JPS5896891A - Production of bright tin plated steel plate having excellent paint adhesion - Google Patents

Abstract

PURPOSE:To permit production of a bright tin plated steel plate having excellent high temp. water resistance of paint adhesion by forming a metallic chromium layer and a chromium hydrated oxide layer by electroplating on the surface of a tin plated steel plate. CONSTITUTION:After a cold rolled steel plate for plating is defatted and washed, tin plating is carried out and further the tin is melted to apply a brightening treatment. Thereafter, the steel plate is subjected to a cathodic treatment for a short time at 30-100A/dm<2> current density in an aq. soln. contg. 0.05-10.0g/l one or >=2 kinds fluorine compds such as FH, H2SiF6, HBF4 or sulfur compds. such as H2SO4, phenol sulfonic acid or the like at 10-100g/lCrO3 as additives. 30-100mg/m<2> metallic Cr and 5-25mg/m<2> Cr hydrated oxide as content of Cr are deposited on the tin plate steel plate. The bright tin plated steel plate for canning which has excellent high temp. water resistance of paint adhesion and permits seaming of can bodies with adhesive agents is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a bright tin-plated steel sheet having excellent paint adhesion, particularly paint adhesion and high temperature water resistance.

Tin-plated steel sheets, so-called electroplated tin, are most widely used as materials for beverage cans, food cans such as fish and meat cans, 5-gallon cans, etc., due to their excellent corrosion resistance and metallic luster in appearance. On the other hand, recent can manufacturing methods include, in addition to traditional soldering,
Electrolytic chromic acid treated steel sheet, i.e. tin-free steel (
With the advent of tin free 5teel), can body joining methods using organic adhesives (hereinafter referred to as adhesives) such as nylon adhesives have been developed and diversified. In such a bonding part, the coating side and the coating surface are overlapped and bonded using a nylon adhesive. Therefore, the adhesive strength depends on the adhesive strength between the nylon adhesive and the paint film, the adhesive strength between the paint film and the steel plate, and the cohesive strength of the nylon adhesive and the paint film. The adhesive strength of the adhesive part is determined by: After jl plating,
Ordinary electroplated tin, in which tin is melted and then electrolytically treated in a sodium dichromate solution, has poor adhesion to paint (and it is difficult to join can bodies using adhesives for electroplated tin). It has been.

The present invention provides a bright tin-plated steel sheet that can be joined to the can body using an adhesive, and at the same time has a hardness of about 90% at normal pressure.
So-called hot packs, which are immediately filled with contents that have been heat sterilized at a temperature of ~100°C, and so-called retort sterilization, which is heat sterilized at temperatures exceeding 100°C using pressurized steam after the hot pack, i.e., high-temperature packs. The present invention provides a bright tin-plated steel sheet that can be joined to a can body using an adhesive for applications requiring water resistance.

U.S. Patent No. 3.2 improves the adhesion of paint.
No. 45.577 is shown. This patent is for chromium plating on a tin layer, and the one shown here has a plating bath with a chromic acid concentration of 245 f/(1, and a processing current density of IOA/di. Japanese Patent Publication No. 47-45253 discloses a method in which chromium plating is applied on the layer.This patent relates to a method for manufacturing unpainted highly corrosion-resistant tinplate, but the examples also mention paint adhesion. There is.

Both of the above-mentioned patents use baths in which the concentration of chromic anhydride ranges from 100 to 450 f/l, which is commonly used as a chromium plating bath composition. Even if chromium plating is performed on the tin layer at such a bath concentration, the primary adhesion of the paint is improved, but the high temperature water resistance and retort resistance of the paint adhesion are hardly improved.

As a result of studying the high-temperature water resistance and retort resistance of bright tin-plated steel sheets, we found that the uniformity of the chromium hydrated oxide layer and the metallic chromium layer has a significant effect on paint adhesion, high-temperature water resistance, and retort resistance. To explain in more detail, when 10cm of the bonded area in contact with high-temperature contents or water vapor is forcibly peeled off, the chromium hydrated oxide layer on the outermost surface of the bright tin-plated steel sheet and the paint film are separated. There is a distance of 711 between them.

