JP2002004094A - Nickel-tungsten alloy electrode and method of manufacturing the same - Google Patents

Abstract

(57) [Problem] To provide a nickel-tungsten alloy electrode suitable for use as an anode for electroplating a nickel-tungsten alloy. SOLUTION: An electrode used as an anode for nickel-tungsten alloy plating, which contains 50 to 80% by weight of nickel and the balance is substantially tungsten. This alloy anode electrode is composed of 50 to 80% by weight of nickel powder and 20 to 5%.
A step of mixing 0% tungsten powder, a step of forming the obtained mixed powder into a predetermined shape, and a step of sintering the obtained molded body at 1000 to 1300 ° C. in a non-oxidizing atmosphere. Manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nickel-tungsten alloy electrode suitable for use as an anode for electroplating a nickel-tungsten alloy.

[0002]

2. Description of the Related Art Nickel-tungsten (Ni-W) alloy plating is high in hardness and excellent in abrasion resistance and corrosion resistance. Therefore, industrial products such as molding dies, casting molds and rolls, and electronic parts. It is used for plating small items such as ornaments. In this Ni-W alloy plating, conventionally, a salt such as sodium tungstate or ammonium tungstate has been used as a tungsten component in a plating solution.

When the pH of the plating solution becomes acidic at 4 or less, the solubility of the tungstic acid is remarkably reduced.
To about 12 is maintained. On the other hand, nickel ions and the like, which are alloy plating components of the plating solution, form hydroxides and precipitate in this pH range. For this reason, an organic complexing agent is added to the plating solution in order to complex tungstate ions and nickel ions so as to stably exist in the plating solution. As the complexing agent, sodium, potassium, ammonium salts such as citric acid, malonic acid and tartaric acid are used.

On the other hand, in the electroplating of a tungsten alloy, electric nickel, platinum, stainless steel or the like is used for the anode. Since these anodes hardly dissolve in the plating process, when industrially performing continuous plating of nickel-tungsten alloy, nickel ions and tungsten ions in the plating solution are consumed with the deposition of the plating film, The concentration changes with the passage of the electrolysis time, and there is a problem that a change in the alloy composition of the plating film, cracking of the plating film, formation of pits, deterioration of physical properties of the plating film, etc. occur.

In the case of continuously performing electroplating of a tungsten alloy, it is necessary to supply nickel metal ions and tungstate ions consumed by depositing as a plating film to a plating solution. When an electric nickel electrode plate is used as the anode, it is possible to dissolve with a dissolution efficiency of 5 to 40%, but the potential becomes higher than the decomposition potential of an organic complexing agent such as citric acid on the nickel electrode, There is a problem in that the complexing agent is decomposed, and the decomposition products float in the plating solution, metal salts are precipitated in the plating solution, and defects such as pits and cracks occur in the plating film.

In order to promote the dissolution of the electric nickel anode in the plating solution, if the plating solution contains a halogen component such as chlorine, nickel can be dissolved in the organic complexing agent at a potential lower than the decomposition potential. . However, when a halogen component such as chloride is added to the plating solution, the internal stress of the Ni—W alloy plating film increases, and the plating deforms the product or cracks the plating film.

Further, when an insoluble anode such as stainless steel or a noble metal oxide electrode is used, nickel cannot be reinforced from the anode by electric melting, and the plating time must be reduced in order to maintain the nickel ion concentration in the plating solution. Accordingly, nickel salts such as nickel sulfate must be replenished. In this case, irrelevant ions such as sulfate ions are accumulated in the plating solution according to the replenishment, and when these are accumulated in the plating solution,
Defects in the plating film due to an increase in the viscosity of the plating solution and precipitation of a metal salt in the plating solution occur.

