KR800001350B1 - Electro-plated steel sheet for coating - Google Patents

Abstract

This invention relates to the electroplated steel sheet for very thin tin coating. The steel the working corrosion resistance. The steel sheet or the steel-tin alloy sheet having the tin sheet is aimed at removing the defect of the tin free steel, sticking the paint and improving coating layer of 0.05-0.60 g/m2 electroplates the chrome hydrated oxide layer having 0.005-0.05 g.m2 chrome.

Description

Surface-treated steel sheet for painting

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1, 2, 3, and 4 are enlarged cross-sectional views of a steel sheet treated with electrolytic chromic acid together.

The present invention relates to a steel sheet treated with an electrochromic acid subjected to extremely thin tin plating.

Conventionally, a tin plated steel sheet, that is, a “tin plate”, has been widely used as a material of a can. In recent years, as a can material for carbonated beverages, electrolysis has been started with metal chromium as a lower layer and chromium hydride oxide as an upper layer.

Tin used in electric tin plate is a valuable metal that is depleted in the world, and replacement of TFS (Tin Free Steel), which is inexpensive in expensive tin plate, and reduction of tin plating amount in electroplate, Has been reviewed.

When TFS is used as a can, the rust is formed under the coating layer in the processed part (especially in the glossy part of the ken and the polished surface of both copper plates), and local corrosion is caused by minute cracks in the coating film. Afterwards, the eluted iron may deteriorate the taste of the contents, so TFS is not satisfactory as a material for cans.The cause of such local corrosion and rust is that the TFS film made of metal chromium and chromium hydride has a machinability. In the case of weak and slight processing, if cracks occur or the contents penetrate the coating film, it forms a state of being adhered to the metal iron of the base or a local battery is formed between the metal chromium and the iron so that the metal chromium is formed. It becomes a cathode to iron to promote the corrosion of iron, and the TFS coating does not dissolve in the contents of the can at all. 부식) Corrosion is less likely to occur, but corrosion is concentrated in the exposed parts of local iron such as processed parts. Therefore, it is locally corroded in carbonated beverages with low pH in contents. Rust grows

In such a situation, in order to improve the corrosion resistance of the base metal iron in order to obtain the TFS and the TFS having good corrosion resistance against acidic contents, especially carbonated beverages, a method of adding various elements during steelmaking (Patent No. 46-39577) , 48-3049, 48-3050, and 48-3051), but there was a risk of black scratches on the surface during steelmaking or deterioration of the contents due to elution of added elements.

On the other hand, in the steel sheet of the present invention, since the workability of the ultrathin tin layer under the chromium hydride oxide layer is superior to that of the TFS metal chromium layer, no cracking occurs in the coating film. Although there is no potential with respect to metal iron, the power supply difference between tin and iron is smaller than the potential difference between metal chromium and iron in TFS, and tin is slightly dissolved. Accordingly, in the steel sheet of the present invention, the degree of corrosion of the metal iron which is the basis is small, and in particular, in the processing part, local corrosion of iron is more difficult than that of TFS, and the degree of corrosion in the surface is slightly.

The present invention aims to solve all the problems of TFS as described above and to provide a surface-treated steel sheet for coating excellent in corrosion resistance to paints, acidic beverages, vegetables, fish meat, and the like. Will have.

That is, the plating layer having a three 0.05-0.60g / m ² very thin steel sheet, or a small amount of iron, a very thin three-seat-plated steel sheet having a tin plating layer of 0.05-0.60g / m ² on the alloy layer having a chromium amount of 0.005 It is to provide an electrolytic chromic acid treated steel sheet having a chromium hydride oxide layer containing -0.05 g / m ² .

The surface-treated steel sheet of the present invention can be manufactured without modifying the conventional continuous electric tin plate manufacturing equipment and the continuous TFS manufacturing equipment, and for example, many tanks as in the conventional electric tin plate manufacturing equipment even when new equipment is installed to carry out the present invention. The equipment is inexpensive because it does not require.

In addition, high-speed continuous production is possible and the use of expensive tin is extremely low, so it is inexpensive mass and has excellent adhesion and corrosion resistance as a characteristic, resulting in improved performance of the cans for carbonated beverages used in large quantities. Needless to say, it is possible to replace acidic beverage cans, such as fruit juices made of conventional electroplating, and to lower the cost of such fruit juice cans.

Since the surface-treated steel sheet of the present invention is excellent in corrosion resistance, it can be applied as a two-piece can, for example, an Ovalu can or a DR can (Drawn and Redrawn can), which does not require bonding by an organic adhesive and soldering. .

Hereinafter, the practice of the present invention will be described. First, the surface of the steel sheet is degreased, acid washed, and electroplated by a conventional method, followed by electrolytic chromic acid treatment after washing with water, followed by washing with water, drying and oiling.

