Method for producing specially shaped electric nickel

Abstract

To provide a method for producing special shape electric nickel capable of reducing the generation rate of connection defects.SOLUTION: The method for producing the special-shaped electric nickel includes an electrowinning step of performing electrowinning while supplying an electrolyte which is an aqueous nickel chloride solution to an electrolytic cell in which a cathode and an anode obtained by covering the surface of a metal plate with an insulating layer except a plurality of electrodeposition parts are inserted. The pH and nickel concentration of the electrolytic feed solution in the electrowinning step satisfy the following formula (1). Y ≤ -0. 003X + 3.43 (1) wherein Y is the pH of the electrolyte solution, and X is the nickel concentration [g / L] of the electrolyte solution.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for producing specially shaped electrolytic nickel. More specifically, the present invention relates to a method for producing specially shaped electrolytic nickel by electrowinning using a mother plate masked with an insulator. [Background technology]

[0002] In the electrowinning of nickel, a commonly used method is to use a metal plate made of a reusable material other than nickel as a cathode, perform electrolysis for a predetermined time, and then peel off the electrodeposit from the metal plate and recover it. In this case, by masking the surface of the metal plate with an insulating material except for the electrodeposit, electrodeposits of any special shape can be obtained.

[0003] The electrolytic nickel used as an anode for electroplating is preferably in the shape of a small, rounded lump (e.g., hemispherical or disk-shaped) without sharp corners, from the viewpoints of ease of filling into the anode box of an electrolytic plating apparatus and ease of handling. In order to produce such hemispherical or disk-shaped electrolytic nickel by electrowinning, electrolysis is carried out using a cathode (mother plate) in which the surface of a metal plate is masked with an insulator while leaving a large number of circular electrodeposited portions as described above (e.g., Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-108592 Summary of the Invention [Problem to be solved by the invention]

[0005] In the production of specially shaped electrolytic nickel, multiple adjacent electrodeposits may connect to each other. Electrodeposits in which multiple electrodeposits are connected are defective products, and this defect is called poor connection. Defective products with poor connection are remelted and cannot be used as products. Therefore, if the defect rate increases, production efficiency decreases and manufacturing costs increase.

[0006] In view of the above circumstances, the present invention aims to provide a method for producing specially shaped electrolytic nickel that can reduce the incidence of poor connection. [Means for solving the problem]

[0007] The method for producing special-shaped electrolytic nickel of the first aspect comprises an electrowinning step of electrowinning while supplying an electrolytic solution, which is an aqueous nickel chloride solution, to an electrolytic cell in which a cathode and an anode, each of which is covered with an insulating layer except for a plurality of electrodeposited portions on the surface of a metal plate, are inserted, and the pH and nickel concentration of the electrolytic supply solution in the electrowinning step satisfy the following formula (1): Y≦-0.003X+3.43 (1) Here, Y is the pH of the electrolytic feed solution, and X is the nickel concentration [g / L] of the electrolytic feed solution. The method for producing special-shaped electrolytic nickel of the second aspect is characterized in that, in the first aspect, the pH of the electrolytic feed solution is 3.2 or less. A third aspect of the method for producing special-shaped electrolytic nickel is characterized in that, in the first or second aspect, the nickel concentration of the electrolytic feed solution is 100 g / L or less. The method for producing special-shaped electrolytic nickel of a fourth aspect is characterized in that in any one of the first to third aspects, the pH and nickel concentration of the electrolytic feed solution in the electrowinning step satisfy the following formula (2). Y≧-0.02X+4.60 (2) Here, Y is the pH of the electrolytic feed solution, and X is the nickel concentration [g / L] of the electrolytic feed solution. [Effects of the Invention]

[0008] According to the present invention, the incidence of poor connection of specially shaped electrolytic nickel can be reduced. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. [Figure 2] 1 is a graph showing the relationship between the pH and nickel concentration of the electrolytic feed solution and the occurrence of poor connection and pinholes. DETAILED DESCRIPTION OF THE INVENTION

[0010] Next, an embodiment of the present invention will be described with reference to the drawings. A method according to one embodiment of the present invention is a method for producing specially shaped electrolytic nickel. Specially shaped electrolytic nickel refers to electrolytic nickel of any shape, such as a hemispherical or discoidal shape, obtained without cutting, as opposed to the rectangular electrolytic nickel obtained by cutting a plate-shaped electrodeposit into a lattice shape.

[0011] Special-shaped electrolytic nickel is obtained by electrowinning (electrowinning process). Generally, electrolysis equipment has multiple electrolytic cells. Electrolysis equipment also has a liquid feed adjustment equipment. The liquid feed adjustment equipment is supplied with a nickel chloride aqueous solution from the equipment in the previous process. The liquid feed adjustment equipment adjusts the nickel chloride aqueous solution to the desired pH by adding an alkali such as sodium hydroxide or an acid such as hydrochloric acid. The liquid feed adjustment equipment also adjusts the nickel concentration by concentrating or diluting the nickel chloride aqueous solution.

