JPH06180000A - Metallic ion supply method - Google Patents

Abstract

PURPOSE:To prevent the generation of sludge in a plating soln. in the plating device of Fe-Zn, etc., using an insoluble anode and a metallic granular material as the metallic ion source by fixing the difference in pH between the plating solns. before and behind a metal dissolving tank. CONSTITUTION:An insoluble anode is used, and the metal ion consumed in the plating reaction is replenished by dissolving a granular metal to carry out the plating of Fe-Zn, etc. In this case, a waste plating soln. from a circulating tank 1 as the plating tank is sent to a dissolving device 2 contg. granular Fe-Zn by a pump 3 to dissolve the Fe-Zn as the Fe<2+> and Zn<2+> ions, which are replenished, and then returned to the tank 1. The pH of the plating soln. before entering the dissolving device 2 is measured by a pH meter 4 and the pH of the soln. having dissolved the Fe and Zn by a pH meter 5, the discharge of the soln. from the tank 1 is controlled so that the difference is adjusted to <=0.5 to prevent the generation of sludge in the soln., and the metallic ion is supplied to the soln.

Description

Detailed Description of the Invention

[0001]

The present invention relates to Fe--Zn or Fe.
-A method of supplying metal ions in electroplating of Ni or the like.

[0002]

2. Description of the Related Art Zn, Fe-Zn and N are applied to metal strips such as steel strips.
When electroplating of i-Zn or the like is performed by an insoluble anode method, it is necessary to replenish metal ions from outside the system. As a method of replenishing this metal ion, there are a method of replenishing with a metal salt and a method of replenishing with a metal metal.

[0003]

Among them, the method of replenishing with metal metal has the merit that the equipment can be made compact, and there are many places to adopt this method, but on the other hand, it is possible to use F in the plating solution.
In the case of containing e ³⁺ ions, the pH at the outlet side of the melting device increases (hydrogen ion concentration decreases) as the metal is dissolved, and the reaction shown in the following chemical formula 1 or chemical formula 2, chemical formula 3 or chemical formula 4 may occur. The Fe (OH) ₃ sludge is likely to be generated due to the increase of pH in the melting apparatus (Chemical formula 1, Chemical formula 2, Chemical formula 3) and in the plating tank (Anodic reaction, Chemical formula 4) respectively.

[0004]

[Chemical formula 1] Zn + 2H ⁺ → Zn ²⁺ + H ₂ ↑ (pH increase)

[0005]

[Chemical formula 2] Fe + 2H ⁺ → Fe ²⁺ + H ₂ ↑ (pH increase)

[0006]

Embedded image Fe ³⁺ +3 (OH) ⁻ → Fe (OH) ₃ (sludge generation)

[0007]

^{Embedded image} Fe ²⁺ → Fe ³⁺ + e ⁻ (Fe ³⁺ generation)

Therefore, a plating quality defect (defect) is generated due to the increase of the sludge, and in plating such as Fe-Zn, a required amount of metal (Fe) is dissolved.

The present invention was made in view of the above problems, and Fe (OH) _{3 is} supplied by dissolving and supplying metal ions while controlling the difference in hydrogen ion concentration before and after melting of metal metal to a predetermined value or less. It was made by finding that sludge generation can be reduced and metal ions can be efficiently supplied.

[0010]

Therefore, according to the metal ion supplying method of the present invention, when the metal metal is dissolved and the metal ion is supplied into the plating solution containing Fe ³⁺ ions, the metal metal is dissolved. The pH of the plating solution is measured at the plating solution inflow part and the discharge part where the plating solution is allowed to flow in or out of the bath, and the difference in the plating solution hydrogen ion concentration between the inflow part and the discharge part becomes a certain value or less. The basic feature is to control the plating solution supply flow rate as described above.

[0011]

In the initial reaction in the metal-metal melting apparatus (for example, Fe-Zn metal melting apparatus), the Fe ³⁺ reduction reaction as shown in the following chemical formulas 5 and 6 occurs preferentially, so that the plating solution inflow site The pH of the bath in the dissolution apparatus is controlled by controlling the flow rate of the plating solution so that the difference between the hydrogen ion concentrations of the plating solution becomes less than a certain value after measuring the pH at the discharge site.
It suppresses the rise and makes it difficult for the reaction of Chemical formula 3 to proceed.

