JPH11222700A - Method for supplying consumed metal ion to alloy plating bath and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To supply the metal ion consumed in plating to a plating bath at the time of electroplating a steel sheet with a nickel alloy or a cobalt alloy by anodically dissolving metallic nickel or cobalt. SOLUTION: A drum or disk cathode 11 is rotatably disposed in an elecrolytic cell 1, a titanium mesh basket is used as an anode 12, sulfur-contg. metallic nickel or cobalt is packed in the basket, and elecrtolysis is conducted with a plating soln. used in alloy plating as an electrolyte 14. A part of the nickel or cobalt eluted from the anode by electrolysis is deposited on the cathode 11 as an alloy, and the deposited metal is stripped off from the cathode face by rotating the cathode 11 and sent outside the cell 1. The remaining nickel or cobalt is retained in the electrolyte as the ion, and the electrolyte 14 supplied with the metal ion is used in the alloy plating. Accordingly, the alloy 8 deposited on the cathode 11 is dissolved in the plating soln. and reutilized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a metal ion supply method for replenishing a plating solution used for plating a nickel alloy or a cobalt alloy with nickel or cobalt ions consumed in a plating step.
The invention also relates to a metal ion supply device for use in performing the method.

[0002]

2. Description of the Related Art Nickel alloy plating which achieves high corrosion resistance by combining nickel and a base metal, such as zinc-nickel plating and tin-nickel plating, is widely used. Similarly, cobalt alloy plating that achieves high corrosion resistance by combining cobalt and a base metal, such as zinc-cobalt plating, is also performed. Since nickel alloy plating and cobalt alloy plating are very similar technologies,
Take nickel alloy plating as a representative and add explanation.

[0003] As the plating proceeds, ions of nickel and other metals in the plating bath are naturally consumed, and cations such as metal ions are replaced with hydrogen ions, so that the pH of the plating solution decreases. In replenishing the plating bath with metal ions, base metals such as zinc and tin are ionized by a chemical reaction simply by throwing metal particles into the plating bath having a reduced pH. However, metals having high corrosion resistance, such as nickel, do not ionize even if the metals are put into a plating bath having a lowered pH, and cannot be easily replenished. For this reason, at present, nickel ions are replenished to the nickel alloy plating bath in the form of carbonate.

[0004] However, nickel carbonate is not only relatively expensive but also difficult to obtain in a pure form. A commercially available product is called basic nickel carbonate and contains sodium carbonate in addition to nickel hydroxide. When this is used for the plating bath, p
There is a possibility that the H balance may be lost or nickel hydroxide having low solubility may be supplied to the plating line in an undissolved state, thereby deteriorating the quality of the product.

As one solution to this problem, it has been proposed to ionize metallic nickel by electrolysis and to replenish the plating bath (see, for example, JP-A-4-13900).
No., JP-A-6-25900).

In these methods, electrolysis is performed using nickel metal as an anode, a material having a low hydrogen overvoltage such as a platinum group metal is used as a cathode, and hydrogen gas is generated from the cathode.
In other words, by giving priority to the hydrogen gas generation reaction at the cathode,
The principle is to prevent cathodic deposition of nickel, which would otherwise occur, and to dissolve nickel ions in the solution.

However, no matter how low the hydrogen overvoltage is, and even if an electrode material that is active against the generation of hydrogen is used, it is practically impossible to suppress the deposition of metal such as nickel by 100% over a long period of time. Therefore, efforts have been made to increase the yield of nickel ions by re-dissolving nickel deposited on the cathode by reverse energization, that is, by energizing while changing the polarity. However, when the reverse energization is repeated, the cathode surface having a high hydrogen generation catalytic function is eluted and loses its activity, and the original electrode function is impaired. If so, the life of the electrode will not be long enough for practical use.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems encountered when replenishing nickel or cobalt ions to a plating bath for nickel alloy plating and cobalt alloy plating. There is no need to use expensive electrode materials such as group metals, and there is no need to consider electrode wear over a long period of time, so both equipment costs and running costs are economical.
An object of the present invention is to provide a method for supplying consumed metal ions to a plating bath for alloy plating, and to provide an apparatus used for carrying out the method.

