JPH0359145B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing sulfur-containing electrolytic nickel suitable for use as an anode for nickel plating. For example, 0.005 ~ as an anode for nickel metal
Nickel plates containing 0.040% sulfur are preferred in the plating industry for their high activity and uniform dissolution. Conventionally, the method for manufacturing sulfur-containing electrolytic nickel uses nickel pine or coarse nickel as an anode, and a sulfur-containing inorganic compound that is soluble in the electrolytic solution and a sulfur-containing fine particle that is insoluble in the electrolytic solution as the sulfur source to be included in the electrolytic nickel. Alternatively, a sulfur-containing organic compound soluble in the electrolytic solution is added to the electrolyte bath, electrolyzed, and the sulfur content is deposited on the nickel seed plate, which is the cathode.
A method of obtaining 0.005 to 0.040% by weight of electrolytic nickel has been used. Among the above sulfur sources used, additives other than sulfur-containing inorganic compounds that are soluble in the electrolyte may cause relatively large variations in the distribution of sulfur in the resulting electrolyzed nickel, or may cause problems in the electrolyte purification process. When the incompletely decomposed decomposition products are reused as an electrolyte, the surface of the electrolytic nickel tends to become uneven, and the concentration of additives in the electrolyte becomes difficult to control. As a result, sulfur-containing inorganic compounds are widely used. As such sulfur-containing inorganic compounds, alkali metal sulfites, thiosulfates, thionates, etc. are usually used. However, these sulfur-containing inorganic compounds actually differ individually in their effects on the properties of the sulfur-containing electrolytic nickel obtained and on the control of electrolytic operations, and not all of them are necessarily effective. In general, these inorganic compounds do not have sufficient stability in the electrolyte, and it is difficult to control the concentration of sulfur to make them work effectively. Countermeasures are desired, including issues such as the uniformity of the distribution of sulfur, which affects the electrolytic process, and electrodeposition distortion, which causes uneven current density distribution and short circuits during electrolytic operation. There is. The present inventors investigated the electrolytic conditions in order to eliminate the various drawbacks that occur when using these sulfur-containing inorganic compounds, and found that they found extremely The present invention was completed by discovering specific electrolytic conditions. According to the present invention, when producing sulfur-containing electrolytic nickel using a nickel pine or coarse nickel anode and a metal nickel plate cathode using a sulfate-chloride mixture or single chloride electrolytic bath, A tetrathionate salt is used as the sulfur-containing compound, which is characterized in that a reverse current is applied for a short period of time prior to electrolysis. The nickel source used for the anode may be so-called nickel pine containing about 20% by weight of sulfur or metallic nickel, and the electrolyte may be a sulfate-chloride mixed bath or a chloride single bath. Tetrathionate, which is added to the electrolyte as a sulfur source, is relatively stable in the electrolyte among various sulfur-containing inorganic compounds, and the sulfur in the electrodeposit is uniformly distributed.
It is also known to have the least distortion due to electrodeposition. However, when cutting the sulfur-containing electrolytic nickel product using an electrolytic solution containing this, for example, the interface between the metal nickel cathode surface and the electrodeposited nickel layer immediately before the start of electrolysis, or during electrolysis operation. There is a tendency for the electrodeposited nickel layers to peel off at the interface between them when the current is interrupted. In order to prevent this peeling phenomenon, it has been found that it is necessary to flow a reverse current for a short period of time at the start of electrolytic current application. This prevents peeling phenomena such as the conductive film that was formed on the cathode surface at the start of electrolytic energization being oxidized and cleaned, and the formation of unevenness on the cathode surface due to partial dissolution. It is assumed that this is the case, but the details are unknown.
By flowing a reverse current in this manner, the above-mentioned peeling phenomenon can be completely prevented. If you measure the content of tetrathionate in the electrolyte from time to time and replenish the deficiency to maintain the content between 5 and 25 mg, the sulfur content of the resulting electrolytic nickel can be reduced.
