JPH04214899A - Insoluble electrode - Google Patents

Abstract

PURPOSE:To offer insoluble electrode highly durable against >200A/dm<2> high current density. CONSTITUTION:This insoluble electrode is prepared by forming valve metal layer on the surface of the main body of electrode faced to members to be plates, and forming IrO2 reactive sputtering film, IrO2 reactive vapor deposited film or IrO2 reactive ion plating film on the surface of the valve metal layer and additionally forming IrO2 coated baked film on to this layer or forming IrO2 coating baked on to this surface of valve metal layer and additionally forming IrO2 reactive sputtering film, IrO2 reactive vapor deposited film or IrO2 reactive ion plating film on valve metal layer, respectively.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to insoluble electrodes.

0002

[Prior Art] Generally, when electroplating metal materials, an insoluble electrode is used in an electroplating bath, and metals such as Zn, Sn, and Ni are electroplated on the surface of the metal material to be plated, which serves as a cathode. ing. Furthermore, when electrorefining metals, an insoluble electrode is used in a refining bath to electrorefine metals such as Mn and Zn. The most commonly used of these insoluble electrodes are
Examples include Pb-based alloys. This electrode can be used in electroplating baths,
In an electrorefining bath, especially in a sulfuric acid solution, PbO2 is generated on the surface during the current treatment. Although the PbO2 functions as an insoluble electrode, the adhesion between the generated PbO2 and Pb is weak and it mixes into the electrolytic solution, resulting in poor plating or impurity-containing refined metal.

Therefore, as a countermeasure, IrO2, which is a platinum group oxide that is the most electrochemically stable in an electroplating bath, an electrorefining bath, and especially a sulfuric acid solution, has been added to the base metal valve metal (Ti, Ta, Zr). Japanese Patent Publication No. 48-3954 discloses an electrode coated on a layer of metal such as, which forms an insulating oxide layer on the surface and stops the current flow when energized. Furthermore, in order to suppress oxidation of the valve metal layer or improve adhesion, Ta2O is added to the intermediate layer.
Japanese Patent Publication No. 46-21884 describes a method of using an insoluble electrode in which a film containing IrO2 and the like is formed, and an IrO2 layer is further formed.
JP-A-63-235493. The maximum coating thickness is 5 μm, and the electrode structure is shown in FIG. 1 is a SUS electrode base material, 2 is a valve metal layer, 3 is an IrO2-Ta2O5 layer, and 4 is an IrO2 layer. The construction method for the layers 3 and 4 is a so-called coating and baking method, in which a solution that becomes an oxide is repeatedly applied onto the valve metal layer and then fired at a temperature that becomes an oxide.

0004

[Problem to be solved by the invention] Japanese Patent Publication No. 46-2188
An insoluble electrode having a layer mainly composed of IrO2 by the coating and baking method proposed in Publication No. 4 and Japanese Unexamined Patent Publication No. 63-235493 has a low current density (~100 A/dm2).
) can be used for a long time, but when conducting a galvanic corrosion test under high current density, especially at 200 A/dm2 in a sulfuric acid solution,
000 to 4000 hours, a sudden voltage increase occurs and the electrode becomes unusable. The corrosion mechanism of this electrode will be explained from the electrode structure with reference to FIG. layer 3 containing IrO2,
No. 4 is due to heat treatment of the solution, so there are pores due to volatilization of solution components. Further, many hexagonal cracks 5 are generated due to the difference in thermal expansion between the valve metal layer and IrO2. Direct current conduction with the valve metal layer 2 occurs due to these pores and cracks, causing corrosion of the valve metal layer or formation of an insulating oxide film 6 on the surface of the valve metal layer. Furthermore, the insulating oxide film 6 increases as a result of energization, causing a voltage increase and causing the electrode to lose its function.

