JPS58177487A - Method and device for diaphragm electroplating - Google Patents

Abstract

PURPOSE:To prevent the deterioration in performance and damage owing to swelling, burn, etc. of an anion exchange membrane diaphragm and to increase the high current density of plating in the stage of plating a metal to be plated with the insoluble anode in the anode chamber separated with said diaphragm, by bringing the liquid in the anode chamber into contact with the diaphragm after cooling the same in a circulation system. CONSTITUTION:An insoluble porous anode 8 is provided in an anode chamber 2 which is separated with an anion exchange membrane diaphragm 3 from the plating bath of an aq. soln. 1 contg., for example, sulfate of a plating metal, and a steel plate 4 to be plated is electrified to negative charge and is plated. Here, a space 9 is formed behind the anode 8 in the chamber 2 so that an anolyte, for example, an aq. Na2SO4 soln. circulates therein. The gaseous O2 generated on the surface of the anode 8 is removed with a gas venting device 10 of the circulation system to prevent interpole electrode. The anolyte removed of the gas is stored in a tank 11, whereafter the anolyte is cooled in a heat exchanger 13, and is recirculated to the chamber 2. While the cooled anolyte passes between the membrane 3 and the anode 8, the anolyte is deprived of the Joule heat generated in the membrane 3 so that the membrane 3 is cooled at all times.

Description

[Detailed description of the invention] The present invention relates to a diaphragm electrolytic plating method and apparatus.

Diaphragm electrolytic plating, as described in Japanese Patent Publication No. 51-2900, uses an insoluble anode in electrolytic plating and supplies the plating metal in the form of metal sulfate or chloride. While ions are taken out of the yarn by plating, anions such as 804... or C1- accumulate in the plating bath and increase the pH of the plating bath.
Therefore, in order to take the gold out of the gold plating bath system, an anion exchange membrane is used as a complete diaphragm, and the entire anode chamber is formed in a separate manner from the plating bath, and all electrolytic plating is performed.

A solution containing an electrolyte is usually used as the anode chamber solution, for example, plated metal? When supplemented in the form of sulfate, H
2SO4 or Na2SO4 is used.

Ion exchange membranes are generally made by mixing styrene and divinylbenzene with fine polymer powder such as polyvinyl chloride.
It can be produced by applying it to a cloth, heating it and polymerizing it to form a film, and then introducing an exchange group, or by dipping the cloth in styrene straw butadiene latex, drying it, and then introducing an exchange group. For this reason, the heat resistance of an ion exchange membrane depends on the heat resistance of the polymer material used, and generally the limit of heat resistance is 60°C.1] Ion exchange membrane? When used in the above-mentioned diaphragm electrolytic plating, the diaphragm is a resistor, so it is difficult to use.

Joule heat is generated by the electric current, 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 in terms of plating efficiency and is necessary for actual industrial plating, but the higher the current density, the greater the amount of heat generated by the diaphragm. , swelling or thermal burning of the diaphragm can lead to serious problems. Actually, the plating bath temperature was 60℃ and 40A/d.
If plating is carried out at a high current density of more than m, the diaphragm will be damaged due to burning. Therefore, unless the heat generation problem of the diaphragm is solved, it is impossible to perform highly efficient electrolytic plating using an ion exchange membrane diaphragm. In addition, even in technologies such as salt electrolysis for diaphragm Til, the maximum current density that has not been put into practical use is approximately 30 A/dm.
Therefore, the purpose of the present invention is to cool the diaphragm so as to
Completely prevents performance deterioration or damage due to diaphragm swelling, burning, etc.
An object of the present invention is to provide a diaphragm electrolytic plating method and apparatus capable of increasing the current density of electrolytic plating. In order to achieve the above object, the inventors of the present invention have conducted various studies on means for cooling diaphragms. First, in the method of cooling the diaphragm by heating the plating bath, the electrical conductivity of the plating bath is directly proportional to the temperature, so lowering the temperature of the plating bath lowers the electrical conductivity of the plating bath. It was found that this resulted in a disadvantage in terms of power efficiency and caused problems such as unevenness in the plating film. However, on the other hand, what about the anode chamber liquid? Using a diaphragm? The cooling method is that the anode chamber solution is usually a highly concentrated acid (e.g. 0.5-3NH2SO
4) Since the plating bath is usually used at 50°C, the electrical conductivity is
The height is as high as 150-500 m07cm at 50℃. Therefore, even if the temperature of the anode chamber liquid is lowered to about 20℃,
It has been found that the entire diaphragm can be effectively cooled without being less than mc5/c11L, and there is no disadvantage in terms of power efficiency.

That is, in the present invention, when plating in a diaphragm electrolytic tank in which insoluble anodes are all installed in four anode chambers separated from the plating bath by anion exchange membrane diaphragm number ζ, heat exchange is performed in the circulation system of the anode chamber liquid. The present invention is characterized in that a container is provided to cool the anode chamber liquid, and the anode chamber liquid is brought into contact with the cooled anode chamber i'al-anion exchange membrane diaphragm to cool the diaphragm.

Next, the present invention will be explained based on the accompanying drawings. .

