JPH08253893A - 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 layer of the electrode is a conductive layer containing IrO ₂ as a main component, there are 10 conductive particles between the electrode base material and the outermost layer of the electrode. The surface is covered with an insulating oxide layer dispersed at a ratio of ˜40% by volume, and the valve metal porous film has a layered structure parallel to the electrode base material. IrO is contained in the pores.
An intermediate layer filled with a conductive oxide containing ₂ as a main component is provided. [Effect] There is no corrosion of the electrode base material and formation of an insulating film,
Excellent durability 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,
Electrodes are used in an electroplating bath to electroplate metals such as Zn, Sn, Ni and Cr on the surface of a metal material to be plated which is a cathode. Further, in the electric refining of metals, electrodes are used in a refining bath to electrorefine metals such as Mn and Zn.

At this time, the most commonly used electrode is a Pb-based alloy electrode. This electrode is
In an electroplating bath or an electric refining bath, especially in a sulfuric acid solution, PbO ₂ is formed on the surface of the surface during electric current treatment. This PbO
₂ shows the function as an electrode, but the generated PbO
The adhesion between ₂ and Pb metal is weak, and it mixes in the sulfuric acid solution of the electroplating bath to cause plating failure, or mixes in the electrorefining bath to produce refined metal containing PbO ₂ as an impurity.

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 conductive layer containing IrO ₂ as a main component. The Ta-SiO ₂ layer 2 is formed by the PVD method, and the conductive layer 3 containing IrO ₂ as a main component is prepared by applying a solution of an Ir compound on the electrode base metal and baking the solution at a temperature at which it becomes an oxide. , A so-called coating and baking method.

[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 formed with a conductive layer containing O ₂ as a main component is subjected to a current oxidation test of 200 A / dm ^{2 in} a sulfuric acid solution.
A rapid voltage rise occurs in 1000 to 1400 hours, and the electrode becomes unusable.

The oxidation mechanism of this electrode will be described with reference to FIG. Since the conductive 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 and the electrode base material 1
And a hexagonal crack generated due to the difference in thermal expansion between the conductive layer 3 containing IrO ₂ as a main component and the conductive layer 3 containing IrO 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 the pores and cracks 4 in the conductive layer containing IrO ₂ as a main component, and the electrode base material 1 and Ta-S.
It is necessary to suppress oxidation toward the interface with the iO ₂ layer 2. 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 has conductive particles of 10 to 40% by volume.
An intermediate layer consisting of a porous coating of valve metal, which is covered with an insulating oxide layer dispersed at a ratio of 1 and has a layered structure parallel to the electrode base material, and whose pores are filled with a conductive material. The present invention relates to an insoluble electrode provided 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. Between the outermost surface of the electrode and the surface of the pores are covered with an insulating oxide layer in which conductive particles are dispersed in a ratio of 10 to 40% by volume, and a layered structure parallel to the electrode base material is formed. It consists of a porous coating of the valve metal that has
An insoluble electrode provided with an intermediate layer filled with a conductive oxide containing rO 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 the surface of the electrode outermost layer and the surface of the pores have 10 to 40 volumes of conductive particles on the electrode base material. % Of a porous coating film of a valve metal which is covered with an insulating oxide layer dispersed at a ratio of 100% and has a layered structure parallel to the electrode base material, and whose pores are made of IrO ₂ as a main component. An intermediate layer filled with a functional oxide is provided, and an outermost layer of the electrode 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 metal coating of the valve metal having a porosity of 5 to 40%. Conductive particles are dispersed on the surface of the porous coating film at a ratio of 10 to 40% by volume, and a solution containing an insulating compound precursor is applied and heat treatment is repeated in an oxidizing atmosphere to repeat the operation.
After forming an insulating oxide layer in which conductive particles were dispersed at a ratio of 10 to 40% by volume on the surface of the electrode outermost layer side and the surface of pores of the porous coating of the valve metal, Ir compound was further formed thereon. The operation of applying the solution containing the main component and performing the heat treatment in an oxidizing atmosphere is repeated to fill the holes in the porous coating of the valve metal with the conductive oxide containing IrO ₂ as the main component, and to form the intermediate layer. There is a point in forming.

