JP3432637B2 - Tin-plated steel sheet with excellent paint adhesion - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tin-plated steel sheet having excellent paint adhesion. 2. Description of the Related Art Metal containers can be roughly classified into three-piece cans consisting of a canopy, a canopy, and a trunk, and two-piece cans integrating a canopy and a trunk. Both the three-piece can and the two-piece can use a surface-treated steel sheet in which a steel sheet is plated with tin. In the case of a two-piece can, two drawing operations and two or three ironing operations (Iro)
(Ning) processing. After the molding can is removed from the lubricating oil for molding with an alkali degreasing agent, the can is subjected to a coating base treatment with chromic acid or a phosphate or the like, so that the can has excellent paint adhesion. These two-piece cans are mainly used as beverage cans filled with beer or carbonated beverages, and the number of cans manufactured each year is increasing. 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. Tinned steel sheet is used for the welding can. The tin-plated steel sheet used for the welding can is cold-rolled, annealed, and after cleaning the surface of the steel sheet after pressure regulation, electro-tin plating is performed in a tin plating bath. A molten tin treatment for heating the tin plating layer by heating or induction heating is performed. Thereafter, chromate treatment is performed in a solution mainly composed of chromate or dichromate,
A film (chromate film) containing chromium metal or hydrated chromium oxide as a component is formed. [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. As for the corrosion resistance on the inner surface of the can, a tin film having a large plating amount was sometimes used in the past, but recently, the corrosion resistance is secured by an organic coating film. Therefore, if any defect occurs in the organic coating film on the inner surface of the can, dissolution of tin or iron in the contents occurs,
Changes in taste, flavor, appearance, etc. may occur and may result in defective products. Further, in the case of severe, there is a danger that it becomes a perforated can and may lead to a leak accident. [0005] As described above, the tin-plated steel sheet used for the welding can is subjected to a chromate treatment in order to prevent the above-mentioned defective product or paint adhesion failure leading to a leakage accident. However, in the current chromate treatment on tin plating, since a uniform chromate film is not generated, tin oxide is generated in a short period of time after the product is manufactured, starting from a defective portion of the chromate film. Since 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 is
It has been revealed by many researchers in the past, for example,
Book "Tin and Tin Free Steel" (Agne,
(Issued in 1970) (p.173-1)
82). The present invention has been found as a result of various studies on the problem of poor paint adhesion of tin-plated steel sheets caused by the formation of tin oxide. SUMMARY OF THE INVENTION The present invention is characterized by performing chromate treatment on an electro-tin-plated steel sheet having a sulfate ion or a tin-plated steel sheet which has been subjected to a molten tin treatment, thereby obtaining excellent paint adhesion. An object of the present invention is to provide a tin-plated steel sheet having a property. The gist of the present invention is that 0.002 mg
/ M ² or more to form a layer containing the sulfuric acid ion, further the
A tin-plated steel sheet having excellent paint adhesion, characterized by forming a chromate treatment layer thereon. The basic concept of the present invention will be described below. In general, it is known that the formation of a chromate film requires an auxiliary agent such as sulfuric acid or fluorine ion in a chromate treatment bath in which hydrogen is generated by electrolysis in a chromate film forming body (usually a steel plate) (for example, Izumiya et al .;
12, 2275 (1973). ). Hydrogen generation causes an increase in pH in the vicinity of the steel sheet, and forms a chromic chromate film made of hexavalent or trivalent chromium at the steel sheet interface. On the other hand, the auxiliary is taken into the chromic chromate film, and is considered to act as a catalyst for converting the chromic chromate film into a chromate film. Chromate treatment of an industrially produced tin-plated steel sheet is performed by a similar mechanism. But,
Since a non-uniform chromate film is formed, it is in a situation in which sufficient paint adhesion is not practically satisfied. The present inventors have energetically studied such a phenomenon and have clarified the cause. The cause is described below. In the tin-plated steel plate manufactured in industry, tin oxide is generated on the tin-plated surface in part or a considerable part before the chromate treatment by the drying process after tin plating or the molten tin treatment performed as necessary. I do. When such a tin-plated steel sheet is subjected to a chromate treatment, the hydrogen generation overvoltage is different between a portion where tin oxide is present and a portion where tin oxide is not present, resulting in non-uniform hydrogen generation. As a result, the pH rise near the steel