JP2001158998A - Continuous plating method for ni-w alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow continuous plating without aging a plating liquid in electroplating of an Ni-W alloy. SOLUTION: A plating device of a two-tank structure separated to an anode chamber and a plating chamber by using a cation exchange membrane is used in the electroplating of the Ni-W alloy, by which the oxidation decomposition of an organic complexing agent contained in the plating liquid on anodes is suppressed. The nickel component and tungsten component in the plating liquid are replenished according to a deposition quantity by using the two soluble anodes of metal nickel and metal tungsten, by which the continuous plating is executed without aging the plating liquid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the formation of an electroplated Ni-W alloy having high hardness, excellent wear resistance and excellent corrosion resistance, and relates to thick plating of a forming die, a casting mold and a roll. The present invention provides plating films for industrial plating, electronic components, decorative small items, and the like.

[0002]

2. Description of the Related Art In an electroplating solution of a Ni--W alloy, salts of sodium or ammonium tungstate are used as a tungsten component. Since the solubility of tungstic acid is extremely low when the pH of the plating solution becomes acidic at 4 or less, the pH of the provided plating solution is maintained at about 5 to 12. 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 and to make them stably exist in the plating solution. As the organic complexing agent, sodium, potassium, ammonium salts such as citric acid, malonic acid and tartaric acid are used.

In the electroplating of a tungsten alloy, nickel, platinum, stainless steel or the like is used for the anode.
These anodes hardly dissolve during the plating process. Therefore, during plating, an oxidative decomposition reaction of an organic complexing agent such as citric acid and oxygen generation occur on the anode. In the oxidative decomposition of the organic complexing agent, carbon dioxide is generated by oxidation of the carboxyl group component, and the remaining portion is oxidized and aminated to produce an organic polymer having a complicated structure. When the organic complexing agent decomposes at the anode, the precipitation of tungstate due to a decrease in the concentration of the complexing agent in the plating solution and the resulting change in the alloy composition of the plating film, an increase in plating stress due to the accumulation of decomposition products, and plating Cracking of the film,
Since a defect such as a pit occurs, the plating solution after being electrolyzed for a certain period of time is disposed as an aging waste solution.

[0004] Therefore, a metal oxide anode has been developed as an anode for suppressing the decomposition reaction of the organic complexing agent in the plating process. Such an electrode is disclosed in
No. 03800, a noble metal oxide composed of an oxide of iridium and tantalum or an oxide of ruthenium and titanium is used. When these electrodes are used for tungsten alloy plating, it is said that the decomposition rate of the complexing agent in the plating solution can be reduced to 1/5 that of stainless steel electrodes.
However, these electrodes are complicated and expensive to fabricate, making it difficult to produce electrodes that maintain uniform electrode catalysis over the entire electrode surface.In addition, the performance of the oxide layer on the electrode surface deteriorates when continuous plating is used. And the problem of electrode life. Further, even if such a metal oxide electrode is used, the oxidative decomposition reaction of the organic complexing agent at the anode cannot be completely suppressed, and the life of the solution is only extended.

When a tungsten alloy is electroplated continuously, an insoluble anode is used. Therefore, a method of replenishing plating metal ions and tungstate ions consumed by deposition as a plating film is required. By using a nickel electrode for the anode, a nickel
Although it is possible to dissolve it with an efficiency of 40% to 40%, it is not desirable in continuous plating because the decomposition reaction of citric acid occurs at the nickel anode as described above. When using an insoluble anode, such as a stainless steel or a noble metal oxide electrode, in which it is difficult for citric acid to decompose, nickel is not supplied from the anode. For this reason, a nickel salt such as nickel sulfate must be supplied in accordance with the plating time. In this case, sulfate ions accumulate in the plating solution according to the plating time.

