JPH0355558B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to an electrode suitably used for surface treatment of various electrochemical reaction devices, etc., and a method for manufacturing the same. Conventional technology Conventionally, electrolytic deposition of metal thin films for magnetic devices,
From fields such as circuit formation using gold plating for connectors and electrodeposited copper for printed wiring boards, to surface treatments such as zinc plating (plating with zinc alone or zinc alloy) on steel plates that make up automobile bodies, etc. 2. Description of the Related Art Surface treatment techniques using electrolytic deposition reactions are widely used in the field of surface treatment, such as tin plating of steel plates for can manufacturing. In such surface treatment, the electrolytic deposition is performed by immersing the object to be treated in an electrolytic bath in which an electrode is immersed, and applying electricity between the electrode and the object to be treated. It is known that the material of the electrodes used in such electrolytic treatment has a great influence on electrolytic phenomena. Traditionally, such electrodes have been made using lead oxide (PbO ₂ ).
Electrodes, ferrite electrodes, or platinum-plated titanium electrodes were used. Electrodes made of these materials decompose organic chemicals and organic additives in the electrolyte relatively quickly, thereby leading to deterioration of the electrolyte, and to clean such electrolytes, e.g. activated carbon is used. It is necessary to overwork. For this reason, there was a problem in that the entire production line including this electrolytic process had to be stopped. Furthermore, in industrial fields where gold plating, bright copper plating, tin plating for can manufacturing, etc. are performed, platinum/titanium electrodes are used as anodes for plating. Various organic chemicals and organic additives are used in the plating solution used to perform these types of plating, and as with the conventional example described above, there is the problem that these decompose at a high speed. be. Furthermore, in order to obtain a predetermined electrolysis rate, the applied voltage must be set relatively high, resulting in a problem that a large amount of power is consumed. Also, as the plating process progresses, the electrode becomes passivated.
There is a problem that the life span as an electrode is relatively short. Furthermore, when gold plating is performed, for example, the oxidation number of the plating metal (gold) increases, resulting in an increase in power consumption. That is, when gold plating is performed, the oxidation number of gold is increased by the following reaction. Au ⁺ →Au ³⁺ ...(1) Therefore, in order to precipitate gold ions, which have become trivalent cations, on the coated material, the reduction action shown by the following equations 2 and 3 is required. must be performed, and the electric power for performing the reduction action shown by the second equation is wasted. Au ³⁺ →Au ⁺ ……(2) Au ⁺ →Au ……(3) Furthermore, as another conventional technology, JP-A-55-38951
can be mentioned. This is titanium (Ti), tantalum (Ta), niobium (Nb), zinc (Zn), etc.
An alloy containing 10% by weight is used as a base, and a mixed oxide film of tantalum and iridium is formed on this base. Further, as another prior art, Japanese Patent Application Laid-open No. 192281/1983 can be mentioned. This forms metal oxides such as iridium oxide (IrO ₂ ) and tantalum oxide (Ta ₂ O ₅ ) on a titanium substrate, but between these metal oxides such as niobium oxide (Nb ₂ O ₅ ) and oxide A conductive oxide layer such as tantalum is formed to a thickness of 0.001 to 1 g/m ² in terms of metal content. These prior art techniques attempt to extend the life of the electrode by suppressing the progress of the electrode into a passive state, and to save energy by lowering the electrode voltage. However, all of these involve a firing process in which a mixed oxide of multiple types of metals is formed on the substrate, for example, by heating at 450°C for one hour or more, and the products manufactured in this way The problem was that the electrodes decomposed organic substances in various electrolytes. Problems to be Solved by the Invention The present invention has been made in view of the problems of the above-mentioned prior art, and its purpose is to significantly reduce energy consumption and extend life. It is an object of the present invention to provide an electrode and a method for manufacturing the same, which can be obtained by reducing the decomposition effect of organic substances significantly compared to conventional techniques and improving manufacturing efficiency. Means for Solving the Problems The present invention provides a mixture of iridium oxide (IrO ₂ ) and tantalum oxide (Ta ₂ O ₅ ), the weight ratio of iridium to tantalum being 1:1.5 to 1:4. The electrode is characterized in that a coating made of such a mixture selected from the range is formed on a titanium (Ti) substrate. Furthermore, in the present invention, an alcohol solution of each chloride of iridium (Ir) and tantalum (Ta) is applied onto a titanium base material, dried at about 120°C, and the application process and drying process are repeated multiple times. A method for manufacturing an electrode, comprising heating at 350°C to 400°C for 20 minutes in an oxidizing atmosphere. Effect According to the present invention, an alcoholic solution of each chloride of iridium (Ir) and tantalum (Ta) is coated and dried on a titanium base material, and then heated at 350°C to 350°C in an oxidizing atmosphere.