[0012] The nickel chloride aqueous solution, whose pH and nickel concentration have been adjusted in the feed solution adjustment equipment, is continuously supplied to the electrolytic cell as the electrolyte. The electrolyte discharged from the feed solution adjustment equipment and supplied to the electrolytic cell is called the electrolytic feed solution.

[0013] A plurality of anodes and a plurality of cathodes are inserted alternately in the electrolytic cell. An insoluble electrode equipped with an anode box is used as the anode. A mother plate 1 shown in FIG. 1 is used as the cathode. The mother plate 1 is a stainless steel or titanium metal plate 11 whose surface is covered with an insulating layer 13, leaving a plurality of electrodeposited portions 12. The metal plate 11 is rectangular, for example, 1,000 to 1,200 mm long and 800 to 900 mm wide. A beam 15 made of copper or a clad material containing copper is attached to the upper edge of the metal plate 11 via a hanger 14.

[0014] In the example shown in FIG. 1, a metal plate 11 is masked with a pattern in which numerous circular electrodeposited portions 12 are arranged in a staggered pattern. For example, the diameter of the electrodeposited portions 12 is 12 to 16 mm. The shortest distance between adjacent electrodeposited portions 12 is 5 to 6 mm. Both sides of the metal plate 11 are masked. The number of electrodeposited portions 12 on both sides of the metal plate 11 is 3,000 to 5,000. The shape of the electrodeposited portions 12 is not limited to a circle, and may be other shapes such as an oval or a rectangle.

[0015] Electrowinning is carried out by passing a current between the anode and cathode. By passing a current for a predetermined time (for example, 4 to 10 days), electrolytic nickel is electrodeposited on the electrodeposit portion 12 of the base plate 1. If the shape of the electrodeposit portion 12 is circular, the electrodeposit grows into a button shape with a flat center and a raised periphery.

[0016] Electrowinning is performed under conditions that allow the electrodeposit to grow to the target size. Specifically, the operating conditions, such as the composition of the electrolyte, the current between the anode and cathode, and the duration of current application, are set so that the electrodeposit grows to the target size. For example, after electrowinning is complete, the electrodeposit is button-shaped, with a diameter of 16 to 19 mm and a thickness of approximately 5 mm.

[0017] After the specified time of application of electricity, the mother plate 1 is removed from the electrolytic cell. The mother plate 1 is vibrated by a method such as hammering to peel off the electrodeposit that has been electrodeposited on the mother plate 1. The electrodeposit that has been peeled off from the mother plate 1 is polished, washed, and dried to become a product.

[0018] In the electrowinning process, the shape of the nickel deposit becomes unstable depending on the pH and nickel concentration of the nickel chloride aqueous solution, which is the electrolyte. That is, even if the shape of the electrodeposit 12 is circular, the electrodeposit may not be button-shaped, and the shape of the electrodeposit may differ from the intended shape. As a result, adjacent electrodeposits may connect to each other, resulting in poor connection.

[0019] In order to suppress the occurrence of poor connection, it is preferable to adjust the pH and nickel concentration of the electrolytic feed solution in the electrowinning process to values ​​that satisfy the following formula (1). The pH and nickel concentration of the electrolytic feed solution can be adjusted using a feed solution adjustment facility. In this way, nickel can be electrodeposited into the desired shape, and the occurrence of poor connection in special-shaped electrolytic nickel can be reduced. Y≦-0.003X+3.43 (1) where Y is the pH of the electrolysis feed solution and X is the nickel concentration in the electrolysis feed solution [g / L].

[0020] Furthermore, the pH of the electrolytic feed solution is preferably 3.2 or less. By setting the pH of the electrolytic feed solution to 3.2 or less, the occurrence rate of poor connection of special-shaped electrolytic nickel can be reduced even in a region where the nickel concentration of the electrolytic feed solution is relatively low, ie, 70 g / L or less.

[0021] Furthermore, the nickel concentration of the electrolysis feed solution is preferably 100 g / L or less. If the nickel concentration of the electrolysis feed solution is too high, the viscosity of the electrolyte increases. If the viscosity of the electrolyte is high, the resistance to the passage of the electrolyte through the diaphragm in the anode box increases, resulting in a high electrolysis voltage. Furthermore, if the nickel concentration of the electrolyte is too high, the cathode is more likely to be passivated, and the resulting electrolytic nickel is likely to be brittle. These problems can be suppressed by keeping the nickel concentration of the electrolysis feed solution 100 g / L or less.