On the other hand, as a method for replenishing tungstate ions deposited as a plating film, sodium or ammonium salts of tungstate are used. JP 63
JP-203800 proposes a replenishment method using a mixed solution of ammonium paratungstate and citric acid, particularly as a replenishment method for tungstate ions. Also 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. In Japanese Patent Application Laid-Open No. 4-214892, a continuous replenishment device for tungstate is devised, but accumulation of ammonium salts and citrate decomposition products is inevitable. If sulfate ions, ammonium ions, sodium ions, etc. unrelated to the plating reaction accumulate in the plating solution in a certain amount or more, the viscosity of the plating solution increases, the precipitation of chemicals occurs, the composition and physical properties of the plating film change, and Plating defects such as burning, pits and cracks in the plating film occur in the current density region. For this reason, the replenishment of the metal salt is limited to a certain amount, and the solution plated for a certain time is discarded as an aging waste solution.

[0007] A method of adding a sacrificial anodizing agent such as formic acid, which is decomposed at a lower potential than the organic complexing agent at the anode, to the plating solution to reduce the decomposition rate of the organic complexing agent and prolong the bath life. Is Japanese Patent Application Laid-Open No. H11-229176.
There is a number. In this method, the decomposition of the organic complexing agent can be suppressed by the effect of the sacrificial anodic decomposition agent, but unless the anodic current density is kept in a low region of ^{2 A} / dm ² or less.
Decomposition of citric acid occurs. Since this current density is often difficult to achieve in a limited plating tank, it does not completely suppress the decomposition of the organic complexing agent. As a method of replenishing nickel, a chemical such as nickel formate containing a component of a sacrificial anodic decomposition agent is used. To maintain the nickel component in the bath, replenishment must be repeated frequently, and the plating solution composition during that time is required. And the work is complicated.

[0008]

As described above, in the electroplating of tungsten alloy, the organic complexing agent, which is a component of the plating solution, is not decomposed at the anode, and sulfate ions, sodium ions, and ammonium ions are supplied by chemical replenishment. It is necessary for the industrial use to establish a continuous plating method that does not accumulate.

SUMMARY OF THE INVENTION An object of the present invention is to provide a plating apparatus capable of preventing the oxidative decomposition of an organic complexing agent, which is an effective component of a plating solution, in order to overcome the above-mentioned drawbacks in the electroplating of a tungsten alloy. That is the task.
Also, to provide a continuous plating method that does not use a waste bath by replenishing metal ions in the case of continuous plating using a soluble anode so as not to accumulate sulfate ions, sodium ions, ammonium ions, and the like that are components of the replenishing solution. As an issue.

[0010]

According to the present invention, a cation-selective diaphragm is fixed between the anode and the plating chamber to prevent the insoluble anode such as stainless steel and platinum from coming into contact with the plating solution. A plating apparatus consisting of two tanks is used. As a diaphragm for blocking the plating solution and the anolyte, it is possible to use a membrane such as cellophane having selectivity of particle or molecule size, cloth or anion exchange membrane having ion selectivity, and cation exchange membrane. . In the present invention, the presence of the organic complexing agent such as citric acid in the Ni-W alloy plating solution is an anion, so that the anion does not pass through the cation exchange membrane as a selective membrane. This is used as a diaphragm between the anode chamber and the plating chamber.

When the anode compartment where the insoluble anode is located and the plating compartment are separated by a cation exchange membrane, anions of an organic complexing agent such as citric acid cannot pass through the cation exchange membrane. On the other hand, cations such as hydrogen ions can easily permeate the cation exchange membrane, and no large electrical resistance is generated by the diaphragm. By using the cation exchange membrane, direct contact between the insoluble anode and the plating solution is prevented, and the migration of anions of the plating solution to the anode chamber does not occur. Therefore, even when continuous plating is performed, the oxidative decomposition of the organic complexing agent, which is an effective component of the plating solution, on the anode can be completely prevented.

The solution components in the anode compartment include hydrochloric acid,
Nickel salts other than nitric acid and its salts or sulfuric acid can be used. Hydrochloric acid, nitric acid and its salts
It is not used because it generates harmful chlorine gas and nitric oxide gas on the insoluble anode. When a sulfate containing nickel is used, the anolyte gradually changes to dilute sulfuric acid due to the generation of oxygen on the insoluble anode. The hydrogen ions generated at the insoluble anode can pass through the cation exchange membrane according to the flow rate of the current and are carried to the plating chamber, so that the concentration of the anode chamber is kept constant. The volume of the anode chamber is p
A small one is desired so as not to affect H. Also,
The structure and arrangement of the insoluble anode are desirably a mesh structure in which the generated oxygen gas is quickly separated from the electrode and liquid movement is easy.

