JPH06330394A - Insoluble electrode - Google Patents

Abstract

(57) [Summary] [Object] An object of the present invention is to provide an insoluble electrode which has excellent corrosion resistance even when electrolysis is performed at a high current density of 100 A / dm ² or more, and which can be used for a long time. According to the insoluble electrode of the present invention, the electrode base material is a conductive metal, the electrode outermost layer is a conductive layer containing IrO _{2 as a} main component, and the nonconductive layer is provided between the electrode base material and the electrode outermost layer. It is characterized in that a coating is provided and an intermediate layer is formed by filling a conductive material in a plurality of voids formed so as to penetrate the electrode base material in a direction substantially perpendicular to the non-conductive coating. [Effect] The formation of an oxide film of the electrode base material can be prevented, and the durability in a sulfuric acid bath under a high current density is excellent.

Description

Detailed Description of the Invention

[0001]

This invention relates to an insoluble electrode.

[0002]

2. Description of the Related Art Generally, when electroplating a metal material, an insoluble electrode is used in an electroplating bath to electroplate a metal such as Zn, Sn, Ni, Cr on the surface of a metal material to be plated which is a cathode. Has been done. When electrorefining metal, an insoluble electrode is used in the refining bath to remove Mn, Zn
Electric refining of metal such as is performed. The most commonly used insoluble electrode at this time is a Pb-based alloy. In this electrode, PbO ₂ is produced on the surface of the electrode in an electroplating bath, an electrorefining bath, especially in a sulfuric acid solution when an electric current is applied. Although PbO ₂ exhibits the function of an insoluble electrode, the generated PbO ₂ and Pb have a weak adhesive force and are mixed in the electrolytic solution to cause defective plating or refined metal containing impurities.

Therefore, as a countermeasure, an electroplating bath, an electrorefining bath, especially IrO ₂ , which is a platinum group oxide which is the most electrochemically stable in a sulfuric acid solution, is coated on a conductive metal as an electrode base material. The insoluble electrode is shown in Japanese Patent Publication No. 48-3954. Furthermore, in order to suppress the oxidation of the conductive metal layer which is the electrode base material or to improve the adhesion of IrO ₂ , a coating film in which Ta ₂ O ₅ or the like is added is formed on the intermediate layer, and the IrO ₂ layer is formed thereon. The method of using the formed insoluble electrode is disclosed in JP-B-46-21884 and JP-A-63-
No. 235493. FIG. 4 shows the insoluble electrode structure. 1 is an electrode base material, 2 is IrO ₂ —Ta ₂ O
Layers ₅ and 3 are IrO ₂ layers. The layers 2 and 3 are applied by applying a solution containing an Ir compound precursor and a Ta compound precursor on the electrode base material and heat-treating in an oxidizing atmosphere.
This is a so-called coating and baking method in which a conductive layer made of rO ₂ and Ta ₂ O ₅ is formed.

[0004]

[Problems to be Solved by the Invention] Japanese Patent Publication No. 46-2188
No. 4, JP-A-63-235493, an insoluble electrode having a layer mainly composed of IrO _{2 formed} by a coating and baking method can be used for a long time at a low current density (-10 A / dm ² ). However, when conducting an energization test under a high current density, especially in a sulfuric acid solution at 100 A / dm ² , 3000-4
A sudden voltage increase occurs at 000 hours, and the electrode becomes unusable.

The mechanism of voltage increase of the insoluble electrode will be described with reference to FIG. Since the layers 2 and 3 containing IrO ₂ are produced by the coating and baking method, pores due to the volatilization of the solution components, and a hexagonal crack 4 in the coating film due to the difference in thermal expansion between the electrode base material 1 and the IrO ₂ layer. It has occurred. For this reason, the porosity of the coating is as large as 10 to 30%, direct current is applied to the electrode base material 1 from these pores and cracks, an insulating oxide 5 is formed on the surface of the electrode base material, and further the electrode base material and IrO.
Oxidation of the electrode base material progresses through the _two- layer interface, causing a voltage rise and losing the function as an electrode.

As a countermeasure against this, it is necessary that the electrode base material is not exposed at the cracks and pores of the IrO ₂ layer. It is an object of the present invention to provide an insoluble electrode which has excellent corrosion resistance even when electrolysis is carried out at a high current density of 100 A / dm ² or more and can withstand long-term use.

