JP3140305B2 - Manufacturing method of tin-coated steel sheet with excellent paint adhesion - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a steel sheet having a tin plating film, and industrially relates to a method for producing a product used in large quantities as a steel sheet for containers such as beverage cans and food cans. is there.

[0002]

2. Description of the Related Art When metal containers are classified from the viewpoint of can bodies, they can be broadly classified into three-piece cans consisting of a canopy, a canopy, and a body, and two-piece cans having a can body and a canopy integrated. Both the three-piece can and the two-piece can use a product obtained by applying a tin plating to a steel plate. In the case of a two-piece DI can, two drawing operations (Drawing) and two or three ironing operations (Ir)
oning). After removing the lubricating oil for molding with an alkali degreasing agent, the can after molding is subjected to a coating base treatment with chromic acid or a phosphate, etc., so that the can has excellent paint adhesion. The DI cans include beverage cans filled with beer, carbonated beverages and the like, and aerosol cans filled with antiperspirants, shaving creams, and the like.

On the other hand, three-piece cans are currently represented by adhesive cans and welded cans, and tin-free steel (a steel plate having a two-layer film of chromium metal and hydrated chromium oxide) is used for the adhesive can. Tin-plated steel sheets are used for the cans. Tin-plated steel sheets used for welding cans
It is manufactured by cleaning the surface of the steel sheet after annealing and pressure regulation, performing electrotin plating in a tin plating bath, and heating and melting the electrodeposited tin by resistance heating and / or induction heating. This is required for forming a tin-iron alloy layer, adjusting plating luster, and the like, and is a main process for tinplate production. Thereafter, chromate treatment is performed in a solution mainly composed of chromate or dichromate,
A film containing chromium metal and / or hydrated chromium oxide as a component is formed. By this treatment, oxidation resistance, paint adhesion and the like are imparted, and a product is obtained.

[0004]

In recent years, the main market for welded cans in Japan is beverage cans, and most cans are used with their inner surfaces painted. In the past, the corrosion resistance on the inner surface of a can has sometimes depended on a tin film having a large weight per unit area in the past, but recently, the corrosion resistance has been secured by an organic coating film. Therefore, if any defect occurs in the organic coating film on the inner surface of the can, tin or iron is dissolved in the content, and the taste, flavor, appearance and the like are changed, which may result in defective products. If it is more severe, it becomes a perforated can and there is a risk that the contents may leak.

[0005] In the case of tin-plated steel sheets used for welding cans,
As described above, there is a step of melting the electrodeposited tin, and a tin oxide film is inevitably generated in this step. The generated tin oxide film remains on the steel sheet surface without being completely removed in the chromate treatment bath. Since the tin oxide is mechanically brittle, when an external force is applied to the coating film after coating, the tin oxide cohesively breaks and causes peeling of the coating film. This phenomenon has been clarified by many researchers in the past. (Eg, Tinplate and Tin Free Steel) (Agne, 1970) 17
3-182). The present invention has been found as a result of various studies on fundamental measures for the problem of poor paint adhesion of tin-plated steel sheets caused by the presence of a tin oxide film.

[0006]

According to the present invention, a steel sheet having an electrodeposited tin film formed by an electroplating method is subjected to a hot-melt tin treatment by resistance heating or / and induction heating, if necessary, and after cooling with water, the pH is reduced. After immersion or / and electrolytic treatment in an acidic solution of 2.5 or less, washing with water, and performing cathodic electrolytic treatment in an aqueous solution mainly containing chromic acid, a chromate film containing metallic chromium on a tin plating film Is characterized by having excellent paint adhesion and good gloss,
Or a method for producing a semi-gloss tin-plated steel sheet. Considering the basic idea of the present invention, it is important to suppress the formation of the tin oxide film as much as possible, and it is more advantageous to omit the hot-melt tin treatment. However, in order to secure performance such as corrosion resistance, appearance, and weldability by forming an alloy layer or the like, it is quite difficult to omit the hot-melt tin treatment, and in many cases, practically the hot-melt tin treatment is involved. Even if the hot-melt tin treatment can be omitted, the current line has a facility configuration in which drying is performed once before chromate treatment, and it is considered that formation of a tin oxide film is inevitable.

In the present invention, a tin-plated steel sheet after plating or molten tin treatment is immersed in an acidic solution having a pH of 4 or less and / or subjected to electrolytic treatment to dissolve and remove the tin oxide film. As a method of dissolution removal, a method of reducing by cathodic electrolysis,
The method is divided into a method of dissolving the substrate and dropping the oxide. In the case of reduction by cathodic electrolysis, a method of performing high coulomb treatment in an acidic solution having a pH of 4 or less in a high temperature bath of 40 to 80 ° C. is effective. As the acidic solution, a single or mixed solution of organic acids such as sulfuric acid, sulfate, phosphoric acid, phosphate, citric acid or the like is used.
The following solutions are used: In particular, sulfuric acid or a salt thereof is most recommended because of its excellent conductivity, economy, chemical dissolving ability, and the like. Cathode reduction electricity is reduced at 50 coulombs / m ² or more, preferably 500 to 5,000 coulombs / m ² .