[0005] In order not to lose the electrode function, it is necessary to produce a homogeneous film free of pores and cracks. Previously published in Special Publication No. 46-21884, Journal of the Photographic Society of Japan [Vo
l. 51, No. 1, p. 3 (1988)] discloses a reactive sputtering method, a reactive vapor deposition method, and a reactive ion plating method in which Ir metal is sputtered, vapor-deposited, or ion-plated and oxidized near the substrate. The IrO2 coating produced by this reactive sputtering method, reactive vapor deposition method, or reactive ion plating method (hereinafter referred to as IrO2 reactive sputtering coating, IrO2 reactive vapor deposition coating, or IrO2 reactive ion plating coating) is homogeneous with no cracks or pores. It has the advantage of being almost non-existent.

However, when current is applied at a low current density of 100 A/dm2, there is a drawback that the current flow stops after a short period of time. The reason for this is that the optimum film thickness for producing the IrO2 reactive sputtering film, IrO2 reactive vapor deposition film, and IrO2 reactive ion plating film is extremely thin, ranging from 100 angstroms to several thousand angstroms, and the current per unit cross-sectional area is constant. This is because in the case of , the specific surface area is smaller than that of a coated and baked IrO2 film, the amount of oxygen generated per unit area is large, and the melting speed is fast. Furthermore, in order to improve the durability of IrO2-reactive sputtered coatings, IrO2-reactive vapor deposition coatings, and IrO2-reactive ion plating coatings, it is necessary to increase the thickness of homogeneous coatings.
The disadvantage is that thicker films tend to peel off more easily. The present invention provides an insoluble electrode that has excellent corrosion resistance even when electrolyzed at a high current density of 200 A/dm2 or more and can withstand long-term use.

[0007]

[Means for Solving the Problems] The structure of the insoluble electrode of the present invention is as follows. (1) A valve metal layer is formed on the surface of the electrode base material, an IrO2 reactive sputtering film is formed on the surface of the valve metal layer, and an IrO2 coating and baking film is further formed on the surface of the valve metal layer, or an IrO2 coating and baking coating is formed on the valve metal layer surface. An insoluble electrode characterized by forming a film and further forming an IrO2 reactive sputtered film thereon. (2) A valve metal layer is formed on the surface of the electrode base material, an IrO2 reactive vapor deposition film is formed on the surface of the valve metal layer, and an IrO2 coating and baking film is further formed on it, or an IrO2 coating and baking coating is formed on the valve metal layer surface. An insoluble electrode characterized by forming a film and further forming an IrO2 reactive vapor deposition film thereon. (3) A valve metal layer is formed on the surface of the electrode base material, an IrO2 reactive ion plating film is formed on the surface of the valve metal layer, and an IrO2 coating and baking film is further formed on the surface of the valve metal layer, or an IrO2 reactive ion plating film is formed on the surface of the valve metal layer. This is an insoluble electrode characterized by forming a coating and baking film and further forming an IrO2 reactive ion plating film thereon.

The structure of the insoluble electrode according to the present invention is schematically shown in FIG. FIG. 1(a) shows the case where an IrO2 reactive sputtering coating, an IrO2 reactive vapor deposition coating, or an IrO2 ion plating coating is formed on the valve metal layer, and an IrO2 coating is further formed on the coating by a coating and baking method. In FIG. 1(b), an IrO2 film is formed on the valve metal layer by a coating and baking method, and then IrO
2 reactive sputter coating or IrO2 reactive vapor deposited coating,
Or when an IrO2 reactive ion plating film is formed. 2 is a valve metal layer, 7 is an IrO2 reactive sputtered coating, or an IrO2 reactive vapor deposited coating, or an IrO2 reactive sputtered coating, or an IrO2 reactive vapor deposited coating;
O2 reactive ion plating coating, 4 is IrO2 applied baking coating.