[0007]

The insoluble electrode of the present invention comprises:
The electrode base material is a conductive metal, and the outermost layer of the electrode is mainly composed of I
In an insoluble electrode that is a conductive layer made of rO ₂ , a plurality of non-conductive coatings are provided between the electrode base material and the outermost surface layer of the electrode, and a plurality of holes are formed so as to penetrate the electrode base material in a direction substantially perpendicular to the non-conductive coating. Having an intermediate layer filled with a conductive material in the voids, the volume ratio of the non-conductive film to the conductive material is 60:40 to 99: 1, and the thickness of the intermediate layer is 0. It is characterized in that it is between 1 and 100 μm.

[0008]

First, the insoluble electrode of the present invention will be described with reference to FIGS.
Explained by. Since the insoluble electrode of the present invention has a layer composed of the non-conductive coating film 7 and the conductive material 8 in the intermediate layer 6, the crack 4 existing in the conductive layer whose main component of the electrode outermost layer 9 is IrO ₂ The pores 4'do not penetrate into the electrode base material 1 and the electrode base material 1 is not exposed to the electrolyte surface.
Further, since the filled portion of the conductive material 8 in the intermediate layer 6 is present intermittently, the progress of oxidation of the electrode base material toward the interface between the electrode base material 1 and the intermediate layer 6 is suppressed. For this reason, the oxidation of the electrode base material can be suppressed, and even if electrolysis is performed at a high current density of 100 A / dm ² or more, the corrosion resistance is excellent and it can withstand long-term use.

Next, the insoluble electrode of the present invention will be described. The electrode base material 1 used in the present invention may be a conductive metal, but a valve metal (T
i, Ta, Zr, etc. Metals that have almost no erosion damage in sulfuric acid baths)
It is preferable that This is because the corrosion resistance in a sulfuric acid bath is excellent and the breakdown voltage is high.

In the insoluble electrode of the present invention, the material of the non-conductive coating 7 forming the intermediate layer 6 is preferably an oxide which is stable in the plating solution, such as SiO ₂ , Al ₂ O ₃ or ZrO ₂ . Further, the coating film is required to have a thickness of 100 μm or less because it becomes easy to peel off when it is made thicker, and 0.1 μm or more in order to obtain the effect of suppressing the oxidation of the electrode base material.

As a method for forming the non-conductive coating 7, a solution of a non-conductive compound precursor such as a metal alkoxide, a β-diketone chelate, a β-ketoester chelate or a carboxylate is applied and then heat treated. , The so-called sol-gel method, and the particle size of the non-conductive compound precursor is 20 to 40 μm.
A so-called thermal spraying method in which the raw material powder of m is sprayed on the electrode base material by a spraying gun can be adopted.

A plurality of voids penetrating the electrode base material 1 in the substantially vertical direction of the non-conductive coating 7 are formed by evaporating the components of the electrically conductive coating by laser processing to form holes, or by a mechanical method, that is, a cemented carbide drill or the like. It can be formed by perforating a non-conductive coating until the base material is exposed.

It is desirable that the voids formed at this time be opened in a direction substantially perpendicular to the electrode base material, that is, within an inclination of about ± 30 ° with respect to the vertical direction of the electrode base material. This is because if the inclination is larger than this, the exposed portion of the surface of the electrode base material becomes large relative to the void diameter, leading to a reduction in the life of the insoluble electrode.

There is no problem with the void having any shape. The diameter of the void is 1 μm or more for filling the conductive material 8,
Further, since the electrode base material has a size of about 500 × 100 mm, it is desirable that the size is 5000 μm or less.

Since the void is filled with a conductive material to serve as the electrode base material and the conductive portion of the outermost layer 9 of the electrode, the volume ratio of the non-conductive coating 7 and the conductive material 8 is 60:40 to 99: 1, that is, The area ratio of the horizontal cross section of the coating is 60:40 to 9
It should be 9: 1. This is because when the area ratio of the non-conductive coating is less than 60%, even when the intermediate layer 6 is provided, the effect of reducing the exposed area of the electrode base material 1 by this layer cannot be obtained and the life of the insoluble electrode is improved. This is because there is no effect, and when the area ratio is more than 1%, the resistance of the coating film is large and the current flow is hindered. Also, in order to supply current evenly,
The voids are preferably uniformly dispersed on the surface of the insoluble electrode.

As the method of filling the voids of the non-conductive coating film 7 with the conductive material 8 in the present invention, so-called coating baking method and electroplating method can be adopted. The coating and baking method is mainly composed of I
This is a method of forming a coating film by coating a solution of an r compound precursor, drying it, and then performing heat treatment in an oxidizing atmosphere one or more times.