[0009]

According to the present invention, there is provided a method for supplying consumed metal ions to an alloy plating bath, comprising the steps of: providing a plating solution containing nickel or cobalt ions in a bath for plating a nickel alloy or a cobalt alloy; A metal nickel or cobalt containing sulfur as an anode and an electrolytic cell equipped with a rotatable metal drum or disk serving as a cathode, a nickel alloy or a cobalt alloy plating bath. The plating solution is received from the circulating tank, and electrolysis is performed using the plating solution as an electrolyte to elute nickel or cobalt ions into the electrolytic solution.The nickel or cobalt alloy deposited on the cathode is continuously rotated by rotating the cathode to form an electrolytic cell. While supplying the electrolyte replenished with nickel or cobalt ions Wherein the return of the circulation tank.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The method of supplying consumed metal ions to an alloy plating bath according to the present invention comprises a method of mixing nickel or cobalt with a base metal, such as zinc-nickel alloy plating, tin-nickel plating, and zinc-cobalt plating. Although the present invention can be applied to plating of an alloy, zinc-nickel alloy plating will be described below as a representative.

FIG. 1 shows the overall configuration of a nickel ion supply apparatus for carrying out the above method, including a plating line, and FIG. 2 shows a nickel plating line (5). A device for supplying a plating solution containing nickel ions to a nickel alloy plating bath used in (1), comprising: a cathode (11) which is a rotatable metal drum or disk; An electrolytic cell (1) having an anode (12) formed of a perforated plate and partially surrounding a cathode for eluting ions, a nickel supply means (2) for supplying metal nickel containing sulfur to the anode, Metal foil removing means (3) for continuously removing the nickel alloy deposited on the cathode by electrolysis to the outside of the electrolytic bath, and a plating solution from a circulating bath of the nickel alloy plating bath. Acceptance, and a nickel ion containing liquid circulation means for feeding electrolyte nickel ions was supplemented with (14) (4).

It is preferable that at least the surface of the rotatable metal drum or disk constituting the cathode is formed of titanium or a titanium alloy, lead or a lead alloy, aluminum or an aluminum alloy, or stainless steel. This surface may also be a layer of hard chrome plating. By forming the surface with these materials, the deposited nickel alloy is easily peeled off. Regardless of which material is used, the surface of the cathode should be finished to a smooth mirror surface as much as possible. A cathode having a smooth surface has little adhesion of nickel and can be used for a long time.

Titanium is the most suitable material, but pure titanium is a soft material and is easily scratched. Also,
Due to the stickiness, mirror finishing of the surface is difficult. In order to solve this problem, a titanium alloy having an appropriate composition may be used, or the surface of titanium may be hardened by a surface hardening treatment such as quenching or nitriding. More aggressive measures
A device for polishing the surface of the cathode is provided at a position after the metal electrodeposited by a doctor blade or a scraper described later is peeled off, so that a fresh smooth surface can always be obtained.

Although the cathode is most simple in the form of a drum, it can also be in the form of a disk, in which nickel alloy is deposited on both side surfaces. In the latter case, the anode is provided so as to sandwich the lower part of the disk.
Two or more disk-shaped cathodes can be stacked at predetermined intervals to increase the surface area. The shape of the cathode is not limited to the drum and the disk, but may be modified in an intermediate shape such as a combination of several cones. In general, a disk-shaped cathode can realize a larger cathode area than the installation area of the apparatus.

As shown in FIG. 1, a nickel ion-containing liquid circulation means (4) is provided with a plating liquid receiving pipe (41) for receiving a plating liquid from a circulation tank of a nickel alloy plating bath.
And an electrolyte delivery pipe (42) for sending the electrolyte supplemented with nickel ions back to the circulation tank (5). In FIG. 2, reference numeral (13) indicates a power supply for supplying a direct current to the electrolytic cell. Metal nickel supply means (2)
Comprises a hopper (21) for storing nickel metal pellets of an appropriate size, and a belt conveyor (22) for transporting nickel pellets taken out of the hopper. The nickel pellets supplied to the electrolytic cell (1) come into contact with an anode (12) formed by two porous plates and elute as ions. The pellets dissolved and reduced in volume are replenished one after another. The anode has a cage shape that is curved corresponding to the shape of the cathode. With this structure, the distance between the anode and the anode is kept constant, so that the electrochemical reaction at both electrodes is kept constant, and the balance of the material balance in the electrolytic cell is not broken.

