JP3158786B2 - Method for producing sulfur-containing electric nickel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing sulfur-containing electric nickel for plating using a nickel chloride electrolyte.

[0002]

2. Description of the Related Art Electric nickel containing, for example, 50 to 250 ppm of sulfur, which is used as an anode in nickel plating, has the following advantages in nickel plating.

[0003] 1) Unlike ordinary electric nickel containing no sulfur or carbon, the surface becomes spongy due to local dissolution due to passivation, and the nickel particles do not fall off without being dissolved. 2) Therefore, electric nickel can be sequentially supplied to the anode holder such as a titanium basket by melting smoothly. 3) Since the voltage at the beginning of melting is low and the operating voltage is low, the generation of gas is small and the power can be saved. 4) High activity as anode even when various plating bath compositions and current densities are selected. 5) Little dissolved residue.

As a method for producing such sulfur-containing electric nickel, there is a method described in US Pat. No. 2,392,708. In this method, crude nickel is used as an anode, thiosulfate of an alkali metal is used as a sulfur source, and the sulfur source is added to the electrolyte solution at 0.05 to 0.25 g / l to adjust the pH to 1.5 to 6
To obtain sulfur-containing electric nickel.

[0005] In this method, the sulfur content of the obtained sulfur-containing electric nickel is as wide as 0.007 to 0.11% by weight, and the distribution of sulfur in the electric nickel is not uniform. Further, there is a problem that the residue generation rate when used as an anode is high.

As a method of improving this problem, Japanese Patent Publication No. Sho 58
There is a method proposed by JP-7715. This method reduces the concentration of Cl ₂ coexisting in the electrolyte to 0.0002 g / l.
The following, and then sodium thiosulfate 0.003-
It is added to the electrolyte so as to have a concentration of 0.01 g / l. According to this method, unnecessary decomposition of sodium thiosulfate in the electrolytic solution can be prevented, and the sulfur content is reduced to 0.00.
Electric nickel having a relatively uniform sulfur distribution in the range of 5 to 0.025% by weight is obtained.

However, in order to reduce manufacturing costs in recent years,
There are many methods in which nickel matte is leached with chlorine to form an electrolytic solution, and electrolysis is performed to obtain electric nickel. Even when the above-mentioned method is used using this electrolytic solution, the sulfur content is 0.005.
~ 0.025% by weight of electric nickel cannot be obtained. This is attributed to the extremely large amount of Cl ₂ generated during electrolysis.

To solve this problem, Japanese Patent Publication No. Sho 59-2
A method disclosed in Japanese Patent Publication No. 5037 is proposed. In this method, a thiocyanate such as potassium thiocyanate which is hardly decomposed into Cl ₂ is used as a sulfur source to prevent diffusion of Cl ₂ generated at the anode to the cathode side. In this method, an insoluble anode is placed in the anode box, the inside of the anode box is set at a negative pressure, the liquid level in the anode box is higher than the liquid level in the cathode box, and the liquid in the anode box is discharged out of the system together with the chlorine gas that generates the liquid. It is extracted and a new electrolytic solution is supplied to the cathode box. This method has a problem that a harmful cyan compound is used.

In the method proposed in Japanese Patent Publication No. 60-53116, a cathode and an anode are separated from each other by an ion-permeable membrane, and a new electrolyte is supplied to the cathode box.
Although the electrolytic solution is taken out of the cathode chamber out of the system and Cl ₂ is not mixed into the cathode box, it is not economical in that an expensive ion-permeable diaphragm is used.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for economically producing sulfur-containing electric nickel for plating using an electrolytic solution containing nickel chloride as a main component.

[0011]

Means for solving the problems according to the present invention are as follows. An insoluble anode is inserted into an anode box provided with a diaphragm, and a cathode is inserted into a cathode box provided with a diaphragm. A nickel electrolyte mainly comprising chloride is supplied to the cathode box, and the liquid level in the cathode box is 5 mm higher than the liquid level in the electrolytic cell.
While keeping the anode box at a high level and discharging chlorine gas generated in the box from the anode box together with the electrolytic solution in the anode box to the outside of the anode box, the liquid level in the anode box is at least 10 mm higher than the liquid level in the electrolytic cell. The present invention relates to a method for producing sulfur-containing electric nickel, characterized in that electrolysis is carried out while keeping the temperature low.

