JPH07278812A - Method for producing insoluble iridium oxide coated electrode - Google Patents

Abstract

(57) [Summary] [Purpose] To form a dense and uniform iridium oxide film with no pores or cracks on the surface of the valve metal with good adhesion. [Structure] In a vacuum container, an iridium oxide film is coated by subjecting a valve metal to a treatment using both iridium vapor deposition and oxygen ion beam irradiation. [Effect] Extending the life of the iridium oxide-coated electrode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an insoluble iridium oxide-coated electrode used for electroplating or the like.

[0002]

2. Description of the Related Art Generally, in electroplating a metal material, an insoluble electrode is used as an anode in an electroplating bath, and a metal material to be plated is used as a cathode, and a metal such as Zn, Sn, Ni, Cr, or Cu is used as a metal surface. Is being plated. Further, in the electrorefining of metals, insoluble electrodes are used in a refining bath to electrorefine metals such as Mn, Zn, and Cu. What is most commonly used as these insoluble electrodes is a Pb-based alloy, but this electrode is used on the surface of an electroplating bath or an electrorefining bath, especially when it is energized in a sulfuric acid solution. PbO ₂ is produced and exerts an insoluble function. However, since the generated PbO ₂ and Pb have a weak adhesive force, they are mixed in the electrolytic solution to cause plating failure, or mixed in the refined metal as an insoluble matter to reduce the purity.

As a countermeasure, iridium oxide, which is a white metal oxide which is the most electrochemically stable in a sulfuric acid solution in an electroplating bath or an electric refining bath, is used as a base valve metal (for example, Ti or Ta). , Zr, etc., an electrode coated with a non-conductive film formed thereon, which has excellent corrosion resistance and high breakdown voltage, is disclosed in Japanese Patent Publication No. 48-3954. Further, in order to suppress the oxidation of the base metal or improve the adhesiveness, an insoluble electrode having an iridium oxide film containing Ta ₂ O ₅ or the like formed on the intermediate layer and an iridium oxide layer formed thereon is disclosed in Japanese Patent Publication No. -21884
JP-A-63-235493.

The iridium oxide insoluble electrode prepared by the coating and baking method disclosed in these publications has a low current density (1
00A / dm ² or less), it can be used for a long time, but especially in sulfuric acid solution, high current density (200A / dm ² )
When the current-carrying corrosion test is conducted, the voltage suddenly rises in 3000 to 4000 hours, and the electrode becomes unusable. The reason for this is that in the case of an iridium oxide film formed by the coating and baking method, a large number of pores remain due to the treatment in the atmosphere, and a hexagonal crack occurs due to the difference in thermal expansion between the base metal and the iridium oxide layer. This is because many occur. That is, when direct current is applied to the base metal due to the pores and cracks, the base metal is corroded, or the insulating oxide film on the base metal surface increases to cause a voltage increase. , Because it loses its function as an electrode. Therefore, in order to maintain the electrode function, it is necessary to form a homogeneous film without pores and cracks.

As a conventional technique, Japanese Patent Publication No. 46-21884.
Issue and the journal of the Photographic Society of Japan (issued in 1988 by Vo
l. 51, No. 1, page 3), iridium metal,
Reactive sputtering methods and reactive evaporation methods of sputtering and oxidizing near the substrate are shown.
However, the insoluble electrode provided with the iridium oxide film obtained by this method is 100 A / dm ² in a sulfuric acid solution.
The energization at a low current density causes the energization to stop in a short time. The reason for this is that the iridium oxide film formed by the above-mentioned sputtering method and vapor deposition method is easily peeled off when the film thickness is increased (0.1 μm or more), and there is a process difficulty such as film formation time. Therefore, the optimum film thickness that can be formed is as thin as 100 to several 1000 angstroms, and if there is a slight defect such as a pinhole, the base material surface is oxidized from the defective part to stop the energization. It is thought that it is because it ends up. Further, although ion plating and the like capable of forming a highly dense and uniform film have been carried out, a method of ionizing gas has not been conventionally used.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and its main purpose is to provide a dense and uniform iridium oxide film free from pores and cracks. It is an object of the present invention to provide a method for forming good adhesion on the surface of a valve metal.