Figure 1 shows an outline of an electrolytic plating apparatus that implements the entire method of the present invention.
It shows. In Figure 1, ■ is a salt of the metal to be plated, generally a sulfate of the metal to be plated? 2 is an anode chamber separated by an anion exchange membrane diaphragm 3 in the plating bath 1;
After being charged to e by the energizing roll 5, the plating bath 1
After the plating process, the material to be plated, such as an O-steel plate 4, which is a band-shaped steel plate, is led out of the plating bath by an energized roll 6 and supplied to the next step. Reference numeral 7 denotes a zinc roll located in the plating bath 1 for guiding the steel plate 40. In the above configuration, the anode chamber 2 is formed in a shape extending along the traveling direction of the steel plate 4.
1 An anion exchange membrane diaphragm 3 is provided at a position facing the steel plate 4. The anode chamber 2 further includes an insoluble porous anode, for example, an insoluble anode 8 made of Ti-Pt plated xeno-kunded metal. (Fig. 2) is provided,
A space 9 is formed behind the anode through which the anode chamber liquid circulates. Is the anode chamber fluid an electrolyte? For example, when using a metal sulfate aqueous solution as a plating bath, a H2SO4 aqueous solution or a NazS
O4 aqueous solution, especially H2S at a high concentration of about 0.5 to 3N
04 An aqueous solution is preferably used. 0 10 is a degassing device for degassing the anode chamber liquid. 0 On the surface of the insoluble anode 8, water electrolysis (2H20"4H
02 gas is generated by ++4e+Oz↑). This 0
If the two gases are left alone, the pressure in the interelectrode chamber will increase, which is undesirable. Therefore, after all the anode chamber liquid has been extracted from the anode chamber 2 and gas degassing processing has been performed, the oll that is installed so that it can be recirculated to the anode chamber 2 is an anode chamber liquid tank, which is degassed by the gas degassing device 10. The anode chamber liquid in the tank 11, which is provided to store the purified anode chamber liquid, is recirculated to the anode chamber 2 by a pump 12. Reference numeral 13 denotes a heat exchanger provided within the circulation system of this anode chamber liquid.

Now, when the anode chamber liquid is circulated in the above configuration, after the 02 gas is removed from the anode chamber liquid by the degassing device 10, it is stored in the anode chamber liquid tank 11, and then it is removed by the heat exchanger 13. It is cooled and recycled to the anode chamber 2. When this cooled anode chamber liquid passes through the entire gap between the anion exchange membrane diaphragm 3 and the insoluble anode 8 in the anode chamber 2,
The Joule heat generated in the diaphragm 3 is taken away and the diaphragm 3 is cooled. At this time, since the anode chamber liquid is constantly circulated, the diaphragm 3 is effectively cooled by the cooled anode chamber liquid.
゛The temperature of the cooled anode chamber liquid is selected to be a temperature that can prevent deterioration of the diaphragm 3 due to heat and also keep the decrease in electrical conductivity within an allowable range゛In general, the temperature of the diaphragm 3 In order to prevent deterioration due to heat, it is effective to keep the total temperature of the anode chamber liquid below 50°C.

On the other hand, from the standpoint of electrical conductivity, the temperature of the anode chamber liquid is 20°C.
It is preferable that it is above. It is preferable to cool the mixture at a constant temperature.

Next, the effects of the present invention will be illustrated by experimental examples.

The diaphragm electrolytic plating apparatus shown in Fig. 1 was used, and the plating bath was a Fe=Zn alloy metal bath (FeSO4・7H202
50g/l, ZnS04150. ! i'/l, Naz
SO4100,9/IA'.

Using 2.0 NH2S04 as the anode chamber solution and varying the plating bath temperature and H2SO4 temperature, plating was performed and the state of the diaphragm was investigated.

The diaphragm is Neosepta A manufactured by Tokuyama Soda.
C-45T was used.

Plating bath temperature, H2SO4 temperature, current density and )h
Table 1 shows the relationship between the S04 flow rate and the condition of the plating film and diaphragm.

Note that the H2SO4 flow rate (V) has a current density of 60A/d.
m", an increase in interelectrode voltage was observed when v = 3 cm/sec, but no voltage increase was observed at ■ = 5 CrIL/SeC or higher, confirming that there was a sufficient degassing effect. San〇Table 1

[Brief explanation of the drawing]

Is Figure 1 the invention? A schematic diagram showing an example of the diaphragm electrolytic plating equipment used, Figure 2 is the positive room? FIG. 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 (Fig. 1) 490- Second agony

Claims (1)

[Claims] (1) When plating in a diaphragm electrolytic tank in which an insoluble anode is installed in an anode chamber separated from the plating bath by an anion exchange membrane diaphragm, a heat exchanger is installed in the circulation system of the anode chamber liquid. an anode chamber containing an insoluble anode formed therein, characterized in that the cooled anode chamber is brought into contact with an anion exchange membrane diaphragm to completely cool the diaphragm; A diaphragm electrolytic plating apparatus 0 characterized in that an anode chamber liquid degassing device and a heat exchanger are provided in an anode chamber liquid circulation system.