It can be maintained at 0.005 to 0.040% by weight, and the distribution of sulfur can be kept almost uniform. If the content of tetrathionate exceeds 0.025g/, the distribution of sulfur becomes uneven and the surface condition of the electrolytic nickel tends to be poor. Furthermore, when this electrolytic nickel is used as an anode for plating, This is not desirable as the slime generation rate increases. Reverse electrolysis performed at the start of electrolysis for the above purpose is similar to the positive current conditions during electrolysis operation, and it is sufficient to simply reverse the polarity during electrolysis operation, and the current density is usually ^about 0.5 to 4 A/dm2. be. This current density does not change whether the anode (during reverse electrolysis) is a nickel seed plate or sulfur-containing electrolytic nickel, and the energization time is about 2 to 15 minutes. The electrolytic conditions during electrolytic operation may be conventional conditions. For example, the electrolyte in the cathode box has a pH of
is 2.0 to 3.2, the temperature is 45 to 75°C, and the amount of electrolyte supplied to the cathode box is approximately 50 to 400 ml/A.H. The sulfur-containing electrolytic nickel produced in accordance with the present invention has a substantially uniform distribution of sulfur, and the electrodeposition strain is comparable to or less than that of sulfur-free electrolytic nickel. Next, the present invention will be explained in more detail with reference to Examples. Example 1 Ni9.12%, S0.01%, Fe3.5% as anode,
Cu2.7%, Co0.4% (each weight%), size 100mm×
Using a 150mm x 15mm coarse metal nickel plate, place an 80mm x 108mm x 0.2mm electric nickel seed plate as the cathode in a cathode box with inner dimensions 100mm x 160mm x 25mm, and place the above two anode plates in the electrolytic cell. were placed facing each other on both sides of the single cathode plate. The electrolyte is
Ni80g/, SO ₄ 127g/, Cl64g/, Na38
g/, with a composition of H ₃ BO ₃ 10 g/approximately 80
then add sulfuric acid to adjust the PH to 2.5 ± 0.05, and then add sodium tetrathionate to 0.015
g/containing, feed liquid temperature 60℃,
Electrolysis was carried out under the conditions of supplying liquid to the cathode box: 100 ml/A.H. The cathode current density is 2A/ ^dm2 ,
The electrolyte drained from the cathode box was not circulated. Prior to the start of electrolysis, reverse electrolysis was performed for 5 minutes in which the polarity of the electrolysis was simply reversed. Further, after performing the subsequent positive direction electrolysis for 3 hours, the current was turned off again to correct the distortion of the cathode. After correcting this distortion, reverse direction electrolysis was performed again for 5 minutes in the same manner as before to change to forward direction electrolysis. Subsequent electrolysis was carried out for 8 consecutive days. As a result, as electrolytic nickel with good surface condition, Ni99.97%, Co00.01%, Fe0.004
%, Cu 0.002%, and S 0.019% (each weight %) and a thickness of about 8 mm was obtained. The sulfur distribution in this electrolytic nickel was almost uniform, with an average S content of 0.019% by weight, but in the lower corner, the concentration was 0.021% by weight on the liquid supply side and 0.020% by weight on the opposite side. This electrolytic nickel was cut into 10 mm square pieces with a cutting machine except for the plating test described below, but no peeling of the electrolytic nickel from the seed plate was observed in any of the sections. Using this electrolytic nickel (50 mm x 100 mm), 450 g of nickel sulfamate/30 g of H ₃ BO ₃ /
As a result of conducting a plating test in a bath with pH 4.0 and a cathode current density of 2 A/dm ² , an anodic flow efficiency of 100.05% and a slime generation rate of 0.087% by weight were obtained. Comparative Example 1 Electrolysis was carried out under substantially the same conditions as in Example 1, except that the reverse current was applied prior to the start of electrolysis, the electrolysis was interrupted for 3 hours, and the reverse electrolysis was not performed prior to restarting electrolysis.