plate becomes non-uniform, and a non-uniform chromic chromate film is formed, which leads to the generation of a non-uniform chromate film. The present inventors have conducted intensive studies on a technique capable of forming a uniform chromate film on a tin-plated steel sheet in which tin oxide is present. As a result, if the steel sheet in which sulfate ions are present on the tin-plated surface is subjected to chromate treatment. It has been clarified that a tin-plated steel sheet having uniform chromate and excellent paint adhesion can be provided. This principle is considered to be because a chromate film is easily formed at the time of chromate treatment by pre-existing sulfate ions acting as a catalyst for the formation of a chromate film on the tin plating, and uniform coverage is improved. Therefore, it is desirable that the sulfate ions on the tin plating exist uniformly. In addition, the existence form is such that a highly polar sulfate group (SO ₄ , HSO _4, etc.) molecule is
It is considered that they are chemisorbed on the surface in the order of several atomic layers. There is no particular restriction on the method of providing such sulfate ions on the tin plating. For example, immersion treatment or electrolytic treatment may be performed in a solution containing sulfate ions,
A solution containing sulfate ions may be applied. Further, the effect of the present invention does not change even if sulfate ions are applied to tin plating by a dry process (physical and chemical vapor deposition). Further, the tin-plated steel sheet to which the sulfate ions have been provided by the above-described manufacturing method is subjected to a chromate treatment. The method of chromate treatment is not particularly limited, but in order to stably produce a uniform chromate film industrially, electrolytic chromate treatment usually used for tin-plated steel sheets is desirable. As the treatment bath, for example, a chromic acid-sulfuric acid type bath or a chromic acid-sulfuric acid-fluorine bath may be used. In this way, the tin-plated steel sheet having the manufactured chromate film can ensure excellent paint adhesion. Embodiments of the present invention will be described below in detail. Example 1 After cleaning the surface of an annealed and pressure-regulated steel plate having a thickness of 0.19 mm, using a tin phenolsulfonate bath, 5.8 g.
/ M ² of electrotin plating. After washing with water and drying, the steel sheet was heated to 280 ° C. by electric heating, cooled in water immediately after melting the plated tin, and dried to obtain a tin-plated steel sheet having a good gloss. Next, it is immersed in a 10% sulfuric acid solution at 25 ° C.
Cathodic electrolysis was performed at a current density of 20 A / dm ^{2 for} 0.8 seconds to give sulfate ions. This tinned steel sheet is
In a chromate treatment bath composed of 5 g at 100 g / l chromic acid and 0.6 g / l sulfuric acid, a current density of 35 A / dm
^{At 2,} a cathodic electrolysis treatment was performed for 0.5 seconds. Example 2 After annealing and pressure-adjusting a steel plate having a thickness of 0.19 mm and cleaning the surface, 1.6 g using a tin phenolsulfonate plating bath.
/ M ² of electrotin plating. After washing with water and drying, the steel sheet was heated to 280 ° C. by electric heating, cooled in water immediately after melting the plated tin, and dried to obtain a semi-gloss tin-plated steel sheet. Next, it was immersed in a 5% sulfuric acid solution at 40 ° C. and subjected to anodic electrolysis at a current density of 15 A / dm ^{2 for} 0.2 seconds to give sulfate ions. 55 degreeC,
In a chromate treatment bath composed of 100 g / l of chromic acid and 0.6 g / l of sulfuric acid, a cathodic electrolysis treatment was performed at a current density of 35 A / dm ^{2 for} 0.5 seconds. Example 3 After annealed and pressure-adjusted steel sheet having a thickness of 0.19 mm was cleaned, 2.8 g of the phenol sulfonate tin plating bath was used.
/ M ² of electrotin plating. After washing with water and drying, the steel sheet was heated to 280 ° C. by electric heating, cooled in water immediately after melting the plated tin, and dried to obtain a tin-plated steel sheet having a good gloss. Next, it is immersed in a 15% sulfuric acid solution at 55 ° C.
Sulfate ions were provided. This tinned steel sheet is 55
In a chromate treatment bath composed of 100 g / l of chromic acid and 0.8 g / l of sulfuric acid, the current density was 35 A / dm ^2.
For 0.5 seconds. Example 4 After the surface of an annealed and pressure-regulated steel sheet having a thickness of 0.19 mm was cleaned, 3.0 g of the steel sheet was subjected to a tin phenolsulfonate plating bath.
/ M ² of electrotin plating. After washing with water and drying, 25 ° C
And a cathodic electrolysis treatment at a current density of 20 A / dm ^{2 for} 0.8 seconds to give sulfate ions. This tin-plated steel sheet was treated at 55 ° C. with chromic acid 100 g /
In a chromate treatment bath composed of 1 g of sulfuric acid and 0.6 g / l of sulfuric acid, a cathodic electrolysis treatment was performed at a current density of 35 A / dm ^{2 for} 0.5 seconds. Example 5 After the surface of an annealed and pressure-regulated steel sheet having a thickness of 0.19 mm was cleaned, 5.8 g of the steel sheet was subjected to tin phenolsulfonate plating bath.
