JPH08246196A - Insoluble electrode and manufacturing method thereof - Google Patents

Abstract

(57) [Summary] [Object] The present invention provides an insoluble electrode having excellent corrosion resistance even when electrolysis is performed at a high current density of 100 A / dm ² or more, and capable of withstanding long-term use, and a method for producing the same. [Constitution] In an insoluble electrode in which the electrode base material is made of a conductive metal and the outermost surface layer of the electrode is a conductive layer containing IrO ₂ as a main component, a porous insulating surface is provided between the electrode base material and the outermost surface layer of the electrode. A porous coating of valve metal covered with a conductive oxide layer and having a layered structure parallel to the electrode base material, the pores of which are provided with an intermediate layer filled with a conductive material. [Effect] Corrosion of the electrode base material and formation of the insulating coating can be prevented, and the durability is excellent under high current density.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insoluble electrode used for electroplating a metal material or electrorefining a metal, and a method for producing the same.

[0002]

2. Description of the Related Art Generally, when electroplating a metal material,
Insoluble electrodes are used in an electroplating bath, and metals such as Zn, Sn, Ni and Cr are electroplated on the surface of a metal material to be plated which is a cathode. Also, when electrorefining metals, use an insoluble electrode in the refining bath
Electrorefining of metals such as n and Zn is performed.

The most commonly used insoluble electrode at this time is a Pb-based alloy insoluble electrode.
PbO ₂ is produced on the surface of the insoluble electrode in an electroplating bath or an electrorefining bath, particularly in a sulfuric acid solution, during electric current treatment. This PbO ₂ functions as an insoluble electrode, but the adhesion between the PbO ₂ and Pb metal produced is weak, and it mixes in the sulfuric acid solution of the electroplating bath to cause plating failure.
Alternatively, PbO ₂ was mixed as an impurity in the electric refining bath.
Produces refining metal containing.

As a countermeasure, a platinum group oxide, IrO ₂ , which is the most electrochemically stable in an electroplating bath or an electrorefining bath, especially in a sulfuric acid solution, is coated on an electrode base material made of a conductive metal. The converted insoluble electrode is disclosed in Japanese Patent Publication No. 48-3954.

Further, in order to suppress the oxidation of the electrode base metal or to improve the adhesion of IrO ₂ to the electrode base metal, a film whose main component is Ta metal is formed as an intermediate layer, Japanese Unexamined Patent Publication No. 6-146047 discloses a method of using an insoluble electrode having a layer containing IrO ₂ as a main component.

FIG. 3 shows the electrode structure. Reference numeral 1 is an electrode base material, 2 is a Ta-SiO ₂ layer, and 3 is a layer containing IrO ₂ as a main component. The Ta-SiO ₂ layer 2 is formed by the PVD method.
The layer 3 containing IrO ₂ as a main component is prepared by a so-called coating baking method in which a solution of an Ir compound is applied on the electrode base metal and firing is performed at a temperature at which it becomes an oxide.

[0007]

[Patent Document 1] Japanese Patent Application Laid-Open No. 6-14604
Ir by the coating and baking method as presented in Japanese Patent Publication No.
The insoluble electrode on which the layer containing O ₂ as a main component was formed was 10 A when subjected to a current oxidation test of 200 A / dm ^{2 in} a sulfuric acid solution.
A sharp voltage rise occurs at 00 to 1400 hours, and the electrode becomes unusable.

The oxidation mechanism of this electrode will be described with reference to FIG. Since the layer 3 containing IrO ₂ as a main component is prepared by applying a solution of an Ir compound and heat-treating it, pores generated by volatilization of the solution component, the electrode base material 1 and Ir.
There is a hexagonal crack generated in the coating due to the difference in thermal expansion from the layer 3 containing O ₂ as a main component.