On the other hand, as a method of replenishing the plating solution with tungstate ions, a sodium salt or an ammonium salt of tungstic acid is used. JP-A-63-20380
No. 0 describes a replenishment method using a mixed solution of ammonium paratungstate and citric acid, particularly as a replenishment method for tungstate ions. In this case, sodium ion, ammonium ion, citrate ion and the like, which are components of the salt added for replenishment of tungstate ions, accumulate in the plating solution as replenishment. JP-A-4-
No. 214892 proposes an apparatus for continuous replenishment of tungstate, but this method still cannot avoid accumulation of ammonium salts and citrate decomposition products.

As described above, in the method of replenishing the nickel or tungsten component to the plating solution with chemicals, when a certain amount or more of sulfate ions, ammonium ions, sodium ions, etc., unrelated to the plating reaction, accumulate in the plating solution, Increases in viscosity and the precipitation of metal salts,
Variations in the composition and properties of the plating film, burning in a high current density region, and plating defects such as pits and cracks in the plating film occur. Therefore, the amount of replenishment with the chemical is limited to a certain amount, and the solution plated for a certain time must be discarded as an aging waste solution.

Further, as a method of replenishing a nickel component to a plating solution, a method using a chemical such as nickel formate, and a method using a metal tungsten for replenishing a tungsten component are described in JP-A-11-229176. is there. In this case, since formic acid is decomposed at the anode, accumulation in the plating solution is not large. However, to keep the nickel concentration of the plating solution component constant in continuous plating,
It is necessary to frequently replenish nickel formate, and the composition of the plating solution fluctuates during that time.

As a method of simultaneously replenishing nickel and tungsten components consumed during plating from the anode,
Insoluble anode, soluble S-Ni anode (nickel electrode containing a small amount of sulfur of about 0.1%), soluble W anode
There is a method described in JP-A-11-341785 using two electrodes in combination. This method prevents decomposition of an organic complexing agent such as citric acid on the anode by installing an insoluble anode in an anode chamber using an ion exchange membrane,
The combination of the i-anode and the metal tungsten (W) anode keeps the plating solution composition constant. However, this method has a problem that the control is complicated because it is necessary to hold three types of electrodes in the plating tank and three currents must be controlled by three types of power sources.

[0012]

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention improves a conventional method for continuously replenishing nickel and tungsten components in a plating solution lost during plating, and is suitable for electroplating. It is an object of the present invention to provide a soluble nickel (Ni) -tungsten (W) alloy anode that can be used and a method for producing the same.

[0013]

In order to solve the above problems, the present invention provides the following anode electrode. First,
The nickel-tungsten alloy electrode according to the present invention is an electrode used as an anode for nickel-tungsten alloy plating, and contains tungsten in a weight ratio of 20 to 50.
%, And the balance is substantially nickel. In addition, the method for producing a nickel-tungsten alloy electrode according to the present invention includes a step of mixing nickel powder having a weight ratio of 50 to 80% and a tungsten powder having a weight ratio of 20 to 50%; And molding the obtained molded body in a non-oxidizing atmosphere at 1000 to
And a step of sintering at 1300 ° C. to obtain a sintered nickel-tungsten alloy electrode.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below. The anode electrode of the present invention is made of an alloy of nickel and tungsten. In this case, when the composition ratio of nickel and tungsten matches the target alloy composition of the plating film, the amount of nickel ions and tungstate ions lost during plating can be balanced.

The nickel-tungsten alloy electrode is
It can be manufactured by powder metallurgy. To exemplify this production method specifically, first, nickel powder and tungsten powder, which are raw materials, are mixed at a predetermined ratio, mixed by a mixer or the like, and the obtained alloy powder is subjected to pressure molding using a mold. The obtained molded body is pre-sintered at a temperature of 400 to 700 ° C. in a non-oxidizing atmosphere, for example, a reducing atmosphere such as hydrogen gas, and then heated and sintered at a predetermined temperature in a non-oxidizing atmosphere (even in a vacuum). Main sintering). The obtained sintered body is subjected to necessary processing such as cutting, grinding, and the like to obtain a product.

