JPH05255884A - Method for repairing stainless steel cathode plate for electrolysis of copper - Google Patents

Abstract

PURPOSE:To repair the stainless steel cathode plate for electrolysis of copper, the surface of which is corroded and discolored by repetitive use and has problems in use so that the cathode plate can be used in a good condition. CONSTITUTION:The stainless steel cathode plate for electrolytic refining of copper, such as stainless steel base plate used for production of a seed plate for electrolytic refining of copper and stainless steel cathode plate used for electrolytic refining of copper or electrolytic sampling of copper, is immersed for 30 seconds to 3 minutes in an aq. soln. contg. 3 to 10wt.% hydrochloric acid and 0.3 to 1.0wt.% hydrogen peroxide and is then subjected to a passivation treatment, by which the cathode plate is reproduced and repaired so as to be well usable.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a stainless steel base plate used for producing a seed plate used as a cathode for copper electrolytic refining and a stainless steel cathode used for copper electrolytic refining and copper electrowinning. The present invention relates to a method for repairing a stainless cathode plate for copper electrolysis.

[0002]

2. Description of the Related Art A stainless steel plate is used as a mother plate for producing a seed plate used as a cathode for electrolytic copper refining and a cathode plate for copper electrolytic refining or electrowinning because of its touch resistance and workability. There is. The mother plate and the cathode are repeatedly used by peeling off the electrodeposited copper plate. However, as the number of times of repeated use increases, corrosion or discoloration of the surface thereof progresses, making it difficult to peel off the electrodeposited copper plate or causing electrodeposition failure, making it difficult to reuse.

In order to be able to favorably reuse this, in actual operation, the mother plate and the above-mentioned cathode (hereinafter, these stainless steel cathode plates for copper electrolysis are referred to as "repair") on a regular basis or each time as "repair". The surface of a mother board, etc.) is polished.
For this polishing, a manual polishing using sandpaper or a sandblasting method is usually adopted.

However, these methods have the following drawbacks. For example, in the method using sandpaper, it is necessary to install a local hood or other dustproof equipment or wear a protective mask in order to prevent the worker from inhaling the generated abrasive powder, etc., because the polishing work itself is done manually. Not only is it necessary, but the roughness of the obtained surface varies, and a surface having a uniform roughness cannot be obtained. Further, in the case of sandblasting, not only the installation of dustproof equipment and the wearing of a protective mask as described above are indispensable, but also the work place itself needs to be isolated, and the obtained surface becomes rough. However, the unevenness of roughness tends to increase, and when the obtained mother plate or the like is operated, the electrodeposited copper plate spontaneously peels or the peeling becomes difficult.

As described above, the conventional repairing method requires not only the installation of at least some dustproof equipment and the wearing of a protective mask, but also the work efficiency is poor, and a sufficient repair result is always obtained. There wasn't.

[0006]

DISCLOSURE OF THE INVENTION The present invention is intended for repairing a mother plate or the like, and when the mother plate or the like is used, the produced electrodeposited copper plate keeps a good appearance and does not naturally peel off from the mother plate or the like. Another object of the present invention is to provide a repairing method capable of easily and stably obtaining a mother board or the like that can be easily peeled off from the mother board.

[0007]

SUMMARY OF THE INVENTION In the present invention, a mother board or the like whose surface is corroded or discolored is treated with 3-10% by weight of hydrochloric acid and 0.3-1.
After being immersed in an aqueous solution containing 0% by weight of hydrogen peroxide for 30 seconds to 3 minutes, a passivation treatment is performed.

The passivation treatment is carried out by a conventional method such as nitric acid treatment, potassium dichromate potassium nitric acid solution treatment, hydrofluoric acid nitric acid solution treatment, electrolytic cleaning (anodic oxidation) and the like.

[0009]

According to the treatment of the method of the present invention, the surface roughness of the mother plate or the like ensures that the copper is electrodeposited more reliably than the case where the passivation treatment is performed after the etching treatment using another etching agent, Moreover, the surface of the mother plate or the like can be uniformly formed with a roughness that allows easy peeling.

The present invention will be further described with reference to the following study examples. (1) Kind of treatment liquid The present invention is basically based on etching of a stainless steel surface. Therefore, it seems that there is no problem as long as the treatment liquid can etch the stainless steel surface. However, in order to solve the problem of the present invention, a proper degree of etching is just needed. Therefore,
It does not mean that anything that can be etched is acceptable. The following studies were conducted for the purpose of confirming this point and selecting the most suitable processing solution.