In the case of continuous plating using a plating tank using a cation exchange membrane, nickel ions in a plating solution are reduced by an electrodeposition reaction in a plating chamber. To replenish this, a metallic nickel anode is used. Examples of the metal nickel anode include plates and chips that can be used for known nickel plating such as electrolytic nickel and S-nickel. When chips are used, they are used in a titanium basket. Since the dissolution state of the nickel anode is cationic, the arrangement of the metal nickel electrode is as follows:
It may be arranged in either the plating chamber or the anode chamber. When an electrolytic nickel anode is used as the anode, a very small amount of chloride ions must be added to the plating solution so that nickel has an anode efficiency of 100%. S-
Nickel can be dissolved according to the amount of electricity supplied regardless of the presence or absence of chloride ions, so there is no need to add chloride.

Similarly, the concentration of the tungsten component in the plating solution is reduced by the incorporation into the plating film. As a method of replenishing the plating solution with tungstic acid, there is a method of replenishing a sodium salt or an ammonium salt of tungstic acid. However, as described above, when these salts are continuously supplied to the plating solution, sodium and ammonium ions accumulate in the plating solution. To prevent this, metal tungsten is used for the anode, and a tungsten component is supplied to the plating solution. A plate-shaped or chip-shaped tungsten anode is used. When chips are used, they are used in a titanium basket.

[0015] Using the above plating bath, metallic nickel,
To perform continuous plating using metal tungsten as the anode,
It is important to control the current flowing to each of the metal nickel, metal tungsten, and insoluble anode in accordance with the deposition reaction of the plating film. For example, 35 wt% of tungsten
If the deposition current efficiency of the plating film containing is 60%, the current according to the tungsten deposition amount of the plating film is applied to the tungsten anode, the current corresponding to the nickel deposition amount is applied to the nickel anode, and the remaining hydrogen generation amount is increased. A corresponding current must be passed through the insoluble anode. By changing this current value according to the plating film having an arbitrary composition obtained by Ni-W alloy plating, the ionic composition and pH of the plating solution in continuous plating can be kept constant. In Table 1,
The example of the current sharing ratio to each anode by the current efficiency of a plating film and tungsten content is shown.

[Table 1]

[0016] In the case where the plating solution is pumped out of the plating tank to a separate tank by a pump or the like, the metal nickel anode and the metal tungsten anode are electrolyzed to supply metal ion components and return to the original plating tank. Item 1 can be used.

[0017]

(Embodiment 1) The structure of a plating apparatus of Embodiment 1 will be described with reference to FIG. 1 is a plating room,
Reference numeral 2 denotes an anode chamber, and a cation exchange membrane 4 is provided in a hole 3 provided between the anode chamber 2 and the plating chamber 1. Reference numeral 5 denotes an insoluble anode, and a platinum titanium electrode, lead, platinum, a noble metal oxide electrode, or the like can be used. Reference numeral 6 denotes a metal nickel anode, which is a metal plate or a chip. When nickel is used as a chip, it is housed in a general titanium basket and used as an anode. The position of the metal nickel anode 6 can be set in either the plating chamber 1 or the anode chamber 2. Reference numeral 7 denotes a metal tungsten anode, which may be a metal plate, a metal chip, or the like. In the case of a metal chip, it is housed in a general titanium basket and used as an anode. 8 is a plated product. 9,10,1
Reference numeral 1 denotes an ammeter, which measures a direct current flowing through each of the anodes 5, 6, and 7, and measures 12, 13, and 14 so that the current becomes a calculated amount.
To control the DC power supply. The control of the direct current flowing through each of the anodes 5, 6, and 7 can reduce the number of power supplies by using a distributor and a resistor.