That is, the high temperature water resistance of paint adhesion is affected by the quality of the chromium hydrated oxide layer, and it is desirable that the film be uniform and free of defects. Although it is difficult to directly measure the uniformity of Jl in a minute region of a chromium hydrated oxide film with an Iv of about 5 to 207+m, it is thought to be correlated with the uniformity of precipitation of metallic chromium.

The present invention examines the manufacturing method of bright tin-plated steel sheets from this point of view, and provides a post-treatment method for bright tin-plated steel sheets with excellent high-temperature water resistance and retort resistance. That is, when chromium plating is applied on a tin layer in a bath with a chromic acid concentration of 100 to 450 f/II, which is a normal chromium layer, metallic chromium is precipitated on the tin layer. In contrast, according to the method of the present invention, the tin layer is coated with fine and uniform metallic chromium. Furthermore, chromic acid a
ll! In the case of treatment with a bath of 100t/1 or more,
While the thickness of the chromium hydrated oxide layer is usually not sufficient, the method of the present invention makes it possible to obtain the necessary and sufficient thickness of the chromium hydrated oxide layer. . As described above, according to the method of the present invention, a bright tin-plated steel sheet with excellent paint adhesion and high-temperature water resistance is produced by a uniform metallic chromium layer and a uniform chromium hydrated oxide layer with a necessary and sufficient thickness. can be obtained.

The method of the present invention will be explained in detail below.

A cold-rolled steel sheet for plating is degreased with alkaline, pickled, and then washed with water in a known tin sulfate plating bath using a conventional method (both sides and one side).
After applying tin plating at a rate of 1.0 to 11.2 f/r1f, a brightening treatment is applied to melt the tin, and then a 10-1
00 f/l chromic anhydride as the main ingredient and one or more fluorine compounds or sulfur compounds as auxiliary agents.
05 to 10.0 V/l in a melt containing 30 to 100 A/d of current density for a short period of time to cathodize the tin-plated steel plate at 30 to 100 Da/d, chromium. Water tag oxide is precipitated in an amount of 5 to 25 Q/d as chromium, and oil is applied as necessary. By using this method, the metallic luster that is the advantage of υ rice's so-called electroplating tin can be achieved (
It is possible to obtain a tin-plated steel sheet with excellent temperature-directed water resistance of coating strength of +4 without any damage. The basis weight of tin is 1.0 to 1.
There is almost no effect on high temperature water resistance in the range of 1.2r~. If the concentration of chromic anhydride is more than 1OOf/1, the effect of the present invention will be poor, and if it is less than 10t/l, the electric resistance of the bath will be large, making it impractical from the point of view of energy efficiency;
Desirably, it is in the range of 60 Vl. An auxiliary agent consisting of one or more fluorine compounds or sulfur compounds is 10
If it is r/6 or more, the tin layer will dissolve during treatment and tin crystal grains will appear, impairing the appearance and deteriorating the treatment bath, which is not desirable. On the other hand, if it is 0.059171 or less,
The effects of the present invention cannot be obtained. Current density is 100 A/d
Even if it is less than 100 k/dvf, it does not impede the effects of the present invention, but it increases the equipment cost during production, so from the viewpoint of cost efficiency, it is desirable that it is 100 k/dvf or more.

The effect of the present invention decreases below 30 k/dnl.

It is necessary for the amount of metallic chromium to be 30 to 1 to maintain high-temperature water resistance, and even if it is present to 10 to 1, there is little contribution to improving high-temperature water resistance.
00 call β is suitable. If the amount of chromium in aqueous chromium oxide is less than 5 da β, stable paint adhesion cannot be obtained. On the other hand, if the β is 25 or more, the interference color of the oxide film becomes visible, which is unfavorable in terms of appearance, and the β should be 5 to 25.

The bath temperature is not particularly limited, but for operational reasons it is
A range of 60°C to 60°C is suitable.