To explain this in detail, electroplating uses a known tin plating tank, and any of an acid tin tank such as a tin sulfate tank and a hydrochloric acid tank, or an alkali tank such as a stone acid soda tank or a stone acid tank is used. Used. Particularly, generation of hydrogen gas as possible at the time of plating, such as weakly acidic tin tanks or known alkali tin tanks, in which the tin ion concentration described in Patent Publication No. 46-25603 in comparison with a conventional acidic tin tank is known. When the tin plating is carried out using a tank that can be seen, a dense tin plating layer can be obtained, and a small amount of dense iron and tin alloy layers are formed under the tin plating layer, thereby confirming the effects of corrosion resistance and the casting resistance of the tin plating layer.

The thickness of the seating plate layer that wishes to form is good in a range of 0.05-0.60g / m ² 0.05g / m ² or less in the chromium hydrated oxide layer carried over the metal or chromium layer and a chromium hydrated oxide layer is configured with electrolytic chromic acid treated steel sheet The corrosion resistance of remarkably falls. This tendency is that the smaller the amount of chromium in the upper chromium hydride oxide layer and the higher the tin plating layer is 0.90 g / m ² or more, the characteristics are not deteriorated, but the use of expensive stones is not economical.

Next, electrolytic chromic acid treatment is also carried out using a known electrochromic acid treatment tank, and a bichromic acid soda tank which is usually used as a post treatment of an electric tin plate, and chromic anhydride used in the production of TFS. Any of the tanks to which one or two kinds of preparations such as sulfonic acid and thiourea are added is used. Among these tanks, the surface-treated steel sheet of the present invention can be obtained by electrolytic treatment using a tin-plated steel sheet as a cathode in any of these tanks. However, in the case of a soda dichromate tank, the conventional electroplated slabs are subjected to post-treatment. In the amount of electricity of about cron / dm ² , since the chromium hydroxide oxide film including the amount of chromium required for the treated steel sheet of the present invention is not formed, it is necessary to pass through about 4-20 times the amount of electricity. In the case of tanks in which one or more preparations such as sulfuric acid fluorine compound, aromatic paper, sulfonic acid and thiourea are added to chromic anhydride, when cathodic treatment is carried out with an electric quantity of about 50-15 kron / dm ² , which is normally required for TFS production, Since the chromium hydride oxide film and the metal chromium layer containing the amount of chromium more than necessary are precipitated and the surface-treated steel sheet which this invention aims at is not obtained, it is necessary to carry out electrolytic treatment with a small electric quantity of about 5-20 micron / cm <^2> .

Well and the chromium amount in the chromium hydrated oxide coating formed kojeo is 0.005-0.5g / m ^2, when 0.05g / m ² or more, the workability of the hydrated chromium oxide film is decreased are both the adhesion and corrosion resistance of the coating decrease because of this. Moreover, when it becomes 0.005 g / m <^2> or less, corrosion resistance will fall, especially the oxidation inhibitory effect of the tin layer in a lower layer will fall, and adhesiveness of a paint will fall after time passes.

When cathodic electrolytic treatment is carried out in a tank containing chromic anhydride as a main component and sulfuric acid, a fluorine compound, an aromatic sulfonic acid, or a iodine preparation, metal chromium is precipitated under the chromium hydroxide oxide film. should be suppressed below / m ² . As described above, the metal chromium is not dissolved in food, and if the amount is increased, the workability of the metal chromium layer is deteriorated. This also adversely affects the machinability of the steel, which promotes the corrosion of iron, which is the basis of the processing, so that it is not good to increase the amount of elution, the occurrence of rust, and the progress of local corrosion. Therefore, the metal chromium is preferably not formed, but is inevitably formed when the electrolytic treatment is performed by the tank described above, and it is limited to 0.005 g / m ² or less.

Here, the film structure of the electrolytic chromic acid treated steel plate of this invention, and its aspect are shown and shown in an enlarged cross section.

1 is a surface-treated steel sheet composed of an extremely thin plated stone layer 7 on the surface of a cold rolled steel sheet 5 and a chromium hydride oxide layer 9 formed on the upper layer, and an oil film 10 (the oil film is generally It is formed from cottonseed oil, dibutyl sebacate, or geoctyl sebacate, etc. to be used).

FIG. 2 shows an aspect in which the metal chromium layer 8 is interposed between the tin layer 7 and the chromium hydride oxide layer 6 of FIG. 1, but the metal chromium layer 8 is preferably very small. Ideally, it is preferable to set it to 0 as mentioned above.

In addition, FIG. 1 and FIG. 4 of FIG. 3 show an aspect in which the alloy layer 6 of iron and tin is formed between the respective cold rolled steel sheet 5 and the tin layer 7. It goes without saying that any of the embodiments within the scope of the present invention.