Therefore, the porosity of the coating is as large as 10 to 30%, and direct current is applied to the electrode base material 1 when the electrode is used due to pores and cracks 4, and the surface of the electrode base material 1 is insulated. Of the conductive oxide film 5, the electrode base material 1 is further oxidized in the direction of the interface between the electrode base material 1 and the Ta-SiO ₂ layer 2, causing a voltage increase and losing the function as an electrode. .

As measures against this, it is necessary to prevent the electrode base material 1 from being exposed due to pores and cracks 4 in the coating and baking coating, and to oxidize the electrode base material 1 and the Ta-SiO ₂ layer 2 in the direction of the interface. It is necessary to suppress it. The present invention provides an insoluble electrode having excellent corrosion resistance even when electrolysis is performed at a high current density of 100 A / dm ² or more, and capable of withstanding long-term use, and a method for producing the same.

[0011]

The present invention relates to an insoluble electrode in which the electrode base material is made of a conductive metal and the outermost surface layer of the electrode is a conductive layer containing IrO ₂ as a main component. Between the surface layers, the surface was covered with a porous insulating oxide layer and consisted of a valve metal porous film having a layered structure parallel to the electrode base material, and the pores were filled with a conductive material. The present invention relates to an insoluble electrode provided with an intermediate layer and a method for manufacturing the same.

That is, the first aspect of the present invention is an insoluble electrode in which the electrode base material is made of a conductive metal and the electrode outermost layer is a conductive layer containing IrO ₂ as a main component. The outermost surface of the electrode and the surface of the pores are covered with a porous insulating oxide layer, and are composed of a valve metal porous coating having a layered structure parallel to the electrode base material. Is an insoluble electrode provided with an intermediate layer filled with a conductive oxide containing IrO ₂ as a main component.

In particular, the valve metal and Ir forming the intermediate layer
The volume ratio to the conductive oxide containing O ₂ as a main component is 60: 4.
It is characterized in that it is in the range of 0 to 95: 5 and that the thickness of the intermediate layer is in the range of 5 to 100 μm.

In the first aspect of the invention, the method for producing an insoluble electrode consisting of the electrode base material, the intermediate layer and the outermost layer of the electrode is as follows.

That is, in the insoluble electrode of the present invention, the electrode base material is composed of a conductive metal layer, and on the electrode base material, the surface of the electrode outermost layer side and the surface of the pores are porous insulating oxide layers. An intermediate layer, which is covered with a porous coating film of a valve metal having a layered structure parallel to the electrode base material and whose pores are filled with a conductive oxide whose main component is IrO ₂ , is provided. The surface layer is formed by a coating and baking method to form a conductive layer containing IrO ₂ as a main component.

The manufacturing method is characterized in that the valve metal is sprayed on the electrode base material to form a porous coating of valve metal having a porosity of 5 to 40%, and then a porous coating of valve metal. By repeating the operation of applying a solution containing an insulating compound precursor to the surface and performing heat treatment in an oxidizing atmosphere, the surface of the electrode and the pore surface of the porous coating of the valve metal are porous insulating After the oxide layer is formed, the operation of applying a solution containing an Ir compound as a main component on the oxide layer and performing a heat treatment in an oxidizing atmosphere is repeated to form IrO _{2 in the} pores of the valve metal porous film. The point is to fill the conductive oxide containing as a main component to form the intermediate layer.

A second aspect of the present invention is an insoluble electrode in which the electrode base material is made of a conductive metal and the outermost layer of the electrode is a conductive layer containing IrO ₂ as a main component. Between the surface layers, the outermost surface of the electrode and the surface of the pores are covered with a porous insulating oxide layer, and are composed of a valve metal porous coating having a layered structure parallel to the electrode base material. An intermediate layer in which the conductive oxide containing IrO ₂ as a main component is filled up to a depth of 5 to 95 μm from the coating surface on the electrode outermost layer side of the pores and the remainder on the electrode base material side is filled with a conductive metal is provided. Insoluble electrode.

In particular, the volume ratio of the valve metal forming the intermediate layer to the total of the conductive metal and the conductive oxide containing IrO ₂ as a main component is in the range of 60:40 to 95: 5, and The thickness of the intermediate layer is in the range of 10 to 100 μm.