As the nickel pellets, 0.00
One containing about 3 to 0.5% sulfur is used.
Thereby, nickel can be eluted as ions without causing passivation of nickel at the anode. The plating solution received in the electrolytic cell, that is, the plating solution in which nickel has been consumed has a sulfuric acid concentration of 10 to 40 g / l.
Unless nickel is sulfur-added, it is not efficiently dissolved by passivation.

The electrolysis conditions can be selected from a relatively wide range, but the preferred cathode current density is 1 to 70 A /
dm ² . If the current density is low, it goes without saying that an unnecessarily long time is required to elute the required nickel ions. On the other hand, when electrolysis is performed at a high current density exceeding 70 A / dm ² , a side reaction occurs to generate oxygen, which may lower the efficiency. Generally, current density 20A / dm
^{About 2} is advantageous because nickel dissolution efficiency is high and operation stability is easily obtained.

The electrolytic solution, that is, the plating solution replenished with nickel ions, is used to remove a solid component which may be present in the solution.
To the circulation tank (5). The solids filtered off by this filter are sometimes backwashed and drained (4
4), the drain is further separated into solid and liquid by a sludge filter (45), and the sludge is separated into a sludge storage tank (4).
6). The liquid is returned to the electrolytic cell (1) for use, or subjected to detoxification treatment and discarded.

The nickel alloy deposited on the cathode (11), particularly a zinc-nickel alloy, rotates the cathode,
A doctor blade (31) is applied to this to separate it from the cathode, take it out little by little and remove it out of the electrolytic cell. The deposited alloy is more likely to peel off as the thickness increases, and when it reaches about 100 μm, it floats up due to the stress generated inside itself, so that it can be easily peeled off. The precipitated alloy reacts with the electrolytic solution, and hydrogen is generated by the reaction. Hydrogen evolution is seen where the alloy on the drum exits the electrolyte, which pushes up the electrodeposited metal layer and aids in delamination. The alloy pieces on the doctor blade may be washed away by spraying an electrolytic solution. Reference numeral (33) indicates a container of the alloy deposited and exfoliated at the cathode. When the cathode has a disk shape, as shown in FIG. 3, as a doctor for the cathode surface, a scraper (32) equipped with a gutter is applied, the precipitated alloy is scraped, and the electrolytic solution is poured out and poured. Guide outside.

The reason why the electrodeposited metal is led out of the electrolytic cell is that when the electrodeposited metal is present in the electrolytic cell, it reacts with the electrolytic solution and is dissolved to generate hydrogen gas. The metal pieces to which the hydrogen gas adheres float on the surface of the electrolytic cell and accumulate between the cathode and anode, causing a short circuit. Therefore, it is preferable to lead all of them to the outside of the electrolytic cell as much as possible. If it is unavoidable that a certain amount will fall into the electrolytic cell, it is recommended to create a flow on the surface layer of the electrolytic solution in the electrolytic cell to push the floating electrodeposited metal pieces out of the electrolytic phase. Good.

When using a doctor blade (31) or a scraper (32) for stripping the electrodeposited metal on the cathode surface, the material and the accuracy of the attachment are important. The material should have a hardness lower than that of the cathode material. Suitable materials are high density polyethylene, polypropylene, polyvinyl chloride, synthetic resin such as PTFE, or fluoro rubber, EPDM, Hypalon,
It can be selected from elastomers such as silicone rubber and butyl rubber. If an appropriate material is not selected or the mounting accuracy is poor, countless scratches are made on the cathode surface during operation, and these scratches cause the electrodeposited metal to adhere to the cathode surface, making peeling difficult.

