X-rays according to the set conditions, and the fluorescent X-ray intensity is measured. Next, the amount of tin deposited in the tin-based plating layer is determined from the fluorescent X-ray intensity using the calibration curve. Furthermore, the measurement points are defined as circular areas with a diameter of 30 mm on the surface of the coating layer. Measurements are taken at any five measurement points on the surface of the coating layer, and the arithmetic mean of these measurements is taken as the measurement result. When measuring the amount of tin deposited in a tin-based plating layer, it is not necessary to remove the coating layer; the amount of tin deposited can be measured directly from the surface of the coating layer using fluorescent X-rays while the coating layer is still present.

[0029] To determine the amount of iron deposited in a tin-based plating layer (the amount of iron in the tin-iron alloy layer), the electrolytic stripping method (constant current electrolytic method) is used. Specifically, the following method is used: After cutting a tin-plated steel sheet into a test piece measuring 20 mm x 50 mm, the surface is measured over a 4 cm² area. 2 After sealing the area other than the measurement area, i.e., the area of ​​the surface other than the measurement area and the entire surface opposite to the surface, with tape, it was immersed in 1 mol / L, 150 mL, 25°C hydrochloric acid, with a Pt plate as the counter electrode and a silver / silver chloride electrode (saturated KCl) as the reference electrode, for 4 cm 2An anode current of 0.02A is passed through the tin-plated steel sheet, and the tin-based plating is dissolved while measuring the potential. In the time domain from the start of measurement, the region (A) where the potential of the tin-plated steel sheet relative to the silver / silver chloride electrode (saturated KCl) is -0.4V or less is the time domain in which non-alloyed tin is detected, the region (B) where it is greater than -0.4V and less than or equal to -0.3V is the time domain in which tin plating containing iron (tin-iron alloy layer) is detected, and the region where it is greater than -0.3V is the time domain in which the underlying steel sheet portion is detected. The length of region (B) (time T(B)(seconds)) is measured, and the amount of tin in the tin-iron alloy layer (g / m) is calculated from the following formula. 2 )

[0030] Tin amount (g / m 2 )={118.7×0.02×T(B) / (96500×2)}×2500

[0031] From this tin content, the amount of iron in the plating layer can be calculated using the following formula.

[0032] Iron amount (g / m 2 )=[Tin amount]×55.85 / 293.25

[0033] The above measurements were performed at five arbitrary locations on the tin-based plating layer, and the arithmetic mean of the results was taken as the iron content.

[0034] (1.3 Coating layer containing zirconium oxide and tin sulfide) The tin-plated steel sheet according to this embodiment has a film layer containing zirconium oxide and tin sulfide on the surface of the steel sheet having the tin-based plating layer described above. The film layer may also contain substances other than zirconium oxide and tin sulfide, such as compounds containing P (phosphorus) or F (fluorine), as long as they do not hinder the effects of the present invention. Furthermore, the content of organic components in the film layer is preferably 0.1% by mass or less. In this embodiment, organic components such as polymer compounds and organic compounds are not intentionally added, but may be unavoidably included as long as they do not hinder the effects of the present invention. While the film layer may contain various substances other than zirconium oxide and tin sulfide as described above, it is sufficient that the amount of Zr and sulfur described below are ensured in the entire film layer, and the composition of the film layer is not necessarily limited in this invention.

[0035] By forming the zirconium oxide and tin sulfide described above on the surface of the tin-plated steel sheet, the resistance to yellowing can be further improved. The reason for this is not entirely clear, but based on detailed investigations by the inventors, we believe the following:

[0036] Conventional films containing zirconium oxide, such as those shown in Patent Document 4 or Patent Document 5, are formed on the tin-plated surface by utilizing the pH increase resulting from hydrogen generation from the tin-plated surface during cathode electrolysis. However, films containing zirconium oxide formed by this method are relatively rough and therefore easily permeable to oxygen, causing the tin-plated surface to oxidize and yellow. Furthermore, films containing zirconium oxide contain a small amount of tin, and yellowing also occurs due to the oxidation of this tin.

[0037] Therefore, the inventors attempted to improve the yellowing resistance of conventional zirconium oxide-containing coatings and found that by forming a coating containing zirconium oxide and tin sulfide on a tin-plated steel sheet, the growth of tin oxide could be suppressed and yellowing resistance improved. This is presumed to be due to (A) the excellent barrier properties against oxygen permeability of tin sulfide itself, and (B) the increased density of the coating due to the coexistence of zirconium oxide and tin sulfide, which improved the barrier properties against oxygen permeability.

[0038] The amount of zirconium oxide deposited is 0.2 mg / m² in terms of metallic Zr content. 2 More than 50mg / m 2 The following is required: 0.2 mg / m² 2 If the value is less than 50 mg / m², the resistance to sulfurization and blackening is poor. 2 If the concentration exceeds this, the coating adhesion will be poor. The preferred range is 0.5 mg / m². 2 More than 25mg / m 2 The more preferred range is 1.0 mg / m². 2 More than 10mg / m 2 The following applies:

[0039] The amount of Zr deposited is determined by performing X-ray fluorescence measurement on a tin-plated steel sheet with the coating layer according to this embodiment formed on its surface, and the value obtained from the result is defined as the amount of Zr deposited.