[0009]

[Operation] The present invention will be explained in detail below. Coating and baking I
In the rO2 film, an insulating oxide is generated on the surface of the Ti layer due to current flow from the pores and cracks in the film, and the current flow is stopped. An IrO2 reactive sputtered coating, an IrO2 reactive vapor deposition coating, or an IrO2 reactive ion plating coating is a homogeneous coating dotted with pores with a diameter of several tens of angstroms, and has a smaller specific surface area than an IrO2 applied baking coating. The amount of oxygen generated per area is large, resulting in faster corrosion, and the film is thinner, so the electrode function is shorter. Therefore, in order to compensate for these two drawbacks, we considered creating a multilayer structure consisting of an IrO2 applied baked coating and an IrO2 reactive sputtered coating, an IrO2 reactive vapor deposition coating, or an IrO2 reactive ion plating coating.

[0010] Ir fabricated on a Ti plate, which is a valve metal.
The specific surface areas of the O2 homogeneous coating and the IrO2 coated baked coating are as shown in Table 1.
2 reactive sputter coating, IrO2 reactive vapor deposited coating, Ir
It can be seen that it is larger and more porous than the O2 reactive ion plating coating. When these coatings are energized at a constant current density, the amount of oxygen generated per unit specific surface area is Ir
The amount of O2 coated and baked coating is smaller and the speed of erosion is also lower.

[0011]

[Table 1]

[0012] IrO2 applied baked coating and IrO2 reactive sputtered coating, or IrO2 reactive vapor deposited coating, or
When the rO2 reactive ion plating film is multi-layered, the amount of oxygen generated per unit specific surface area can be reduced by the IrO2 applied baking film 4, thereby reducing the unit specific surface area of the IrO2 homogeneous film below or above the IrO2 applied baking film. It is possible to reduce the amount of oxygen generated per unit and reduce the speed of erosion.

In the conventional IrO2 coating and baking film 4, I
It has more pores and cracks than the rO2-reactive sputtered coating, IrO2-reactive vapor deposition coating, or IrO2-reactive ion plating coating 7, and therefore has the disadvantage that it conducts electricity with the valve metal layer 2 to form the insulating oxide layer 6. However, by forming an IrO2-reactive sputtering film, an IrO2-reactive vapor deposition film, or an IrO2-reactive ion-plating film 7 on or below the IrO2 coating and baking film 4, electrical conduction with the valve metal layer 2 can be achieved by IrO2-reactive sputtering. coating, or IrO2 reactive vapor deposited coating, or IrO2 reactive evaporation coating, or
This does not occur until the rO2 reactive ion plating coating 7 is eroded away. Therefore, by forming a multilayer of an IrO2 applied baked coating and an IrO2 reactive sputtered coating, an IrO2 reactive vapor deposition coating, or an IrO2 reactive ion plating coating, the IrO2 applied baked coating alone, an IrO2 reactive sputtered coating, or an IrO2 reactive ion plating coating can be formed. It is possible to conduct electricity for a longer time than with an electrode of a vapor deposited film or an IrO2 reactive ion plating film alone.

[0014]

[Example] [Example 1] SUS electrode base material surface facing the base material to be plated
(1800 x 700 mm) was cladded with Ti and its surface was cleaned using oxalic acid. This Ti clad SU
An electrode made of S was placed facing an Ir plate in a vacuum (8×10 −4 torr). Argon pressure in the vacuum chamber is 1 x 10-
1 to 2 x 10-2 torr, apply a potential of 1 kV to the target, discharge the argon ions, and hit the Ir plate to knock out the Ir atoms, and the gas pressure is 4.5 x 10-4 torr.
IrO2 was applied to the surface of the Ti clad assembly by blowing O2 gas onto the base material at a film formation rate of 2 angstroms/sec.
A 1000 angstrom reactive sputter coating was prepared.

[0015] Further, on this reactive sputtered film, a coating/baking film solution prepared by dissolving H2IrCl6, which becomes IrO2 through thermal decomposition, in butanol and adjusting the Ir metal concentration to 60 g/l, was coated using a method such as drying, and then heated in an electric furnace after drying. and baked at 450℃. This operation of coating, drying, and baking was repeated eight times to form an IrO2 layer of about 5 μm to produce an electrode of the present invention. (Invention product 1)

[0016] Furthermore, an IrO2 coating and baking film of approximately 5 μm was applied to the surface of the Ti-clad SUS electrode by the method described above.
An electrode of the present invention was manufactured by forming an IrO2 reactive sputtering film of 1000 angstroms on the coated and baked film by the method described above. (Product of the present invention 2)

Next, in a 5 wt % sulfuric acid solution at 60° C., the products 1 and 2 of the present invention were used as anodes, the platinum plate was used as a cathode, and the current density was 2.
An electrical corrosion test was conducted at 00 A/dm2, and changes in voltage were measured. These results are shown in FIG. 2.