[0022] Instead of a doctor blade or a scraper, it is advantageous to flush the electrodeposited metal by squirting a fluid onto the cathode surface in order not to damage the cathode surface. In this case, the electrolyte may be used as the fluid.

Since the collected nickel alloy is dissolved in the plating solution, it is crushed and put into a circulation tank (6) to be dissolved.
It can be a source of zinc and nickel ions. The precipitated zinc-nickel alloy is brittle and easily breaks into a powder with only a slight force.

[0024]

EXAMPLE 1 A steel plate having a width of 1820 mm was continuously run at a speed of 90 m / min while continuously using zinc-nickel (Z in weight).
The nickel ion supply technology of the present invention was applied to a line for performing alloy plating of n: Ni = 88: 12). In this line, there is a plating solution circulation tank with a capacity of 50 m ³ ,
From there, the plating solution is circulating in the line at a rate of 144 m ³ / hour. The nickel ion supply device has the configuration shown in FIG. 2, in which the cathode is in the form of a drum whose surface is coated with titanium, and the anode is made of a titanium mesh basket provided with a curve around it. A pellet of nickel metal is supplied.

The amount of plating is 30 g /
m ² , the amount of metal removed from the plating bath is 5
89.7 kg / hour, of which zinc (88%)
It weighs 18.9 kg and nickel weighs 70.7 kg. The supply of zinc ions is performed in the zinc particle dissolving tank (7) shown in FIG.
It suffices if the plating bath is supplemented with kg / hour of nickel ions. The ion concentration in the plating solution is 45 kg / m ^{3 for} zinc,
Since nickel is 86 kg / m ³ , 50-m ³ plating solution contains 50 times as many ions.

The plating solution received from the plating solution circulating tank is supplied from the bottom of the electrolytic cell, and the cathode current density is adjusted to 4%.
Electrolysis was carried out at 0 A / dm ² . The liquid flow rate on the cathode surface was 40 m / min, and the liquid temperature was 65 ° C. Cathode current efficiency is 9
5%.

The zinc-nickel alloy deposited on the cathode was scraped off with a doctor blade as shown in FIG. 2 and continuously removed out of the electrolytic cell. The weight after washing and drying is 84.
It was 42 kg / hour. When the alloy was analyzed, it contained 88% of zinc and 12% of nickel as in the case of the plated metal. Therefore, the amount of metal deposited at the cathode was 74.29 for zinc.
kg / h and nickel at 10.13 kg / h.

On the other hand, the amount of metallic nickel dissolved at the anode was 80.89 kg / hour, and the current efficiency of the anode was almost 100%. The amount of nickel supplied as ions in the plating solution was as follows: elution amount−precipitation amount = 80.89 kg / hour−1
Since 0.13 kg / hr is 70.76 kg / hr, it is understood that the above-mentioned 70.70 kg / hr of nickel consumed in the plating line was supplied. As described above, 74.29 kg / hour of zinc was lost due to the discharge of the alloy foil deposited on the cathode, and 518.9 kg / hour consumed in the plating line.
The timed amount of 593.2 kg / h was replenished by dissolving in a zinc dissolution tank.

[0029]

Example 2 Nickel ions were supplied to the above-mentioned plating line using an apparatus in which the drum-shaped cathode of Example 1 was replaced with a disk-shaped cathode as shown in FIG. The disc had a radius of 600 mm and had both surfaces functioning as cathodes. Four of the discs were fixed coaxially at a pitch of 240 mm. The disk was rotated so that it was immersed in the electrolyte up to 444 mm from the periphery of the disk, and the cathode current density was about 20 mm.
A / dm ² was electrolyzed. The electrolyte temperature was set to 6 as in Example 1.
5 ° C., and a similar value was obtained for the cathode current efficiency.

[0030]

The present invention rejects the idea of completely preventing nickel from being deposited on the cathode, but allows a certain amount of deposition, but measures the difference between the elution content and the ions so that they remain in the solution as ions. Is supplied to the plating bath to supply nickel ions necessary for nickel alloy plating. Therefore, unlike a method that has been proposed so far, a cathode having a particularly low hydrogen overvoltage is not used, so that it is not necessary to use an expensive material such as a platinum group metal, and further, there is a concern about the life of the cathode. There is almost no need. As a result, equipment costs and operating costs can be reduced.