[0008] There are two methods for dissolving the substrate and removing oxides. One is a promotion method by anodic electrolysis, and the other is a chemical dissolution method. In the chemical dissolution method, an acid having a strong dissolving power of sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, or another halogen acid is used alone or as a mixture. The temperature is from room temperature
About 0 ° C. is practical. Although a shorter immersion time is preferred for practical use, a practical range is about 0.2 to 4 seconds. When the base material is dissolved by anodic electrolysis to remove oxides, 2
It is effective to pass an anodic current of 0 coulomb / m ² or more. In this case, by adopting a solution composition effective for chemical dissolution, simultaneous electrolysis and chemical dissolution can be performed, and the processing time can be drastically reduced.
An effective effect can be expected with an electrolysis time of about 2.0 seconds. The composition of the treatment bath is as follows: sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid,
In addition, acids having strong dissolving power such as halogen acids are used alone or in combination. As the temperature, room temperature to about 70 ° C. is practical.

The acid treatment liquid is removed from the tin surface thus activated by washing with water, and immediately introduced into the chromate treatment bath without drying. In this case, it is important that the washing operation is performed within a short period of time so that the oxide film is not formed again. As a chromate treatment bath, a bath containing chromic acid as a main component (concentration: 30 to 150 g / l) and sulfuric acid and a fluorine compound alone or as a mixture and added to the chromic acid at about 1/30 to 1/300. Is used. At a bath temperature of 30 to 70 ° C., preferably 40 to 60 ° C., high current density electrolysis of 20 A / dm ² or more, preferably 30 A / dm ² is performed. It is better to perform electrolysis at a higher current density on the tin surface from which the oxide film has been removed than in the normal case. The high current density electrolysis results in a chromate film containing chromium metal. Even when the coating is baked at a high temperature, the tin oxide film does not grow, and excellent paint adhesion can be maintained. Good paint adhesion can be ensured when the amount of chromium after the chromate treatment is in the range of 0.2 to 30 mg / m ² of chromium metal and 1 to 25 mg / m ² of hydrated chromium oxide (as chromium).

Hereinafter, embodiments of the present invention will be described in detail.

【Example】

Example 1 A slab produced by continuous casting or ingot making / blowing by melting in a converter or an electric furnace was subjected to hot rolling, pickling, cold rolling, annealing, and temper rolling to obtain a sheet thickness of 0.1 mm. A 19 mm steel plate was manufactured. The surface of the annealed and pressure-regulated steel plate having a thickness of 0.19 mm was cleaned, and then electrotin plating was performed at 2.8 g / m ² using a tin phenolsulfonate plating bath. After rinsing and drying, the steel sheet was heated to 250 ° C. by applying current and cooled in water immediately after the plating tin was melted, and dried to obtain a glossy tin plate. Next, the steel sheet was immersed in a tank containing a sulfuric acid solution having a pH of 1.0 (temperature: 45 ° C.) at room temperature, and subjected to cathodic electrolysis at a current density of 20 A / dm ^{2 for} 1.2 seconds. After washing with water for a short time, a cathodic electrolysis treatment was performed at a current density of 35 A / dm ^{2 for} 0.5 second in a chromate treatment bath (55 ° C.) containing 100 g / l of chromic acid and 1.0 g / l of sulfuric acid.

Example 2 The same procedure as in Example 1 described above was used. Board thickness 0.19m
After cleaning the annealed and pressure-regulated steel sheet,
1.4 g / m using tin sulfonate plating bath^Two Electric tin
Plating was performed. After washing and drying, the steel sheet is
Heat to 250 ° C and in water immediately after plating tin melts
After cooling and drying, a semi-gloss tin plate was obtained. Then, always
Containing a sulfuric acid solution (temperature 55 ° C) with pH = 0.8 at room temperature
This steel sheet is immersed in
^Two Dissolves to the extent that tin of the compound melts. After a short water wash,
Chromate treatment of humic acid 100g / l, sulfuric acid 1.0g / l
Current density 35A / dm in bath (55 ° C) ^Two At 0.
The cathode electrolysis treatment was performed for 5 seconds.

Example 3 A device was manufactured in the same manner as in Example 1 above. Board thickness 0.19m
After the surface of the annealed and regulated steel plate of m was cleaned, electrotin plating was performed at 1.3 g / m ² using a tin phenol sulfonate plating bath. After washing with water and drying, the steel sheet was heated to 250 ° C. by current heating, cooled in water immediately after the plating tin was melted, and dried to obtain a semi-gloss tin plate. Next, the steel sheet was immersed in a tank containing a sulfuric acid solution having a pH of 0.5 (temperature: 45 ° C.) at room temperature, and subjected to anodic electrolysis at a current density of 5 A / dm ^{2 for} 0.6 seconds. After washing with water for a short time, in a chromate treatment bath (55 ° C.) of 100 g / l chromic acid and 0.6 g / l sulfuric acid at a current density of 25 A / dm ^2, 0.5
Seconds of cathodic electrolysis.