In the second aspect of the invention, the method for producing an insoluble electrode consisting of three layers of the electrode base material, the intermediate layer and the electrode outermost layer is as follows.

That is, in the insoluble electrode of the present invention, the electrode base material is composed of a conductive metal layer, and on the electrode base material, the surface of the outermost layer of the electrode and the surface of pores are porous insulating oxide layers. It is composed of a porous coating film of a valve metal which is covered and has a layered structure parallel to the electrode base material. IrO ₂ is formed in the pores from the coating surface on the electrode outermost surface side to a depth of 5 to 95 μm.
Is provided as the main component, and an intermediate layer is provided in which the remaining portion on the electrode base material side is filled with the conductive metal, and the outermost layer of the electrode is formed by a coating baking method to contain IrO ₂ as the main component. It is a conductive layer.

The feature of the manufacturing method is that the valve metal is sprayed on the electrode base material to form a porous coating film of the valve metal having a porosity of 5 to 40%. By repeating the operation of applying a solution containing an insulating compound precursor to the surface of the film and performing heat treatment in an oxidizing atmosphere,
After forming a porous insulating oxide layer on the outermost surface of the electrode of the valve metal porous film and on the surface of the pores, electroplating conductive metal with the electrode base material as the cathode to form the porous metal of the valve metal. The lower layer of the porous film except for the depth of 5 to 95 μm from the surface of the electrode on the outermost surface side of the electrode is filled with a conductive metal, and a solution containing an Ir compound as a main component is further provided on the lower layer. Is repeated and the heat treatment is repeated in an oxidizing atmosphere to form I in the holes in the upper layer of the porous coating of the valve metal.
The point is to fill the conductive oxide containing rO ₂ as a main component to form the intermediate layer.

In the insoluble electrode of the present invention, the thickness of the porous insulating oxide layer covering the electrode outermost layer side surface and the pore surface of the valve metal porous coating is 0.05 to 5 μm.
m, and in the manufacturing method thereof, the heat treatment temperature at the time of forming the porous insulating oxide layer on the surface of the electrode metal outermost layer side and the pore surface of the porous coating of the valve metal is 20.
It is characterized in that it is in the range of 0 to 600 ° C.

The electrode base material used in the present invention may be a conductive metal, but is preferably a valve metal (Ti, Ta, Zr, Nb) having excellent durability in a sulfuric acid solution.
The reason is that it has excellent corrosion resistance in a sulfuric acid solution and its breakdown voltage is high.

Further, in the insoluble electrode of the present invention, the material of the porous coating film forming the intermediate layer is required to be a valve metal (Ti, Ta, Zr, Nb) which is stable in a sulfuric acid solution. The valve metal porous coating has a particle size of 20.
It can be formed by spraying a valve metal powder of ˜40 μm by ordinary plasma spraying. The raw material powder is deformed by thermal spraying to form a disk-shaped thin film having a thickness of about 2 μm and a diameter of several 10 μm, which is deposited to form a porous multilayer coating film.

If the thickness of the valve metal porous coating formed by thermal spraying is 100 μm or less, the adhesion is particularly excellent.

On the other hand, in order to prevent the conductive metal used as the base material of the electrode or the filling material for the pores of the porous coating of the valve metal from being exposed, the coating and baking coating of the outermost layer of the electrode should be applied. It is necessary to improve the adhesion by the anchor effect. For this purpose, the porous coating film pores of the valve metal should be formed at a thickness of at least 5 μm from the outermost surface of the electrode.
It is filled with a conductive oxide whose main component is rO ₂ . That is, in the first aspect of the present invention, the thickness of the valve metal porous coating formed by thermal spraying is at least 5 μm or more.

In the second aspect of the present invention, the filling thickness of the conductive metal into the pores of the porous coating is 5 to 95 μm.
At least 10 μm or more. Therefore, the thickness of the porous coating is preferably in the range of 5 to 100 μm in the first aspect of the present invention and in the range of 10 μm to 100 μm in the second aspect of the present invention.