The idea of the present invention is to treat bright tin-plated tin at a lower concentration range and higher current density than in a bath normally known as a chromium plating bath, thereby increasing the unit surface area during the precipitation of metallic chromium. Dramatically increases the number of precipitated nuclei per unit, thereby obtaining a fine and uniform metallic chromium layer, chromium water, and hydroxide oxide layer, thereby providing a bright tin-plated steel sheet with excellent paint adhesion and high-temperature water resistance. There is a particular thing. This point will be explained using the drawings. Figures 1 and 2 both show the transmission of a metallic chromium layer on a bright tin-plated steel plate.
These are microphotographs, and Fig. 1 shows the product treated with the present invention shown in Example 2, and Fig. 2 shows the product treated with a bath used as a normal chromium plating bath shown in Comparative Example 2. It is. It can be seen that in Fig. 4 < 2, the precipitation of granular metallic chromium is clear, whereas in Fig. 1, metallic chromium is deposited finely and uniformly.

Hereinafter, the present invention will be specifically explained with reference to Examples.

Example 1 Board +9! 0.230 cold-rolled steel sheet was electrolytically degreased in a 7% sodium hydroxide solution, washed with water, electrolytically pickled in a 3% sulfuric acid solution, washed with water, and then subjected to a known tin sulfuric acid plating bath. After applying tinning in ~282 ~ and melting the tin, cathodic electrolytic treatment was performed using the composition and treatment conditions shown below.
Octyl Separate (hereinafter referred to as Dos) was applied.

Bath composition Chromic acid 60 t/1 sulfuric acid
0.6? /1 treatment processing density 4
0 Aldd treatment time 0.5 seconds bath mixing 50
°C Example 2 The same pretreatment as in Example 1 was carried out, 282β tin plating was performed in a known acidic tin plating bath, and the tin was melted in the same manner as in Example 1. Then, the following composition and treatment conditions were applied. Cathode electrolyzed with DO8 & oiled O bath composition Chromic acid
30 f/1 Sodium fluoride 2.0 9/e Sulfuric acid 0. 0 5 ta/1 processing current density 50 fi,/dd processing time
05 seconds bath temperature 60
°C Example 3 The same pretreatment as in Example 1 was performed, tin plating was performed at 2.82~ in a known acidic tin plating bath, and the tin was melted in the same manner as in Example 1, then the following composition was prepared. Cathode electrolytic treatment was performed under the following treatment conditions, and DO8 was applied.

Bath composition Chromic acid 30 f/1 Ammonium fluoride 1.7 f/1 Treatment flow rate 90 A/d treatment time
06 seconds bath temperature 60
°C Example 4 After carrying out the same pretreatment as in Example 1, applying tin plating at 2.8 f/I/lff in a known acidic tin plating bath, and melting the tin in the same manner as in Example 1, the following Cathode electrolytic treatment was performed using the composition and treatment conditions shown below, and DO8 was applied.

Bath composition Chromic acid 30 f/1 potassium fluoride
2.89/ll Processing current density ? OA/dgo processing time
05 seconds bath temperature 45
°C Comparative Example 1 The same pretreatment as in Example 1 was performed, 282β tin plating was performed in a known acidic tin plating bath, and after melting the tin in the same manner as in Example 1, the following composition and treatment conditions were used. The cathode was subjected to electrolytic treatment and coated with I) O8.

Bath composition Sodium dichromate 30 f/1 treatment '14 R layer density 4νd door treatment time
1 second bath warm 45
℃ Comparative Example 2 The same pretreatment as in Example 1 was carried out, tin plating was performed at 282 ~ in a known acidic tin plating method, and after melting the tin in the same manner as in Example 1, the following composition and treatment conditions were used. It was subjected to cathodic electrolytic treatment and oiled with DO8.

Bath composition Chromic acid 200 f/1 sulfuric acid
22/l Processing current density 30 kldrd Processing time 05 seconds Bath temperature 45
The bright tin-plated steel sheets obtained in Examples 1 to 4 and Comparative Examples 1 to 2 were evaluated by the following visual inspection and adhesive strength test. In addition, the amount of metallic chromium and the amount of hydrated chromium oxide (as chromium residue) were measured, and the results are shown in Table 1.