The solution whose main component is an Ir compound precursor is, for example, JP-A-62-240780 or JP-A-6-240780.
An alcohol solution comprising a compound precursor such as iridium chloride, tantalum alkoxide, and chloroplatinic acid, which are disclosed in JP-A-3-235493, JP-A-3-193889, and JP-A-59-150091. IrO ₂ was mixed by heat treatment so that the volume ratio was between 50 and 100% and the balance was Ta ₂ O ₅ , Pt, and the like.

The above-mentioned solution is applied onto the non-conductive coating having the perforations by, for example, brush coating, spraying, dipping or the like, and then dried at 150 to 200 ° C. for several tens of minutes to evaporate the solvent. , In an oxidizing atmosphere, for example 300 in air
To 700 ° C. By repeating the operation from this application to the heat treatment once or a plurality of times, the voids of the non-conductive coating can be filled with the conductive material whose main component is IrO ₂ , and the intermediate layer is formed.

The electroplating method is a method in which normal plating is performed using the electrode base material 1 as a cathode, and a conductive material 8 which can be plated can be filled in the voids of the nonconductive coating 7. The conductive material 8 is preferably a platinum group metal having excellent durability in a sulfuric acid bath. For example, the electrode base material 1 having a non-conductive coating and perforated with voids is dipped in a plating solution in which a platinum group metal such as Pt metal is dissolved, and Pt is used for the cathode and the electrode base material 1 is used for the anode. By energizing, the non-conductive film voids can be filled with a conductive material, such as Pt, to form an intermediate layer. In the insoluble electrode of the present invention, the main component of the electrode outermost layer 9 is Ir.
The conductive layer made of O ₂ can be formed by the coating and baking method described above.

When used as an anode in a sulfuric acid bath, the insoluble electrode of the present invention has a longer life than conventional insoluble electrodes. In addition, when the conductive material is filled in the voids of the non-conductive coating by a coating baking method or an electroplating method, the durability is almost the same.

A longitudinal section of the insoluble electrode of the present invention is shown in FIG. 1, and a horizontal section AA 'in the intermediate layer portion is shown in FIG. In the insoluble electrode of the present invention, the main component of the electrode outermost layer 9 is IrO ₂
Even if there are many cracks 4, pores 4 ', etc. in the conductive layer, the crack penetrating into the electrode base material 1 due to the presence of the intermediate layer 6 in which the voids of the non-conductive coating 7 are filled with the conductive material 8. 4. Since there are no pores 4 ', oxidation of the electrode base material 1 can be suppressed. Further, as shown in FIG. 2, since the current-carrying portion in the intermediate layer is present intermittently, the progress of the base material oxidation toward the interface between the electrode base material 1 and the intermediate layer 6 can be suppressed, and the high current density of 100 A / dm ² or more But it can be used for a long time.

[0022]

EXAMPLE A manufacturing flow chart of the insoluble electrode of the present invention is shown in FIG. Hereinafter, the flowchart will be described in detail.

1) Pretreatment of electrode base material 100 × 100 × 20 m using Ti plate as electrode base material
The surface of the electrode base material of m is washed with oxalic acid and then roughened by blasting.

2) Formation of Non-Conductive Film The operation of applying an alcohol solution of silicon alkoxide on the electrode base material by the dipping method and then heat treating it in the air at 50 to 600 ° C. is repeated once or plural times. Form a protective film. Coating thickness: 0.05-200 μm

3) Perforation of the non-conductive coating The perforation of the non-conductive coating is carried out by evaporating the material of the non-conductive coating by laser heating or by punching with a cemented carbide drill until it reaches the electrode base material. Laser method: Used for drilling diameters from 0.5 μm to less than 300 μm Drill method: Used for drilling diameters from 300 μm to 5000 μm

4) Filling the voids of the non-conductive coating with a conductive material Coating and baking method Irradiation from the non-conductive coating with the perforations in the voids by thermal decomposition
H ₂ IrCl ₆ which becomes O ₂ and Ta (OC ₂ H ₅ ) ₃ which becomes Ta ₂ O ₅ by thermal decomposition are mixed at a volume ratio of 9: 1, and a solution dissolved in butanol is applied with a brush and dried. An intermediate layer is formed by performing a heat treatment at 450 ° C. in a furnace several times to fill the voids of the non-conductive film with a conductive material whose main component is IrO ₂ . Electroplating method Electrode base material with non-conductive coating and perforated holes is used as a cathode,
An intermediate layer is formed by immersing Pt in a plating solution containing Pt as an anode and filling Pt in the non-conductive film voids by energization. Current density: 1 A / dm ² Plating component: Pt

5) Film formation of outermost layer of electrode H ₂ IrCl ₆ which becomes IrO ₂ by thermal decomposition from the intermediate layer
And Ta (OC ₂ H ₅ ) ₃ which becomes Ta ₂ O ₅ by thermal decomposition are mixed at a volume ratio of 9: 1 and a solution dissolved in butanol is applied with a brush, dried, put in an electric furnace and baked at 450 ° C. The outermost layer of the electrode was formed by repeating the above step.