[Example 2] SUS electrode base material surface facing the base material to be plated
(1800 x 700 mm) was cladded with Ti and its surface was cleaned using oxalic acid. This Ti clad SU
An electrode made of S was placed facing an Ir plate in a vacuum (8×10 −4 torr). This Ir plate was heated with an electron beam at 200W to evaporate the Ir, and the gas pressure was further increased to 6.5×1
O2 gas was introduced at 0-4, and an IrO2 reactive vapor deposition film of 1000 angstroms was formed on the surface of the Ti clad assembly at a film forming rate of 2 angstroms/sec. Further, IrO2 is deposited on this IrO2 reactive sputtered film by thermal decomposition.
H2IrCl6, which becomes rO2, is dissolved in butanol and I
Apply a coated and baked coating solution adjusted to have a metal concentration of 60 g/l with a brush, dry it, and then put it in an electric furnace 450
Baked at ℃. (Product of the present invention 3)

[0019] Furthermore, the Ti-clad SUS electrode surface was coated with IrO2 by the above-described method and baked to form a film of about 5 %.
.mu.m, and then a 1000 angstrom IrO2 reactive vapor deposited film was formed on the coated and baked film by the method described above to produce an electrode of the present invention (Product 4 of the present invention). Next, in a 5 wt% sulfuric acid solution at 60°C, the present invention product 3 was added to the anode.
4. Use a platinum plate as the cathode, current density 200A/dm2
A galvanic corrosion test was conducted and the change in voltage was measured. These results are shown in FIG. 2.

[Example 3] SUS electrode base material surface facing the base material to be plated
(1800 x 700 mm) was cladded with Ti and its surface was cleaned using oxalic acid. This Ti clad SU
An electrode made of S was installed as an anode in a vacuum (8 x 10-4 torr), an Ir plate was installed as a cathode, and 200 W was applied to deposit Ir ions, and the gas pressure was 4.5
IrO2 reactive ion plating film 1000 was applied to the Ti clad bonding surface by blowing O2 gas onto the substrate at ×10-4 torr and at a film formation rate of 2 angstroms/sec.
angstrom was made.

Furthermore, on this IrO2 reactive ion plating film, H2IrC which becomes IrO2 by thermal decomposition is applied.
Ir metal concentration is 60g/l by dissolving l6 in butanol.
A coating and baking coating solution adjusted to have the following properties was applied with a brush, dried, and then placed in an electric furnace to form a base at 450°C. (Product of the present invention 5)

[0022] Furthermore, an IrO2 coating and baking film of about 5 μm was applied to the surface of the Ti-clad SUS electrode by the above method.
Then, an IrO2 reactive vapor deposition film of 1000 angstroms was formed on the coated and baked film by the method described above to produce an electrode of the present invention (Product 6 of the present invention). Next, in a 5 wt% sulfuric acid solution at 60°C, the present invention products 5 and 6 were placed on the anode.
A galvanic corrosion test was conducted using a platinum plate as a cathode at a current density of 200 A/dm2, and changes in voltage were measured. These results are shown in FIG. 2.