A test base plate made of stainless steel (thickness: 3 mm, width: 20) whose surface is discolored by repeating energization
0 mm, length 220 mm, effective area 170 x 190 mm
The effective part of ² ) is cut out and divided into four to make four sample pieces, and one sample piece is immersed in each of the four types of treatment liquids shown in Table 1 for 3 minutes, washed with water, and washed with ethanol, and then a hair dryer. The sample piece was dried with and the surface condition was observed. As a result, the discoloration cannot be removed with the treatment liquid A, uneven pickling occurs with the treatment liquid B, and cracks occur in the treatment liquid C from the edges toward the inside of the surface, which is good for the first time with the treatment liquid D of the invention. The surface was obtained. This can be said to indicate the effectiveness of the mixed solution of hydrochloric acid and hydrogen peroxide.

[0012]

[Table 1] Treatment liquid Preparation conditions ────────────────────────────── Treatment liquid A 98% concentrated sulfuric acid, 35 % Treatment solution obtained by mixing 1% by volume hydrogen peroxide solution at a ratio of 1: 1 Treatment solution B 61% concentrated nitric acid, 36% concentrated hydrochloric acid, 98% concentrated sulfuric acid, 6.5% by volume Treatment liquid obtained by mixing at a ratio of 2: 1 Treatment liquid C 61% concentrated nitric acid, 36% concentrated hydrochloric acid, water and phosphoric acid in a weight ratio of 0.5: 0.2: 3: Treatment solution in which acetic acid was added at a rate of 0.5 mol per 1 liter of the solution obtained by mixing at a rate of 0.5 Treatment solution D Water was treated with 5 wt% hydrochloric acid and 0.6 wt% peroxide. Treatment liquid containing hydrogen and

(2) Effects of Hydrochloric Acid Concentration and Hydrogen Peroxide Concentration From the above results, it was found that a mixed aqueous solution of hydrochloric acid and hydrogen peroxide was effective in solving the problems of the present invention, but hydrochloric acid and hydrogen peroxide were used. It is expected that the surface condition after repairing will differ depending on the concentrations of and. Therefore, the treatment liquid obtained by combining the hydrochloric acid concentration and the hydrogen peroxide concentration shown in Table 2 has (1)
Similarly to the above, the sample piece obtained by cutting the effective area portion of the test mother plate discolored by use into nine pieces was immersed for 1 minute, and then the surface of the sample piece was observed in the same manner as (1). The results are also shown in Table 2. From this result, the surface of the mother board after the treatment is improved by using the treatment liquid prepared by adding 3 to 10% by weight of hydrochloric acid and 0.3 to 1.0% by weight of hydrogen peroxide to water. Understand.

[0014]

[Table 2] No. Hydrochloric acid concentration Hydrogen peroxide concentration Appearance of mother board after treatment No. (wt%) (wt%) ──────────────────────── ──── 1 15 0.6 Coarse 2 10 0.6 Good 3 5 0.6 Good 4 3 0.6 Good 5 5 10.6 Inadequate pickling 6 5 1.5 Uneven pickling 7 5 1. 0 Good 8 5 0.3 Good 9 5 0.1 Insufficient pickling

Next, the numbers 1, 2, 3, 4, 7, in Table 2
After repairing the discoloration-requiring mother board required for actual operation under the conditions of No. 8, each mother board was immersed in a 20% by weight nitric acid solution for 30 minutes to passivate it, and then under the following electrolysis conditions: Copper electrolysis was performed for a period of time to produce a seed plate, the appearance of which was observed, and then the seed plate was peeled from the mother plate, and the peelability and the appearance of the mother plate after peeling were observed. As a result, the seed plate obtained using the mother plate repaired under the condition of No. 1 was a defective product, and the seed plate was difficult to peel off, and stains were formed on the surface of the mother plate after peeling. However, the appearance of the seed plate obtained by using the mother plate repaired under the other conditions of Nos. 2, 3, 4, 7, and 8 is good, and it does not fall spontaneously during or after electrolysis, Has good peelability,
The surface of the mother board after peeling was also good, and the mother board could be used repeatedly.

Electrolysis conditions Electrode spacing (anode center to cathode center) 105 mm Current density 220 A / m ² Electrolyte temperature 60 ° C. Electrolyte composition Copper 46 g / l Free sulfuric acid 190 g / l glue 80 g / Electrodeposited copper t Thiourea 60 g / electric Copper deposition t Hydrochloric acid 30 mg / l Anode Casting anode Cathode SUS304L Thickness 3 mm Effective area (one side) 1070 × 1050 mm

(3) Treatment time Next, using an aqueous solution containing 5% by weight of hydrochloric acid and 0.6% by weight of hydrogen peroxide, the effectiveness of the test mother plate discolored by use in the same manner as in (1) The area portion was cut into 12 pieces, and the effect of the immersion time was examined using 10 of the sample pieces. That is, the sample piece is immersed in the treatment liquid for a predetermined time, washed with water,
The surface of the sample piece that had been washed with ethanol and dried with a hair dryer, and the sample piece that had been washed with water and then immersed in a 20 wt% nitric acid aqueous solution for 30 minutes to passivate, washed with water, washed with ethanol, and dried with a hair dryer The surface was observed and compared. The results are shown in Table 3 including the conditions.