As the thermal spraying conditions, in the first aspect of the present invention, the volume ratio of the valve metal to the conductive oxide containing IrO ₂ as a main component is used, and in the second aspect of the present invention, the valve metal, the conductive metal and Ir.
The volume ratio to the total of the conductive oxides containing O ₂ as the main component is 6
The durability is excellent when it is in the range of 0:40 to 95: 5, that is, when the porosity is in the range of 5 to 40%.

This is because the volume ratio of the valve metal is 60%.
By the above, the effect of reducing the exposed area of the electrode base material by the valve metal is exerted, and by setting the volume ratio to 95% or less, a sufficient amount of conductive metal for conducting electricity or conductivity containing IrO ₂ as a main component is used. Oxide, or a conductive oxide containing IrO ₂ as a main component, a conductive metal, and pores in the coating film. The porosity of the valve metal porous coating can be calculated, for example, by observing the longitudinal section or the transverse section of the coating and calculating the area ratio thereof.

In the insoluble electrode of the present invention, the material of the porous insulating oxide layer applied to the surface of the electrode metal outermost layer side and the surface of the pores of the porous coating of the valve metal is stable oxidation in the plating solution. Such as SiO ₂ , Al ₂ O ₃ , ZrO ₂
Etc. are preferred. The porous insulating oxide layer has a thickness of 5 μm or less and excellent adhesion, and a thickness of 0.05 μm or more has an excellent effect of suppressing oxidation of the electrode base material.

As a method for forming the insulating oxide layer, a solution of an insulating compound precursor such as a metal alkoxide, a β-diketone chelate, a β-ketoester chelate, or a carboxylate is applied and heat treated. The so-called sol-gel method can be adopted.

Producing cracks in the insulating oxide layer that penetrate through the porous coating of the valve metal, ie,
To make it porous, rapid cooling from a high temperature, for example, 300 ° C. may be performed.

Alternatively, when an organic polymer such as cellulose, polyethylene glycol or urethane is added to the above solution and applied and heat-treated, the organic polymer is decomposed and gas is generated during the heat treatment, so that the coating is porous. Can be converted.

In the case of the second insoluble electrode of the present invention, as described above, after forming the porous insulating oxide layer on the surface of the porous coating of the valve metal, the holes are made electrically conductive by plating. Fill with metal.

As the method, an ordinary electrolytic plating method is performed using the electrode base material as a cathode. Thereby, the holes in the porous coating of the valve metal can be filled with the conductive metal in the required thickness from the surface of the electrode base material.

The filling of the pores with the conductive metal is carried out in the pores of the porous coating of the valve metal from 5 to 95 from the coating surface.
It is necessary to fill the lower layer of the porous film excluding the depth of μm from the electrode base material side.

This is because when the conductive metal can be filled only in a thickness of less than 5 μm from the electrode base material side among the pores of the porous coating of the valve metal, the adhesion with the metal base material due to the filling. When the voids can be left only on the outermost layer of the electrode with a thickness of less than 5 μm, adhesion by the anchor effect to the coating and baking coating on the outermost layer of the electrode Because it is not possible to improve

As the conductive metal used here,
A platinum group metal having excellent corrosion resistance in the sulfuric acid solution of the plating bath is preferable.

As described above, in the second insoluble electrode of the present invention, the adhesion of the outermost layer of the electrode is improved by the anchor effect of the conductive oxide containing IrO ₂ as a main component, and the metal matrix is filled with the conductive metal. In order to obtain the effect of improving the adhesiveness with the material, the thickness of the intermediate layer is preferably at least 10 μm or more.

Examples of the solution containing Ir compound as a main component used for filling the pores of the porous valve metal coating in the present invention are described in, for example, JP-A-62-240780 and JP-A-6-240780.
It is disclosed in JP-A-3-235493, JP-A-3-193889, or JP-A-59-150091. Specifically, iridium chloride is the main component,
It is an alcohol solution containing compounds such as tantalum alkoxide and chloroplatinic acid.