[0040] Furthermore, there is no problem if any element such as Fe, Ni, Cr, Ca, P, Na, Mg, Al, Si, P, F, etc. is included in the zirconium oxide. For example, a zirconium oxide containing these elements may be a composite oxide with zirconium as the main component.

[0041] In other words, zirconium oxide is a substance mainly composed of zirconium and oxygen, represented by the chemical formula, for example, ZrO2. Furthermore, zirconium oxide may contain P or F in solid solution, or P or F may be substituted for some of the oxygen. As mentioned above, Fe, Ni, Cr, Ca, P, Na, Mg, Al, and Si may also be present in solid solution or as substitutions. The presence of zirconium oxide can be detected by X-ray photoelectron spectroscopy (XPS) of the film layer, where Zr3d is present in the range of 182.3 ± 0.5 eV. 5 / 2 This can be confirmed by the appearance of a peak. In addition, P and F may be contained in the zirconium oxide as well as in the coating.

[0042] The composition of the tin sulfide is not particularly limited, but examples include SnS, SnS2, and Sn2S3. The amount of tin sulfide deposited is 0.1 mg / m³ in terms of sulfur content. 2 More than 5mg / m 2 The following is required: Sulfur content of 0.1 mg / m³ 2 If the value is less than 5 mg / m², the improvement in resistance to yellowing is insufficient, and the sulfur content should be 5 mg / m². 2 In the case of excessive amounts, the appearance changes due to the color of the tin sulfide itself, which is undesirable. For example, SnS is grayish-black, and SnS2 and Sn2S3 are yellow, so if the amount is excessive, the appearance will become blackish or yellowish. A more preferable range is 0.2 mg / m². 2 3mg / m or more 2 The following applies. Furthermore, from the viewpoint of improving resistance to yellowing, SnS, such as SnS2 and Sn2S3, which do not have a yellowish color, is preferred as the tin sulfide. The amount of sulfur is determined by performing X-ray fluorescence measurement on a tin-plated steel sheet with the coating layer according to this embodiment formed on its surface, and the value obtained from the result is defined as the amount of sulfur.

[0043] When measuring the amount of Zr deposited and sulfur in a coating layer using X-ray fluorescence analysis, the primary fluorescent X-rays used for measurement are ZrαK (wavelength 0.0787 nm) and SαK (wavelength 0.537 nm). The target of the X-ray tube is Rh, and the tube voltage and tube current are set to appropriate values ​​within the ranges of 30-40 kV and 80-100 mA, respectively. The slit width, spectroscopic crystal, and detector are selected to suit the resolution, Zr deposit amount, and sulfur amount range for the fluorescent X-rays to be measured. A calibration curve is created using the fluorescent X-ray intensities from test specimens with known Zr deposit and sulfur amounts. Then, the coating layer to be measured is irradiated with X-rays according to the set conditions, and the fluorescent X-ray intensity is measured. Subsequently, the amount of Zr deposited and sulfur in the coating layer is determined from the fluorescent X-ray intensity using the calibration curve. Furthermore, the measurement points are defined as circular areas with a diameter of 30 mm on the surface of the coating layer. Measurements are taken at any five locations on the surface of the coating layer, and the arithmetic mean of these measurements is taken as the measurement result.

[0044] Furthermore, the coating layer containing the zirconium oxide and tin sulfide described above may be formed in layers as a coating layer, as shown in Figure 1. In the example shown in Figure 1, there is a layer containing zirconium oxide on top of a tin-based plating layer, and a layer containing tin sulfide on top of that.

[0045] Furthermore, the coating layer may be a dispersed mixture of zirconium oxide and tin sulfide, as shown in Figure 2. In the example shown in Figure 2, zirconium oxide constitutes the matrix of the coating layer, and tin sulfide is dispersed within that matrix.

[0046] Furthermore, as shown in Figure 3, the coating layer may be a dispersed mixture of zirconium oxide and tin sulfide, and a layer containing tin sulfide may be formed on the surface side of the coating layer. In the example shown in Figure 3, zirconium oxide constitutes the matrix of the coating layer, tin sulfide is dispersed in the matrix, and there is also a layer containing tin sulfide on the surface.

[0047] In this embodiment, as shown in Figures 1, 2, and 3, resistance to sulfidation blackening and yellowing can be improved regardless of the state in which zirconium oxide and tin sulfide are present. In the embodiment shown in Figure 1, the presence of layered tin sulfide on the surface side of the coating layer means that, for example, if the tin-plated steel sheet of this embodiment is used as a structural material for a can, even if sulfur (S) is generated from the food filled in the can, the layered tin sulfide acts as a barrier, and the layer made of zirconium oxide also exhibits a barrier effect against the penetration of sulfur (S). As a result, sulfur cannot penetrate to the tin-based plating layer, the formation of new tin sulfide is suppressed, and thus resistance to sulfidation blackening can be improved.

[0048] Furthermore, in the configuration shown in Figure 2, the presence of tin sulfide along with zirconium oxide within the coating layer means that, for example, when the tin-plated steel sheet of this embodiment is formed into a can, cracks may occur in the coating layer, and even if sulfur (S) is released from the food filled into the can with the cracks remaining, almost all of the tin (Sn) contained in the coating layer has been converted into tin sulfide. This suppresses the further formation of tin sulfide, thereby improving resistance to sulfurization and blackening.

