JPH08253894A - Insoluble electrode and manufacturing method thereof - Google Patents

Abstract

(57) [Summary] [Object] To provide 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] Electrode base material is a conductive metal, and the outermost layer of the electrode is IrO
_In the insoluble electrode, which is a conductive layer containing ₂ as a main component, between the electrode base material and the outermost layer of the electrode, on the electrode base material side, from the porous coating of the valve metal having a layered structure parallel to the electrode base material. A layer filled with an insulating oxide in which conductive particles are dispersed in a ratio of 10 to 60% by volume, and an insulating property in which conductive particles are dispersed in a ratio of 10 to 60% by volume on the outermost surface of the electrode. A layer made of oxide is provided. [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,
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.

[0003] This electrode is subjected to PbO on its surface during electric current treatment in an electroplating bath or an electric refining bath, especially in a sulfuric acid solution.
₂ produces. Although this PbO ₂ exerts a function as an electrode, the generated PbO ₂ and Pb metal have a weak adhesive force and are mixed 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. 2 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.

[0006]

[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, the electrode base material 1 is prevented from being exposed due to 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.

[0010]

The present invention provides 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. An intermediate layer consisting of two layers is provided between the surface layers, of which the layer on the electrode base material side is made of a valve metal porous coating having a layered structure parallel to the electrode base material, and the pores are electrically conductive. A layer filled with an insulating oxide in which particles are dispersed in a proportion of 10 to 60% by volume, and a layer made of an insulating oxide in which a layer on the outermost surface side of the electrode is dispersed in conductive particles in a proportion of 10 to 60% by volume. And an insoluble electrode and a manufacturing method thereof.

In particular, the volume ratio of the valve metal and the insulating oxide in which the conductive particles are dispersed at a rate of 10 to 60% by volume, which constitutes the electrode base material side layer of the intermediate layer, is 30. :
70 to 95: 5, the thickness of the intermediate layer on the electrode base material side is in the range of 5 to 100 μm, and the thickness of the intermediate layer on the electrode outermost layer side is 0.1. ~
It is characterized by being in the range of 10 μm.

Further, in the present invention, a method for producing an insoluble electrode comprising three layers of an electrode base material, an intermediate layer and an electrode outermost layer is as follows.

That is, the insoluble electrode of the present invention is (1)
The electrode base material is composed of a conductive metal layer, and (2) a porous valve metal film having a layered structure parallel to the electrode base material is formed on the electrode base material, and conductive particles are present in the pores. Is provided at an electrode base material side intermediate layer filled with an insulating oxide dispersed at a rate of 10 to 60% by volume, and (3) conductive particles are further dispersed on the intermediate layer at a rate of 10 to 60% by volume. After providing an intermediate layer on the electrode outermost layer side made of an insulating oxide, (4) an electrode outermost layer is formed by a coating baking method.
It is a conductive layer containing rO ₂ as a main component.

The manufacturing method is characterized in that (2) -1 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%. ) -2
Next, an operation in which conductive particles are dispersed at a ratio of 10 to 60% by volume and a solution containing an insulating compound precursor is applied to the surface of the porous coating film of the valve metal, and heat treatment is performed in an oxidizing atmosphere. Repeatedly, filling the insulating oxide in which the conductive particles are dispersed in the pores of the valve metal porous coating film at a ratio of 10 to 60% by volume to form an intermediate layer on the side of the electrode base material, and further,

(3) On top of that, conductive particles 10 to 6 are provided.
The operation of applying a solution containing an insulating compound precursor dispersed at a rate of 0% by volume and performing heat treatment in an oxidizing atmosphere is repeated to form an intermediate layer on the outermost surface side of the electrode.
The point is to provide an intermediate layer consisting of layers.

In the insoluble electrode of the present invention, the conductive particles dispersed in the insulating oxide have a particle size of 0.05 to
It is in the range of 5 μm, and in the manufacturing method thereof, the heat treatment temperature at the time of forming the insulating oxide in which the conductive particles are dispersed in the proportion of 10 to 60% by volume, which constitutes the intermediate layer, is 2
It is characterized in that the temperature is in the range of 00 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 film forming the layer on the electrode base material side of the intermediate layer is any of valve metals (Ti, Ta, Zr, Nb) stable in a sulfuric acid solution. It is necessary to be.

The porous coating of valve metal has a particle size of 20-4.
It can be formed by spraying 0 μm valve metal powder by, for example, plasma spraying. The raw material powder is deformed by thermal spraying,
A disc-shaped thin film with a thickness of 2 μm and a diameter of several 10 μm,
This deposits to form a porous multilayer coating. If the thickness of the porous coating film of the valve metal formed by thermal spraying, that is, the layer on the electrode base material side of the intermediate layer is 100 μm or less, the adhesiveness to the electrode base material is particularly excellent.