[Conventional Example] For comparison, an electrode with only an IrO2 coating and baking film was manufactured. First, H2IrCl6.6H2O, Ta(OC4H
9) 5 was dissolved in butanol to a concentration of 80 g/l. The solution was applied to the surface of the Ti-clad SUS electrode (1800 x 700 mm) and baked at 450°C. This operation was repeated three more times to form a layer of approximately 1 μm thick Ir layer.
An O2-Ta2O5 (60:40) film was formed. The above IrO2-Ta2O5 (60
:40) Coating and Baking: The coating was coated on the film and baked at 450°C. This operation was repeated 5 times and the (60 mol% IrO2, 40 mol% Ta2O) on the Ti-clad SUS electrode surface was
5) A conventional electrode was manufactured by forming an IrO2 film on the film to a film thickness of approximately 5 μm (Conventional Product 1)

[0024] Also, IrO2 reactive sputter coating, IrO
2 reactive vapor deposition film, IrO2 reactive ion plating film (film thickness 1000 angstroms) alone (conventional products 2, 3, 4) was applied to the Ti-clad SUS electrode surface (1800 x 700 mm) that had been cleaned with oxalic acid in Example 1. 2,3
Manufactured in a similar manner.

Next, in a 5 wt % sulfuric acid solution at 60° C., using conventional products 1, 2, 3, and 4 as the anode and a platinum plate as the cathode, a galvanic corrosion test was conducted at a current density of 200 A/dm2, and the change in voltage was measured. did. These results are also shown in FIG. 2. As a result of energization of the above-mentioned products of the present invention and conventional products, conventional products 2, 3, and 4 had a high overvoltage and stopped energizing in a very short period of time, and conventional product 1 had a sudden voltage drop after 3000 to 4000 hours. A rise occurred and the electrode became unusable. In the product of the present invention, the voltage did not increase until reaching 12,000 to 14,000 hours, resulting in a significantly longer electrode life.

[0026]

Effect of the invention: The insolubilized electrode of the present invention has a
It has excellent corrosion resistance even when electrolyzed at a high current density of 2 or more and can withstand long-term use, making it extremely useful not only as an electrode for electroplating but also as an electrode for other uses.

[Brief explanation of the drawing]

FIG. 1 shows the electrode structure of the present invention. (a): An electrode structure in which an IrO2-coated baked film is formed on an IrO2-reactive sputtered film, an IrO2-reactive vapor-deposited film, or an IrO2-reactive ion plating film, (b): an IrO2-reactive film on an IrO2-coated baked film. reactive sputter coating, or IrO2 reactive vapor deposition coating, or Ir
This is an electrode structure in which an O2-reactive ion plating film is formed.

FIG. 2 shows the results of galvanic corrosion of the electrode of the present invention and the conventional electrode.

FIG. 3 shows a conventional electrode structure.

FIG. 4 is an explanatory diagram of the corrosion mechanism of a conventional electrode.

[Explanation of symbols]

1 SUS electrode base material 2 Valve metal layer 3 IrO2-Ta2O5 coating and baking film 4 I
rO2 applied baked coating 5 Cracks 6 Insulating oxide 7 IrO2 reactive sputter coating, or IrO2 reactive vapor deposition coating, or IrO2 reactive ion plating coating

Claims (3)

[Claims] Claim 1: A valve metal layer is formed on the surface of the electrode base material, an IrO2 reactive sputtering coating is formed on the surface of the valve metal layer, and an IrO2 coating and baking coating is further formed on the surface of the valve metal layer, or an IrO2 reactive coating is formed on the surface of the valve metal layer. An insoluble electrode characterized in that a coating and baking film is formed and an IrO2 reactive sputtering film is further formed thereon. 2. A valve metal layer is formed on the surface of the electrode base material, an IrO2 reactive vapor deposition film is formed on the surface of the valve metal layer, and an IrO2 coating and baking film is further formed on the surface of the valve metal layer, or an IrO2 reactive coating is formed on the surface of the valve metal layer. An insoluble electrode characterized in that a coating and baking film is formed, and an IrO2 reactive vapor deposition film is further formed thereon. 3. A valve metal layer is formed on the surface of the electrode base material, an IrO2 reactive ion plating film is formed on the surface of the valve metal layer, and an IrO2 coating and baking film is further formed on the surface of the valve metal layer, or the surface of the valve metal layer is formed. to IrO2
An insoluble electrode characterized by forming a coating and baking film and further forming an IrO2 reactive ion plating film thereon.