[0049] Furthermore, in the configuration shown in Figure 3, the effects of the configurations shown in Figures 1 and 2 are both exhibited. Therefore, even if sulfur (S) is generated from the food stored in the can, the formation of new tin sulfides is suppressed, thereby improving resistance to sulfurization and blackening.

[0050] Furthermore, in all of the configurations shown in Figures 1 to 3, since the tin-based plating layer is covered with the film layer, the formation of tin oxide on the surface of the tin-based plating layer is suppressed, thereby improving resistance to yellowing.

[0051] To confirm whether the coating layer of this embodiment is in one of the forms shown in Figures 1 to 3, observation with a transmission electron microscope is performed. Specifically, a thin film sample of the coating layer is prepared by microtome so that the cross-section of the tin-plated steel sheet of this embodiment can be observed. At least five regions of the obtained thin film sample, each measuring 100 nm × 100 nm (a region where the thickness is 100 nm in the direction parallel to the width direction of the sheet and 100 nm in the thickness direction of the sheet), are observed at a magnification of 1,000,000 times using a 200 kV field emission transmission electron microscope (FE-TEM), and elemental mapping is performed using an energy-dispersive X-ray analyzer (EDS). From the elemental mapping results, the regions where Sn, Zr, and S are present are confirmed. If Sn and S are detected at the same location, tin sulfide is present at that location. Also, zirconium oxide is present in the region where Zr is detected. In this way, by confirming the locations of tin sulfide and zirconium oxide, it is possible to confirm which of the forms shown in Figures 1 to 3 it is.

[0052] If the width direction of a thin film sample cannot be uniquely determined, it can be determined as follows. The width direction of a thin film sample is the width direction of the steel sheet before the thin film sample is prepared, and is perpendicular to the rolling direction and the thickness direction. The rolling direction is the direction parallel to the elongation direction of the crystal grains in the metal structure of the steel sheet. The elongation direction of the crystal grains is the direction parallel to the long axis direction of the crystal grains. The long axis directions of all crystal grains are not necessarily all oriented in the same direction and may have some variation. For example, five crystal grains can be arbitrarily selected by image analysis using an electron microscope, the long axis direction of each crystal grain can be determined, a unit vector for each long axis direction can be obtained, and the sum of these unit vectors can be taken to obtain a composite vector. The direction of this composite vector can be defined as the long axis direction of the crystal grains, and the direction parallel to this can be defined as the rolling direction.

[0053] Furthermore, the tin-plated steel sheet according to this embodiment may have a tin-based plating layer and a film layer on at least one side of the steel sheet. The other side of the steel sheet may have either a tin-based plating layer or a film layer, or both, or it may not have both a tin-based plating layer and a film layer. Also, the tin-plated steel sheet may have a tin-based plating layer and a film layer on both sides of the steel sheet. Furthermore, the tin-plated steel sheet according to this embodiment may have a layer or film composed of other components on the other side.

[0054] <2. Cans> The tin-plated steel sheet of this embodiment can be used as a material for cans, for example. Figure 4 shows a DR can, which can be used for food storage, as an example of a can. Cans manufactured using the tin-plated steel sheet of this embodiment can be used as food cans, beverage cans, oil or paint cans, etc., and their use is not particularly limited. The method of manufacturing the can is not particularly limited and can be a general method. For example, for a three-piece can, the tin-plated steel sheet of this embodiment is cut into a predetermined shape, and then the cut tin-plated steel sheet is rolled into a cylindrical shape and both ends are welded to manufacture the can body. The bottom lid and top lid are manufactured by punching the tin-plated steel sheet into a predetermined shape. Then, one of the bottom lid and top lid is crimped and joined to the can body, and after filling with food or other contents, the other of the bottom lid and top lid is crimped and joined to the can body to manufacture a can containing food. At this time, the coating portion according to this embodiment is arranged on the inner surface of at least the can body, bottom lid and top lid. Of course, the coating portion according to this embodiment may also be arranged on the outer surface.

[0055] The can according to this embodiment is made of tin-plated steel sheet according to this embodiment, and since tin-plated steel sheet has excellent resistance to sulfurization blackening and yellowing, concerns regarding food hygiene can be reduced.

[0056] The tin-plated steel sheet according to this embodiment may be manufactured by any method, but for example, it can be manufactured by the method for manufacturing a tin-plated steel sheet described below.

[0057] <3. Manufacturing method for tin-plated steel sheet> An example of a method for manufacturing a tin-plated steel sheet according to this embodiment will be described. In this embodiment, a steel sheet having a tin-based plating layer on at least one side is immersed in a solution containing zirconium ions or subjected to a first cathodic electrolytic treatment in a solution containing zirconium ions to generate zirconium oxide on the tin-based plating layer, and then the steel sheet after the zirconium oxide has been formed is subjected to a second cathodic electrolytic treatment in an electrolyte solution containing sulfur (S). In this embodiment, prior to the first and second cathode electrolytic treatments described above, a steel sheet is prepared, and a tin-based plating layer is formed on at least one side of the steel sheet by tin plating.