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. A layered structure in which the surface of the electrode outermost layer and the surface of pores are covered with an insulating oxide layer in which conductive particles are dispersed at a ratio of 10 to 40% by volume between the surface layers, and are parallel to the electrode base material. With a porous coating of valve metal having a depth of 5 to 95 μm from the coating surface on the electrode outermost surface side of the pores.
It is an insoluble electrode provided with an intermediate layer which is filled with a conductive oxide containing rO ₂ as a main component and the rest of the electrode base material side is filled with a conductive metal.

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 the surface of the electrode outermost layer and the surface of pores have 10 to 40 volume of conductive particles on the electrode base material. % Of the insulating metal oxide layer, which consists of a valve metal porous film having a layered structure parallel to the electrode base material, and the surface of the electrode on the outermost surface of the electrode. To a depth of 5 to 95 μm is filled with a conductive oxide containing IrO ₂ as a main component, and the remaining portion on the electrode base material side is filled with a conductive metal to provide an intermediate layer, and the outermost layer of the electrode is formed by a coating baking method. The film is formed into 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 metal coating of the valve metal having a porosity of 5 to 40%. Conductive particles are dispersed on the surface of the porous coating film at a ratio of 10 to 40% by volume, and a solution containing an insulating compound precursor is applied and heat treatment is repeated in an oxidizing atmosphere to repeat the operation.
After forming an insulating oxide layer in which conductive particles were dispersed at a ratio of 10 to 40% by volume on the surface of the electrode outermost layer side and the surface of pores of the porous coating of the valve metal, the electrode base material was used as a cathode for conductivity. The metal is electroplated to fill the lower layer of the valve metal with a conductive metal except for the pores of the valve metal porous film, except for the depth of 5 to 95 μm from the surface of the electrode outermost layer side.
Furthermore, the operation of applying a solution containing an Ir compound as a main component thereon and performing heat treatment in an oxidizing atmosphere is repeated,
This is to fill the pores in the upper layer of the valve metal porous film with a conductive oxide containing IrO ₂ as a main component to form the intermediate layer.

In the insoluble electrode of the present invention, the insulating oxidation film is formed by covering the surface of the electrode metal outermost layer and the surface of the pores of the porous coating of the valve metal and having conductive particles dispersed in a ratio of 10 to 40% by volume. The thickness of the material layer is in the range of 0.05 to 5 μm, and the diameter of the dispersed conductive particles is 0.05 to 5 μm.
In addition, in the manufacturing method thereof, the heat treatment temperature at the time of forming this insulating oxide layer on the electrode outermost layer side surface and the pore surface of the porous coating of the valve metal is 200 to 6
It is characterized in that the temperature is in the range of 00 ° 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 must be one of valve metals (Ti, Ta, Zr, Nb) which is stable in a sulfuric acid solution. Is. The porous coating of valve metal can be formed by, for example, plasma spraying valve metal powder having a particle size of 20 to 40 μm. The raw material powder is deformed by thermal spraying to form a disk-shaped thin film having a thickness of 2 μm and a diameter of about 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, the thickness of the valve metal porous coating formed by thermal spraying is at least 5 in the first aspect of the present invention.
At least μm. Further, in the second aspect of the present invention, the thickness is at least 10 μm or more according to the filling thickness of the conductive metal in the porous coating film pores of 5 to 95 μm. 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 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 and 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 I are used.
Excellent durability when the volume ratio to the total of conductive oxides containing rO ₂ as the main component is in the range of 60:40 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 IrO ₂ as a main component. 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 porous coating of the valve metal. 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, an insulating oxide layer in which conductive particles are dispersed in a ratio of 10 to 40% by volume is applied to the surface of the electrode metal outermost layer and the surface of pores of the porous coating of the valve metal. Examples of the insulating oxide material include stable oxides in the plating solution, such as SiO ₂ , Al ₂ O ₃ , and ZrO _2.
Etc. are preferred. Further, the material of the conductive particles may be a metal, or a metal nitride, a metal carbide, a metal silicide, or a metal boride, which has the same conductivity as a metal. In particular, platinum group metals or platinum group oxides that are stable in the plating solution,
For example, Pt, IrO _{2 and the} like are preferable.