Such a solution is applied to the surface of the valve metal porous coating film by means such as brush coating, spraying, dipping or the like, and then 10 to evaporate the solvent.
It is dried at 0 to 200 ° C. for several tens of minutes and heat-treated at 300 to 700 ° C. in an oxidizing atmosphere, for example, in the air. By such an operation, a conductive oxide containing IrO ₂ as a main component is formed. By repeating this series of operations a plurality of times, it is possible to fill the pores of the valve metal porous coating with a conductive oxide containing IrO ₂ as a main component, thereby forming an intermediate layer. Further, by repeating the same operation after forming the intermediate layer, a conductive layer containing IrO ₂ as a main component as the outermost layer of the electrode is formed.

[0042]

The structure of the first insoluble electrode of the present invention is shown in FIG.
The structure of the insoluble electrode is shown in FIG. The operation will be described below with reference to these drawings.

In the first insoluble electrode of the present invention, even when a large number of pores and cracks 4 are present in the conductive layer 3 containing IrO ₂ as the outermost layer of the electrode, the porous coating film of the valve metal and IrO ₂ are removed. An intermediate layer 6 composed of a conductive oxide as a main component, in the second electrode of the present invention, the intermediate layer 6 and further,
Since the intermediate layer 7 composed of the porous coating of the valve metal and the conductive metal is present, the pores and cracks 4 present in the outermost layer 3 of the electrode do not penetrate into the electrode base material 1, and therefore the electrode base material 1 is not formed. The exposed area of the material 1 is small.

Further, the porous coating film of the valve metal forming the intermediate layers 6 and 7 is the same material as the electrode base material 1 and there is no difference in the coefficient of thermal expansion, so that it has excellent conductivity.

Further, since the porous insulating oxide layer 8 is coated on the surface of the electrode on the outermost layer side and on the surface of the pores of this porous coating, the oxidation of the valve metal in the interface direction is caused on the surface of the porous coating. It does not proceed, and I on the outermost layer of the electrode
The coating bake coating of the conductive oxide containing rO ₂ as a main component does not peel off.

As described above, the insoluble electrode of the present invention has a small exposed area of the electrode base material and can suppress the progress of oxidation of the valve metal toward the interface on the surface of the porous coating film.
It can withstand long-term use even at a high current density of dm ² or more.

In the invention of Japanese Patent Application No. 4-279315 filed earlier, it is stated that the intermediate layer is made of a porous non-conductive material. However, in the present invention, instead of this, a valve metal of the same material as the electrode base material is used. Is used for the intermediate layer and has excellent adhesion to the base material.

[0048]

EXAMPLES First, (1) the first insoluble electrode of the present invention, that is, the electrode base material is made of a conductive metal, and the electrode outermost layer is I.
In an insoluble electrode having a conductive layer containing rO ₂ as a main component, a surface of the electrode outermost layer and a surface of pores are covered with a porous insulating oxide layer between the electrode base material and the electrode outermost layer, and the electrode An insoluble electrode comprising a porous coating film of a valve metal having a layered structure parallel to the base material, the pores of which are provided with an intermediate layer filled with a conductive oxide containing IrO ₂ as a main component. ,

And (2) The second insoluble electrode of the present invention, that is, the electrode base material is made of a conductive metal, and the outermost layer of the electrode is I.
In an insoluble electrode having a conductive layer containing rO ₂ as a main component, a surface of the electrode outermost layer and a surface of pores are covered with a porous insulating oxide layer between the electrode base material and the electrode outermost layer, and the electrode It is composed of a porous coating film of a valve metal having a layered structure parallel to the base material, and the conductive oxide containing IrO ₂ as a main component is present in the pores from the coating surface on the electrode outermost surface side to a depth of 5 to 95 μm. An example of the method for producing each of the insoluble electrodes, which is characterized in that an intermediate layer is provided in which the intermediate layer is filled with the material and the rest of the electrode base material side is filled with the conductive metal. The manufacturing flowchart is shown in FIG.

