JPH0565691A - Method for electroplating aluminum sheet and aluminum alloy sheet - Google Patents

Abstract

PURPOSE:To form a plating film having excellent adhesion by electroplating an Al sheet with a plating soln. contg. a specified amt. of fluoride ions. CONSTITUTION:An Al sheet and an Al alloy sheet are electrolytically degreased and subjected to Zn plating, Zn-Ni alloy plating, etc., with a plating soln. contg. 10ppm to about 10g/l fluoride ions. NH4F or NaF may be used as the fluoride. Oxide films formed on the surfaces of the sheets are uniformly removed and the objective plating films having excellent adhesion are formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for electroplating on an aluminum plate and an aluminum alloy plate, and more particularly, an electroplating on an aluminum plate and an aluminum alloy plate, which can obtain a plating film having excellent adhesion. It is about the method.

[0002]

2. Description of the Related Art Cold-rolled steel sheets and surface-treated steel sheets are widely used for automobiles and home appliances. However, in recent years, the use of aluminum and aluminum alloy plates, whose specific gravity is significantly smaller than that of iron, by 1/3, has been studied for the purpose of reducing weight and improving corrosion resistance. However, an oxide film is easily formed on the aluminum plate and the aluminum alloy plate even in the atmosphere. With this oxide film, aluminum plate and aluminum alloy plate,
Although excellent corrosion resistance is imparted, on the other hand, there arises a problem in plating adhesion when plating is applied, and also a problem in phosphate treatment that is carried out as a pretreatment for coating.

In order to solve these problems, Japanese Unexamined Patent Publication No. 63-63
-166964 discloses a method of forming zinc plating on the surface of an aluminum plate and an aluminum alloy plate by a vapor deposition method, and Japanese Patent Laid-Open No. 3-104895 discloses a method of performing pulsed current by electroplating method for surface oxidation. A method for obtaining a plating film having excellent adhesion while dissolving the material layer is disclosed.

[0004]

However, the zincate treatment method is complicated in terms of equipment and has various operational problems. Therefore, there is a demand for a method capable of obtaining a coating film having excellent plating adhesion by a normal constant current electroplating method, but such a method has not been proposed yet. Therefore, an object of the present invention is to provide an electroplating method capable of obtaining a plating film having excellent adhesion by a usual constant current electroplating method.

[0005]

The present invention is characterized by performing electroplating using a plating solution containing 10 ppm or more of fluoride ions.

In the present invention, the reason why a plated coating having excellent adhesion can be obtained is as follows. That is, due to the presence of the fluoride ions, the oxide film formed on the surface of the aluminum plate or the aluminum alloy plate is uniformly removed. Because of this, the plating metal is deposited on the aluminum metal, not on the aluminum oxide. As a result, excellent adhesion is obtained. On the other hand, in the plating bath to which the fluoride ion is not added, not only the oxide film is not removed, but also the oxide film removed by the pickling treatment before plating is regenerated, resulting in extremely poor adhesion.

Fluoride ion concentration added is 10 ppm
It is necessary to limit the above. This is because when the fluoride ion concentration is less than 10 ppm, it takes a long time to uniformly dissolve the oxide film. The upper limit of the fluorine ion concentration is not particularly limited, but is preferably about 10 g / l. This is because the dissolution effect of the oxide film is saturated in this concentration range, and the fluoride ion concentration is preferably low from the viewpoint of waste liquid treatment.

[0008]

EXAMPLES The present invention will now be described in more detail with reference to Examples. Aluminum plate and magnesium 4.5 wt.
The aluminum alloy plate containing 10% was electrolytically degreased at 80 ° C. in 40 g / l of sodium orthosilicate for 10 seconds under the condition of 10 A / dm ² . Then, at 50 ° C in 50g / l sulfuric acid for 10 seconds,
Pickled. Then, with a plating solution having the composition shown in Table 1, 20 g / mm ² of zinc plating, zinc-iron alloy plating (iron content 15 wt.%), Zinc-nickel alloy plating was performed on the aluminum plate and the aluminum alloy plate. (Ni content 13
wt.%) and pure nickel plating. The plating conditions were a plating solution flow rate of 2 m / sec, a temperature of 50 ° C., and a current density of 55 A / dm ² .

The samples produced as described above were subjected to a plating film adhesion test with cellophane tape after zero-ty bending shown in FIGS. 1 and 2. The results are shown in Table 1. In the evaluation of the plating film adhesion test in Table 1, the mark ⊚ indicates that no peeling of the film was observed in both the flat surface portion and the bent portion, and that the adhesiveness was extremely excellent. No peeling was observed on the flat surface, but slight peeling was observed on the bent portion, indicating excellent adhesion. △ indicates no peeling on the flat surface. Shows that there is a problem with the adhesiveness because the bent part peels more than 1/4, and the x mark indicates that the flat part and the bent part are peeled off and the adhesiveness is poor. ..

Next, a comparative example will be described. An aluminum plate and an aluminum alloy plate containing 4.5 wt.% Magnesium were placed at 80 ° C in 40 g / l sodium orthosilicate for 10 days.
Electrolytic degreasing was performed under the condition of 10 A / dm ² for ² seconds. Then, using a plating solution containing a fluoride ion concentration outside the scope of the present invention shown in Table 2, 20 g / mm ² zinc plating, zinc-iron alloy plating (iron content 15 wt.%) Zinc-nickel alloy plating (Ni content 13 wt.%) And pure nickel plating. The plating conditions are as follows: plating solution flow rate is 2m / sec, temperature is 50 ℃, and
The current density was 55 A / dm ² . The sample manufactured as described above was subjected to a plating film adhesion test using cellophane tape after zero-ty bending, as in the example of the present invention. The results are shown in Table 2. The evaluation method of the coating adhesion test shown in Table 2 was the same as in Table 2.

As is clear from the results of Tables 1 and 2, it was found that according to the examples of the present invention, peeling of the plating film hardly occurred, and excellent plating adhesion was obtained.

[0012]

As described above, according to the present invention, a useful effect such that a plating film having excellent adhesion can be obtained without performing a pickling as a pretreatment is brought about.

[Brief description of drawings]

FIG. 1 is a partial perspective view of a film adhesion test sample.

FIG. 2 is a plan view showing a state in which a film adhesion test sample is extended.

[Table 1]

[Table 2]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuhiro Koike 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Inside Nihon Kokan Co., Ltd. (72) Yoshinori Aomura 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Nippon Steel Tube Co., Ltd.

Claims (1)

[Claims] 1. Electroplating is performed using a plating solution containing 10 ppm or more of fluoride ions.
Electroplating method on aluminum plate and aluminum alloy plate.