The particle size of the raw material powder is a particle size generally used in powder metallurgy, and is usually several microns to several tens of microns. The molding pressure is a pressure at which a molded body having a desired strength is obtained, and usually may be 0.2 t / cm ² or more. If the sintering temperature is less than 900 ° C., sintering is insufficient, and the powders are not sufficiently bonded. If the sintered body manufactured under such conditions is used as an anode for electroplating, black slime is generated on the electrode surface and slime is diffused into the plating solution, which is not preferable. Further, alloying of nickel powder and tungsten powder is insufficient, and selective dissolution of nickel occurs, so that the anode dissolution ratio of nickel and tungsten cannot be kept constant. Therefore, the main sintering temperature needs to be at least 900 ° C. or more, and preferably 1000 ° C. or more.

On the other hand, when the sintering temperature exceeds 1300 ° C., the alloy particles become coarse, so that the anodic melting shows a limiting current density, and in a potential region exceeding this, decomposition of the organic complexing agent occurs. Therefore, it is not preferable. Therefore,
As a condition for producing a nickel-tungsten alloy anode for plating an electric nickel-tungsten alloy, it is preferable that the main sintering temperature be in the range of 1000 to 1300 ° C.

For continuous plating using a nickel-tungsten alloy anode, the current flowing through the two anodes, the alloy anode and the insoluble anode, is controlled according to the deposition reaction of the plating film. The components can be continuously supplied, and a nickel-tungsten alloy plating film having a stable composition and quality can be obtained. As the insoluble anode, those having a structure separated by a known stainless steel electrode and an ion exchange membrane can be used. The current operation is, for example, if the deposition current efficiency is 60% in a plating film containing 40% by weight of tungsten, the current of 40% corresponding to hydrogen generation is supplied to the insoluble anode, and the remaining 60% of the current is supplied to the nickel-tungsten alloy. Only a connection to the anode is required, and a simpler device for controlling the current of each of the metal nickel electrode and the metal tungsten electrode and current management are sufficient.

The composition of the alloy anode is manufactured according to the composition of the alloy plating film, this is used in combination with the insoluble anode, and the current is controlled according to the deposition efficiency of the plating film.
It is possible to continuously obtain a nickel-tungsten alloy plating film having a desired composition while keeping the plating solution concentration constant.

[0020]

Hereinafter, the features of the present invention will be described more clearly with reference to examples and comparative examples of the present invention. In each of the following Examples and Comparative Examples, first, tungsten powder and nickel powder were blended so as to obtain a nickel-tungsten alloy anode having a desired composition, and mixed by a mixer. Thereafter, the mixed powder was pressed into a predetermined shape using a mold.
The obtained molded body is pre-sintered at 700 ° C. for 1 hour in a reducing atmosphere containing hydrogen, and then heated at a predetermined temperature in the same atmosphere.
The nickel-tungsten alloy anode was obtained by sintering for a certain time. The solubility characteristics of the obtained nickel-tungsten alloy anode were measured in a 0.2M ammonium citrate solution by using a solution pH.
6.0, solution temperature 65 ° C, anode current 160mA, dissolution time 1
The anode was melted under a constant condition of 800 seconds, and the amount of the alloy anode melted was examined by ICP. Also, the anodic current density in a nickel-tungsten alloy plating solution (plating solution composition: 0.2 M nickel sulfate, 0.2 M sodium tungstate, 0.4 M ammonium citrate, solution pH 6.0, bath temperature 65 ° C.) The potential was evaluated using a potentiostat.

Example 1 Nickel-tungsten alloy anodes were manufactured under various conditions by changing the amount of nickel, forming pressure, sintering temperature, etc., and the current efficiency of anode melting and the amount of melting (Ni
Table 1 shows the results obtained by examining the ratios.

