JP3258757B2 - Method and apparatus for re-dissolving nickel deposited in plating solution - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous electrolytic zinc-nickel plating facility for a metal strip such as a steel strip using an insoluble anode, and re-uses nickel which is replaced and deposited when replenishing consumed metal ions in a plating solution. The present invention relates to a dissolving method and an apparatus therefor.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for improved corrosion resistance in automobiles, home electric appliances and the like, and in addition to galvanized steel sheets conventionally used, there has been a remarkable demand for recently developed alloy-coated steel sheets such as zinc-nickel plated steel sheets. Showing an increase. In order to cope with such an increase in demand, a high-speed plating method with a high current density capable of high-efficiency production has been adopted.
In the high-speed plating method, it is more advantageous to use iridium-based insoluble anodes that do not need to be replaced and to continuously replenish the consumed metal ions, rather than the soluble anode method that requires frequent anode replacement. Needless to say,

As a plating solution, a sulfuric acid-based electrolytic solution is usually used. Further, a method for replenishing metal ions such as zinc and nickel into the plating solution includes a method in which metal zinc or nickel is dissolved by directly contacting the plating solution, and a method in which a metal compound such as zinc oxide is dissolved. There is. At first glance, it seems to be more efficient to dissolve the powdered metal compound, but such metal compound powder generally tends to block (block) due to the heat of reaction generated on the powder surface when poured into a liquid. However, a method of directly dissolving granular or massive metallic zinc or metallic nickel is often adopted because of the disadvantage that the agglomerated material hardly dissolves.

[0004] When dissolving metallic zinc in a plating solution in which nickel ions are present, since nickel is noble relative to zinc, a phenomenon occurs in which nickel is deposited instead of zinc. Precipitated nickel does not contribute to plating, so the nickel basic unit deteriorates by the amount of precipitation, and when nickel precipitates on the surface of metallic zinc, the dissolution rate of zinc decreases, and the precipitated nickel further deposits on the surface of the material to be plated. There is a problem in that it causes poor quality such as press flaws due to adhesion.

[0005] As a method of preventing nickel deposition,
There is a method of lowering the pH of the plating solution by adding sulfuric acid or the like, or a method of mixing additives such as cobalt and molybdenum into the plating solution as disclosed in JP-A-63-238300. The method of lowering the pH has the disadvantage that the plating current efficiency in the electroplating process that is essential is reduced, and it is difficult to raise the pH once lowered again. In addition, the method of mixing additives has a new problem that, in addition to the difficulty of controlling the concentration, there is a concern that addition of another metal element to the plating solution may affect plated products.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a method for re-dissolving deposited nickel by extremely easy and reliable means.

[0007]

According to the present invention, there is provided a method for dissolving precipitated nickel in a plating solution, which comprises dissolving metallic zinc into a plating solution in a continuous zinc electroplating equipment for a metal strip using an insoluble anode. The nickel is replaced and separated from the plating solution circulation path by solid-liquid separation means when replenishing, and is redissolved by stirring in the plating solution to which an oxidizing agent is added.

Further, the apparatus for re-dissolving nickel deposited in a plating solution according to the present invention replenishes zinc ions by dissolving metallic zinc in the plating solution in a continuous electro-zinc nickel plating facility for a metal strip using an insoluble anode. Solid-liquid separation means for separating nickel precipitated in the plating solution from a circulation path formed by a pipe connecting the dissolution tank and the plating solution circulation tank, a transfer means for transferring the separated precipitated nickel, and a transferred precipitate A re-dissolving tank provided with a stirring device for re-dissolving nickel, an oxidizing agent supply means for supplying an oxidizing agent to the plating solution in the re-dissolving tank, and a plating solution containing the re-dissolved nickel into the circulation path. And returning means for returning.

[0009]

[Operation] As described above, when zinc metal is dissolved in a plating solution, zinc is ionized and nickel loses electric charge and precipitates. That is, a reaction of Zn + Ni2 ⁺ → Zn2 ⁺⁺ Ni occurs. The precipitated nickel is so fine that it is difficult to catch it with a normal filter.However, it can be separated in a sedimentation tank using the specific gravity difference, or it can be separated using a magnetic separator, etc. it can. When the separated nickel is sent to a re-melting tank by a slurry pump and put into a plating solution to which an oxidizing agent has been added, dissolution is promoted by the action of the oxidizing agent.

[0010] Zinc ion 35g / l, nickel ion 65g
The plating solution having a pH of 1.7 / l and a pH of 1.7 was circulated in the experimental apparatus shown in FIG. 2 to measure the dissolution rate. Adjust the pH with sulfuric acid,
The temperature of the solution was controlled at 50 ± 2 ° C. In FIG. 2, 1 is a zinc dissolving tank, 2 is a circulation tank, 3 is a zinc dissolving tank feed pump,
4 is a valve, 5 is a flow meter, 6 is a zinc dissolution tank outlet pipe, 7
Is a pipe going to a circulation tank, 8 is a pipe going to a zinc dissolving tank, and 10 is a solid-liquid separation means, here a magnet separator.