Example 4 A battery was manufactured in the same manner as in Example 1 above. Board thickness 0.19m
After cleaning the annealed and pressure-regulated steel sheet,
1.3 g / m using tin sulfonate plating bath^Two Electric tin
Plating was performed. After washing and drying, the steel sheet is
Heat to 250 ° C and in water immediately after plating tin melts
After cooling and drying, a semi-gloss tin plate was obtained. Then, always
Containing hydrochloric acid solution (temperature 45 ° C) with pH = 0.8
This steel sheet is immersed in
^Two Dissolves to the extent that tin of the compound melts. After a short water wash,
Chromate treatment of humic acid 100g / l, sulfuric acid 0.6g / l
Current density 25A / dm in bath (55 ° C) ^Two At 0.
Cathodic electrolysis treatment was performed for 5 seconds.

Example 5 A battery was manufactured in the same manner as in Example 1 above. Board thickness 0.19m
After the surface of the annealed and regulated steel plate of m was cleaned, electrotin plating was performed at 1.3 g / m ² using a tin phenol sulfonate plating bath. After washing with water and drying, the steel sheet was heated to 250 ° C. by current heating, cooled in water immediately after the plating tin was melted, and dried to obtain a semi-gloss tin plate. Next, the steel sheet was immersed in a tank containing a mixed solution of sodium sulfate (pH 45) at pH = 0.8 at room temperature, and the current density was 3%.
Cathodic electrolysis treatment was performed at 0 A / dm ^{2 for} 1.2 seconds. After washing with water for a short time, in a chromate treatment bath (55 ° C.) containing 100 g / l of chromic acid and 1.0 g / l of sulfuric acid, a current density of 30 A / l
Cathode electrolysis treatment was performed at dm ^{2 for} 0.5 seconds.

Comparative Example 1 The same method as in Example 1 was used. Board thickness 0.19m
After the surface of the annealed and pressure-regulated steel sheet was cleaned, the sheet was electroplated with 2.8 g / m ² of tin using a phenolsulfonate tin plating bath. After rinsing and drying, the steel sheet was heated to 250 ° C. by applying current and cooled in water immediately after the plating tin was melted, and dried to obtain a glossy tin plate. Then
Cathodic electrolysis was performed at a current density of 35 A / dm ^{2 for} 0.5 second in a chromate treatment bath (55 ° C.) containing 100 g / l of chromic acid and 1.0 g / l of sulfuric acid.

Comparative Example 2 The same method as in Example 1 was used. Board thickness 0.19m
After the surface of the annealed and regulated steel plate of m was cleaned, electrotin plating was performed at 1.3 g / m ² using a tin phenol sulfonate plating bath. After washing with water and drying, the steel sheet was heated to 250 ° C. by current heating, cooled in water immediately after the plating tin was melted, and dried to obtain a semi-gloss tin plate. Next, in a chromate treatment bath (55 ° C.) of chromic acid 100 g / l and sulfuric acid 0.6 g / l, cathodic electrolysis was performed at a current density of 25 A / dm ^{2 for} 0.5 seconds.

An epoxy phenolic resin was applied to the steel sheet prepared by the above method and baked at 210 ° C. for 10 minutes. Thereafter, the coated surfaces were heat-bonded with a nylon adhesive and water-cooled. After standing for 24 hours, a T-peel strength was applied with a tensile tester (one steel plate bonded to a chuck of the tensile tester was sandwiched and bonded to the other chuck). A method of measuring the peel strength of the adhesive surface by sandwiching the other steel plate and pulling it up and down was measured. The results are shown in Table 1. Comparative Example 3
In contrast to the strength of about kg / cm, the examples of the present invention all showed a peel strength of 6 kg / cm or more, which proved to have excellent paint adhesion.

[0018]

[Table 1]

[0019]

By applying the production method of the present invention,
Since a steel sheet having extremely excellent paint adhesion can be obtained, various effects are expected in the production of welded cans. First is an improvement in corrosion resistance. In the can making process, even if various external forces are applied to the surface of the coating film, excellent paint adhesion does not cause coating film defects, so that good corrosion resistance is ensured. The second effect is workability. After welding, when performing necked-in processing (processing to reduce the can diameter) for attaching a small can diameter lid, smooth processing is possible without causing a processing problem due to peeling of the coating film.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C25D 11/38

Claims (2)

(57) [Claims] 1. A steel sheet having a tin plating film formed by an electroplating method is immersed or / and electrolytically treated in an acidic solution having a pH of 2.5 or less, washed with water, and then placed in an aqueous solution mainly containing chromic acid. perform cathodic electrolysis treatment Te, good excellent gloss paint adhesion, characterized in that to form a chromate film containing chromium metal on the tin plating film, there
Or semi-gloss tin-plated steel sheet manufacturing method. 2. A steel sheet having a tin plating film formed by an electroplating method is subjected to a hot-melt tin treatment by resistance heating and / or induction heating, and after cooling with water, is immersed in an acidic solution having a pH of 2.5 or less. And / or performing an electrolytic treatment, washing with water, and performing a cathodic electrolytic treatment in an aqueous solution mainly composed of chromic acid to form a chromium film containing metallic chromium on the tin plating film. A method for producing a glossy or semi-gloss tin-plated steel sheet with excellent paint adhesion.