JPH0118998B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for electroplating a diaphragm. Diaphragm electrolytic plating uses an insoluble anode in electrolytic plating, as described in Japanese Patent Publication No. 51-2900, and when the plating metal is supplied in the form of metal sulfate or chloride, metal ions are removed. is taken out of the system by metal removal, whereas
Since anions such as SO ₄ ... or Cl ^- accumulate in the plating bath and lower the pH of the plating bath, an anion exchange membrane is used as a diaphragm to remove them from the plating bath system. This is a method in which electrolytic plating is performed by forming an anode chamber separately. As the anode chamber solution, a solution containing an electrolyte is usually used, for example, when plating metal is supplied in the form of sulfate, H ₂ SO ₄ or Na ₂ SO ₄ is used. Ion exchange membranes are generally produced by mixing styrene and divinylbenzene with fine polymer powder such as polyvinyl chloride, applying this to cloth, heating and polymerizing it to form a membrane, and then introducing exchange groups, or It is manufactured by a method such as dipping a cloth in styrene-butadiene latex and introducing an exchange group after drying. Therefore, the heat resistance of an ion exchange membrane depends on the heat resistance of the polymer material used, and generally, 60°C is the limit of heat resistance. When an ion exchange membrane is used in the above-mentioned diaphragm electrolytic plating, since the diaphragm is a resistor, the plating current generates Joule heat, causing a heat generation phenomenon. Therefore, the heat resistance of the ion exchange membrane becomes a problem. In particular, plating at a high current density is desirable from the point of view of plating efficiency and is necessary for actual plating on an industrial scale, but the higher the current density, the greater the amount of heat generated by the diaphragm. This can lead to serious problems such as swelling of the diaphragm or heat burns. In fact, when plating is performed at a plating bath temperature of 60° C. and a high current density of 40 A/dm ² or more, the diaphragm is damaged by burning. Therefore, unless the heat generation problem of the diaphragm is solved, it is impossible to carry out highly efficient electrolytic plating using an ion exchange membrane diaphragm. Furthermore, even in technologies such as salt electrolysis that use diaphragms, the highest current density that has been put into practical use is approximately
It is ^about 30A/dm2. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a diaphragm electrolytic plating method and apparatus that can prevent performance deterioration or damage due to swelling, burning, etc. of the diaphragm by cooling the diaphragm, and increase the current density of electrolytic plating. It's about doing. In order to achieve the above object, the inventors of the present invention have conducted various studies on means for cooling the diaphragm. First, the method of cooling the diaphragm by lowering the temperature of the plating bath is based on the electrical conductivity of the plating bath. Since the temperature of the plating bath is directly proportional to the temperature, lowering the temperature of the plating bath will lower the electrical conductivity of the plating bath, which will be disadvantageous in terms of power efficiency and may also cause problems such as unevenness of the plating film. found. However, on the other hand, in the method of cooling the diaphragm using the anode chamber liquid, the anode chamber liquid usually contains a highly concentrated acid (for example, 0.5~
3 ^N H ₂ SO ₄ ) is used, so the electrical conductivity is
While the plating bath is usually 100 m/cm at 50°C, it is high at 150 to 500 m/cm at 50°C. Therefore,
100m even if the temperature of the anode chamber liquid is lowered to about 20℃
It was found that the diaphragm can be effectively cooled without being too disadvantageous in terms of power efficiency since the temperature is less than /cm. That is, the present invention provides a method for plating in a diaphragm electrolytic cell in which an insoluble anode is installed in an anode chamber separated from a plating bath by an anion exchange membrane diaphragm, and a heat exchanger is provided in the circulation system of the anode chamber liquid to remove the anode. The method is characterized in that the chamber liquid is cooled, and the cooled anode chamber liquid is brought into contact with an anion exchange membrane diaphragm to cool the diaphragm. Next, the present invention will be explained based on the accompanying drawings.
FIG. 1 shows an outline of an electrolytic plating apparatus for carrying out the method of the present invention. In Figure 1, 1 is a plating bath filled with an aqueous solution containing a salt of the metal to be plated, generally a sulfate of the metal to be plated, and 2 is a plating bath 1 which is separated by an anion exchange membrane diaphragm 3. This is the anode chamber. 4 is the energizing roll 5