Further, the insulating oxide layer in which the conductive particles are dispersed in a proportion of 10 to 40% by volume has excellent adhesiveness when the thickness is 5 μm or less, and when the thickness is 0.05 μm or more, it becomes a base material of the electrode. Excellent in suppressing oxidation. The conductive particles to be dispersed preferably have a particle size of 0.05 to 5 μm. Particles with a particle size of less than 0.05 μm are fine, it is difficult to disperse them uniformly in a solution, and the particle size is 5 μm.
This is because particles exceeding m are less likely to enter the holes of the valve metal.

On the other hand, the volume ratio of the conductive particles dispersed in the insulating oxide layer needs to be 10 to 40% by volume. This is because when the volume of the insulating oxide is more than 90% of the whole, the conductivity is insufficient, and when the amount of the conductive particles is more than 40% of the whole, oxidation toward the interface between the valve metal and the electrode base material is caused. This is because the effect of prevention cannot be obtained.

As a method for forming an insulating oxide layer in which conductive particles are dispersed in a proportion of 10 to 40% by volume, an insulating compound precursor such as a metal alkoxide, a β-diketone chelate, or a β-ketoester is used. A so-called sol-gel method, in which a solution in which conductive particles are dispersed is applied to a solution of a chelate, a carboxylate or the like and heat treatment is performed, can be adopted.

In the case of the second insoluble electrode of the present invention, as described above, the insulating oxide layer in which the conductive particles are dispersed in the ratio of 10 to 40% by volume on the surface of the porous coating of the valve metal. After forming, the holes are filled with a conductive metal by plating.

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 with a thickness of less than 5 μm from the electrode base material side among the holes of the porous coating of the valve metal,
If the effect of improving the adhesion to the metal base material due to the filling cannot be obtained, and if holes can be left only on the outermost layer of the electrode with a thickness of less than 5 μm, coating and baking of the outermost layer of the electrode This is because it is not possible to improve the adhesion to the coating due to the anchor effect.

The conductive metal used here is
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 is filled with the conductive metal. In order to obtain the effect of improving the adhesion to the base 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.

Conductive particles of 10 to 40 are added to such a solution.
In order to evaporate the solvent, after coating the surface of the porous coating film of the valve metal having the insulating oxide layer dispersed in a volume% ratio on the surface by means such as brush coating, spraying method, dipping method, etc. It is dried at 100 to 200 ° C. for several tens of minutes, and 300 to 7 in an oxidizing atmosphere, for example, in the air.
Heat treatment at 00 ° C. 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.

[0041]

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 if a large number of pores and cracks 4 are present in the conductive layer 3 having IrO ₂ as the outermost layer, which is 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, and in the second electrode of the present invention, an intermediate layer 7 composed of a porous coating of a valve metal and a conductive metal is further provided on the intermediate layer 6. Since it exists, the pores and cracks 4 existing in the outermost layer 3 of the electrode do not penetrate into the electrode base material 1, and therefore the exposed area of the electrode base material 1 is small.

Further, since 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, it has excellent adhesion.

Further, since the surface of the electrode on the outermost layer side and the surface of the pores of this porous coating are coated with an insulating oxide layer 8 in which conductive particles are dispersed at a ratio of 10 to 40% by volume, the valve is Oxidation of the metal in the direction of the interface with the porous coating does not proceed, and the coating and baking coating of the conductive oxide containing IrO ₂ as the main component on the outermost layer of the electrode 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, but 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.

[0047]

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 the insoluble electrode was conductive layer mainly composed of and rO _2, dispersed the between the electrode base material and the electrode outermost layer, the electrode outermost layer side surface and the pore surface conductive particles in a proportion of 10 to 40 vol% Made of a valve metal porous film having a layered structure parallel to the electrode base material and covered with the insulating oxide layer, and the holes are filled with a conductive oxide containing IrO ₂ as a main component. An insoluble electrode characterized by having an intermediate layer

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 the insoluble electrode was conductive layer mainly composed of and rO _2, dispersed the between the electrode base material and the electrode outermost layer, the electrode outermost layer side surface and the pore surface conductive particles in a proportion of 10 to 40 vol% It is composed of a valve metal porous film having a layered structure that is covered with the insulating oxide layer and is parallel to the electrode base material.
Each of insoluble electrodes 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 up to 95 μm, and the remainder on the electrode base material side is filled with a conductive metal. An example of the manufacturing method will be described. 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 × 200 mm was washed with oxalic acid, and then roughened by blasting. I got faced.