[0058] (3.1 Preparation of steel plates) First, prepare the steel sheet that will serve as the base material for the tin-plated steel sheet. There are no specific requirements regarding the manufacturing method or material of the steel sheet to be used; for example, it can be manufactured through processes such as casting, hot rolling, pickling, cold rolling, annealing, and temper rolling. The annealing process can be continuous annealing or batch-type box annealing.

[0059] (3.2 Formation of tin-based plating layer) Next, a tin-based plating layer is formed on at least one surface of the steel sheet. There are no specific requirements for the method of applying the tin-based plating layer to the surface of the steel sheet, but for example, a known electroplating method is preferred, and a hot-dip plating method in which the steel sheet is plated by immersing it in molten tin may also be used.

[0060] For electroplating, electrolytic methods using well-known ferrostan baths, halogen baths, or alkaline baths can be employed. Furthermore, if necessary, the steel sheet may be cleaned by degreasing and pickling before forming the tin-based plating layer. Any method that removes oil, oxides, and other foreign matter from the steel sheet surface is acceptable. Examples include chemical treatments such as degreasing and subsequent pickling, and mechanical treatments such as shot blasting, sandblasting, grit blasting, and dry ice blasting. Combinations of these chemical and mechanical treatments are also acceptable.

[0061] For degreasing, for example, in an aqueous sodium hydroxide solution with a concentration of 10-50 g / L, at 20-80°C and a current density of 5-40 A / dm². 2 Therefore, cathodic or anodic electrolytic degreasing can be applied for 0.2 to 5 seconds.

[0062] In pickling, the method is not limited to electroless pickling, where the steel sheet is simply immersed, but also includes cathodic electrolytic pickling and anodic electrolytic pickling, which have a greater cleaning effect on the steel sheet surface. From an industrial production perspective, cathodic electrolytic pickling is common and preferred because it has a greater cleaning effect on the steel sheet surface and is less likely to result in over-pickling. For example, in a pickling bath with a sulfuric acid concentration of 5-40% and a temperature of 30-90°C, the current flow rate is 5-50 C / dm 2 Cathodic electrolytic pickling can be applied.

[0063] There are no specific requirements for the method of applying the tin-based plating layer to the surface of the steel sheet, but known electroplating methods are preferred. As for electroplating methods, for example, well-known acidic baths such as sulfuric acid baths, borofluorin baths, phenol sulfonic acid baths, and methanesulfonic acid baths, as well as electrolytic methods using alkaline baths, can be used.

[0064] Alternatively, a hot-dip plating method may be used in which a tin-based plating layer is formed by immersing a steel plate in a molten Sn plating bath.

[0065] Furthermore, after tin plating, the steel sheet with the tin-based plating layer may be subjected to a heat melting treatment, in which it is heated to a temperature of 231.9°C or higher, which is the melting point of tin. This heat melting treatment not only provides a glossy surface to the tin-plated steel sheet, but also creates an iron-tin alloy layer, which is an alloy layer of tin and Fe, between the tin-based plating layer and the steel sheet, further improving its corrosion resistance.

[0066] (3.3 Cathodic electrolysis) The following describes a method for producing a coating layer containing zirconium oxide and tin sulfide according to this embodiment.

[0067] [First cathodic electrolysis treatment] To produce the coating layer according to this embodiment, first, a coating containing zirconium oxide is formed on a tin-based plating layer formed on a steel plate.

[0068] A film containing zirconium oxide can be formed on a tin-based plating layer by immersing a steel sheet having a tin-based plating layer in a solution containing zirconium ions, or by performing a first cathodic electrolytic treatment on a steel sheet having a tin-based plating layer in a solution containing zirconium ions.

[0069] In addition to cathode electrolysis, it is also possible to form a coating by immersion treatment. However, in immersion treatment, the surface of the tin-based plating layer is etched to create a coating containing zirconium oxide, which tends to result in uneven adhesion, and the treatment time is also longer, making it less industrially feasible compared to cathode electrolysis.

[0070] In cathodic electrolysis, a uniform film can be obtained through the combined effects of forced charge transfer, surface cleaning due to hydrogen generation at the interface between the tin plating layer and the electrolyte, and adhesion promotion due to pH increase. Furthermore, in the first cathodic electrolysis, the coexistence of nitrate ions and ammonium ions in the treatment solution allows for short-time processing of several seconds to tens of seconds, which is extremely advantageous from an industrial perspective. Therefore, it is preferable to use a cathodic electrolysis method to produce a film containing zirconium oxide according to this embodiment.

[0071] The concentration of zirconium ions in the solution used for the first cathode electrolysis treatment (hereinafter referred to as the cathode electrolyte) can be adjusted as appropriate according to the production equipment and production speed (capacity), but for example, the zirconium ion concentration is preferably between 100 ppm and 4000 ppm. Furthermore, there is no problem if the cathode electrolyte containing zirconium ions contains other components such as fluoride ions, ammonium ions, nitrate ions, sulfate ions, and phosphate ions.

[0072] Here, the temperature of the cathode electrolyte is not specifically defined, but it is preferable to set it in the range of 10°C to 50°C. Performing cathode electrolysis at 50°C or below makes it possible to create a dense and uniform film structure consisting of very fine particles. Furthermore, by setting the temperature of the cathode electrolyte to 50°C or below, it is possible to prevent the occurrence of defects, cracks, microcracks, etc. in the structure of the zirconium oxide film that is produced, thereby preventing a decrease in coating adhesion. In addition, by setting the temperature of the cathode electrolyte to 10°C or above, the efficiency of film formation can be improved, and cooling of the solution can be eliminated even when the ambient temperature is high, making it economical.

