JP3032112B2 - Method for producing high Ni-containing Zn-Ni plated steel sheet excellent in corrosion resistance and powdering resistance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel sheet for automobiles and home appliances, and relates to a method for producing a high Ni-containing Zn-Ni plated steel sheet having excellent 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 vehicle body corrosion due to scattered rock salt for preventing road freezing in winter in cold regions. In the prior art, the improvement in the corrosion resistance of a Zn—Ni plated steel sheet is due to the
Although it is possible to increase the i content, there are many problems in terms of reduction in powdering resistance and reduction in weldability.

[0003]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a Zn-
An object of the present invention is to provide a method for producing a Zn—Ni plated steel sheet in which the corrosion resistance is improved by increasing the Ni content in Ni plating.

[0004]

The gist of the present invention is to provide an electric Z
In producing an n-Ni plated steel sheet, Zn ²⁺ ions,
Corrosion resistance, wherein electroplating is performed using a plating bath containing Ni ²⁺ ions and 0.01 to 1.0 g / l of 2-ethoxy-α-naphthylaminesulfonic acid;
This is a method for producing a high Ni-containing Zn-Ni plated steel sheet having excellent powdering resistance.

[0005]

The present invention will be described below. 2-ethoxy-
The amount of α-naphthylaminesulfonic acid added is 0.01 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 and the like. In addition, 1.0 g /
If it exceeds l, the powdering resistance will decrease,
The plating current efficiency is reduced, causing a problem in productivity.

FIG. 1 shows the relationship between the amount of 2-ethoxy-α-naphthylaminesulfonic 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 rating of the powdering resistance is 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 drops to 6 or less.

As the plating bath, any of a sulfuric acid bath, a chloride bath and a mixed bath thereof can be used. 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, burning of the plating tends to occur. If it exceeds 200 g / l, waste of ions due to drag-out cannot be ignored, and crystallization may occur when the liquid temperature is lowered. Other plating conditions are not particularly limited, but a preferred range is 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, optimal conditions can be adopted in consideration of the target plating composition and current efficiency. A conductivity aid such as Na ⁺ , NH ₄ ⁺ ions or the like may be added to the plating bath, and there is no essential problem in 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 decreases.

[0008]

EXAMPLE A cold-rolled steel sheet was alkali-degreased, pickled with 5% sulfuric acid, and electroplated under the conditions shown in Tables 1 and 2. A sulfuric acid bath was used as the plating bath, and the coating weight was 3
0 g / m ² . Table 2 shows the evaluation of the plating composition, corrosion resistance, and powdering resistance obtained in this manner. The corrosion resistance was determined in the following manner by performing a salt spray test (based on JIS Z2371) for 500 hours. ◎: Red rust 1% or less, Δ: Red rust
10% or less, Δ: Red rust 50% or less, ×: Red rust 50% or more Regarding powdering resistance, the tape was peeled after OT bending, and a 10-point rating was given based on the amount of plating adhered to the tape. The above was regarded as a pass level.

[0009]

[Table 1]

[0010]

[Table 2]

In Tables 1 and 2, Comparative Example 1 does not contain 2-ethoxy-α-naphthylamine sulfonic acid. Therefore, when powdering resistance is ensured, only those in the region where the Ni content is low are obtained, and the corrosion resistance is low. Is declining. In Comparative Example 2, as a result of increasing the Ni content without adding 2-ethoxy-α-naphthylaminesulfonic acid, powdering resistance could not be ensured. Comparative Example 3 was 2-ethoxy-α
-An appropriate amount of naphthylamine sulfonic acid was added, but the Ni content in the plating layer was too high, so that the powdering resistance was reduced.

In Comparative Example 4, since the addition of 2-ethoxy-α-naphthylaminesulfonic acid was small, the powdering resistance was reduced 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 not effective.
When the content is increased, the powdering resistance decreases. On the other hand, in each case, the present invention has a high N of 14% or more.
It can be seen that the corrosion resistance is good and the powdering resistance is good as well as the i content.

[0013]

As described above, according to the present invention, by adding 2-ethoxy-α-naphthylaminesulfonic acid to a Zn-Ni plating bath, the powdering resistance at the time of high Ni content, which has been conventionally difficult, is improved. An object of the present invention is to provide a method for producing a Zn-Ni plated steel sheet which is secured and has excellent corrosion resistance. This is extremely effective in producing a rust-preventive steel sheet which is required to have high corrosion resistance and powdering resistance mainly for automotive applications.

[Brief description of the drawings]

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

Continuation of the front page (56) References JP-A-4-362190 (JP, A) JP-A-3-24295 (JP, A) JP-A-62-287093 (JP, A) JP-A-63-24093 (JP, A) , A) JP-A-7-278874 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C25D 3/00-3/66 C25D 5/26

Claims (1)

(57) [Claims] When producing an electric Zn-Ni plated steel sheet, Zn ²⁺ ions, Ni ²⁺ ions and 0.01 to 1.
Electroplating using a plating bath containing 0 g / l of 2-ethoxy-α-naphthylamine sulfonic acid. .