[0018]

[Table 3] Number Pickling time Presence or absence of passivation treatment Appearance of mother board after treatment ────────────────────────────── 10 5 minutes Yes No pickling unevenness 11 5 minutes No pickling unevenness 12 4 minutes Yes No pickling unevenness 13 4 minutes No No pickling unevenness 14 3 minutes Yes Good 15 3 minutes No Good 16 2 minutes Yes Good 17 2 minutes No Good 18 1 min Yes Good 19 1 min No Good 20 30 seconds Yes Good 21 30 seconds No Good 22 20 seconds Yes No cleaning 23 20 seconds No cleaning Not enough

Next, an actual discoloring mother plate requiring repair was treated under the conditions of Nos. 10 to 21 in Table 3, copper electrolysis was performed in the same manner as in (2) below to obtain a seed plate, and its appearance was observed. Then, the seed plate was peeled from the mother plate, and the peelability and the appearance of the mother plate after peeling were observed. The results are shown in Table 4.

[0020]

[Table 4] Number Seed board appearance Appearance of mother board after seed board peeling Seed board peelability ───────────────────────────── ─── 10 Pinhole Yes No abnormality Spontaneous peeling 11 Smooth discoloration occurrence spontaneous peeling 12 Pinhole Yes No abnormality Natural peeling 13 Sudden discoloration occurrence Spontaneous peeling 14 No abnormality No abnormality Good 15 Electroplating failure Discoloration occurrence Good 16 No abnormality Abnormal None Good 17 Electro-deposition failure Discoloration occurrence Good 18 Abnormality Abnormality None Good 19 Abnormality Stain Existence Good 20 Abnormality Abnormality None Good 21 Scrape discoloration Occurrence good

From the above results, it is possible to easily and stably obtain a mother plate that can be repeatedly used by immersing the mother plate in the treating solution having the composition of the present invention for 30 seconds to 3 minutes and then passivating the mother plate according to a conventional method. You can see that

As mentioned above, when repairing the mother board, etc., it is immersed for 30 seconds to 3 minutes in an aqueous solution containing 3 to 10% by weight of hydrochloric acid and 0.3 to 1.0% by weight of hydrogen peroxide. Then, if passivation treatment is performed according to a conventional method, the mother plate that can be used repeatedly can be easily regenerated without requiring dust removal equipment.

[0023]

EXAMPLE In order to confirm the effect of the present invention, one of three new mother boards of the same lot (A) was immersed in 3% by weight hydrochloric acid and 0.6% by weight aqueous solution for 3 minutes. Then, wash it with water, wash it with ethanol, and dry it with a drier. Manually polish one sheet (B) with sandpaper # 180 for 20 minutes, and one sheet (C) for sandblasting made by Ube Industries, Ltd. Sandblasting using stone, average surface roughness Ra (μm) and range R before and after repair at 100 points selected to be as evenly spaced as possible on the surface of the mother board
R ′ was compared. The results obtained are shown in Table 5.

[0024]

[Table 5] Average surface roughness Ra (μm) Treatment method Before repair After repair Average value R Average value R ′ ───────────────────────── ── (A) 0.48 0.16 0.38 0.13 (B) 0.45 0.14 0.18 0.05 (C) 0.38 0.17 3.25 2.35

From Table 5, it can be seen that the surface roughness is greatly reduced by sandpaper repair, and there is a high risk of spontaneous fall.
It can be seen that repairing by sandblasting often results in excessive surface roughness, making it difficult to separate from the seed plate. Further, it can be seen that if the method of the present invention is used for repair, the surface roughness that is not so different from that before the treatment can be maintained. Therefore, if the mother plate or the like is repaired by the method of the present invention, good surface roughness can be maintained, so that the period required from repair to re-repair can be extended, and the life of the mother plate or the like as a whole can be improved. It can be seen that the extension of

[0026]

The repair method of the present invention does not require any special dust removing equipment and is simple, so that work efficiency can be improved and repair work can be reduced, and the mother board repaired by the method of the present invention Electrodeposited copper plate obtained by using such as not only spontaneous peeling from the mother plate and the like, while maintaining a good appearance, not only can be easily peeled off from the mother plate, the repair method of the present invention Since the surface roughness of the mother plate is kept optimal, the life of the mother plate can be extended.

Claims (1)

[Claims] 1. A stainless steel cathode plate whose surface is corroded or discolored is used in an amount of 3 to 10% by weight of hydrochloric acid and 0.3 to 1.0% by weight.
The method for repairing a stainless steel cathode plate for copper electrolysis, which comprises immersing in an aqueous solution containing hydrogen peroxide for 30 seconds to 3 minutes and then passivating the solution.