[0073] Furthermore, while there is no specific requirement for the pH of the cathode electrolyte, it is preferably between 3.0 and 5.0. If the pH is 3.0 or higher, the zirconium oxide generation efficiency can be improved, and if the pH is 5.0 or lower, the generation of large amounts of precipitates, such as zirconium hydroxide, in the cathode electrolyte can be prevented, thereby improving continuous productivity.

[0074] Furthermore, to adjust the pH of the cathode electrolyte or increase the electrolysis efficiency, substances such as nitric acid or aqueous ammonia may be added to the cathode electrolyte.

[0075] Furthermore, the current density during cathode electrolysis is, for example, 0.05 A / dm². 2 More than 50A / dm 2 The following is preferable: Current density of 0.05 A / dm 2 When the above conditions are met, the zirconium oxide generation efficiency can be sufficiently high, enabling the formation of a stable zirconium oxide-containing film layer, resulting in excellent resistance to sulfurization blackening and yellowing. Current density: 50 A / dm 2 In the following cases, the zirconium oxide generation efficiency can be moderated, and the generation of coarse and poorly adhering zirconium oxide can be suppressed. A more preferable current density range is 1 A / dm 2 More than 10A / dm 2 The following applies:

[0076] Furthermore, when forming a film containing zirconium oxide, the cathode electrolysis time should be adjusted appropriately according to the current density and the desired amount of Zr deposition. Specifically, the cathode electrolysis time may be in the range of 0.4 to 5 seconds.

[0077] For example, distilled water can be used as the solvent for the solution used in cathode electrolysis, but it is not limited to water such as distilled water, and can be appropriately selected depending on the material to be dissolved and the method of production.

[0078] For zirconium in cathode electrolysis, zirconium complexes such as H2ZrF6 can be used as a source of zirconium. In such Zr complexes, the Zr is released due to the increase in pH at the cathode electrode interface. 4+ These Zr ions then exist in the cathode electrolyte. These Zr ions further react in the cathode electrolyte to form zirconium oxide. If the electrolyte contains phosphoric acid, zirconium phosphate is also produced.

[0079] Furthermore, there is no problem whether the current is applied continuously or intermittently during cathode electrolysis.

[0080] During cathode electrolysis, it is preferable to maintain a relative flow velocity of 50 m / min or more between the cathode electrolyte and the steel sheet. A relative flow velocity of 50 m / min or more makes it easier to uniformize the pH on the steel sheet surface due to hydrogen generation during energization, and suppresses the formation of coarse zirconium oxide. There is no specific upper limit for the relative flow velocity. The relative flow velocity between the cathode electrolyte and the steel sheet is the velocity difference between the flow velocity of the cathode electrolyte and the speed at which the steel sheet passes. When the cathode electrolyte is a stationary bath, i.e., when the flow velocity of the cathode electrolyte is 0 m / min, the relative flow velocity is the speed at which the steel sheet passes.

[0081] [Second cathodic electrolysis treatment] The film layer containing zirconium oxide and tin sulfide according to this embodiment is obtained by further performing a second cathodic electrolytic treatment in a sulfur-containing electrolyte solution on a steel sheet on which the above-mentioned film containing zirconium oxide has been formed on a tin-based plating layer. The specific components of the electrolyte solution used are not particularly defined, but for example, an aqueous sodium thiosulfate solution containing sodium thiosulfate as the electrolyte can be cited.

[0082] The concentration of sodium thiosulfate is not particularly limited, but for example, 10 to 40 g / L of sodium thiosulfate is preferred. The electrolysis conditions are also not particularly limited, but a solution temperature of 30 to 60°C and an energization rate of 0.5 to 10 C / dm² are preferred. 2 It is preferable to do so. As long as the above current flow range is met, the current value and electrolysis time are not particularly limited. More preferable conditions are a sodium thiosulfate concentration of 20-30 g / L, a solution temperature of 40-50°C, and a current flow of 1-5 C / dm 2 Within these ranges, tin sulfides are efficiently formed and the process is industrially suitable. The Sn source for the tin sulfides formed in the second cathode electrolytic treatment is the Sn contained in the tin-based plating layer.

[0083] For the solvent used in the cathode electrolysis solution, distilled water can be used, for example, but it is not limited to water such as distilled water. Furthermore, there is no problem with the current application pattern during cathode electrolysis, whether it is continuous or intermittent.

[0084] Furthermore, by appropriately adjusting the conditions of the second cathode electrolysis treatment, including the electrolysis time, it becomes possible to create the coating layer in the forms shown in Figures 1 to 3.

[0085] By setting the concentration of sodium thiosulfate in the solution, the temperature of the solution, and the amount of current to the above ranges, and further reducing the electrolysis time to 2.0 seconds or less, a film layer in which zirconium oxide and tin sulfide are dispersed and mixed can be formed, as shown in Figure 2. This is presumed to be because, due to the short electrolysis time of 2.0 seconds or less, the amount of tin sulfide precipitated is relatively small, and the tin sulfide is mainly formed inside the film layer, thereby obtaining a film layer in which zirconium oxide and tin sulfide are dispersed and mixed. It is preferable that the lower limit of the electrolysis time be 0.4 seconds or more in order to ensure a sufficient amount of tin sulfide deposition.