A zinc dissolving tank 1 is filled with zinc particles Zn to a thickness of 300 mm, and a zinc solution Zn is passed through the plating solution at a flow rate of 2.0 cm / sec.
Zinc particles Zn were replenished every hour, and the dissolution rate was calculated by regarding the total replenishment for a total of 8 hours as the dissolution amount. Next, the precipitated nickel separated by the solid-liquid separator 10 is poured into a fixed amount (for example, 5 liters) of a plating solution, and dissolved for a certain time (for example, 3 minutes) with stirring. The dissolution rate was measured by weighing. Then, the difference in the dissolution rate between the case where the plating solution was dissolved only with no oxidizing agent and the case where air, oxygen gas and hydrogen peroxide solution were added to the plating solution was compared. Assuming that the dissolution rate in the plating solution when the oxidizing agent is not added is 1,
When air is blown into the plating solution at a rate of 5 ml / l in terms of atmospheric pressure, and oxygen gas is also applied to the plating solution.
The dissolution rate of precipitated nickel when blowing at a rate of 5 ml / l was 1.3, and the dissolution rate when 35% H ₂ O ₂ water was added at a rate of 0.5 g / l was 1.5, which was 30 to 50%. The dissolution rate was improved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic diagram showing a part of a steel strip continuous electric zinc nickel plating line according to an embodiment of the present invention. The same reference numerals are used for the same components as those in FIG.
10 is a solid-liquid separation means, in this embodiment a settling tank, 11 is a slurry pump, 12 is a re-dissolution tank, 13 is a stirrer, 14 is a return pump,
15 is an oxidant supply means, 16 is an oxidant supply source, 17 is an air supply pump, 18 is a flow meter, 19 is a pipe going to a nickel melting tank, 20 is a nickel melting tank feed pump, 21 is a nickel supply device, and 22 is nickel. A dissolution tank, 23 is a stirrer, 24 is a return pump, and 25 is piping to a circulation tank. Nickel is nickel carbonate (Ni
CO ₃ ) is supplied to the plating solution and supplied from the nickel dissolution tank 22 to the circulation tank 2.

In this embodiment, an oxygen gas is used as an oxidizing agent, and a solid-liquid separation means 10 is provided in the middle of the pipe 6 on the outlet side of the zinc dissolution tank and the pipe 7 going to the circulation tank, so that a solid component in the plating solution is deposited. The nickel was separated, and the separated precipitated nickel was sent to the remelting tank 12 by the slurry pump 11. The re-dissolving tank 12 is provided with a stirrer 13 and further provided with an oxidizing agent supply means 16 including an oxidizing agent supply source 16 (in this case, an oxygen tank), an air supply pump 17 and a flow meter 18. Oxygen gas is blown into it. The plating solution containing nickel which has been ionized and redissolved is returned to the circulation tank 2 by the return pump 14.

The oxidizing agent used in the oxidizing agent supply means of the present invention may be a gas such as air or oxygen gas, a liquid such as hydrogen peroxide solution, or a powdered solid oxidizing agent. Therefore, it is important that the plating has no adverse effect on quality. When gas is used, a stirring effect by bubbling can be expected.

The solid-liquid separating means 10 includes a cyclone and a filter with a high mesh in addition to the above-mentioned settling tank and magnet separator. The position where the solid-liquid separation means 10 is provided is most suitable in the middle of the pipes 6 and 7 connecting the dissolution tank 1 and the circulation tank 2, but may be another position. The position at which the plating solution containing the re-dissolved nickel is returned is not particularly limited as long as it is within the circulation path of the plating solution. For example, in the case of a structure in which the plating solution is directly dropped into the circulation tank and returned, the return means 14 may be a very simple gutter. , And no pump or piping is required.

[0016]

According to the present invention, the re-dissolution of the deposited nickel prevents the reduction of the nickel basic unit, and the occurrence of the pressing flaw caused by the deposited nickel adhering to the surface of the material to be plated. This has the excellent effect of improving the productivity and quality of continuous electroplating using an insoluble anode.

[Brief description of the 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]

 DESCRIPTION OF SYMBOLS 1 Zinc dissolution tank 2 Circulation tank 3 Zinc dissolution tank feed pump 4 Valve 5 Flowmeter 6 Zinc dissolution tank outlet pipe 7 Pipe to circulation tank 8 Pipe to zinc dissolution tank 10 Solid-liquid separation means 11 Slurry pump 12 Re-dissolution tank 13 Stirrer 14 Return pump 15 Oxidant supply means 16 Oxidant supply source 17 Air supply pump 18 Flow meter 19 Pipe for nickel dissolution tank 20 Nickel dissolution tank feed pump 21 Nickel supply device 22 Nickel dissolution tank 23 Stirrer 24 Return pump 25 Pipe for circulation tank

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C25D 21/14 C25D 3/56 C25D 21/18

Claims (4)

(57) [Claims] In a continuous electro-zinc nickel plating equipment for a metal strip using an insoluble anode, nickel which is displaced and precipitated when metal zinc is dissolved in a plating solution to replenish zinc ions is passed through a plating solution circulating route. A method for re-dissolving precipitated nickel in a plating solution, wherein the nickel is separated by a separating means and redissolved by stirring in a plating solution to which an oxidizing agent has been added. 2. The method according to claim 1, wherein the oxidizing agent is added to the plating solution by blowing air or oxygen gas into the plating solution.
A method for re-dissolving precipitated nickel in a plating solution as described above. 3. The method according to claim 1, wherein the addition of the oxidizing agent to the plating solution is an addition of a hydrogen peroxide solution to the plating solution. 4. A continuous electro-zinc nickel plating facility for a metal strip using an insoluble anode, comprising a dissolving tank (1) for dissolving metallic zinc in a plating solution to replenish zinc ions and a plating solution circulation tank (2). Solid-liquid separation means (10) for separating nickel precipitated in the plating solution from within a circulation path composed of connecting pipes (6, 7, 8), and transfer means (11) for transferring the separated precipitated nickel; A re-dissolving tank (12) provided with a stirrer (13) for re-dissolving the transferred deposited nickel in the plating solution, and an oxidizing agent supplying means for supplying an oxidizing agent to the plating solution in the re-dissolving tank (12) (15) An apparatus for re-dissolving nickel deposited in a plating solution, comprising: a return means (14) for returning a plating solution containing re-dissolved nickel into the circulation path.