JPH06316795A - Method and device for feeding metal ion into plating liquid - Google Patents

Abstract

PURPOSE:To improve the dissolving velocity of metal powder in a plating liquid in an electroplating device using an insoluble anode by feeding an oxidizing agent into the plating liquid together with metal powder when plating metal ions are replenished. CONSTITUTION:When metal, such as Zn is applied to electroplate the surface of a steel strip, an insoluble anode, such as Ir is used as an anode. And for plating metal Zn, Zn powder is fed into a plating liquid to keep the Zn ion concentration in the plating liquid constant. In this case, the plating liquid where the Zn ion concentration has been decreased from a plating line is fed into a circulating tank 2 by piping 22 and also sent to a dissolving tank 1. Into the dissolving tank 1, metal Zn powder m from a hopper 8 and also an oxidizing agent, such as air and oxygen from an oxidizing agent mixing-in means 10 are fed. The metal Zn powder M is rapidly dissolved in the plating liquid in the presence of the oxidizing agent to turn into Zn ions and the plating liquid having a high Zn concentration thus obtained is returned to the plating line by piping 21 through the circulating tank 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for supplying metal ions for replenishing the plating solution with consumed metal ions in a continuous electrogalvanizing equipment for metal bands such as steel bands using an insoluble anode, and a method therefor. Regarding the device.

[0002]

2. Description of the Related Art In recent years, the demand for improved corrosion resistance in automobiles, home appliances and the like has increased, and in addition to the galvanized steel sheets that have been conventionally used, there is a demand for alloy-plated steel sheets such as zinc-nickel plated steel sheets that have been recently developed. It shows a significant increase. (Note that, in the present specification, such alloy plating is also included in “zinc plating”.) In order to cope with such an increase in demand, a high-speed plating method with high current density capable of high-efficiency production is adopted. However, in the high-speed plating method, a method of continuously replenishing consumed metal ions by using an insoluble anode such as an iridium-based material that does not require anode replacement, rather than a soluble anode method that requires frequent anode replacement. Needless to say, is more advantageous.

As the plating solution, a sulfuric acid type electrolytic solution is usually used. In addition, as a method of supplying metal ions such as zinc and nickel to the plating solution, a method of dissolving metal zinc or nickel by directly contacting the plating solution and a method of dissolving a metal compound such as zinc oxide are used. There is. The method of directly dissolving granular or lumpy metallic zinc or metallic nickel has a low dissolution rate, and it seems that it is more efficient to dissolve the metallic compound in powder form, but such metallic compound powder is generally found in liquid. When charged into the powder, the reaction heat generated on the surface of the powder tends to cause agglomeration (blocking), and the agglomerated material hardly dissolves. In order to improve this point, for example, Japanese Patent Publication No. 58-13639 discloses that a compound such as zinc oxide or a basic salt is previously dispersed in water and then added to a plating bath.

However, according to this method, although agglomeration is prevented, a high-speed stirrer (homogenizer) or the like for dispersion treatment is required, and water is excessively supplied into the plating solution, so that the evaporator is used. However, there is a problem that a water removing means such as the above is required. In addition, JP-A-57-
According to Japanese Patent No. 171700, when the metal ions in the plating bath are replenished in the form of a basic compound such as zinc oxide or nickel carbonate, the basic compound is powdered and plated with air or a carrier gas such as nitrogen gas. By blowing into the bath, it has been proposed to diffuse into the bath without agglomeration due to the stirring action of the carrier gas, but this approach is only applicable to powders and the equipment is rather complicated .

Further, according to Japanese Patent Laid-Open No. 62-7200,
A zinc ion-containing aqueous solution obtained by dissolving metal zinc in a solution in which a trivalent iron ion and a metal ion such as nickel or bismuth having a higher potential than zinc and a hydrogen overvoltage lower than that of zinc coexist It is described that the solution is supplied to a galvanizing bath to promote dissolution without causing an acid burning phenomenon.

[0006] However, trivalent iron ions are not preferable in terms of quality because they cause coloring called "plating burn", so it is better to minimize them. If nickel, bismuth, etc. are ionized, they become impurities for pure zinc plating. ,
There is a problem that corrosion resistance and appearance are deteriorated.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to provide a method for promoting the dissolution of metal ions by a very easy and reliable means.

[0008]

The present invention relates to a continuous electrogalvanizing equipment for metal strips using an insoluble anode, in dissolving a metal in a plating solution to supplement a metal ion,
A method for supplying metal ions to a plating solution, which comprises adding an oxidizing agent to the plating solution to improve the dissolution rate.

[0009]

[Operation] According to the present invention, by adding an oxidizing agent such as air, oxygen gas, or hydrogen peroxide solution to the plating solution,
By oxidizing the hydrogen gas generated by the dissolution of the metal to H ₂ 0, the hydrogen gas on the metal surface is removed, the metal surface easily comes into contact with H ⁺ ions, and the dissolution is promoted.

Zinc ion 35g / l, nickel ion 65g
/ L, trivalent iron ion 300mg / l, divalent iron ion 800
A plating solution of mg / l and pH 1.7 was circulated in the experimental apparatus shown in FIG. 2 to measure the dissolution rate. The pH was adjusted with sulfuric acid, and the temperature of the solution was controlled at 50 ± 2 ° C. In FIG. 2, 1 is a dissolution tank, 2 is a circulation tank, 3 is a pump, 4 is a valve, 5
Is a flow meter, 6 is a circulation tank return pipe, 7 is a circulation tank return pipe, 10 is an oxidant mixing means, 11 is an oxidant supply source such as a tank or a storage tank, 13 is a pump, 14 is a valve, and 15 is a flow meter. is there.