On the other hand, in order to prevent the conductive metal used as the electrode base material from being exposed, it is necessary to improve the adhesion to the coating and baking coating of the outermost layer of the electrode by the anchor effect. To this end, the porous coating film pores of the valve metal are filled with an insulating oxide in which conductive particles are dispersed at a rate of 10 to 60% by volume from the electrode outermost layer side for a thickness of at least 5 μm or more. That is, the thickness of the valve metal porous coating formed by thermal spraying is at least 5 μm.
That is all. Therefore, the thickness of the porous coating is 5 to 100.
It is preferably in the range of μm.

As a thermal spraying condition, the volume ratio of the valve metal to the insulating oxide in which the conductive particles are dispersed in a proportion of 10 to 60% by volume is in the range of 30:70 to 95: 5, that is, the valve. The durability is excellent when the porosity of the metal is in the range of 5 to 70%. Because the volume ratio of the valve metal is 30% or more, the conductive particles are 10 to 10%.
The adhesiveness of the insulating oxide dispersed in the proportion of 60% by volume is excellent, and by setting the volume ratio to 95% or less, the insulating oxide in which the conductive particles are dispersed in the proportion of 10 to 60% by volume,
This is because the pores of the valve metal porous film can be filled with a sufficient amount of electricity.

The porosity of the valve metal porous coating can be calculated, for example, by observing a longitudinal section or a transverse section of the coating and calculating the area ratio thereof.

In the insoluble electrode of the present invention, as a material of the insulating oxide which constitutes the intermediate layer and in which the conductive particles are dispersed in a proportion of 10 to 60% by volume, a stable oxide in a plating solution, such as SiO 2, is used. ₂ , Al ₂ O ₃ , ZrO _{2 and the} like are preferable.

The material of the conductive particles is metal,
Alternatively, a metal nitride, a metal carbide, a metal suicide, or a metal boride having conductivity similar to that of a metal may be used. Particularly, a platinum group metal or a platinum group oxide, such as Pt or IrO ₂ , which is stable in the plating solution is preferable.

As a method for filling or forming an insulating oxide in which conductive particles are dispersed in a proportion of 10 to 60% by volume, an insulating compound precursor such as a metal alkoxide,
A so-called sol-gel method in which a solution in which conductive particles are dispersed is applied to a solution of a β-diketone chelate, a β-ketoester chelate, a carboxylic acid salt or the like and heat-treated can be employed.

The particle size of the conductive particles dispersed in the insulating oxide is preferably in the range 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 needs to be 10 to 60% by volume. This is because the volume of insulating oxide is 90% of the total volume.
This is because if the amount is larger than that, the conductivity is insufficient, and if the amount of the conductive particles is more than 60% of the whole, the pores of the valve metal porous coating cannot be uniformly and densely filled.

Of the intermediate layer, the layer on the electrode outermost layer side made of an insulating oxide in which conductive particles are dispersed in a proportion of 10 to 60% by volume, when the thickness is 0.1 μm or more,
It has an excellent effect of preventing the porous coating film of the valve metal from being exposed, and when it is thicker than 10 μm, it becomes easy to peel off.

In the present invention, the outermost layer of the electrode is formed by forming a conductive oxide containing IrO ₂ as a main component by repeating the steps of applying a solution containing an Ir compound as a main component and performing heat treatment in an oxidizing atmosphere. It can be provided by a so-called coating baking method.

Examples of the solution containing an Ir compound as a main component are described in, for example, JP-A-62-240780 and JP-A-63-2.
No. 35493, JP-A-3-193889, or JP-A-59-150091.

Specifically, it is an alcohol solution containing iridium chloride as a main component and compounds such as tantalum alkoxide and chloroplatinic acid. Such a solution is applied to the surface of the intermediate layer by means of brushing, spraying, dipping or the like, and then 100 to 2 to evaporate the solvent.
It is dried at 00 ° C. for several tens of minutes and heat-treated at 300 to 700 ° C. in an oxidizing atmosphere, for example, in the air. By repeating such an operation a plurality of times, IrO as the outermost layer of the electrode is formed.
A conductive layer containing ₂ as a main component is formed.

[0031]

The structure of the insoluble electrode of the present invention is shown in FIG. The operation will be described below with reference to this drawing. In the insoluble electrode of the present invention, even when a large number of pores and cracks 4 are present in the conductive layer 3 having IrO ₂ as the outermost layer of the electrode, the layer 6 on the electrode base material side of the intermediate layer is present. The pores and cracks 4 existing in the outermost surface layer 3 of the electrode do not penetrate into the electrode base material 1.