Table 1 shows examples of the insoluble electrode of the present invention and the results of durability test. The durability of the produced insoluble electrode was evaluated by the following method. The insoluble electrodes (1) to (8) of the present invention, conventional products (9), and comparative products (10) to the anode
(16) Using a platinum plate as the cathode, an energization test was conducted at a current density of 200 A / dm ² in a 5 wt% sulfuric acid solution at 60 ° C., and the time until the voltage increased by 10 V was measured. In Table 1, ∘ indicates an insoluble electrode having a service life of 6000 hours or more. Table 1 shows that the insoluble electrode of the present invention has a life of 6000 hours or more and is excellent in durability. Incidentally, this time, the outermost layer of the electrode contained IrO ₂ and Ta ₂ O ₅ in a volume ratio of 9: 1.
The results of durability evaluation were shown for the insoluble electrode, which is No. _{2, and the} outermost layer of the electrode contains IrO ₂ in a volume ratio of 50 to 1
If it is 00 vol%, similar durability is exhibited.

[0029]

[Table 1]

[0030]

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 extremely useful as an insoluble electrode for applications.

[Brief description of drawings]

FIG. 1 shows a longitudinal section of an insoluble electrode of the present invention.

FIG. 2 is a cross-sectional view taken along the line AA ′ of the insoluble electrode of the present invention in the horizontal direction.

FIG. 3 is a production flowchart of the insoluble electrode of the present invention.

FIG. 4 shows a conventional insoluble electrode structure.

FIG. 5 is an explanatory diagram of an oxidation mechanism of a conventional insoluble electrode base material.

[Explanation of symbols]

1 the electrode base material ₂ IrO 2 -Ta 2 O ₅ layer 3 IrO ₂ layer 4 Crack 4 'pores 5 insulating oxide 6 intermediate layer 7 non-conductive film 8 conductive material 9 electrode outermost layer

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] August 10, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

A plurality of voids penetrating the electrode base material 1 in a substantially vertical direction of the non-conductive coating 7 are made non-conductive by laser processing .
It can be formed by evaporating and perforating the conductive coating component, or by perforating the non-conductive coating by a mechanical method, that is, a cemented carbide drill or the like until the electrode base material is exposed.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction content]

The solution whose main component is an Ir compound precursor is, for example, JP-A-62-240780 or JP-A-6-240780.
3-235493, JP-A No. 3-193889, JP-shown in JP-A-59-150091,
For example, iridium chloride, tantalum alkoxide, an alcohol solution consisting of a compound precursor such as chloroplatinic acid,
IrO ₂ was mixed by heat treatment so that the volume ratio was between 50 and 100% and the balance was Ta ₂ O ₅ , Pt, and the like.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction content]

The electroplating method is a method in which normal plating is performed using the electrode base material 1 as a cathode, and a conductive material 8 which can be plated can be filled in the voids of the nonconductive coating 7. The conductive material 8 is preferably a platinum group metal having excellent durability in a sulfuric acid bath. For example, the electrode base material 1 having non-conductive coating and perforated holes is immersed in a plating solution in which a platinum group metal such as Pt metal is dissolved, and Pt is used for the anode and the electrode base material 1 is used for the cathode. By energizing, the non-conductive film voids can be filled with a conductive material, such as Pt, to form an intermediate layer. In the insoluble electrode of the present invention, the main component of the electrode outermost layer 9 is Ir.
The conductive layer made of O ₂ can be formed by the coating and baking method described above.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsuhiro Minami 5-10-1 Fuchinobe, Sagamihara-shi, Kanagawa Nippon Steel Corporation Electronics Research Laboratories

Claims (3)

[Claims] 1. An insoluble electrode in which the electrode base material is a conductive metal and the outermost layer of the electrode is a conductive layer containing IrO _{2 as a} main component, and a nonconductive coating is provided between the electrode base material and the outermost layer of the electrode. An insoluble electrode comprising an intermediate layer formed by filling a conductive material in a plurality of voids formed so as to penetrate the electrode base material in a direction substantially perpendicular to the non-conductive coating. 2. The insoluble electrode according to claim 1, wherein the volume ratio of the non-conductive coating film to the conductive material is 60:40 to 99: 1. 3. The insoluble electrode according to claim 1, wherein the thickness of the intermediate layer is between 0.1 and 100 μm.