[0086] Furthermore, by setting the concentration of sodium thiosulfate in the solution, the temperature of the solution, and the amount of current to the above ranges, and then extending the electrolysis time to more than 2.0 seconds, a film layer can be formed in which zirconium oxide and tin sulfide are dispersed and mixed, and a layer of tin sulfide is formed on the surface side, as shown in Figure 3. This is presumed to be because, due to the long electrolysis time of more than 2.0 seconds, tin sulfide is generated not only inside the film layer but also on the surface of the film layer, thereby resulting in a film layer in which zirconium oxide and tin sulfide are dispersed and mixed within the film layer, and a layer of tin sulfide is formed on the surface. It is preferable to set the upper limit of the electrolysis time to 10 seconds or less in order to prevent excessive deposition of tin sulfide.

[0087] Furthermore, by increasing the concentration of sodium thiosulfate in the solution to a high concentration of 55-70 g / L, and keeping the solution temperature and current within the above range, and reducing the electrolysis time to 0.8 seconds or less, a film layer consisting of a zirconium oxide layer and a tin sulfide layer can be formed, as shown in Figure 1. This is presumed to be because, by increasing the concentration of sodium thiosulfate and reducing the electrolysis time to 0.8 seconds or less, tin sulfide is generated only on the surface of the film layer, thereby obtaining a film layer consisting of a zirconium oxide layer and a tin sulfide layer. The lower limit of the electrolysis time is preferably 0.4 seconds or more in order to ensure a sufficient amount of tin sulfide is deposited.

[0088] As described above, the tin-plated steel sheet of this embodiment can be manufactured. [Examples]

[0089] Next, the tin-plated steel sheet and the method for manufacturing the tin-plated steel sheet according to the present invention will be described in detail with reference to examples and comparative examples. It should be noted that the following examples are merely examples of the tin-plated steel sheet and the method for manufacturing the tin-plated steel sheet according to the present invention, and the method for manufacturing the tin-plated steel sheet and the method for manufacturing the tin-plated steel sheet according to the present invention is not limited to the examples below.

[0090] <Test material> For a 0.2 mm thick low-carbon cold-rolled steel sheet, the pretreatment involved electrolytic alkaline degreasing, water washing, dilute sulfuric acid electrolytic pickling, and water washing. Following this, electroplating was performed using a phenol sulfonic acid bath, and then a heat melting treatment was carried out. The amount of tin plating layer was approximately 2.8 g / m² of metallic tin per side. 2 While the standard was used, the amount of tin plating layer adhesion was altered by changing the energizing time for some test materials. In addition, test materials were also prepared in which no heat melting treatment was performed after electroplating. The example of the material without heat melting is No. A18 in Table 1 (B18 in Table 2). The amount of tin plating layer adhesion was determined by measuring using the X-ray fluorescence method (ZSX Primus, Rigaku Corporation). The measurement conditions were as described above.

[0091] A steel sheet having the tin-plated layer prepared as described above was subjected to cathode electrolysis in an aqueous solution containing zirconium fluoride (first cathode electrolysis treatment) to form a zirconium oxide layer on the tin-plated layer. The current density, flow rate, pH, and bath temperature were changed as appropriate.

[0092] Furthermore, tin-plated steel sheets with a zirconium oxide layer were subjected to cathode electrolysis in a 5-70 g / L sodium thiosulfate aqueous solution (second cathode electrolysis treatment) to produce tin sulfides. The bath temperature was 20-65°C, and the amount of electricity for cathode electrolysis was 0-15 C / dm². 2 This was done. Note that No. a1 in Table 1 (No. b1 in Table 2) was treated by immersion rather than cathode electrolysis.

[0093] The conditions for the first and second cathode electrolytic treatments are shown in Table 1.

[0094] [Table 1]

[0095] The tin-plated steel sheets prepared as described above were subjected to various evaluations as shown below.

[0096] [Amount of adhesion] The amount of Zr deposited and sulfur per side was determined by X-ray fluorescence (using a Rigaku ZSX Primus). The measurement conditions were as described above.

[0097] [Structure of tin sulfide] Sn3d 5 / 2 , and S2p 3 / 2 The peak position of the bond energy was investigated. In determining the peak position, the entire spectrum was shifted so that the peak position of carbon (C1s) detected on the surface of the sample was 284.8 eV, and then the Sn3d 5 / 2 , and S2p 3 / 2 The bond energy position was determined.

[0098] Sn3d 5 / 2 The peak position is in the range of 485.4~485.9eV, and S2p 3 / 2 SnS was determined to be present if the peak position of the spectroscopy satisfies the range of 160.1 to 163.9 eV. Also, Sn3d 5 / 2 The peak position is in the range of greater than 485.9 and greater than 486.4 eV, and S2p 3 / 2 Sn2S3 was determined to be present if the peak position satisfies the range of 160.1 to 163.9 eV. Furthermore, Sn3d 5 / 2 The peak position is in the range of greater than 486.4 and greater than 487.9 eV, and S2p 3 / 2 SnS2 was determined to be present if the peak position of the signal satisfies the range of 160.1 to 163.9 eV.