The surface of the valve metal forming the electrode base material side layer 6 of the intermediate layer is covered with the electrode outermost layer 7 of the intermediate layer, and the valve metal is not exposed.
The layer 6 on the electrode base material side of the intermediate layer is the electrode base material 1
Since it is made of the same valve metal as the above, it has excellent adhesion. In addition, the holes of the valve metal are filled with an insulating oxide in which conductive particles are dispersed at a rate of 10 to 60% by volume. Therefore, the oxidation in the direction of the interface between the electrode base material and the porous coating of the valve metal is unlikely to proceed.

As a result, the conductive layer 3 having IrO ₂ as the main component, which is the outermost layer of the electrode, is not peeled off. Insoluble electrode of the present invention as described above, without the electrode base metal is exposed, the oxidation progress of the interface direction between the porous coating of the electrode base material and the valve metal can also be suppressed, 100A / dm ² or more high It can withstand long-term use even with current density.

[0034]

EXAMPLE An insoluble electrode of the present invention, that is, an insoluble electrode in which the electrode base material is composed of a conductive metal and the electrode outermost layer is a conductive layer containing IrO ₂ as a main component, the electrode base material and the electrode outermost layer are An intermediate layer consisting of two layers is provided between them, and the layer on the electrode base material side is composed of a valve metal porous coating having a layered structure parallel to the electrode base material, and conductive particles are present in the pores. A layer filled with an insulating oxide dispersed at a rate of 10 to 60% by volume was used, and a layer on the outermost layer side of the electrode was a layer made of an insulating oxide having conductive particles dispersed at a rate of 10 to 60% by volume. An example of a method for producing the insoluble electrode is described below.

Manufacturing method of insoluble electrode: (1) Treatment of electrode base material; using a Ti plate as an 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 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 sprayed onto the electrode base material by the usual plasma spraying method. Then, a porous coating film of valve metal was formed on the electrode base material. Coating thickness: 5-100 μm Porosity: 5-70%

(2-2) 10 to 60% by volume of conductive particles
Filling of the insulating oxide dispersed in the ratio of, and formation of a layer on the electrode outermost surface side of the intermediate layer. A solution prepared by mixing IrO ₂ particles or TiN particles in an alcohol solution obtained by hydrolyzing a silicon alkoxide is used as a valve metal. The operation of coating the porous coating by the dipping method and heat-treating it in the atmosphere is repeated once or multiple times to remove the insulating oxide in which the conductive particles are dispersed in the pores of the porous coating of the valve metal. Filled.

Further, by repeating this operation, a layer of the intermediate layer on the electrode outermost layer side was formed to have a predetermined thickness. Conductive particle diameter: 0.05 to 5 μm Conductive particle volume ratio: 5 to 70 vol% Heat treatment temperature: 200 to 600 ° C. Thickness of the electrode outermost layer side of the intermediate layer: 0.1 to 10 μm
m

(3) Formation of outermost layer of electrode; I by thermal decomposition
90 parts of H ₂ IrCl ₆ to be rO ₂ was Ta-decomposed by thermal decomposition.
10 parts of Ta (OC ₂ H ₅ ) ₃ to be ₂ O ₅ was mixed and the solution dissolved in butanol was applied on the surface of the intermediate layer formed in (2-2) above with a brush, and at 120 ° C. After drying for 20 minutes, it was placed in an electric furnace and baked at 450 ° C. a plurality of times to form the outermost layer of the electrode.

Table 1 shows the durability test results of the insoluble electrode of the present invention thus obtained, together with the conventional product and the comparative example. 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.
Current density 200 A / dm ² in 5 wt% sulfuric acid solution at ℃
Was conducted and the time until the voltage increased by 10 V was measured. In Table 1, ∘ indicates the service life of 4000 hours or more, and x indicates the insoluble electrode whose life was less than 4000 hours. 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 is an electrode manufactured under conditions different from those of the present invention. In Comparative Example 12, the volume ratio of the conductive particles was small and it was impossible to conduct electricity. In Comparative Example 13, the volume ratio of the conductive particles was too large, and the effect of applying the intermediate layer was not obtained.

[0042]

[Table 1A]

[0043]

[Table 1B]

[0044]

INDUSTRIAL APPLICABILITY The insoluble electrode of the present invention is excellent in corrosion resistance even when electrolyzing 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 the structure of an insoluble electrode of the present invention.

FIG. 2 shows a conventional electrode structure.