/ M ² of electrotin plating. After washing with water and drying, the steel sheet was heated to 280 ° C. by electric heating, cooled in water immediately after melting the plated tin, and dried to obtain a tin-plated steel sheet having a good gloss. Next, this steel sheet was mounted in a closed container, and after decompression, sulfuric acid was evaporated to give sulfate ions. The tin-plated steel sheet is subjected to a cathodic electrolysis treatment at a current density of 35 A / dm ^{2 for} 0.5 second in a chromate treatment bath composed of 55 ° C., 100 g / l chromic acid, and 0.6 g / l sulfuric acid. Was. Example 6 An annealed and pressure-regulated steel sheet having a thickness of 0.19 mm was cleaned, and then 1.4 g using a tin phenolsulfonate plating bath.
/ M ² of electrotin plating. After washing with water and drying, the steel sheet was heated to 280 ° C. by electric heating, cooled in water immediately after melting the plated tin, and dried to obtain a tin-plated steel sheet having a good gloss. Next, it is immersed in a 15% sulfuric acid solution at 55 ° C.
Sulfate ions were provided. This tinned steel sheet is 55
In a chromate treatment bath composed of 100 g / l of chromic acid, 0.4 g / l of sulfuric acid, and 0.8 g / l of free fluorine, a cathodic electrolysis treatment was performed at a current density of 35 A / dm2 for 0.5 ^second at a temperature of 35 ° C. went. COMPARATIVE EXAMPLE 1 Annealed and pressure-adjusted steel sheet having a thickness of 0.19 mm was cleaned, and then 5.8 g in a tin phenolsulfonate plating bath.
/ M ² of electrotin plating. After washing with water and drying, the steel sheet was heated to 280 ° C. by electric heating, cooled in water immediately after melting the plated tin, and dried to obtain a tin-plated steel sheet having a good gloss. This tin-plated steel sheet was subjected to chromic acid 10 at 55 ° C.
In a chromate treatment bath composed of 0 g / l and sulfuric acid 0.6 g / l, a cathodic electrolysis treatment was performed at a current density of 35 A / dm ^{2 for} 0.5 seconds. Comparative Example 2 Annealed and pressure-regulated steel sheet having a thickness of 0.19 mm was cleaned, and then 5.8 g in a tin phenolsulfonate plating bath.
/ M ² of electrotin plating. After washing with water and drying, the steel sheet was heated to 280 ° C. by electric heating, cooled in water immediately after melting the plated tin, and dried to obtain a tin-plated steel sheet having a good gloss. This tin-plated steel sheet was subjected to chromic acid 10 at 55 ° C.
In a chromate treatment bath composed of 0 g / l and sulfuric acid 0.6 g / l, a cathodic electrolysis treatment was performed at a current density of 35 A / dm ^{2 for} 0.5 seconds. An epoxy phenol resin was applied to the steel sheet prepared by the above method and baked at 210 ° C. for 10 minutes. Then, the coated surfaces are heat-bonded with a nylon adhesive, water-cooled, and allowed to stand for 24 hours. T-peel strength is then applied by a tensile tester. A method of measuring the peel strength of the bonded surface by sandwiching the other bonded steel plate and pulling it up and down was measured. The results are shown in Table 1.
Comparative examples have a strength of about 3 kg / cm, whereas all examples of the present invention show a peel strength of 7 kg / cm or more,
It has proven to have excellent paint adhesion. [Table 1] 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 coating film surface, excellent coating resistance does not cause coating film defects, so that good corrosion resistance is ensured. The second effect is workability. When performing necked-in processing (processing to reduce the can diameter) for attaching a small can diameter lid after welding, smooth processing can be performed without causing a processing problem due to peeling of the coating film.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-7-11483 (JP, A) JP-A-4-128387 (JP, A) JP-A-52-103333 (JP, A) JP-A-53-103 72742 (JP, A) Patent 3140305 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) C25D 5/48 C23C 28/00 C25D 5/26 C25D 11/38

Claims (1)

(57) [Claims 1] 0.002 mg / m ^{2 on the} tin plating layer surface
A layer containing the above sulfate ions is formed , and
Tin-plated steel sheet with excellent paint adhesion characterized by forming a romate treatment layer .