As a Ni-W alloy plating solution, 5 L of a plating solution of nickel sulfate 0.2 M, sodium tungstate 0.2 M, ammonium citrate 0.4 M and sodium formate 0.2 M was used. Continuous plating was performed using a plating apparatus. A DSA electrode (titanium plate with ruthenium oxide) was used for the insoluble anode, and the amount of liquid in the anode chamber was about 0.3 L. A titanium basket containing an S-nickel chip (about 100 g) was placed on the nickel anode, and a metal tungsten tip (about 100 g) was placed on the tungsten anode.
A titanium basket containing g) was used. Using a copper plate (area 0.5 dm ² ) for the cathode, which is a plated product, with a liquid temperature of 65
° C, pH 6.0, electricity amount 5A (plating current density 10A /
Continuous plating was performed under the plating conditions of dm ² ). When plating, the DSA electrode was charged according to the deposition efficiency of 2.2.
A, 1.8A for nickel electrode, 1.A for tungsten electrode.
Fine adjustment was made by passing a current of 0 A in accordance with the amount of deposition. During continuous plating, nickel chips and tungsten chips were appropriately supplied to each anode basket, and pure water was supplied to the anode chamber. Even after 100 hours of electrolysis, no off-flavor or precipitation was observed at all, and the fluctuation of the pH of the plating solution was 0.3 or less. The obtained plating film was stable with a W content of about 35 to 40% and a plating current efficiency of about 60% as shown in FIG. The dissolution efficiency of each of the nickel and tungsten anodes was about 102%. Also, the amount of citric acid in the plating solution did not decrease even after 100 hours.

(Comparative Example 1) As a Ni-W alloy plating solution, a plating solution of nickel sulfate 0.2M, sodium tungstate 0.2M and ammonium citrate 0.4M 0.5L was used. A copper plate was used as the cathode, the liquid temperature was 65 ° C., the pH was 6.0, the amount of electricity was 0.5 A (the plating current density was 10 A / dm ² , and the anode current density was 0.1 A / dm.
Continuous plating was performed under the plating conditions of ² ). Nickel sulfate and sodium tungstate were added to the plating solution every hour according to the amount of plating film deposited. For adjusting the pH of the bath, dilute sulfuric acid and aqueous ammonia were used. In the electrolysis for 2 hours, the plating solution turned yellow-green and further generated odor. After the electrolysis time of 15 hours, a precipitate was formed in the plating solution, the insoluble product floated in the plating solution, and the plating film composition could not be maintained. The obtained plating film had a W content of about 32 to 35% and an initial current efficiency of 58% as shown in FIG. 3, but increased to 65% after 15 hours. The citric acid concentration in the plating solution after 15 hours is
It decreased by about 20%.

(Comparative Example 2) As a Ni-W alloy plating solution, a plating solution 0.5L of nickel sulfate 0.2M, sodium tungstate 0.2M, ammonium citrate 0.4M and sodium formate 0.2M was used. A nickel plate for the anode, a copper plate for the cathode, continuous plating under the plating conditions of a liquid temperature of 65 ° C., a pH of 6.0, a current of 0.5 A (plating current density of 10 A / dm ² , anode current density of 0.1 A / dm ² ). Was done. To the plating solution, nickel formate and sodium tungstate corresponding to the amount of plating film deposited and formic acid corresponding to the calculated amount of formic acid decomposed at the anode were added every hour. For adjusting the pH of the bath, dilute sulfuric acid and aqueous ammonia were used. Odor generation was observed after 7 hours of electrolysis. The obtained plating film had a W content of about 35 as shown in FIG.
~ 40%, plating current efficiency about 60%, but stable
After time, the amount of citric acid in the plating solution had decreased by about 15%.

[0021]

As described above, according to the present invention, the use of a plating apparatus that separates the anode chamber and the plating chamber by a cation exchange membrane allows the organic complexing agent such as citric acid to be decomposed without decomposing the Ni complex. -W alloy plating becomes possible. In continuous plating, the plating composition and current efficiency can be stabilized by controlling the current flowing through the insoluble anode, nickel, and tungsten anodes using this apparatus, and the continuous plating can be performed without generating a waste bath. Can be plated.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a plating apparatus using a cation exchange membrane according to the present invention.