The material to be plated, for example, a strip-shaped steel plate, is electrically charged by the plating bath 1, and then guided into the plating bath 1 and subjected to the plating treatment in the plating bath 1. After the plating process, the steel plate 4 is led out of the plating bath by an energized roll 6 and supplied to the next process. 7 is a sink roll placed in the plating bathroom 1 to guide the steel plate 4. In the above configuration, the anode chamber 2 is formed in a shape extending along the traveling direction of the steel plate 4, and the anion exchange membrane diaphragm 3 is provided at a position facing the steel plate 4.
The anode chamber 2 is further provided with an insoluble porous anode, for example, an insoluble anode 8 (FIG. 2) made of expanded metal plated with Ti-Pt, and a space 9 is formed behind this anode. The anode chamber liquid is circulated. When using a solution containing an electrolyte as the anode chamber solution, for example, a metal sulfate aqueous solution as the plating bath,
H ₂ SO ₄ aqueous solution or Na ₂ SO ₄ aqueous solution, especially 0.5
A high concentration H ₂ SO ₄ aqueous solution of about 3N is preferably used. 10 is a degassing device for degassing the anode chamber liquid. On the surface of the insoluble anode 8, O ₂ gas is generated by electrolysis of water (2H ₂ O→4H ⁺ +4e+O ₂ ↑). If this O ₂ gas is left undisturbed, the voltage between electrodes will increase, which is undesirable. For this reason, the anode chamber 2 is provided so that the anode chamber liquid can be extracted from the anode chamber 2 and recirculated to the anode chamber 2 after being subjected to a degassing process. 11 is an anode chamber liquid tank, and gas venting device 10
The tank 11 is provided to store the anode chamber liquid degassed by the tank 11, and the anode chamber liquid in the tank 11 is recirculated to the anode chamber 2 by the pump 12. 13 is
This is a heat exchanger installed within the circulation system of this anode chamber liquid. Now, when the anode chamber liquid is circulated in the above configuration, the anode chamber liquid is removed by the gas venting device 10.
After the O ₂ gas is removed, it is stored in the anode compartment liquid tank 11 and then cooled by the heat exchanger 13 and recycled to the anode compartment 2 . This cooled anode chamber liquid is transferred to an anion exchange membrane diaphragm 3 in an anode chamber 2.
When passing through the gap between the anode 8 and the insoluble anode 8, the diaphragm 3
The diaphragm 3 is cooled by removing the Joule heat generated in the diaphragm 3. At this time, since the anode chamber liquid is constantly being circulated, the circulation 3 is effectively cooled by the cooled anode chamber liquid. The temperature of the cooled anode chamber liquid is:
A temperature is selected that can prevent the diaphragm 3 from deteriorating due to heat and can keep the decrease in electrical conductivity within an allowable range. Generally, in order to prevent deterioration of the diaphragm 3 due to heat, it is effective to keep the anode chamber liquid at 50° C. or lower. On the other hand, from the viewpoint of electrical conductivity, the temperature of the anode chamber liquid is preferably 20° C. or higher. Therefore, when performing electrolytic plating at a current density of 40 to 60 A/ ^dm2 , the anode chamber solution should be
It is preferable to cool to about 50°C. Next, the effects of the present invention will be illustrated by examples. The diaphragm electrolytic plating device shown in Fig. 1 was used, and the plating bath was an Fe=Zn alloy plating bath ( _FeSO4 .
7H ₂ O 250g/, ZnSO ₄ 150g/, Na ₂ SO ₄ 100
g/, PH=2) as the anode chamber solution, 2.0 ^N H ₂ SO ₄
The condition of the diaphragm was investigated by plating by changing the plating bath temperature and H ₂ SO ₄ temperature variously.
The diaphragm is NeoseptaACH manufactured by Tokuyama Soda.
−45T was used. plating bath temperature, _H2SO4 temperature, current density _and
Table 1 shows the relationship between the H ₂ SO ₄ flow rate and the condition of the plating film and diaphragm. In addition, the H ₂ SO ₄ flow rate (V) has a current density of 60A/
In the case of dm ² , an increase in interelectrode voltage was observed at v = 3 cm/sec, but no voltage increase was observed at v = 5 cm/sec or higher, confirming that there was a sufficient degassing effect. Ta. 【table】

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example of a diaphragm electrolytic plating apparatus for carrying out the present invention, and FIG. 2 is a schematic diagram showing an anode chamber. 1... Plating bathroom, 2... Anode chamber, 3... Diaphragm, 4... Material to be plated (steel plate), 8... Insoluble anode, 10... Gas venting device, 11... Anode chamber liquid tank, 13... …Heat exchanger.

Claims (1)

[Scope of Claims] 1. When plating in a diaphragm electrolytic cell in which an insoluble anode is installed in an anode chamber separated from a plating bath by an anion exchange membrane diaphragm, a heat exchanger is provided in the circulation system of the anode chamber liquid. A diaphragm electrolytic plating method characterized by cooling an anode chamber liquid and bringing the cooled anode chamber liquid into contact with an anion exchange membrane diaphragm to cool the diaphragm. 2 An anode chamber that is separated from the plating bath by an anion exchange membrane diaphragm and houses an insoluble anode therein is provided in the plating bath, and an anode chamber liquid degassing device and a heat exchanger are connected to the anode chamber liquid circulation system. A diaphragm electrolytic plating device characterized by being installed in a diaphragm electrolytic plating device.