The diaphragm has a water permeability measurement height of 200 mm H ₂ O.
Water permeability measured at 0.04 to 0.08 l / m ² / sec
It is better to use As the diaphragm, a cloth or felt made of acid-resistant synthetic fiber, or a ceramic plate having continuous ventilation holes can be used. The electrolysis conditions are at a temperature of 60 to 70.
° C, nickel concentration 40-80 g / l, pH 1.0-2.0.
5, sodium thiosulfate concentration 0.006 to 0.012 g /
It is preferable to adjust the cathode current density to 1.0 to 2.5 A / dm ² while supplying 1 electrolyte to the cathode box.

[0013]

According to the present invention, a nickel electrolytic solution mainly comprising chloride containing sodium thiosulfate is supplied to the cathode box, and the liquid level in the cathode box is maintained at least 5 mm higher than the liquid level in the electrolytic cell. The reason why the chlorine gas generated in the box is discharged from the anode box together with the electrolytic solution in the anode box to the outside of the anode box, and the liquid level in the anode box is kept at least 10 mm lower than the liquid level in the electrolytic cell for electrolysis. Is to prevent chlorine gas generated at the insoluble anode from moving into the cathode box. This also makes it possible to use sodium thiosulfate, which is easily decomposed but is inexpensive, harmless and easy to handle, as a sulfur source.

In order to manage the liquid levels in the cathode box and the anode box as described above, the amount of liquid supplied to the cathode box and the amount of liquid discharged from the anode box are also involved. The water permeability of the diaphragm is also related to the anode box. The water permeability was measured by attaching a diaphragm to be measured to one end of a measuring tube provided so that the diameter of the passing portion was 70 mm, and setting the head difference to 200 mm from the pipe connected to the other end so that water at 30 ° C. Through water, 1
This is done by determining the amount of water passing per hour.

The water permeability of this membrane is 0.04 l / m ² / sec
Below c, the voltage drop due to the cloth increases to 0.08
If it exceeds 1 / m ² / sec, a large amount of electrolyte must be supplied into the cathode box in order to maintain the liquid level difference. Streaks are generated on the surface of the nickel electrolysis due to the flow of the electrolytic solution at the surface, and deteriorate the appearance of the product.

In order to maintain the liquid level in the cathode box as described above, it is necessary to appropriately adjust the flow rate of the electrolytic solution into the cathode box due to the head difference from the cathode box to the electrolytic cell. Therefore, it is necessary to use a diaphragm having an appropriate water permeability in the range of the above water permeability.On the other hand, in the anode box, in order to prevent chlorine gas generated at the anode from diffusing into the electrolytic cell and the cathode box, the above-mentioned water permeability is used. It is necessary to use an appropriate diaphragm having a water permeability within the range of the water degree.

The amount of the liquid supplied into the cathode box is obtained by dividing the amount of current flowing through the cathode by the area of both surfaces of the cathode to a cathode current density A / dm ² and supplied to one cathode box in one hour. It is necessary to supply the liquid at a rate of 170 ml / AH or more to maintain the liquid level in the cathode box, expressed as ml / AH, which is obtained by dividing the amount of electrolytic solution ml / H by the amount of current A flowing to the cathode. However, even if the supply amount is too large, it overflows from the cathode box and the amount of the electrolyte discharged from the electrolytic cell increases, which is uneconomical. .

The electrolyte used in the method of the present invention is a chloride bath obtained by leaching a nickel matte with chlorine. The leaching solution usually obtained by leaching chlorine from nickel matte contains metals other than nickel as impurities, so that the leaching solution is purified in a liquid purification process, the nickel concentration is adjusted to 40 to 80 g / l, and used as an electrolyte. If the nickel concentration is low, concentration polarization occurs on the cathode surface during electrolysis, causing electrodeposition failure.On the other hand, if it is too high, the electrodeposition stress will be excessive, the cathode will be distorted, and the cathode box will be broken or short-circuited Because you do.