[0007]

Means for Solving the Problems As a result of intensive studies by the present inventors in order to solve such problems, they have found the following method. That is, in a vacuum container, the insoluble iridium oxide-coated electrode is characterized by coating the valve metal with a combination of vapor deposition of iridium and ion beam irradiation of oxygen to coat the iridium oxide film. It is a manufacturing method, in particular, film formation is started by simultaneous irradiation with an ion beam of an inert gas such as argon and iridium vapor deposition, and the ion beam of the inert gas is switched to an oxygen ion beam stepwise or continuously. , A method of manufacturing an insoluble iridium oxide-coated electrode, which is characterized in that film formation is completed by simultaneous treatment of oxygen ion beam irradiation and iridium vapor deposition, or film formation is started by simultaneous treatment of iridium ion beam irradiation and iridium vapor deposition Switch the iridium ion beam to the oxygen ion beam stepwise or continuously, and A method for producing an insoluble iridium oxide coated electrode, characterized in that to finish the film deposition in the simultaneous processing of a beam irradiation and iridium deposited.

[0008]

[Function] This is mainly due to the fact that the irradiation of oxygen which is ionized and has high chemical activity effectively promotes the chemical reaction with the deposited iridium, and the high kinetic energy of the ion beam causes the base material and the film to be separated. This is because a mixed layer is formed at the interface. In addition, it has been found that it is effective to form a metal iridium layer as an intermediate layer in order to further enhance the adhesion between the titanium base material having greatly different physical and chemical properties and the iridium oxide film. Furthermore, when the metal iridium layer that is the intermediate layer is formed, simultaneous irradiation with an inert gas such as argon or an ion beam of iridium is performed to make the film dense and increase the adhesion to the titanium base material, It was found that the adhesiveness between the iridium oxide film and the titanium substrate can be greatly improved by changing the composition stepwise or continuously from the metal iridium layer to the iridium oxide layer.

[0009]

The present invention will be described in detail below with reference to specific examples. First, a valve metal is installed in the processing chamber, and the processing chamber is evacuated. At this time, the degree of vacuum is generally evacuated to about 10 ^-6 Torr. After evacuation, the material surface is cleaned by ion bombardment treatment or the like. In this ion bombardment process, an ion source for film formation may be used, or a dedicated ion source, a plasma source, or the like may be separately provided.

Next, oxygen gas is supplied to the ion source, and irradiation of oxygen ion beam from the ion source and iridium vapor deposition from the vapor deposition source are started to form a film. Metal iridium is used as the evaporation source. This is because when iridium oxide is dissolved, it decomposes into oxygen and iridium at 1100 ° C. to cause volume contraction, and there is a possibility that the evaporation source decreases and the crucible is destroyed, which is a process difficulty.
The metal base material used in the present invention is excellent in corrosion resistance and has a high breakdown voltage. Therefore, the valve metal itself or the one provided with a valve metal layer is desirable. However, the shape of the base material is not particularly limited as long as it is contained in the closed container.

Irradiation of oxygen which is ionized and has high chemical activity effectively promotes the chemical reaction between the vapor-deposited iridium and oxygen to form an iridium oxide film. Further, a high kinetic energy of the oxygen ion beam forms a mixed layer at the interface between the titanium base material and the iridium oxide film, so that high adhesion can be obtained. At the same time, by irradiating the film with an ion beam, a dense and uniform film quality without pores and cracks can be obtained. Furthermore, in order to further enhance the adhesion between the titanium base material and the iridium oxide film, which have greatly different physical and chemical properties, a film is formed by simultaneous treatment with ion beam irradiation of an inert gas such as argon or iridium and iridium vapor deposition. Then, the ion beam of the inert gas or iridium is switched to the oxygen ion beam stepwise or continuously, and the film formation is finished by the simultaneous treatment of the oxygen ion beam irradiation and the iridium vapor deposition. Thereby, the metal iridium layer is formed as an intermediate layer, and the metal iridium layer is simultaneously irradiated with an inert gas such as argon or an ion beam of iridium during the film formation, whereby the film becomes dense, In addition, the adhesion with the titanium base material is improved. further,
By changing the composition from the metal iridium layer to the iridium oxide layer stepwise or continuously, the adhesion between the iridium oxide film and the titanium base material is greatly enhanced. When the metal iridium layer is present in 50% or more of the total film thickness, it may dissolve in the plating solution. Therefore, the iridium oxide layer is preferably 50% or more of the total film thickness.