FIG. 2 is a graph showing a change over time in plating current efficiency, tungsten content, and citric acid concentration in a plating solution when continuous plating is performed by a plating apparatus using a cation exchange membrane according to the present invention.

FIG. 3 is a diagram showing, as Comparative Example 1 for the present invention, changes over time in current efficiency, tungsten content, and citric acid concentration in a plating solution in continuous plating using a normal plating apparatus.

FIG. 4 is a diagram showing, as Comparative Example 2 for the present invention, changes over time in the current efficiency, the tungsten content, and the concentration of citric acid in the plating solution in continuous plating using a sacrificial anodic decomposition agent.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plating chamber 2 Anode chamber 3 Hole 4 Cation exchange membrane 5 Insoluble anode 6 Nickel anode 7 Tungsten anode 8 Plating product 9-11 Ammeter 12-14 DC power supply

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[Procedure amendment]

[Submission date] July 7, 2000 (200.7.7)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Name of invention

[Correction method] Change

[Correction contents]

Patent application title: Continuous plating method of Ni-W alloy

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction contents]

[0009] The present invention has an object to overcome the aforementioned drawbacks in the electroplating of a tungsten alloy, it can prevent oxidation degradation of the organic complexing agent which is an active ingredient of plating solution, also continuous plating It is an object of the present invention to provide a continuous plating method that does not use a waste bath by replenishing metal ions in the case of using a soluble anode, so as not to accumulate sulfate ion, sodium ion, ammonium ion and the like which are components of the replenishing solution. .

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction contents]

[0016] Incidentally, pumping out a plating solution in a separate vessel by a pump or the like from the plating bath, where the even if the metallic nickel anode and metal tungsten anode electrolyte to replenish the metal ion component, such as back to the original plating tank Can be used.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction contents]

[0021]

According to the present invention described above, according to the present invention, by <br/> be partitioned between the anode chamber and plating chamber by a cation exchange membrane, without decomposing organic complexing agent such as citric acid, Ni can -W alloy plating and Do Ri, also, an insoluble anode, nickel, by controlling the current flowing in the anodes of tungsten, a plating composition and current efficiency can be stabilized, continuously without generating waste bath Can be plated.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Tsutomu Morikawa 2-7-1, Ayumino, Izumi City, Osaka Prefecture Inside the Osaka Prefectural Institute of Industrial Science (72) Masayuki Yokoi 2-7-1, Ayumino, Izumi City, Osaka Prefecture No. Within the Osaka Prefectural Institute of Industrial Science and Technology (72) Inventor Takuo Nakade 2-7-1, Ayumino, Izumi City, Osaka Prefecture Inside the Osaka Prefectural Institute of Industrial Science and Technology (72) Yukihiro Sato 2-chome Ayumino, Izumi City, Osaka Prefecture No.7-1 Inside Osaka Prefectural Industrial Technology Research Institute (72) Inventor Kohei Ishida 5-12-20 Himejima, Nishiyodogawa-ku, Osaka-shi, Osaka Nomura-gilding Co., Ltd. (72) Inventor Susumu Yuya Chokoji, Toyonaka-shi, Osaka Kita 1-chome 5-37 Limited company wing F term (reference) 4K023 AB20 BA06 BA16 CB03 DA03 DA07 DA08

Claims (3)

[Claims] In an electroplating of a Ni—W alloy,
An electroplating apparatus for a Ni-W alloy using a cation exchange membrane, wherein an anode chamber containing an insoluble anode and a plating chamber are separated using a cation exchange membrane. 2. Ni containing an organic complexing agent in an anionic state.
A tungsten and nickel soluble anode for replenishing a tungsten component and a nickel component respectively to an electroplating solution of a W alloy, and an insoluble anode in an electrolytic solution separated by using the plating solution and a cation exchange membrane in parallel. A method for continuous plating of a Ni-W alloy, characterized by energizing. 3. The method according to claim 2, wherein a current corresponding to the amount of tungsten deposited on the plating film is supplied to the tungsten anode, a current corresponding to the amount of nickel deposited is supplied to the nickel anode, and a current corresponding to the amount of generated hydrogen is supplied to the insoluble anode. N characterized by
A continuous plating method for an i-W alloy.