[0099] [Yellowing Resistant] A tin-plated steel sheet prepared by the method described above in <Test Material> was subjected to a wetting test by placing it in a constant temperature and humidity chamber maintained at 40°C and 80% relative humidity for 4 weeks, and the color difference b before and after the wetting test was measured. * Change in value △b * To achieve this, we evaluated its resistance to yellowing.

[0100] △b * A value of 1 or less was rated as Excellent (E), a value greater than 1 and less than or equal to 2 was rated as Very Good (VG), a value greater than 2 and less than or equal to 3 was rated as Good (G), and a value greater than 3 was rated as Poor (P). Ratings E, VG, and G were considered passing. Also, Δb * Even if the value of is 2 or less, the b before the wet test (initial) * A value of 6 or higher was given a rating of G. In addition, b * The values ​​were measured using a commercially available colorimeter, the SC-GV5 manufactured by Suga Test Instruments. * The measurement conditions were light source C, total internal reflection, and a measurement diameter of 30 mm.

[0101] [Coating adhesion] The adhesion of the coating film was evaluated as follows: After the tin-plated steel sheet prepared by the method described in <Test Material> above was subjected to a wet test by the method described in [Yellowing Resistance], a commercially available epoxy resin paint for cans was applied to the surface at a dry weight of 7 g / m². 2 The coating was applied, baked at 200°C for 10 minutes, and left at room temperature for 24 hours to form a coating film. Subsequently, a cross-cut test was performed on the tin-plated steel sheet with the coated film. In the cross-cut test, a grid pattern of cuts reaching the surface of the steel sheet was made in the coating film, adhesive tape was applied to the grid pattern areas, and the adhesive tape was peeled off within 5 minutes to evaluate the degree of coating film peeling. The grid pattern cuts were formed by making seven linear scratches each in the vertical and horizontal directions at 3 mm intervals using a cutting tool with a blade. The relative angle between the vertical and horizontal cuts was set to 90°.

[0102] After tape removal, the following evaluations were used: Excellent (E) if no coating (test surface) on the grid pattern area (test surface) had peeled off at all; Very Good (VG) if less than 10% of the coating on the test surface had peeled off; Good (G) if more than 10% but less than 20% of the coating on the test surface had peeled off; and Poor (P) if more than 20% of the coating on the test surface had peeled off. Evaluations E, VG, and G were considered pass, and P was considered fail.

[0103] [Sulfurization resistance] Sulfurization resistance was evaluated as follows: On the surface of the tin-plated steel sheet prepared and wet-tested using the method described above under [Yellowing Resistance], a commercially available epoxy resin paint for cans was applied at a dry weight of 7 g / m². 2 After application, the coating was baked at 200°C for 10 minutes and then left at room temperature for 24 hours to form a coating film. Subsequently, the tin-plated steel sheets with the coating film were cut to the specified size and immersed in aqueous solutions containing 0.3% sodium dihydrogen phosphate, 0.7% sodium hydrogen phosphate, and 0.6% L-cysteine ​​hydrochloride, respectively. These were then retorted in a sealed container at 121°C for 60 minutes. The appearance after retorting was evaluated.

[0104] The test surface was evaluated as follows: Excellent (E) if no blackening was observed before and after the test; Very Good (VG) if blackening was observed in less than 5% of the test surface; Good (G) if blackening was observed in more than 5% but less than or equal to 10% of the test surface; and Poor (P) if blackening was observed in more than 10% of the test surface. Tests with evaluations E, VG, and G were considered pass, and P was considered fail.

[0105] [Corrosion resistance after painting] The corrosion resistance after painting was evaluated as follows. On the surface of the tin-plated steel sheet prepared and wet-tested using the method described above under [Yellowing Resistance], a commercially available epoxy resin paint for cans was applied at a dry weight of 7 g / m². 2After application, the coating was baked at 200°C for 10 minutes and then left at room temperature for 24 hours to form a coating film. Subsequently, the tin-plated steel sheets with the coating film formed were cut to a predetermined size and immersed in commercially available tomato juice at 60°C for 7 days. The presence or absence of rust was then visually evaluated.

[0106] The test surface was evaluated as follows: Excellent (E) if no rust was observed at all, Very Good (VG) if rust was observed in less than 5% of the test surface, and Poor (P) if rust was observed in more than 5% of the test surface. Evaluations E and G were considered passing grades, and P was considered failing grades.

[0107] Table 2 shows the results of investigations into the tin deposition amount of the tin-based plating layer, the zirconium deposition amount of the film layer, the sulfur deposition amount, and the structure of tin sulfides, as well as various performance characteristics, obtained from the manufacturing conditions shown in Table 1 for tin-plated steel sheets.

[0108] As is clear from Table 2, all of the B1 to B23 ranges of the present invention showed good performance. In particular, when the zirconium deposition amount was 1.0 to 10 mg / m² 2 Furthermore, the sulfur deposition amount is 0.2-3 mg / m². 2 Furthermore, B16, B17, and B19-B21, whose tin sulfide structure is SnS, exhibit particularly excellent performance in all aspects.