Even without considering the above-mentioned re-use of the cathode-deposited nickel alloy, compared with the case where nickel ions are supplied using conventional nickel carbonate,
An obvious cost reduction can be enjoyed. The reuse of the cathodic deposited nickel alloy is easy, which allows for further cost reduction.

[Brief description of the drawings]

FIG. 1 is a flowchart showing the overall configuration of an apparatus that performs nickel alloy plating using a nickel ion supply apparatus of the present invention.

FIG. 2 is a cross-sectional view of a device centering on an electrolytic cell, showing details of a nickel ion supply device in the device of FIG. 1;

3 is a view showing another embodiment of the electrolytic cell in the nickel ion supply device of FIG. 2, wherein A is a cross-sectional view similar to FIG. 2, and B is a longitudinal cross-sectional view.

[Explanation of symbols]

 1-4 Nickel ion supply device 1 Electrolyzer 11 Cathode 12 Anode 13 Power supply 14 Electrolyte 2 Metal nickel supply means 21 Hopper 22 Belt conveyor 3 Cathode deposited metal removing means 31 Doctor blade 32 Scraper 33 Precipitated alloy container 4 Nickel ion Containing liquid circulation means 41 Plating solution receiving pipe 42 Electrolyte sending pipe 43 Nickel ion-containing liquid filter 44 Drain tank 45 Sludge filter 46 Sludge storage tank 5 Plating line 5A Metal plate before plating 5B Metal plate after plating 6 Circulation tank 7 Zinc particles Melting tank 8 Cathode deposition alloy

Claims (7)

[Claims] 1. A method for supplying a plating solution containing nickel or cobalt ions to a bath for plating a nickel alloy or a cobalt alloy, wherein metal nickel or cobalt containing sulfur is used as an anode, A plating solution is received from a circulating bath of a nickel alloy or cobalt alloy plating bath into an electrolytic bath equipped with a rotatable metal drum or disk serving as a cathode,
This is used as an electrolyte to perform electrolysis to elute nickel or cobalt ions in the electrolytic solution.The nickel or cobalt alloy deposited on the cathode is continuously removed outside the electrolytic cell by rotating the cathode, while nickel is removed. Alternatively, a method of supplying consumed metal ions to an alloy plating bath, wherein an electrolytic solution supplemented with cobalt ions is sent out and returned to the circulation tank. 2. The method of claim 1, wherein the nickel alloy plating is zinc-nickel alloy plating. 3. The method according to claim 1, wherein the nickel alloy deposited on the cathode is dissolved in a plating solution in a circulation tank and reused. 4. The method of claim 1, wherein the cobalt alloy plating is a zinc-cobalt alloy plating. 5. The method according to claim 1, wherein the cobalt alloy deposited on the cathode is dissolved in a plating solution in a circulation tank and reused. 6. An apparatus for supplying a plating solution containing nickel or cobalt ions to a bath for plating a nickel alloy or a cobalt alloy, wherein the cathode is a rotatable metal drum or disk. (1
1) and an anode (1) composed of a perforated plate for eluting nickel or cobalt ions from sulfur-containing metallic nickel or cobalt partially surrounding the cathode (1).
2), a metal supply means (2) for supplying metallic nickel or cobalt containing sulfur to the anode, and an alloy of nickel or cobalt deposited on the cathode by electrolysis continuously outside the electrolytic cell. Metal ion removing means (3), and a metal ion-containing liquid circulating means (4) for receiving a plating solution from a circulating bath of an alloy plating bath and sending out an electrolytic solution supplemented with nickel or cobalt ions. A device that supplies metal ions consumed to an alloy plating bath. 7. The method according to claim 7, wherein the surface of the metal drum or disc is titanium or titanium alloy, lead or lead alloy, aluminum or aluminum alloy, stainless steel,
Or a hard chromium plating layer.
Equipment.