Hereinbelow, examples of the surface-treated steel sheet of the present invention will be described and described in detail.

Example 1

After degreasing and pickling the cold rolled steel sheet by a conventional method, electro tin plating is carried out under the conditions shown in (A), and then electrochromic acid treatment is carried out under the conditions shown in (B). An oil film of sebacate was formed.

The electrolytic chromic acid-treated steel sheet thus obtained was subjected to various application shown below, and the adhesiveness of the paint, the processing corrosion resistance to the acidic solution and the emulsion resistance were evaluated, and the results are shown in the first table.

(1) paint adhesion test

50 mg / dm ² of phenol epoxy paint (trade name SJ-6256: manufactured by Kansai Paint Co., Ltd.) was applied to the surface of the sample, baked at 210 ° C. for 12 minutes, punched into a disc of 80 mm in diameter, and had a tightening ratio of 2.0. After processing into a cylindrical cup, the outer bottom of the cylindrical cup was cut out with a razor blade + shape, and then the outer bottom and the outer surface of the adhesive tape were attached to each other, and then sharply peeled off to evaluate the presence or absence of the chart peeling from the sample.

(2) processing corrosion resistance test for acidic solution

Apply 50mg / dm ² of SJ-6256 to the sample surface and bake at 210 ℃ for 12 minutes, cut into 15mm width and 100mm length, fold the test piece in two, sandwich a 0.28mm plate thickness between them, 150mm height The weight of 3kg was dropped to the above-mentioned gluing part and processed to be completely folded at 180 degrees, and paraffin was applied except for the cut-off part.

The test piece was immersed in 300 ml of 0.01 mol / 1 lean acid containing CO ₂ at room temperature for 1 week to measure the amount of iron eluted, and the change in appearance was again observed. The same shape of the test piece was immersed for 1 week in 300 ml of 0.01 mol / 1 citric acid solution containing 0.3% sodium chloride through CO ₂ to measure the amount of eluted iron, and the appearance observation was observed.

(3) Oil painting test.

The cylindrical cup used for the paint adhesiveness test of the above-mentioned (2) was adjusted to pH 3.5 with an aqueous solution of 10 g / l of sodium emulsion (9 water salt) to lactic acid, immersed at 90 ° C for 1 hour, and coated on the outer surface of the cup. The discoloration state of the surface-treated steel sheet which passed through was evaluated.

Example 2

After pretreatment of the same cold rolled steel sheet as in Example 1, electro tin plating was carried out under the conditions shown in (A), and then electrochromic acid treatment was carried out under the conditions shown in (B). The same oil film was formed.

The obtained surface-treated steel sheet was subjected to various tests as in Example 1, and the results are shown in the first table.

Example 3

Using a cold rolled steel sheet subjected to pretreatment as in Example 1, electroplating was carried out under the conditions shown in (A), and electrochromic acid treatment was performed under the conditions shown in (B) to form an oil film as in Example 1 on the surface.

The obtained surface-treated steel sheet was subjected to various tests as in Example 1, and the results are shown in the first table.

Example 4

Using a cold rolled steel sheet subjected to pretreatment as in Example 1, electroplating was carried out under the conditions shown in (A), and electrochromic acid treatment was performed under the conditions shown in (B) to form an oil film as in Example 1 on the surface.

The various tests similar to Example 1 were performed about the obtained electrolytic chromic acid treated steel plate, and the result was shown to the 1st table | surface.

Although the above Example was shown, the comparative example for contrast with this is shown next.

Comparative Example 1

Using a cold rolled steel sheet subjected to pretreatment as in Example 1, electro tin plating was carried out under the conditions shown in (A), and electrochromic chromic acid treatment was performed under the conditions shown in (B) to form an oil film as in Example 1 on the surface. The obtained comparative materials were subjected to the same tests as in Example 1, and the results are shown in the first table.

Comparative Example 2

Using a cold rolled steel sheet subjected to pretreatment as in Example 1, electrochromic chromic acid treatment was carried out under the conditions shown below, and the same oil film as in Example 1 was formed on the surface. The various tests similar to Example 1 were performed about the obtained TFS, and the result was shown to the 1st table | surface.

Electrolytic Chromic Acid Treatment Condition

As is clear from the above Table 1, the surface-treated steel sheet of the present invention is optimal as a tin-saving can material having excellent properties of adhesion of paints, corrosion resistance to acidic solutions and emulsification resistance.

[Table 1]

Claims (1)

Tin-plated layer The surface-treated steel sheet for coating which formed the chromium hydride oxide layer containing 0.005-0.5g / m <^2> as an amount of chromium on the ultra-thin tin-plated steel plate which has 0.05-0.60g / m <^2> .

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