[0012]

Embedded image Fe + 2Fe ³⁺ → 3Fe ²⁺

[0013]

Embedded image Zn + 2Fe ³⁺ → Zn ²⁺ + 2Fe ²⁺

[0014]

EXAMPLES Examples of the present invention will be described below.

FIG. 1 shows a circulation tank 1 which constitutes a plating tank in which Fe-Zn electroplating is performed on a steel strip, and a melting apparatus 2 which supplies Fe ²⁺ ions to the plating solution in the circulation tank 1. FIG. 3 is a schematic diagram of a circulation system showing a plating liquid circulation state between and.

The melting apparatus 2 shown in the figure is composed of a Fe melting tank having a capacity of 3 m ³ , and the Fe chips are automatically replenished so that the chip filling amount becomes 18 to 20 tons depending on the load cell value installed in this tank. ing. On the other hand, the plating solution conditions for the circulation tank 1 are Zn ²⁺ : 4 to 6 g / l, Fe ²⁺ : 9
0 to 100 g / l, and Fe ³⁺ on the inlet side: 3 g / l
l, pH: 2.0 is controlled.

With the above apparatus configuration, the present inventors have controlled the pump of the plating solution supply device 3 so that the flow rate of the plating solution supply to the dissolution device 2 is 3 m ³ / min (constant), At 2, Fe ions were supplied.

On the other hand, in order to carry out the method of the present invention, pH meters 4 and 5 are provided on the inlet side and outlet side of the dissolution apparatus 2 and the value of the pH meter 4 on the inlet side (controlled at 2.0 ± 0.05). )), The plating solution supply flow rate was controlled so that the value of the pH meter 5 on the outlet side was +0.05. Flow rate range is 2.5-4.0 m ³ / mi
It was in the range of n. FIG. 2 shows the relationship between the Fe chip filling amount and the plating liquid flow rate at that time.

Table 1 below shows a comparison of the sludge formation rate when the above-mentioned conventional method and the method of the present invention are carried out. It can be seen that the sludge generation rate is lower in the method of the present invention than in the case of the conventional method. The sludge production rate was calculated by the following equation 1.

[0020]

[Table 1]

[0021]

[Equation 1]

FIGS. 3 and 4 are graphs showing the relationship between the sludge production rate and the Fe chip filling amount. In the conventional method shown in FIG. 3, the sludge generation rate increases as the Fe chip filling amount increases, whereas in the method of the present invention shown in FIG. 4, regardless of the Fe chip filling amount, It can be seen that the sludge production rate is constant and kept low.

Further, FIG. 5 is a graph showing the relationship between the difference in pH between the inlet side and the outlet side and the amount of sludge generated. In order to prevent the generation of sludge, the difference in pH is preferably 0.05 or less.

[0024]

As described in detail above, according to the method of the present invention,
Fe (OH) ₃ sludge generation can be reduced and metal ions can be efficiently supplied to the plating solution.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a circulation system in which a plating solution is circulated in a plating tank in which Fe-Zn electroplating is performed.

FIG. 2 is a graph showing the relationship between the Fe chip filling amount and the plating solution flow rate when the method of the present invention is carried out in the above circulation system.

FIG. 3 Sludge generation rate and Fe when the conventional method is carried out
It is a graph which shows the relationship of a chip filling amount.

FIG. 4 shows the sludge generation rate and F when the method of the present invention is carried out.
It is a graph which shows the relationship of e chip filling amount.

FIG. 5 is a graph showing a relationship between a difference in pH between an inlet side and an outlet side and a sludge generation amount.

[Explanation of symbols]

 1 Circulation tank 2 Dissolution device 3 Plating liquid supply device 4, 5 pH meter

Claims (1)

[Claims] 1. When the metal metal is dissolved and the metal ion is supplied into the plating solution containing Fe ³⁺ ions, the plating solution is caused to flow into or out of the bath in which the metal metal is dissolved. The pH of the plating solution is measured at the plating solution inflow site and the discharge site, and the plating solution supply flow rate is controlled so that the difference in the plating solution hydrogen ion concentration between the inflow site and the discharge site becomes a certain value or less. Metal ion supply method.