Heat at 400℃. At this time, the blending ratio of each chloride of iridium and tantalum is selected so that the weight ratio of iridium and tantalum is in the range of 1:1.5 to 1:4. Even when the electrode manufactured in this way obtains the same electrolysis rate as the conventional technology,
The applied voltage required for this can be reduced.
Further, the effect of converting cations into multivalent ions in the processing liquid in which such an electrode is immersed is suppressed as much as possible, thereby significantly reducing energy consumption. Further, such an electrode is suppressed from changing into a passive state, and can have a long life as an electrode. Furthermore, even if the processing solution contains various organic substances, it will not be decomposed, and therefore the processing solution will be kept in a clean state, and the manufacturing process using such an electrode will not be included. Processing operations such as stopping the production line and purifying the processing liquid are suppressed as much as possible. This greatly improves work efficiency. Example () Example of manufacturing process of the present electrode In manufacturing the present electrode, a base material made of metallic titanium (Ti) is prepared. An alcoholic solution of iridium (Ir) and tantalum (Ta) chlorides (IrCl ₄ and TaCl ₅ ) (the solvent may be any of various alcohols such as methanol, butanol, and isopropanol) is applied onto this substrate. At this time, the weight ratio of iridium (Ir) and tantalum (Ta) in the alcohol solution is
The ratio is selected in the range of 1:1.5 to 1:4. After this,
After drying at a temperature of about 120℃, then drying at a temperature of 350℃ for 20
Bake for a minute. The coating process, semi-drying process, and firing process are repeated a desired number of times to produce a desired electrode. () First Example (a) Experiment Details A 20% hydrochloric acid solution of iridium chloride (IrCl ₄ ) is evaporated, the resulting paste is dissolved in methanol, and then mixed with a methanol solution of tantalum chloride (TaCl ₅ ). Meanwhile, the titanium (Ti) substrate to which the mixture is applied is polished, then surface treated with 7% hydrochloric acid at 70° C., washed with water, wiped with Kimwipe, and air-dried. The mixture is applied onto the base material thus obtained, heated at 120° C. for 10 minutes to semi-dry it, and then heated at 350° C. for 20 minutes to bake. Such coating, drying and firing steps are repeated, for example, six times to obtain a thin film of about 1 μm on the titanium substrate. In this way, an electrode according to the present invention (hereinafter referred to as the present electrode) was obtained. Note that if the firing temperature is below 350°C, the mixture of iridium chloride and tantalum chloride will not be sufficiently oxidized, making it impossible to manufacture the desired electrode. (b) About the blending ratio of iridium and tantalum and the firing temperature Figure 1 shows the electrode manufactured in this way, with the electrode manufactured by changing the blending ratio of iridium and tantalum and the firing temperature as an anode. It is a graph showing changes in the amount of carbon dioxide gas (CO ₂ ) generated by the anode when used.
In Figure 1, lines l1 to l5, firing temperature
Corresponds to 550℃, 500℃, 450℃, 400℃, and 350℃ respectively. In the graph, the vertical axis is the amount of carbon dioxide gas generated (cm ³ ), and the horizontal axis is the blending ratio of iridium to the total amount of iridium and tantalum (Ir/Ir + blending ratio of iridium to the total amount (Ir/(Ir+Ta)), weight %)
It is. This experimental example uses nickel sulfate _NiSO4 .