[0022]

[Table 1]

The dissolution efficiency of the embodiment of the present invention is about 100% as shown in Table 1. Further, in the positive polarization in the plating solution (potential is applied to the anode side), +0.8 V (vs. Ag / A) which is a potential at which decomposition of citric acid occurs.
gCl) showed an anode current density of 4 A / dm ² or more, and the nickel-tungsten alloy anode could be dissolved without decomposing citric acid. EDX
When the electrode surface was observed using a scanning electron microscope attached to the analyzer, the nickel powder and the tungsten powder were uniformly alloyed, and no selective dissolution of the alloy components was observed. After dissolution, the electrode surface turned gray, but no slime was formed. Even if the amount of tungsten changes, if the sintering temperature is maintained properly, the anodic solubility of the alloy anode is good, the melting efficiency is 90-105%, and the error of the molten metal ratio is about 5%. I knew I could do it.

(Comparative Example 1) With respect to alloy anodes of various compositions manufactured under different manufacturing conditions (forming pressure, sintering temperature) from the above, the dissolution amount of the alloy anode in a citric acid solution and the amount of each metal component in the alloy anode Table 2 shows the results of examining the anode dissolution efficiency and the metal ratio.

[0025]

[Table 2]

The melting efficiency of the nickel-tungsten alloy anode manufactured at a sintering temperature of 900 ° C. or lower is 115% or more as shown in Table 2, and the difference between the dissolved tungsten component ratio and the composition of the manufactured alloy anode is as follows. Was 5% or more. Slime composed of black fine particles was observed on the electrode surface after dissolution, and the slime was also found to fall off in the solution. When the electrode surface was observed using a scanning electron microscope attached to an EDX analyzer, the alloying of the nickel powder and the tungsten powder was not uniform, and the nickel-enriched region was selectively melted by anodic spraying. The melting efficiency of the nickel-tungsten alloy anode produced at the main sintering temperature of 1400 ° C is 6
The dissolution potential was 0% or less, indicating a potential of +1.5 V or more, which was higher than the decomposition potential of citric acid. Observation of the electrode surface using a scanning electron microscope attached to the EDX analyzer revealed that the nickel powder and the tungsten powder were sufficiently alloyed, but the alloy particles were large in size and were in a molten state with huge pits.

[0027]

As is apparent from the above description, the nickel-tungsten alloy electrode according to the present invention is suitable for use as an anode for electro-nickel-tungsten alloy plating, and can be subjected to continuous plating. It is. Further, according to the manufacturing method of the present invention, a nickel-tungsten alloy electrode having preferable performance can be easily manufactured.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masayuki Yokoi 2-7-1, Ayumino, Izumi-shi, Osaka Inside the Osaka Prefectural Institute of Advanced Industrial Science and Technology (72) Inventor Takuo Nakade 2-7-1, Ayumino, Izumi-shi, Osaka No. 1 Inside the Osaka Prefectural Institute of Industrial Science and Technology (72) Yukihiro Sato 2-7-1, Ayumino, Izumi-shi, Osaka Prefecture Inside the Osaka Prefectural Institute of Industrial Science and Technology (72) Inventor Naoyoshi Akiyoshi 26 Ikeda-Nishimachi, Neyagawa-shi, Osaka −5 Toho Metal Co., Ltd. Technology Development Department (72) Inventor Shuji Kobayashi 26-5 Ikeda Nishimachi, Neyagawa-shi, Osaka Toho Metal Co., Ltd. Technology Development Department

Claims (3)

[Claims] 1. An electrode used as an anode for plating a nickel-tungsten alloy, comprising nickel in a weight ratio of 50 to 80%, and the balance being substantially tungsten. Alloy electrode. 2. The nickel-tungsten alloy electrode according to claim 1, wherein the nickel content is 60 to 70% by weight. 3. a step of mixing 50 to 80% by weight of nickel powder and 20 to 50% of tungsten powder by weight;
A step of molding the obtained mixed powder into a predetermined shape, and a step of molding the obtained molded body in a non-oxidizing atmosphere at 1000 to 1300 ° C.
And obtaining a sintered nickel-tungsten alloy electrode through a step of sintering.
Manufacturing method of tungsten alloy electrode.