[0022] Incidentally, hydrogen gas may be generated on the surface of the cathode along with nickel deposition. In particular, in the production of special-shaped electrolytic nickel, a base plate 1 masked with an insulator is used as the cathode, which reduces the effective electrodeposition area and tends to increase the current density in the electrodeposited area 12. Furthermore, while the conductive surface of the anode is basically flat, the electrodeposited area 12 of the cathode is geometrically restricted by the insulator, which makes it easy for current to concentrate around the periphery of the electrodeposited area 12, resulting in high current density. This makes it easy for hydrogen gas to be generated. When electrodeposition occurs while trapping bubbles of the generated hydrogen gas, electrolytic nickel is produced, mainly with holes on the surface. This type of electrolytic nickel has an appearance defect known as a pinhole defect.

[0023] In order to suppress the occurrence of pinholes, it is preferable to set the pH and nickel concentration of the electrolytic feed solution in the electrowinning step to values ​​that satisfy the following formula (2). In this way, the generation of hydrogen gas can be suppressed, and the occurrence rate of pinholes in special-shaped electrolytic nickel can be reduced. Y≧-0.02X+4.60 (2) where Y is the pH of the electrolysis feed solution and X is the nickel concentration in the electrolysis feed solution [g / L]. [Example]

[0024] Next, an example will be described. An operation was carried out to manufacture special-shaped electrolytic nickel. A stainless steel plate measuring 1,090 mm in length and 830 mm in width was used as the mother plate. An insulating layer was formed on both sides of the stainless steel plate in a staggered pattern of 15 mm diameter electrodeposited circles. The number of electrodeposited areas was 2,021 on each side of the stainless steel plate (4,042 on both sides).

[0025] The cathode current density during electrolysis is set to 200-400A / m 2 The temperature of the electrolyte in the electrolytic cell was adjusted to 55 to 65°C. The electrolyte was an aqueous solution of nickel chloride. The pH and nickel concentration of the electrolytic feed solution were measured.

[0026] After 7-10 days of application of electricity, the mother board was removed and the electrodeposit was peeled off. 3-4 tons of produced electrodeposits were counted as one lot, and 10 kg of electrodeposit was extracted from each lot. Each 10 kg of electrodeposit was visually inspected by a human by comparing it with a limit sample. Electrodeposits in which two or more pieces were connected were judged to have poor connections. Electrodeposits in which 10 or more pinholes of 2 mm or larger were detected were judged to have pinhole defects. The entire lot in which 5% or more of the 10 kg of electrodeposits were found to have poor connections was judged to have poor connections (poorly connected lot), and the entire lot in which 5% or more of the pinhole defects were found was judged to have pinhole defects (poorly pinhole lot) and was rejected.

[0027] The above operation was repeated to investigate the relationship between the pH and nickel concentration of the electrolysis feed solution and the occurrence of poor connection and pinhole defects. The results are shown in Figure 2. The equation for approximation line 1 in the graph of Figure 2 is "Y = -0.003X + 3.43." In the region with a lower pH and lower nickel concentration than approximation line 1, the occurrence of poor connection was suppressed. This confirmed that the occurrence of poor connection can be reduced by adjusting the pH and nickel concentration of the electrolysis feed solution to values ​​that satisfy equation (1). Furthermore, in the region with a relatively low nickel concentration of 70 g / L or less, the occurrence of poor connection can be reduced by adjusting the pH of the electrolysis feed solution to 3.2 or less.

[0028] The equation for approximation line 2 in the graph of Figure 2 is "Y = -0.02X + 4.60". In the region of higher pH and higher nickel concentration than this approximation line, the occurrence of pinholes can be suppressed. This confirmed that the occurrence rate of pinholes can be reduced by setting the pH and nickel concentration of the electrolytic feed solution to values ​​that satisfy the above equation (2). [Explanation of symbols]

[0029] 1 Motherboard 11 Metal plate 12 Electroplating Department 13 Insulating layer 14 Hanging handle 15 Beam

Claims

1. The method includes an electrowinning step of electrowinning while supplying an electrolytic solution, which is a nickel chloride aqueous solution, to an electrolytic cell in which a cathode and an anode, each of which is covered with an insulating layer except for a plurality of electrodeposited portions on the surface of a metal plate, are inserted, The pH and nickel concentration of the electrolytic feed solution in the electrowinning step satisfy the following formula (1): A method for producing special-shaped electrolytic nickel. Y≦-0.003X+3.43...(1) Here, Y is the pH of the electrolytic feed solution, and X is the nickel concentration [g / L] of the electrolytic feed solution.

2. The pH of the electrolytic feed solution is 3.2 or less.

2. The method for producing specially shaped electrolytic nickel according to claim 1.

3. The nickel concentration of the electrolytic feed solution is 100 g / L or less.

2. The method for producing specially shaped electrolytic nickel according to claim 1.

4. The pH and nickel concentration of the electrolytic feed solution in the electrowinning step satisfy the following formula (2):

2. The method for producing specially shaped electrolytic nickel according to claim 1. Y≧-0.02X+4.60...(2) Here, Y is the pH of the electrolytic feed solution, and X is the nickel concentration [g / L] of the electrolytic feed solution.

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