When the electrolytic nickel obtained as a result was cut into 10 mm square pieces using a cutting machine, peeling of the electrolytic nickel from the seed plate was observed in most of the cut pieces. Example 2 The sodium tetrathionate content in the electrolyte was
Electrolysis was carried out under substantially the same conditions as in Example 1, except that three types of electrolytic solutions prepared by adding sodium tetrathionate at concentrations of 0.010, 0.020, and 0.025 g were used. The surface condition of the electrolytic nickel obtained as a result is good, and its sulfur content is
They were 0.015, 0.026, and 0.035% by weight. When these electrolytic nickels were cut into 10 mm square pieces using a cutting machine, no peeling from the seed plate was observed in any of them. Using these electrolytic nickels, plating tests similar to those in Example 1 were conducted, and the results shown in Table 1 were obtained.

[Table] Comparative Example 2 The content of sodium thiosulfate in the electrolyte was
Electrolysis was carried out in the same manner as in Example 1, except that it was added and electrolyzed at a concentration of 0.016 g. When we investigated the sulfur distribution in the electrolytic nickel obtained as a result, we found that the average S content was 0.013% by weight, but in the lower corner, it was 0.014% by weight on the liquid supply side and 0.017% by weight on the opposite side.
It was hot. Reference Example 1 In order to compare the electrodeposition strain that occurs in the electrodeposited nickel when producing sulfur-containing electrodeposited nickel by carrying out the present invention with the electrodeposition strain that occurs when other sulfur sources are used, spiral ( It was measured using a helical torsion spring type electrodeposition stress meter. A test electrolytic solution having the same composition as that used in Example 1 was prepared, and a predetermined sulfur source was added thereto. An electric nickel plate was used as the anode, cathode current density 2A/dm ² , electrolysis temperature 55
Electrolyze at ~60℃ and use a cathode spiral plate (width b = 13
mm, thickness s = 0.2 mm), the spiral elasticity k・Kg・mm/degree twist angle α degrees and electrodeposited film thickness dmm were measured, and the electrodeposition stress σKg/ mm ² was calculated and shown in Table 2. σ=2·k·α/b·s·d Note that the numerical value of the electrodeposition stress was calculated by obtaining data for an electrodeposited film thickness of around 20 μm and correcting it as a film thickness of 20 μm. As shown in Table 2, the addition of tetrathionate is superior to thiosulfate in terms of electrodeposition stress;
It was found that the results were equivalent to or better than those without additives.

[Table] Reference Example 2 The electrolytic nickel containing 0.019% by weight of sulfur obtained in Example 1 was anodically polarized at a potential increase rate of 0.15V/mm.
It was measured by the potentiostatic method. The electrolyte is nickel sulfamate 450g/and H ₃ BO ₃ 30g/
It is a sulfamic acid bath with a pH of 4.0.
The liquid temperature was 50°C. As a result, this sulfur-containing electrolytic nickel enters the active dissolution region from 0.25V (vs. SCE), and the amount of electricity in that region is 88 coulombs/d.
It was ^m2 . From the above, the method of the present invention can uniformly contain a desired amount of sulfur, have a small electrodeposition strain comparable to or lower than that of electrolytic nickel that does not contain sulfur, is difficult to peel off, and has excellent anodic solubility. It can be seen that sulfur-containing electrodeposited nickel can be stably produced.

Claims (1)

[Claims] 1. A nickel pine or coarse nickel anode,
A method for producing sulfur-containing electrolytic nickel using a metal nickel plate cathode and an electrolytic bath of a sulfate-chloride mixture or single chloride containing a sulfur-containing compound, using a tetrathionate as the sulfur-containing compound, and A method for producing sulfur-containing electrolytic nickel characterized by flowing a reverse current for a short period of time prior to electrolysis.