Manufacturing method of insoluble electrode: (1) Treatment of electrode base material; using a Ti plate as the electrode base material, the surface of the electrode base material having a thickness of 100 × 100 × 20 mm was washed with oxalic acid, and then roughened with a plast. I got faced.

(2) Formation of intermediate layer; (2-1) Formation of porous coating of valve metal First, four types of valve metals, Ti, Ta, Zr, and Nb, are selected, and a normal plasma spraying method is applied to each of them. Thus, the electrode base material was sprayed to form a porous coating of valve metal on the electrode base material. Coating thickness: 5-100 μm Porosity: 5-40%

(2-2) Formation of Porous Insulating Oxide Layer An alcohol solution obtained by hydrolyzing a silicon alkoxide is applied on the porous coating film of the valve metal by the dipping method, and heat treatment is performed in the atmosphere. One or more times,
After forming the non-conductive coating, it was rapidly cooled from 300 ° C. Heat treatment temperature: 200 to 600 ° C. Coating thickness: 0.05 to 5 μm

(2-3) Filling by plating Regarding the second insoluble electrode of the present invention, the above (2-2)
After forming a porous insulating oxide layer on the surface of the porous coating of the valve metal applied to the electrode base material with, soak it in the plating solution,
Pt was plated using this electrode base material as a cathode. By this method, the pores of the valve metal porous coating were filled to a predetermined thickness. Plating method: Electrolytic plating Current density: 1 A / dm ² Plating component: Pt

(2-4) Filling with a conductive oxide containing IrO ₂ as a main component 90 parts of H ₂ IrCl ₆ which becomes IrO ₂ by thermal decomposition and Ta (OC ₂ H ₅ which becomes Ta ₂ O ₅ by thermal decomposition) ₅ ) ₃ to 10
Partly mixed and dissolved in butanol, the solution was applied on the surface of the porous coating film of the valve metal having a porous insulating oxide layer formed thereon with a brush, and after drying at 120 ° C. for 20 minutes,
The operation of placing in an electric furnace and baking at 450 ° C. was repeated several times. In this way, the holes in the porous coating of the valve metal are
A conductive oxide containing rO ₂ as a main component was filled to form a target intermediate layer. Further, the same operation as this was repeated to form the outermost surface layer of the electrode.

Table 1 shows the durability test results of the first and second insoluble electrodes of the present invention thus obtained, together with the conventional product and the comparative product.

The durability of the produced insoluble electrode was evaluated by the following method. That is, a conventional product, a comparative product, and the insoluble electrode of the present invention were used as the anode, and a platinum plate was used as the cathode, and the current density was 200 A in a 5 wt% sulfuric acid solution at 60 ° C.
A current test of / dm ² was performed, and the time until the voltage increased by 10 V was measured. In Table 1, ○ indicates a life of 4000
An insoluble electrode having a durability of not less than hr and a life of less than 4000 hr was insoluble. It can be seen from Table 1 that each of the insoluble electrodes of the present invention has a life of 4000 hours or more and is excellent in durability.

[0057]

[Table 1]

In Table 1, 11 is an electrode manufactured by a conventional coating and baking method for comparison, and 12 is an electrode manufactured under conditions different from those of the present invention for comparison. Comparative product 12 had a short life because the anchor effect of the conductive layer containing IrO ₂ as the outermost layer of the electrode was not obtained.

[0059]

INDUSTRIAL APPLICABILITY The insoluble electrode of the present invention has excellent corrosion resistance even when electrolysis is carried out at a high current density and can withstand long-term use. It is also extremely useful as an electrode for use in.

[Brief description of drawings]

FIG. 1 shows a structure of a first insoluble electrode of the present invention.

FIG. 2 shows a structure of a second insoluble electrode of the present invention.