(1) Appearance inspection Surface gloss was evaluated by visual inspection.

(2) Paint adhesion test at room temperature Apply epoxy/phenol paint to one side of the sample at a rate of 60/d.
Dry curing was performed at 10° C. for 12 minutes. Furthermore, the same paint was applied to the back side and dried and cured under the same conditions. This sample is
N, cut out to a length of 100 fi, overlap the above-mentioned front and back surfaces, sandwich a nylon adhesive tape between the two specimens, and press at 200°C for 120 min using a hot press.
After preheating for seconds, under pressure of 31g7c4
'C, crimping was performed for 30 seconds. This adhesive specimen was peeled off using a tensile tester, and its adhesive strength was expressed as 915 MnM.

(3) High-temperature water resistance test for paint adhesion The adhesive specimen from (2) above was immersed in a 4% citric acid solution at 90°C for 3 days, and then toughened using a tensile tester.

The adhesive strength was expressed in kg/5 tm.

(4) Retort resistance test for paint adhesion A painted sample was prepared in the same manner as in (2) above, cut into pieces of 70 fl in diameter and 60 fl in length. 8t
They were overlapped by z, a nylon adhesive tape was sandwiched between them, and heat and pressure bonded under the same conditions as the previous 1ll). 10 sets of these test pieces were made, and after rounding them in advance to a radius of about 100 degrees like can bodies, they were fixed to the angle of the bottom 701111.
The number of 6-6 pieces separated out of 10 sets was expressed after aging for 60 minutes and 120 minutes in a retort pot of 1.6-1.7 kgμ at 125-130°C.

As is clear from Table 1, the primary adhesion of the paint at room temperature is the same in both Example and Comparative Example 2;
Regarding the high temperature water resistance and retort resistance of paint adhesion, which are the objectives of the present invention, there is a remarkable difference between the examples and comparative examples, and the bright tin-plated steel sheet manufactured by the present invention has excellent properties. ing.

[Brief explanation of the drawing]

Figure 1 is a 20,000x transmission electron micrograph of the metallic chromium layer of the bright tin-plated steel sheet obtained by the method of Example 2, and Figure 2 is a transmission electron micrograph of the metallic chromium layer of the bright tin-plated steel sheet obtained by the method of Comparative Example 2. This is a 20,000x transmission electron micrograph of the metallic chromium layer of a plated steel sheet. Figure 1 Figure 2 1.

Claims (3)

[Claims] (1) In the method for manufacturing bright tin-plated steel sheets in which a film of metallic chromium and hydrated chromium oxide is applied to a tin-plated steel sheet, after melting the tin of the tin-plated steel sheet, 10 to 1009/l of chromic anhydride is added as the main ingredient. and one or more fluorine compounds or sulfur compounds as an auxiliary agent of 0.05-10.
In a solution containing 0 f/l, the current t! i30~100
Paint adhesion characterized by cathodic treatment at k/dd for a short time to deposit 30 to 100 W/d of metallic chromium and 5 to 25 W/d of chromium aqueous oxide on a tin-plated steel plate. Manufacture of superior bright tin-plated steel sheets. (2) The fluorine compound is hydrofluoric acid or hydrofluorosilicic acid. A glossy tin with excellent appetizing properties, characterized in that it is borohydrofluoric acid or a fluoride, silicofluoride, or fluoride of an alkali metal, ammonium, or aluminum. Manufacturing method for galvanized steel sheets. (3) The sulfur compound is sulfuric acid, phenolsulfonic acid, phenolsulfonic acid, or alkali metal, ammonium, or aluminum sulfates, sulfites, thiosulfates, or phenolsulfonates. A method for producing a bright tin-plated steel sheet with excellent paint adhesion Φ according to claim 1, characterized in that the phenol sulfonate is used as a phenol sulfonate.