JPH07278873A - Production of highly ni containing zn-ni plated steel sheet excellent in corrosion resistance and powdering resistance - Google Patents

Abstract

PURPOSE:To impart powdering resistance in the case of highly containing Ni, which is conventionally difficult, and to produce a rust preventive steel sheet excellent in corrosion resistance by adding metallic ions of Zn, Ni and 2-ethoxy- a-naphthylamine sulfonic acid into a plating bath. CONSTITUTION:Electroplating is executed by using the plating bath containing m<2+> ion and 0.01-1.0g/l 2-ethoxy-a-naphthyl amine sulfonic acid. As the plating bath, any of a sulfonic acid bath, a chloride bath and their mixture bath can be adopted. The total conc. of Zn<2+> ion and Ni<2+> is controlled preferably to 30-200g/l. Though the other plating conditions are not limited particularly, the preferable condition is 0.5-0.3 in pH, 40-70 deg.C in bath temp., >=1m/min in liquid flow rate and >=200/dm<2> in current density and the optimum condition can be adopted considering a desired plating composition or current density.

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 Zn-Ni plated steel sheet having a high Ni content, which relates to a steel sheet for automobiles and home appliances and which is excellent in corrosion resistance and powdering resistance.

[0002]

2. Description of the Related Art Electric Zn-Ni plated steel sheets are widely used mainly for automobiles and home appliances. Among them, in automobile applications, higher corrosion resistance is required in order to prevent car body corrosion due to sprayed rock salt for road freezing prevention in winter in cold regions. In the prior art, the improvement of the corrosion resistance of the Zn-Ni plated steel sheet is due to the increase of the coating amount or N
Although it is possible to increase the i content, there are many problems in that the powdering resistance and weldability are deteriorated.

[0003]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention aims to solve the problems of Zn-- while maintaining powdering resistance.
The present invention provides a method for producing a Zn-Ni plated steel sheet in which the Ni content in Ni plating is improved to improve the corrosion resistance.

[0004]

The gist of the present invention is to provide an electric Z
When manufacturing an n-Ni plated steel sheet, Zn ²⁺ ions,
Corrosion resistance characterized by performing electroplating using a plating bath containing Ni ²⁺ ions and 0.01 to 1.0 g / l of 2-ethoxy-α-naphthylamine sulfonic acid,
It is a method of manufacturing a high Ni-containing Zn-Ni plated steel sheet having excellent powdering resistance.

[0005]

The present invention will be described below. 2-ethoxy-
The addition amount of α-naphthylamine sulfonic acid is 0.01 to
It is set to 1.0 g / l. If it is less than 0.01 g / l, there is no effect of improving the powdering resistance, and if the Ni content is 14 wt% or more, there is a problem in press formability. In addition, 1.0 g /
If it exceeds 1, the powdering resistance will decrease,
Plating current efficiency decreases, causing a problem in productivity.

FIG. 1 shows the relationship between the amount of 2-ethoxy-α-naphthylamine sulfonic acid added and the powdering resistance.
The plating conditions are adjusted so that the Ni% in the plating becomes three levels of 11%, 14%, and 17%. Other plating bath compositions are the same. When 2-ethoxy-α-naphthylaminesulfonic acid is less than 0.01 g / l, the powdering resistance has a rating of 6 or less, but in the range of 0.01 to 1.0 g / l, the rating is 7 or more. If it exceeds, the score will drop to 6 or less.

As the plating bath, any of a sulfuric acid bath, a chloride bath and a mixed bath thereof can be applied. Regarding the metal ion concentration, the total of Zn ²⁺ ions and Ni ²⁺ ions is 30 to
200 g / l is preferred. If it is less than 30 g / l, the supply of ions tends to be insufficient at a high current density, and as a result, plating burn is likely to occur. If it exceeds 200 g / l, the waste of ions due to dragout cannot be ignored, and there is a concern of crystallization when the liquid temperature becomes low. Other plating conditions are not particularly limited, but preferable ranges are pH = 0.5 to 3.0, bath temperature 40 to 70 ° C., liquid flow rate 1 m / min or more, and current density 20 A / dm ² or more. Therefore, the optimum conditions can be adopted in consideration of the intended plating composition and current efficiency. A conductivity auxiliary agent such as Na ⁺ and NH ₄ ⁺ ions may be added to the plating bath, and there is no essential obstacle to the production method of the present invention. The Ni content in the plating layer is preferably 10 to 17%.
If it is less than 10%, the corrosion resistance is poor, and if it exceeds 17%, the powdering resistance is deteriorated.

[0008]

EXAMPLE A cold rolled steel sheet was degreased with alkali, pickled with 5% sulfuric acid, and then electroplated under the conditions shown in Tables 1 and 2. A sulfuric acid bath is used as the plating bath, and the coating weight is 3
It was set to 0 g / m ² . Table 2 shows the evaluation of the plating composition, corrosion resistance, and powdering resistance thus obtained. The corrosion resistance was evaluated by a salt spray test (according to JIS Z2371) for 500 hours and the following procedure. ◎: Red rust 1% or less, ◯: Red rust
10% or less, △: Red rust 50% or less, ×: Red rust 50% For powdering resistance, peel the tape after OT bending and give a 10-point rating according to the amount of plating adhered to the tape, and score 7 points. The above is the passing level.

[0009]

[Table 1]

[0010]

[Table 2]

In Tables 1 and 2, Comparative Example 1 does not contain 2-ethoxy-α-naphthylamine sulfonic acid, so that if powdering resistance is secured, only Ni content in the low region is obtained and corrosion resistance is improved. It is falling. Further, in Comparative Example 2, as a result of increasing the Ni content without adding 2-ethoxy-α-naphthylamine sulfonic acid, the powdering resistance cannot be secured. Comparative Example 3 is 2-ethoxy-α.
-Although a proper amount of naphthylamine sulfonic acid was added, the powdering resistance was lowered because the Ni content in the plating layer was too high.

In Comparative Example 4, since the addition of 2-ethoxy-α-naphthylamine sulfonic acid was small, the powdering resistance was lowered when the Ni content in the plating was increased. Also,
Comparative Example 5 had no effect because the amount of 2-ethoxy-α-naphthylaminesulfonic acid added was too large, and Ni during plating was
When the content is increased, the powdering resistance is lowered. On the other hand, in all the cases of the present invention, high N of 14% or more was obtained.
It can be seen that the content is i and the corrosion resistance is good, and the powdering resistance is also good.

[0013]

As described above, according to the present invention, by adding 2-ethoxy-α-naphthylamine sulfonic acid to the Zn-Ni plating bath, the powdering resistance at the time of containing high Ni, which has been difficult in the past, can be obtained. It is intended to provide a method for manufacturing a Zn-Ni plated steel sheet which is secured and also has excellent corrosion resistance. This is extremely effective for producing a rust-preventive steel plate which is required to have high corrosion resistance and powdering resistance mainly for automobiles.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the amount of 2-ethoxy-α-naphthylamine sulfonic acid added and powdering resistance.

Claims (1)

[Claims] 1. When manufacturing an electric Zn-Ni plated steel sheet, Zn ²⁺ ions, Ni ²⁺ ions and 0.01-1.
Electrolytic plating is performed using a plating bath containing 0 g / l 2-ethoxy-α-naphthylamine sulfonic acid, and a method for producing a high Ni-containing Zn-Ni plated steel sheet having excellent corrosion resistance and powdering resistance. .