(2) Formation of intermediate layer; (2-1) Formation of porous coating of valve metal First, four kinds 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) 10-40% by volume of conductive particles
Of an insulating oxide layer dispersed at a ratio of: a solution obtained by mixing IrO ₂ particles with an alcohol solution obtained by hydrolyzing a silicon alkoxide is applied on the porous coating of the valve metal by the dipping method, and then in the atmosphere. The heat treatment operation was repeated once or plural times to form an insulating oxide layer in which conductive particles within the following condition range were dispersed. IrO ₂ particle size: 0.05 to 5 μm IrO ₂ volume ratio: 5 to 50 vol% Heat treatment temperature: 200 to 600 ° C. Coating thickness: 0.05 to 5 μm

(2-3) Filling by plating: For the second insoluble electrode of the present invention, the insulating oxide layer in which the conductive particles are dispersed in the proportion of 10 to 40% by volume in the above (2-2). After forming a valve metal porous coating film whose surface was covered with the electrode base material on the electrode base material, it was immersed in a plating solution and Pt was plated using the 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; H ₂ Ir which becomes IrO ₂ by thermal decomposition
Ta (O), which becomes Ta ₂ O ₅ by thermal decomposition, into 90 parts of Cl ₆
10 parts by weight of C ₂ H ₅ ) ₃ was added and mixed, and a solution prepared by dissolving in butanol was added to the surface of the valve metal having an insulating oxide layer formed by dispersing conductive particles at a ratio of 10 to 40% by volume. The porous coating film was coated on the surface with a brush, dried at 120 ° C. for 20 minutes, placed in an electric furnace, and baked at 450 ° C. for several times. By this method, the pores of the valve metal porous coating were filled with a conductive oxide containing IrO ₂ as a main component 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 example, and the insoluble electrode of the present invention were used as the anode, and a platinum plate was used as the cathode.
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.

In Table 1, 11 is an electrode prepared by a conventional coating and baking method for comparison, and 12 and 1 are also shown.
For comparison, 3 and 14 are electrodes manufactured under conditions different from those of the present invention. In Comparative Example 12, the Pt plating was too thick,
The coating and baking coating had poor adhesion and had a short life. Comparative Example 1
In No. 3, the volume ratio of the conductive particles was small and the current could not be passed. In Comparative Example 14, the volume ratio of the conductive particles was too large, and the insulating effect by the insulating oxide layer was not obtained.

[0057]

[Table 1A]

[0058]

[Table 1B]

[0059]

INDUSTRIAL APPLICABILITY The insoluble electrode of the present invention does not corrode the electrode base material or form an insulating film, has excellent corrosion resistance even when electrolysis is performed at a high current density, and is used for a long time. Endure. It is extremely useful not only as an electrode for electroplating but also as an electrode for other purposes such as electric refining.

[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]

1 the electrode base material 2 Ta-SiO ₂ layer (cross hatched portion) 3 IrO ₂ conductive layer mainly composed of (dense hatched portion) 4 pores and cracks 5 insulating oxide film (black portion) of the six-layer 8 on the surface Porous coating of valve metal with Ir and Ir
A layer composed of a conductive material containing O ₂ as a main component 7 A layer composed of a porous coating of valve metal having a layer 8 on its surface and a conductive metal 8 Conductive particles (white circles) 10 Insulating oxide layer dispersed at a ratio of -40% by volume (black portion)