FIG. 3 shows a structure of a conventional electrode.

FIG. 4 is an explanatory diagram of an oxidation mechanism in a conventional electrode.

FIG. 5 shows a flowchart for manufacturing an insoluble electrode according to the present invention.

[Explanation of symbols]

Porous insulation first electrode base material 2 Ta-SiO ₂ layer conductive layer mainly composed of (cross-hatched portion) 3 IrO ₂ (densely hatched portion) 4 pores and cracks 5 insulating oxide film (black portion) 6 surface Of a valve metal having a porous oxide layer 8 and a conductive oxide containing IrO ₂ as a main component 7 A porous film of a valve metal having a porous insulating oxide layer 8 on the surface And a conductive metal layer (coarse hatched portion) 8 Porous insulating oxide layer (black portion)

[Procedure amendment]

[Submission date] June 2, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction content]

On the other hand, in order to prevent the conductive metal used as the base material of the electrode or the filling material for the pores of the porous coating of the valve metal from being exposed, and for the coating and baking coating of the outermost layer of the electrode. Improve adhesion by anchor effect
Therefore, the porous coating film pores of the valve metal are filled with a conductive oxide containing IrO ₂ as a main component for a thickness of at least 5 μm or more from the electrode outermost surface side. That is, in the first aspect of the present invention, the thickness of the valve metal porous coating formed by thermal spraying is at least 5 μm or more.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0029

[Correction method] Change

[Correction content]

This is because the volume ratio of the valve metal is 60%.
With more, exposed area reduction effect of the electrode base material by the valve metal is exhibited and the main component sufficient of the conductive metal to the conduction by the volume ratio of 95% or less, or IrO ₂ The conductive oxide or the conductive oxide containing IrO ₂ as a main component and the conductive metal are filled in the pores in the film. The porosity of the valve metal porous coating can be calculated, for example, by observing the longitudinal section or the transverse section of the coating and calculating the area ratio thereof.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0044

[Correction method] Change

[Correction content]

[0044] For further there is no difference in the thermal expansion coefficient of a porous coating same material as the electrode base material 1 of the valve metal constituting the intermediate layer 6, it is excellent in tight adhesion.

[Procedure amendment 4]

[Document name to be amended] Statement

[Name of item to be corrected] 0058

[Correction method] Change

[Correction content]

[0058] In Table 1, 11 The electrodes were made created by conventional coating baking method for comparison, 12, for comparison, an electrode was fabricated under different conditions as the present invention. Comparative product 12 had a short life because the anchor effect of the conductive layer containing IrO ₂ which is the outermost layer of the electrode as a main component was not obtained.

Claims (10)