Here, the inert gas may be helium other than argon or zenon. The average acceleration energy of an ion beam of oxygen, inert gas, iridium, etc. may be a value of about 1 KeV to 1000 KeV used in a general ion beam process.

As a substrate, a 20 × 20 × 2 mm Ti substrate, the surface of which was previously washed with oxalic acid, was used, and an iridium oxide film was formed on the substrate surface by the ion mixing method under the following conditions.

(Film Forming Condition 1) Iridium oxide is formed by simultaneous processing of iridium vapor deposition and oxygen ion beam irradiation. Average acceleration energy of oxygen ion beam: 20 KeV Iridium vapor deposition rate: 2 Å / sec Vapor deposition iridium / oxygen reaching atomic ratio: 1/2 Film thickness: 2 μm

(Film Forming Condition 2) Film formation is started by simultaneous treatment of iridium vapor deposition and argon ion beam irradiation,
The argon ion beam reduction and the oxygen ion beam increase are continuously performed, and the process is switched to the simultaneous processing of iridium vapor deposition and oxygen ion beam irradiation. Average acceleration energy of oxygen ion beam: 20 KeV Average acceleration energy of argon ion beam: 20 KeV Iridium deposition rate: 2 Å / sec Ratio of deposited iridium / oxygen reaching atoms ratio: 1/2 Ratio of deposited iridium / argon reaching atoms ratio: 5 / 1 film thickness: 2 μm Ion beam switching: Switching starts at 0.1 μm Switching ends at 0.5 μm

(Film Forming Condition 3) Film formation is started by simultaneous treatment of iridium vapor deposition and iridium ion beam irradiation, and the iridium ion beam is reduced and the oxygen ion beam is continuously increased to form iridium vapor deposition and oxygen ion beam. Switch to simultaneous processing with irradiation. Average acceleration energy of oxygen ion beam: 20 KeV Average acceleration energy of iridium ion beam: 180 KeV Iridium deposition rate: 2 Å / sec Ratio of deposited iridium / oxygen reaching atoms ratio: 1/2 Ratio of deposited iridium / iridium ion reaching atoms ratio: 10/1 Thickness: 2 μm Ion beam switching: Switching starts at 0.1 μm Switching ends at 0.5 μm

(Conventional method) Hexachloroiridic acid aqueous solution (H ₂ IrC) which becomes iridium oxide by thermal decomposition
l ₆ ) is dissolved in butanol to give an iridium metal concentration of 6
Apply the coating and baking coating solution adjusted to 0 g / l to the titanium substrate, dry and bake at 450 ° C.
Repeatedly apply iridium oxide coating baking method to about 50 μm
A film was formed.

Using the electrode prepared as described above as an anode and a platinum plate as a cathode, a galvanic corrosion test was conducted in a 5 wt% sulfuric acid solution at 60 ° C. at an electric density of 400 A / dm ² . At this time, the change from the initial voltage value of 20 V was measured and evaluated by the energization time of the voltage increase to 35 V. The evaluation of adhesion was performed with a scratch tester.

Table 1 shows the above test results. From this result, it can be seen that the treatment time according to the present invention is longer than that according to the conventional method.

[0020]

[Table 1]

[0021]

As is apparent from the above description, the present invention has a great effect in prolonging the life of the iridium oxide-coated electrode.

Claims (3)

[Claims] 1. An insoluble iridium oxide film, characterized in that a valve metal is subjected to a treatment in which vapor deposition of iridium and irradiation of an oxygen ion beam are used in combination in a vacuum container to coat an iridium oxide film. Method for manufacturing covered electrode. 2. The film formation is started by simultaneous treatment of ion beam irradiation of an inert gas such as argon and iridium vapor deposition, and the ion beam of the inert gas is switched to an oxygen ion beam stepwise or continuously. The method for producing an insoluble iridium oxide-coated electrode according to claim 1, wherein the film formation is completed by simultaneous treatment of ion beam irradiation and iridium vapor deposition. 3. The film formation is started by the simultaneous treatment of iridium ion beam irradiation and iridium vapor deposition, and the iridium ion beam is switched to the oxygen ion beam stepwise or continuously, and the oxygen ion beam irradiation and iridium vapor deposition are performed. The method for producing an insoluble iridium oxide-coated electrode according to claim 1, wherein the film formation is finished by the simultaneous treatment of.