The electrolysis temperature is set at 60 to 70 ° C., which is slightly higher than the temperature applied when producing electric nickel from a normal chloride bath. This is because when the electrolysis temperature is low, the electrodeposition stress increases due to the effect of adding sodium thiosulfate, and distortion occurs, and when it is too high, the working environment deteriorates.

When the pH of the electrolyte is low, the electrodeposition stress increases, the electrodeposit becomes brittle, and the cathode cracks.
On the other hand, if the pH is high, sulfur precipitates abnormally, increasing granular precipitates on the cathode surface, and it is not possible to obtain good sulfur-containing electric nickel. For this reason, the pH of the electrolyte is set to 1.0 to 1.5. This pH adjustment is desirably performed in the liquid purification step in terms of operating efficiency, but there is no problem if a pH adjustment tank is provided immediately before the liquid supply. It is needless to say that hydrochloric acid is used as a regulator, based on the composition of the electrolyte. In addition, depending on the process used, there is no problem even if the adjustment is performed by blowing chlorine gas.

The reason why sodium thiosulfate is used as the sulfur source is that it is inexpensive, harmless and easily decomposed as described above. This is because sodium thiosulfate is decomposed by chlorine generated at the insoluble anode, and has little risk of being accumulated in the electrolyte, and there is little risk of occurrence of trouble due to the accumulated matter.

The sodium thiosulfate is added to the supply pipe and is uniformly mixed with the electrolyte by the movement of the electrolyte in the pipe. No problem. If added too far from the cathode box, sodium thiosulfate will decompose,
Since sulfur is separated, it is not preferable. If it is added at a position too close to the cathode box, it will not be uniformly mixed with the electrolytic solution. Since the position at which the addition is preferable is exclusively dependent on the equipment conditions, it is preferable to determine the optimum addition position depending on the equipment used.

The concentration of sodium thiosulfate is 0.00
If the content is out of this range, the sulfur content in the obtained sulfur-containing electric nickel does not become 0.016 to 0.022% by weight. Because it does not become. If the sulfur content is low, the uniform solubility is poor when used as an anode during plating, and if the sulfur content is high, the slime ratio increases and the uniform solubility deteriorates.

In the method of the present invention, the cathode current density is preferably set to 1.0 to 2.5 A / dm ² . 1.0A / dm
^If it is smaller than ² , productivity becomes low and it is not economical.
If it exceeds A / dm ² , the hardness of the electrodeposited nickel increases, making it difficult to cut the resulting electric nickel into chips as a product, increasing the electrodeposition stress, distorting the electric nickel, and destroying the cathode box. Or a short circuit may occur. Also, abnormal precipitation of sulfur occurs, particles are generated on the surface of electric nickel, the particles are not uniformly dissolved, and the slime ratio is increased.

The electrolytic solution supplied to the cathode box is
After passing through the diaphragm of the cathode box to the electrolytic cell, a part enters the anode box and is then discharged outside the system as an electrolytic drain, and a part is discharged out of the system as an electrolytic drain from the electrolytic tank. In this way, not a small amount of Cl ₂ is present in the electrolytic effluent discharged out of the system. Therefore, either de Cl ₂ to after adjusting composition and the composition adjusted after removing Cl ₂ as the electrolytic solution is supplied to the cathode box with the addition of sodium thiosulfate.

As a method for removing Cl ₂ from the electrolytic waste water,
For example, most of the Cl _{2 is}
Is removed, and then the remaining Cl ₂ is adsorbed and removed with activated carbon or the like. According to this method, an electrolyte having a Cl ₂ concentration of 0.005 g / l or less can be easily obtained. As described in JP-B-58-7715, when the Cl ₂ concentration is lower than 0.005 g / l, when the Cl ₂ concentration is higher than this, sodium thiosulfate is decomposed and the sulfur content is reduced to 0. This is because 0.005 to 0.025% by weight of electric nickel cannot be obtained.

[0027]

【Example】

Example 1 Eight insoluble anodes and seven cathodes were placed in a cathode box and an anode box, respectively, in an electrolytic cell having a capacity of 1.4 m ³ . As the diaphragm of the anode box, a filter cloth of synthetic fiber woven fabric having a water permeability of 0.8 l / m ² / sec was used, and as the diaphragm of the cathode box, the same water permeability of 0.8 l / m ² / sec.
A filter cloth of 6 l / m ² / sec was used. 800 × 1 cathode
An electric nickel plate having a thickness of 000 mm and a thickness of 1 mm was used, and the surface of a Ti net was coated with ruthenium oxide as an anode.
A 0x770 mm insoluble electrode was used.