[Claims] 1. An insoluble electrode in which the electrode base material is made of a conductive metal and the outermost layer of the electrode is a conductive layer containing IrO ₂ as a main component, and an electrode outermost layer is provided between the electrode base material and the outermost layer of the electrode. The surface of the surface layer and the surface of the pores are covered with a porous insulating oxide layer, and are composed of a porous valve metal film having a layered structure parallel to the electrode base material, and the pores contain IrO ₂ as a main component. An insoluble electrode, characterized in that an intermediate layer filled with a conductive oxide is provided. 2. The intermediate layer having a volume ratio of the valve metal to the conductive oxide containing IrO ₂ as a main component in the range of 60:40 to 95: 5. The insoluble electrode described. 3. The insoluble electrode according to claim 1, wherein the thickness of the intermediate layer is in the range of 5 to 100 μm. 4. An insoluble electrode in which the electrode base material is made of a conductive metal and the outermost surface layer of the electrode is a conductive layer containing IrO ₂ as a main component, and an electrode outermost layer is provided between the electrode base material and the outermost surface layer of the electrode. The surface of the surface layer and the surface of the pores are covered with a porous insulating oxide layer and consist of a valve metal porous coating having a layered structure parallel to the electrode base material. An insoluble layer characterized by being provided with an intermediate layer in which a conductive oxide containing IrO ₂ as a main component is filled up to a depth of 5 to 95 μm from the surface of the film, and the remainder on the electrode base material side is filled with a conductive metal. electrode. 5. A valve metal, a conductive metal and IrO ₂
The volume ratio with respect to the total of the conductive oxides containing as a main component is 60:
The insoluble electrode according to claim 4, further comprising an intermediate layer in the range of 40 to 95: 5. 6. The insoluble electrode according to claim 4, wherein the thickness of the intermediate layer is in the range of 10 to 100 μm. 7. The porous insulating oxide layer covering the surface of the electrode metal outermost layer and the surface of the pores of the porous coating of the valve metal is in the range of 0.05 to 5 μm. Item 7. The insoluble electrode according to any one of items 1 to 6. 8. An insoluble electrode comprising three layers of an electrode base material, an intermediate layer and an electrode outermost layer, wherein the electrode base material is composed of a conductive metal layer, and the electrode outermost surface side surface is formed on the electrode base material. And the surface of the pores is covered with a porous insulating oxide layer, and is composed of a valve metal porous coating having a layered structure parallel to the electrode base material, and the pores are electrically conductive with IrO ₂ as a main component. In a method for producing an insoluble electrode in which an intermediate layer filled with a conductive oxide is provided and an outermost layer of the electrode is formed by a coating baking method to form a conductive layer containing IrO ₂ as a main component, a valve metal is sprayed on an electrode base material. To form a porous coating of valve metal having a porosity in the range of 5 to 40%, and then applying a solution containing an insulating compound precursor to the surface of the porous coating of valve metal to form an oxidizing atmosphere. The procedure of heat treatment in the chamber is repeated to charge the porous metal film of the valve metal. After forming the porous insulating oxide layer on the outermost layer side surface and pore surface, further thereon, I
The operation of applying a solution containing the r compound as the main component and performing heat treatment in an oxidizing atmosphere is repeated to fill the pores of the porous coating of the valve metal with a conductive oxide containing IrO ₂ as the main component. A method for producing an insoluble electrode, which comprises forming an intermediate layer of 9. An insoluble electrode comprising three layers of an electrode base material, an intermediate layer and an electrode outermost layer, wherein the electrode base material is composed of a conductive metal layer, and the electrode outermost surface side surface is formed on the electrode base material. And the surface of the pores is covered with a porous insulating oxide layer and is made of a valve metal porous coating having a layered structure parallel to the electrode base material. From 5
A conductive oxide containing IrO ₂ as a main component is filled up to a depth of up to 95 μm, and an intermediate layer is formed by filling the remainder on the electrode base material side with a conductive metal, and the outermost layer of the electrode is formed by coating and baking. In a method of manufacturing an insoluble electrode having a conductive layer containing IrO ₂ as a main component, a valve metal is sprayed on an electrode base material to form a porous coating film of the valve metal having a porosity of 5 to 40%. Next, the operation of applying the solution containing the insulating compound precursor to the surface of the porous coating of the valve metal and performing the heat treatment in an oxidizing atmosphere is repeated, and the surface of the valve metal porous coating on the outermost layer side of the electrode. And after forming a porous insulating oxide layer on the surface of the pores, electroplating a conductive metal using the electrode base material as a cathode, and coating the outermost layer of the electrode among the pores of the porous coating of the valve metal. The coating excluding a depth of 5 to 95 μm from the surface The lower layer is filled with a conductive metal, and a solution containing an Ir compound as a main component is further applied on the lower layer, and heat treatment is performed in an oxidizing atmosphere. A method for producing an insoluble electrode, which comprises filling the conductive oxide containing IrO ₂ as a main component to form the intermediate layer. 10. The heat treatment temperature for forming the porous insulating oxide layer on the surface of the electrode metal outermost layer and the surface of the pores of the porous coating of the valve metal is in the range of 200 to 600 ° C. 10. The method for producing an insoluble electrode according to claim 8 or 9.