JPH04293799A - Electroplating method - Google Patents

Abstract

PURPOSE:To provide the electroplating method. CONSTITUTION:Electroplating is operated without lowering a current density to a non-plating region by selecting plural pieces of discharge surfaces 5 of electrodes 4 according to the passing speed of a material 3 to be plated and energizing these surfaces. A prescribed plating deposition is surely obtd. even at a low passing speed and an exact plating compsn. is obtd. as well. The merchandise value of the plated product is improved and the yield is improved as well.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroplating method.

0002

[Prior art and problems to be solved by the invention] In electrolytic plating, generally multiple plating tanks are installed in series to continuously plate the material to be plated, such as steel strip, and control the coating amount to a predetermined amount. It is something to do. Therefore, in the case of a thin coating amount or during low-speed sheet passing, the current supply to one or more of the plurality of passes is stopped to provide a predetermined coating amount. This is done for the purpose of controlling the coating amount and controlling the quality of appearance etc. by keeping the current density during plating within the appropriate current density range under any condition of sheet passing.

However, in the case of particularly thin plating (for example, one with only one or two current passing paths) or one with a very narrow suitable current density range, the above method
If the number of passes that can stop energization is insufficient, or if the number of passes is changed, the current density may become low and fall outside the appropriate current density range. (This appropriate current density range varies depending on the type, composition, etc. of the plating bath.)

[0004] In such a case, the commercial value will decrease and the yield will decrease. There is a strong demand for a solution to such a decrease in yield.

[0005]

[Means for Solving the Problems] The present invention is characterized in that a plurality of discharge surfaces of the electrode are selected and energized according to the passing speed of the material to be plated, and the current density is reduced to the non-plated area. This is an electroplating method characterized by the fact that it operates without any interference.

In the method of the present invention, when the passing speed of the material to be plated is switched to a low speed, by selectively applying current to a plurality of discharge surfaces of the electrode, the current density is not reduced to a low current density in the unplated area. , which conducts electricity.

For example, a plurality of discharge surfaces are provided on the symmetrical surface of the plated steel strip of the electrode, and the number of discharge surfaces that conduct electricity to the plated steel strip is adjusted according to the passing speed of the plated steel strip, thereby preventing an unplated area. Plating is performed using current density.

That is, as the plate passing speed becomes slower, the number of current-carrying discharge surfaces of the electrode is reduced, and the current-carrying discharge surfaces are energized while maintaining a high current density in order to apply a target plating amount. This eliminates non-plating caused by low current density.

[0009] In actual operation, for example, the low current density area that is the non-plating area is known from the plating bath composition, etc.
Depending on the plate passing speed, and in relation to the target plating amount, the number of electrodes to be energized is adjusted to a number that allows energization at a current density that does not result in unplated surfaces.

The method of the present invention can be effectively applied to electroplating such as chromium plating, tin plating, metal plating, and zinc plating.

Next, embodiments of the method of the present invention will be explained with reference to the drawings. 1 and 2, a steel strip 3 is introduced into a tank 2 filled with a plating bath 1, and electricity is applied using an electrode 4 as an anode and the steel strip 3 as a cathode to perform electrolytic plating. The discharge surfaces 5a, 5b of the electrode 4 are energized according to the
By adjusting the number of 5c, target electrolytic plating is performed at a current density that does not result in an unplated area. 6 in the figure is a conductor roll.

0012

[Examples] Next, examples of the method of the present invention will be described together with comparative examples.

Example-1 (1) Plating bath composition CrO3: 50g/l, H2SO4: 0.3g/l
l, Na2 SiF6: 0.5 g/l (bath temperature: 40°C
) (2) Steel strip width: 1000mm (3) Electrode discharge area: 0.2m2 x 3 pieces Under these conditions, the threading speed was 400m/min, and the current density was 60A/dm2.
Then, electricity was applied from three discharge surfaces, chrome plating (metal) of ±10 mg/m2 was applied, and then the steel strip coil (steel strip) was connected (welded) at the line entry side, so the threading speed was increased to 200 m. /min, the current flow from the two discharge surfaces was stopped and the current flow from one discharge surface (0.2 m2) was stopped.
Current density 60A/dm2), target ±10mg
/m2 metal chromium plating was continuously applied.

[0014] Next, the connection of the steel strips was completed, and the threading speed was increased to 300 m/min.
60A/dm2), and the threading speed was further increased to 400m.
/ minute, electricity is applied from the three discharge surfaces (60A/minute).
dm2), with the target of ±10mg/m in both cases.
2 metal chrome plating was applied.

Comparative Example The plating bath composition and steel strip width were the same as in the example, the electrode discharge area was 0.6 m2 (integrated structure), and the current density was 60 A.
/dm2, ±10mg/m2 at threading speed of 400m/min
metal chrome plating, and then the threading speed was increased to 200
When the current density was lowered to 30 A/dm2, the amount of metallic chromium was less than 1 mg/m2, with most of the chromium oxide being precipitated, and the product was rejected.

When the current density was increased to 57 A/dm2, 13 mg/m2 of metallic chromium was deposited, which exceeded the target plating amount, and the product was also rejected.

[0017]

[Effects of the Invention] By doing so, it is possible to reliably eliminate fluctuations in the amount of metal chromium plating due to changes in the sheet passing speed, and to significantly improve the product yield.

[0018] Also, in actual operation, by selectively applying current to the discharge surface of the electrode, excellent effects such as easy and reliable operation can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a side view showing an embodiment of the method of the present invention.

FIG. 2 is an explanatory front view of an electrode.

[Explanation of symbols]

Claims (1)

[Claims] [Claim 1] The method is characterized in that a plurality of discharge surfaces of the electrodes are selectively energized according to the passing speed of the material to be plated, and the operation is performed without reducing the current density to the non-plated area.
Electroplating method.