[0109] Furthermore, observation using a transmission electron microscope revealed that the morphology of the coatings B1-B18 is as shown in Figure 2. The morphology of the coatings B19-B21 is as shown in Figure 3. The morphology of the coatings B22 and B23 is as shown in Figure 1.

[0110] On the other hand, comparative examples b1 to b18, in which at least one of the zirconium deposition amount or sulfur deposition amount falls outside the scope of the present invention, show inferiority in one or more of the following: resistance to yellowing, coating adhesion, resistance to sulfur blackening, or corrosion resistance after painting.

[0111] b1 has a low amount of Sn deposited in the tin-based plating layer, and the current applied in the second cathode electrolysis treatment is 0C / dm 2Instead of the second cathode electrolytic treatment 2, an immersion treatment was performed. As a result, SnS did not precipitate in the film layer, leading to insufficient resistance to yellowing, paint adhesion, sulfur blackening, and corrosion resistance after painting.

[0112] In b2, the zirconium ion concentration in the first cathode electrolytic treatment was low, resulting in a low amount of metal Zr in the coating layer, and consequently, insufficient resistance to yellowing, sulfidation blackening, and corrosion resistance after painting. In case b3, the zirconium ion concentration in the first cathode electrolytic treatment was excessive, resulting in an excessive amount of metal Zr in the coating layer and insufficient paint adhesion.

[0113] In b4, the liquid temperature during the first cathode electrolytic treatment was low, resulting in a reduced amount of metal Zr in the coating layer, leading to insufficient resistance to yellowing, sulfurization blackening, and corrosion resistance after painting. In case b5, the liquid temperature during the first cathode electrolytic treatment was too high, resulting in an excessive amount of metal Zr in the coating layer, leading to poor resistance to yellowing and insufficient paint adhesion.

[0114] In b6, the pH during the first cathode electrolytic treatment was low, resulting in a reduced amount of metal Zr in the coating layer, leading to insufficient resistance to yellowing, sulfidation blackening, and corrosion resistance after painting. In case b7, the pH was high during the first cathode electrolytic treatment, resulting in an excessive amount of metal Zr in the coating layer and insufficient paint adhesion.

[0115] In b8, the current density in the first cathode electrolytic treatment was low, resulting in a reduced amount of metal Zr in the coating layer, and consequently, insufficient resistance to yellowing, sulfurization blackening, and corrosion resistance after painting. In b9, the current density during the first cathode electrolytic treatment was high, resulting in an excess of metal Zr in the coating layer and insufficient paint adhesion.

[0116] In b10, the relative flow rate in the first cathode electrolytic treatment was low, resulting in a reduced amount of metal Zr in the coating layer, as well as a reduced amount of S, leading to insufficient resistance to yellowing, sulfurization blackening, and corrosion resistance after painting.

[0117] In b11, the sodium thiosulfate concentration in the second cathode electrolytic treatment was low, resulting in a low sulfur content in the coating layer, and consequently, insufficient resistance to yellowing, sulfurization blackening, and corrosion resistance after painting. In b12, the sodium thiosulfate concentration exceeded 40 g / L during the second cathode electrolytic treatment, and the energizing time was 2 seconds, resulting in an excessive amount of sulfur in the coating layer and insufficient resistance to sulfur blackening.

[0118] In b13, the liquid temperature during the second cathode electrolytic treatment was low, resulting in a reduced sulfur content in the coating layer, leading to insufficient resistance to yellowing, sulfurization blackening, and corrosion resistance after painting. In b14, the liquid temperature during the second cathode electrolysis treatment was too high, resulting in an excess of sulfur in the coating layer and insufficient resistance to sulfurization blackening.

[0119] In b15, the current applied during the second cathode electrolytic treatment was low, resulting in a reduced sulfur content in the coating layer, and consequently, insufficient resistance to yellowing, sulfurization blackening, and corrosion resistance after painting. In b16, the current applied during the second cathode electrolysis treatment was too high, resulting in an excess of sulfur in the coating layer and insufficient resistance to sulfurization blackening.

[0120] Because b17 and b18 did not undergo the first cathodic electrolytic treatment, the amount of zirconium oxide deposited in the coating layer was 0 mg / m2 in terms of metallic Zr content, resulting in insufficient resistance to sulfurization blackening and corrosion resistance after painting.

[0121] [Table 2] [Industrial applicability]

[0122] According to the present invention, it is possible to provide a tin-plated steel sheet that is even more superior in resistance to sulfur blackening and yellowing without conventional chromate treatment, thus having industrial applicability.

Claims

1. Steel plate and A tin-based plating layer located on at least one side of the steel plate, The coating layer is located on the tin-based plating layer and contains zirconium oxide and tin sulfide, The amount of the tin-based plating layer is 2.0 g / m² in terms of metallic Sn content. ２ 15g / m or more ２ The following: The amount of zirconium oxide deposited in the aforementioned coating layer is 0.2 mg / m² in terms of metallic Zr content. ２ 50mg / m or more ２ The following conditions apply, and the amount of tin sulfide adhering to the surface is 0.1 mg / m² in terms of sulfur content. ２ 5mg / m or more ２ A tin-plated steel sheet characterized by the following:

2. The tin-plated steel sheet according to claim 1, characterized in that the tin sulfide is SnS.

3. A can made of a tin-plated steel sheet as described in claim 1 or claim 2.

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