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 an insulating oxide layer in which conductive particles are dispersed at a ratio of 10 to 40% by volume, and have a layered structure parallel to the electrode base material. An insoluble electrode comprising a coating film, the pores of which are provided with an intermediate layer filled with a conductive oxide containing IrO ₂ as a main component. 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 an insulating oxide layer in which conductive particles are dispersed at a ratio of 10 to 40% by volume, and have a layered structure parallel to the electrode base material. Of the pores, from the surface of the electrode on the outermost surface side of the electrode to a depth of 5 to 95 μm is filled with a conductive oxide containing IrO ₂ as a main component, and the remainder on the electrode base material side is made of a conductive metal. An insoluble electrode comprising a filled intermediate layer. 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 thickness of the insulating oxide layer, which covers the surface of the electrode outermost layer side and the surface of pores of the porous coating of the valve metal and in which the conductive particles are dispersed at a rate of 10 to 40% by volume, is 0.1. 0
The insoluble electrode according to any one of claims 1 to 6, wherein the conductive particles are in a range of 5 to 5 µm and the dispersed conductive particles have a particle diameter of 0.05 to 5 µm. 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 an insulating oxide layer in which conductive particles are dispersed at a ratio of 10 to 40% by volume, and is made of a valve metal porous coating having a layered structure parallel to the electrode base material. An intermediate layer filled with a conductive oxide containing IrO ₂ as a main component is provided in the voids, and an outermost layer of the electrode is formed by a coating baking method to form an insoluble electrode having a conductive layer containing IrO ₂ as a main component. In the manufacturing method, the valve metal is sprayed on the electrode base material to form a porous metal coating of the valve metal having a porosity of 5 to 40%, and then the surface of the porous coating of the valve metal is electrically conductive. Particles are dispersed at a ratio of 10 to 40% by volume and contain an insulating compound precursor. The solution applied by repeating the operation of performing a heat treatment in an oxidizing atmosphere, the porous coating of the electrode outermost layer side surface and the pore surface to the conductive particles of the valve metal 10
After forming an insulating oxide layer dispersed at a ratio of ˜40% by volume, the operation of applying a solution containing an Ir compound as a main component thereon and performing heat treatment in an oxidizing atmosphere is repeated to form a valve metal. A method for producing an insoluble electrode, characterized in that the intermediate layer is formed by filling the pores of the porous coating film with a conductive oxide containing IrO ₂ as a main component. 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 an insulating oxide layer in which conductive particles are dispersed at a ratio of 10 to 40% by volume, and is made of a valve metal porous coating having a layered structure parallel to the electrode base material. , 5 to 95 μm from the coating surface on the electrode outermost layer side among the pores
Is filled with a conductive oxide containing IrO ₂ as a main component, and the remaining portion on the electrode base material side is filled with a conductive metal to form an intermediate layer.
_{In the} method of manufacturing an insoluble electrode having a conductive layer containing ₂ as a main component, a porosity of 5 to 5 is obtained by spraying a valve metal on the electrode base material.
A porous metal coating of the valve metal is formed in a range of 40%, and then conductive particles are dispersed on the surface of the porous coating metal of the valve metal at a ratio of 10 to 40% by volume, and an insulating compound precursor is added. The operation of applying the containing solution and heat-treating it in an oxidizing atmosphere is repeated, so that 10-40 conductive particles are formed on the surface of the electrode metal outermost layer and the surface of the pores of the porous coating of the valve metal.
After forming an insulating oxide layer dispersed in a volume percentage, electroplating a conductive metal using the electrode base material as a cathode to form a coating on the electrode outermost layer side of the pores of the valve metal porous coating. An operation of filling the lower layer of the film excluding a depth of 5 to 95 μm from the surface with a conductive metal, further applying a solution containing an Ir compound as a main component on the lower layer, and performing heat treatment in an oxidizing atmosphere A method for producing an insoluble electrode, characterized in that the voids in the upper layer of the porous coating film of the valve metal are repeatedly filled with a conductive oxide containing IrO ₂ as a main component to form an intermediate layer. 10. A heat treatment temperature at the time of forming an insulating oxide layer in which conductive particles are dispersed at a ratio of 10 to 40% by volume on the surface of the electrode metal outermost layer side and the surface of pores of the porous coating of valve metal. 10. The method for producing an insoluble electrode according to claim 8 or 9, wherein the temperature is in the range of 600 ° C to 600 ° C.