FIG. 3 is an explanatory diagram of an oxidation mechanism in a conventional electrode.

[Description of Reference Signs] 1 electrode base material 2 Ta-SiO ₂ layer (cross hatched portion) 3 conductive layer containing IrO ₂ as a main component (dense hatched portion) 4 pores and cracks 5 insulating oxide film (black portion) 6 A layer composed of an insulating oxide in which conductive particles (black dots) are dispersed at a ratio of 10 to 60% by volume and a porous coating film of a valve metal 7. Conductive particles (black dots) at a ratio of 10 to 60% by volume Layer consisting of dispersed insulating oxide (dotted pattern)

[Procedure amendment]

[Submission date] May 24, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction content]

On the other hand, the anchor effect of the intermediate layer on the outermost surface side of the electrode
In order to improve the adhesion by the effect, the thickness of the valve metal porous coating formed by thermal spraying is at least 5 μm or more. Therefore, the thickness of the porous coating is preferably in the range of 5 to 100 μm.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0032

[Correction method] Change

[Correction content]

The surface of the valve metal forming the electrode base material side layer 6 of the intermediate layer is covered with the electrode outermost layer 7 of the intermediate layer, and the valve metal is not exposed.
The layer 6 on the electrode base material side of the intermediate layer is the electrode base material 1
Since it is made of the same valve metal as the above, it has excellent adhesion. In addition, the holes of the valve metal are filled with an insulating oxide in which conductive particles are dispersed at a rate of 10 to 60% by volume. Therefore, the oxidation in the direction of the interface between the electrode base material and the porous coating of the valve metal is unlikely to proceed.

Claims (7)

[Claims] 1. 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, and two layers are provided between the electrode base material and the electrode outermost layer. And an electrode base material side layer of which is composed of a valve metal porous film having a layered structure parallel to the electrode base material, and 10 to 60% by volume of conductive particles in the pores. Is a layer filled with an insulating oxide dispersed in a ratio of 10 to 60% by volume, and the layer on the electrode outermost layer side is a layer made of an insulating oxide in which conductive particles are dispersed in a ratio of 10 to 60% by volume. Insoluble electrode. 2. The volume ratio of the valve metal, which constitutes the layer on the electrode base material side of the intermediate layer, and the insulating oxide in which the conductive particles are dispersed in a proportion of 10 to 60% by volume to 30. : 7
The insoluble electrode according to claim 1, which is in the range of 0 to 95: 5. 3. The thickness of the layer on the electrode base material side of the intermediate layer is
The insoluble electrode according to claim 1, which is in the range of 5 to 100 μm. 4. The insoluble electrode according to any one of claims 1 to 3, wherein the intermediate layer has a thickness of a layer on the electrode outermost layer side in the range of 0.1 to 10 μm. 5. The insoluble according to any one of claims 1 to 4, wherein the conductive particles dispersed in the insulating oxide have a particle diameter in the range of 0.05 to 5 μm. electrode. 6. 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 base material is provided on the electrode base material with respect to the electrode base material. And an intermediate layer on the side of the electrode base material filled with an insulating oxide in which conductive particles are dispersed in a ratio of 10 to 60% by volume. Further, an intermediate layer on the electrode outermost layer side made of an insulating oxide in which conductive particles are dispersed in a proportion of 10 to 60% by volume is further provided thereon, and then the electrode outermost layer is formed by a coating and baking method. IrO
_{In the} method for manufacturing an insoluble electrode having a conductive layer containing ₂ as a main component, a porosity of 5 is obtained by spraying a valve metal on an electrode base material.
To 40% by volume of the valve metal porous film is formed, then conductive particles are dispersed on the surface of the valve metal porous film at a rate of 10 to 60% by volume, and an insulating compound precursor By repeating the operation of applying a solution containing the above and performing heat treatment in an oxidizing atmosphere, an insulating oxide in which conductive particles are dispersed in the pores of the valve metal porous coating film at a ratio of 10 to 60% by volume is prepared. After filling and forming an intermediate layer on the side of the electrode base material, further thereon, conductive particles are dispersed in a proportion of 10 to 60% by volume, and a solution containing an insulating compound precursor is applied, A method for producing an insoluble electrode, which comprises repeating an operation of performing heat treatment in an oxidizing atmosphere to form an intermediate layer on the outermost surface side of the electrode and providing an intermediate layer composed of two layers. 7. The conductive particles constituting the intermediate layer are 10 to 10.
7. The method for producing an insoluble electrode according to claim 6, wherein the heat treatment temperature when forming the insulating oxide dispersed at a ratio of 60% by volume is set in the range of 200 to 600 ° C.