Ni concentration 50-70 g / l, Co, Cu,
Fe is 0.001 g / l or less and chlorine ion is 7
2~90g / l, Cl ₂ is 0.0002g / l, pH1.
Sodium thiosulfate was added to a solution of 08 to 1.45 at 64 ° C. to a concentration of 0.012 g / l to form an electrolyte.
Liquid was supplied evenly to each cathode box at a rate of 00 ml / AH (0.6 l / min · cathode box). When the electrolytic solution reached the drain pipe of the anode box, current was supplied so that the cathode current density became 1.15 A / dm ^2, and chlorine generated by vacuum suction and the electrolytic solution were discharged from the drain pipe to the outside of the system.

In this state, a test operation was performed for 8 days to obtain sulfur-containing electric nickel for plating. During the test operation, the liquid level in the cathode box was 5 to 5 times higher than the liquid level in the electrolytic cell.
20 mm higher, the liquid level in the anode box is kept 10-15 mm lower than the liquid level in the electrolytic cell, and the liquid level in the anode box is 15-35 m higher than the liquid level in the cathode box.
m low.

The resulting sulfur-containing electric nickel was smooth and free of distortion. Nine points were selected to be evenly distributed for each sheet of this electric nickel, sampled using a drill, and analyzed to determine the sulfur content, all of which were in the range of 0.014 to 0.020% by weight. Was within. Then, 50 × 100 mm at any position from each electric nickel
A dissolution test was performed using 14 test pieces cut out of each of the electric nickels into two pieces each having a size of.

In the dissolution test, the Ni concentration was 81.8 g / l,
Using a sulfamic acid bath having a pH of 4.0 and boric acid concentration of 30 g / l, each of the above-mentioned test pieces was used as an anode, a stainless steel plate was used as a cathode, an anode current density was 2 A / dm ² , and an electrolyte temperature was 50.
Electrolysis was performed at ~ 55 ° C for 96 hours, and the current efficiency of the anode and the anode slime generation rate were determined. The surface state after dissolution of the anode was observed to determine the suitability of the product. The obtained results show that the anodic current efficiency is 100%, the slime generation rate is 0.1% by weight or less, and the dissolution surface conditions are all good.
It was found to be optimal as sulfur-containing electric nickel for plating.

Example 2 A test operation was carried out in the same manner as in Example 1 except that the temperature of the electrolyte was 55, 57, 60, 63 and 68 ° C., and the concentration of sodium thiosulfate was 0.009 g / l. Cracks occur in the electric nickel obtained at the electrolyte temperature of 55 and 57 ° C., and small granular precipitation is observed on a part of the surface of the electric nickel obtained at 60 ° C., and the electric nickel obtained at 63 ° C. There are slightly small particles and pinholes on the surface,
The surface condition of the electric nickel obtained at 68 ° C. was quite good. 55, 57 ℃
The product obtained at 60 and 63 ° C. could be a sufficient product with some difficulty, and the product obtained at 68 ° C. could be used as a product without any problem.

Comparative Example 1 The liquid level in the anode box was 4 to 8 times higher than the liquid level in the electrolytic cell.
Electric nickel was obtained in the same manner as in Example 1 except that the thickness was reduced by mm. The sulfur content in the obtained electric nickel is 0.0.
10 to 0.014% by weight, which is the object of the present invention.
It did not fall within the range of 016 to 0.022% by weight. When a dissolution test was performed on the obtained electric nickel in the same manner as in Example 1, the slime generation rate was 0.75 to 2.61% by weight, and the dissolution surface was in the shape of a cord, which was not suitable as a product. I understood. This is presumably because Cl ₂ generated at the anode flowed back to the cathode side, and sodium thiosulfate in the electrolytic solution was decomposed in the cathode box.