The dissolution tank 1 was filled with metal particles M to a thickness of 400 mm, and the metal particles M were replenished every hour while the plating solution was being passed at a flow rate of 2.0 cm / sec, for a total replenishment amount of 12 hours. The dissolution rate was calculated by considering it as the amount of dissolution. In the case of metallic zinc having an average particle diameter of 5 mm, if the dissolution rate in the plating solution when no oxidizing agent is added is 1, and when air is blown into the plating solution at a rate of 5 ml / l from the oxidizing agent supply source 11, Similarly, when oxygen gas is blown into the plating solution at a rate of 5 ml / l in terms of atmospheric pressure, the dissolution rate of metallic zinc is
When 1.2 and 35% H ₂ O ₂ water were added at a rate of 0.5 g / l, the dissolution rate was 1.3.

Further, in the case of metallic nickel having an average particle diameter of 5 mm, assuming that the dissolution rate in the plating solution without addition of the oxidant is 1, air from the oxidant supply source 11 to the plating solution is converted into atmospheric pressure at 5 ml / l. The rate of dissolution of nickel metal was 1.1 and that of 35% H ₂ O ₂ water was 0.5 g / l in both cases of blowing oxygen gas into the plating solution and blowing oxygen gas into the plating solution at a rate of 5 ml / l. The dissolution rate when added in a ratio of 1.2 was found to be 20 to 30% higher for both zinc and nickel.

During the experiment, the pH was controlled to be constant while adding sulfuric acid.

[0014]

EXAMPLE FIG. 1 shows a partial configuration diagram of a continuous electrogalvanizing line for steel strips, which is an example of the present invention. Previous figure 2
The same reference numerals are used for the same items. 8 is a metal grain hopper, 9 is a cutting device, 21 is a line tank line, and 22 is a line tank return line.

In this embodiment, oxygen gas is used as an oxidant, and an oxidant supply source 11 (oxygen tank in this case), an air supply pump 13, and a flow rate are provided in the return pipe 7 from the circulation tank 2 to the dissolution tank 1. A pipe from the oxidizing agent mixing means 10 is opened via a total of 15, and oxygen gas is blown into the circulating plating solution. On the other hand, in the melting tank 1, the zinc particles M in the zinc particle hopper 8 are
Is cut out by a cutting device 9 by a predetermined amount and is replenished in the dissolution tank 1.

In the case of a zinc-nickel plating line, a nickel hopper 8 is provided in addition to the zinc grain hopper 8. The metallic zinc is generally zinc particles or zinc powder, and nickel is also used in the form of particles or powder. As the oxidant used in the present invention, air, a gas such as oxygen gas, a liquid such as hydrogen peroxide solution as well as a powdered solid oxidant can be used.
Since it is added to the plating solution, it is important that it does not adversely affect the quality of the plating. When gas is used, a stirring effect due to bubbling can be expected.

The position where the oxidizing agent is mixed may be any position in the circulation piping path connecting the dissolving tank 1 and the circulating tank 2, but when the oxidizing agent is gas or liquid, the plating solution is dissolved as shown in FIG. It is most effective to open the pipe of the oxidant mixing means 10 in the circulation tank return pipe 7 to the tank 1, and in the case of a solid oxidant, the oxidant may be directly fed to the dissolution tank 1.

[0018]

According to the present invention, by improving the dissolution rate of metallic zinc or metallic nickel by 20 to 30%, the productivity of continuous electroplating using an insoluble anode is increased, which is an excellent effect.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a configuration diagram of an experimental device for testing the effect of the present invention.

[Explanation of symbols]

 1 Dissolution tank 2 Circulation tank 3 Pump 4 Valve 5 Flowmeter 6 Circulation tank going pipe 7 Circulation tank return pipe 8 Metal grain hopper 9 Cutting device 10 Oxidizing agent mixing means 11 Oxidizing agent supply source 13 Pump 14 Valve 15 Flowmeter 21 Line tank Outgoing piping 22 Line tank return piping

Claims (4)

[Claims] 1. In a continuous electrogalvanizing equipment for a metal strip using an insoluble anode, when a metal is dissolved in a plating solution to supplement metal ions, an oxidizing agent is added to the plating solution to improve the dissolution rate. A method of supplying metal ions to a plating solution, which is characterized by the above. 2. The addition of an oxidizing agent to the plating solution is blowing air or oxygen gas into the plating solution.
A method for supplying metal ions to the plating solution described. 3. The method for supplying metal ions to a plating solution according to claim 1, wherein the addition of the oxidizing agent to the plating solution is addition of a hydrogen peroxide solution to the plating solution. 4. In a continuous electrogalvanizing equipment for metal strips using an insoluble anode, a circulation pipe of a plating bath circulating tank (2) and a bath for dissolving metal in the plating bath to replenish metal ions. An apparatus for supplying metal ions to a plating solution, characterized in that an oxidant mixing means (10) is provided in the paths (1, 6, 2, 7).