Comparative Example 2 A test operation was carried out in the same manner as in Example 1 except that the concentration of sodium thiosulfate was adjusted to 0.004 g / l. The sulfur content in the obtained electric nickel was 0.008.
〜0.012% by weight, which is the object of the present invention.
It did not fall in the range of 6 to 0.022% by weight. When a dissolution test was performed on the obtained electric nickel in the same manner as in Example 1, the slime generation rate was 1.20 to 2.42% by weight.
As a result, it was found that the dissolving surface also became a mat-like shape and was not suitable as a product. This is probably because the concentration of sodium thiosulfate in the electrolyte was too low.

Comparative Example 3 A test operation was carried out in the same manner as in Example 1 except that the concentration of sodium thiosulfate was adjusted to 0.25 g / l.
The sulfur content in the obtained electric nickel is 0.028 to 0.2.
034% by weight, which is the object of the present invention, 0.016 to 0.0.
It did not fall within the range of 22% by weight. In many cases, the surface state had grains or cracks, and was not suitable as a product. As a precaution, the obtained electric nickel was used in Example 1
When a dissolution test was carried out in the same manner as described above, the slime generation rate was as high as 0.35 to 0.52% by weight, and the dissolution surface was darkened and became a blind. This is probably because the concentration of sodium thiosulfate in the electrolyte was too high.

Comparative Example 4 A test operation was performed in the same manner as in Example 1 except that the nickel concentration in the electrolyte was changed to 30 g / l. Observation of the surface of the cathode during the test operation revealed that electrodeposition was poor, and good electric nickel was not finally obtained.

Comparative Example 5 A test operation was carried out in the same manner as in Example 1 except that the nickel concentration in the electrolytic solution was 90 g / l. The obtained electric nickel was distorted, a short circuit occurred even during electrolysis, the cathode box was damaged, and good electric nickel was not obtained.

Comparative Example 6 A test operation was performed in the same manner as in Example 1 except that the pH of the electrolytic solution was changed to 0.6. All of the obtained electric nickel had cracks and could not be used as products. This seems to be due to the high internal stress generated by electrodeposition.

Comparative Example 7 A test operation was performed in the same manner as in Example 1 except that the pH of the electrolytic solution was changed to 1.7. All of the obtained electric nickel had many particles on the surface and could not be a product.

[0040]

According to the method of the present invention, sodium nickel thiosulfate, which is inexpensive, harmless and easy to handle, is used as a sulfur source, and a sulfur-containing electric nickel optimum for plating can be easily obtained from a chloride bath.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-31876 (JP, A) JP-A-56-93886 (JP, A) JP-A-55-28319 (JP, A) JP-A-54-1983 31025 (JP, A) JP-A-53-5019 (JP, A) JP-A-52-91725 (JP, A) JP-A-56-62980 (JP, A) JP-A-51-50808 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C25C 1/00-7/08

Claims (3)

(57) [Claims] An insoluble anode is inserted into an anode box provided with a diaphragm, and a cathode is inserted into a cathode box provided with a diaphragm. A nickel electrolytic solution mainly containing chloride containing sodium thiosulfate is supplied to the cathode box. While maintaining the liquid level in the cathode box higher than the liquid level in the electrolytic cell by 5 mm or more, while discharging chlorine gas generated in the box from the anode box together with the electrolytic solution in the anode box to the outside of the anode box, A method for producing sulfur-containing electric nickel, characterized in that electrolysis is performed while maintaining the liquid level in the anode box at least 10 mm lower than the liquid level in the electrolytic cell. 2. A water permeability measurement height of 200 mmH as a diaphragm.
_The water permeability measured with ₂ O is 0.04 to 0.08 l / m ² / se
The method for producing sulfur-containing electric nickel according to claim 1, wherein a cloth made of the synthetic fiber of c is used. 3. A temperature of 60 to 70 ° C. and a nickel concentration of 40 to 70 ° C.
A cathode current density of 1.0 to 2.5 A / dm was supplied to the cathode box while supplying an electrolyte of 80 g / l, pH 1.0 to 2.5, and sodium thiosulfate concentration of 0.006 to 0.012 g / l to the cathode box.
^The method for producing sulfur-containing electric nickel according to claim 1 or ² , wherein the electrolysis is performed in (2).