50g/ of 6H ₂ O and 70g/ of Na ₂ WO ₄・2H ₂ O
A Ni--W alloy plating solution containing citric acid at a concentration of 90 g/ was used. In addition, the anode used has an area of 2 cm ² , and the current density
Current was applied at 20 A/dm ² for 25 minutes, that is, with a charge of 600 coulombs. As described in the section on the prior art, when organic substances such as citric acid contained in a plating solution are dispersed by such electric current, carbon dioxide gas is generated. The generation of such gas indicates the progress of decomposition of organic matter, and it is known that this causes deterioration of electrolyte solutions such as plating solutions. As shown in the present experimental example in Figure 1, in order to suppress carbon dioxide gas generation, the iridium blending ratio is in the range of 20 to 40%, and the firing temperature is in the range of 350°C to 450°C within the above blending ratio range. It was confirmed that good results could be obtained. FIG. 2 is a graph showing changes in anode voltage when several types of electrodes having different blending ratios of iridium and tantalum and firing temperatures are used as anodes when electrolyzing the aforementioned nickel-tungsten alloy plating solution. The vertical axis of the graph shows the current density, and the horizontal axis shows the anode voltage 15 minutes after the start of current application. Also, in the graph, line l6 corresponds to the case of a conventional electrode made of platinum, and line l6 corresponds to the case of a conventional electrode made of platinum.
7 to 114 have a combination of iridium and tantalum compounding ratio and firing temperature (3:
7, 450℃), (2:8, 400℃), (3:7,
400℃), (2:8, 350℃), (4:6, 450
℃), (4:6, 400℃), (4:6, 350℃),
and (3:7, 350°C). As shown in Figure 2, the combination of iridium and tantalum ratio and firing temperature that produces particularly good results in terms of reducing the anode voltage is l
12~l14, i.e. (4:6, 400°C),
(4:6, 350℃) and (3:7, 350℃)
It is confirmed that What should be noted here is that the electrode fired at 450°C shows a relatively high anode voltage as shown in line 17. Therefore, it was shown that 350 to 400°C is an appropriate firing temperature for an electrode that does not generate carbon dioxide gas and is effective in reducing the anode voltage, and that 450°C is not an appropriate firing temperature. Table 1 below shows the results of measuring the operating life of selected electrodes with a firing temperature of 350 DEG C. to 400 DEG C. and used as anodes for plating nickel-tungsten alloys. To measure this life, connect a power supply voltage of 10V between the anode and cathode immersed in the electrolytic bath, and adjust the current density applied to the anode using a variable resistor.
It was set at 20A/ ^dm2 . That is,
When electricity is first applied, the voltage drop between the two electrodes is about 3V, but as electrolysis progresses, the electrodes wear out and the iridium/tantalum oxide film on the titanium base material decreases, exposing the base material and leaving the base material intact. It becomes dynamic. Therefore, the voltage drop between the two electrodes rapidly increases from about 3V to 10V.
This point was measured as the lifespan.

[Table] As shown in Table 1, the electrode fired at a firing temperature of 400°C has the longest life. However, it was confirmed that the electrodes fired at 400°C start decomposing organic matter in the electrolyte about 50 hours before reaching the end of their lifespan. Therefore, the useful life without decomposition reactions of organic substances is approximately 4:6 for an electrode with a blending ratio of iridium and tantalum of 4:6.
That's 1350 hours. On the other hand, it was confirmed that the electrodes fired at 350°C and 380°C did not decompose organic matter until the end of their lifespan. Therefore, from the measurement results of the organic substance non-decomposition performance, anode voltage, and life of the electrode shown in this example, the blending ratio of iridium and tantalum is 2:8.
It is concluded that ~4:6 is preferred.
Moreover, it is concluded that the firing temperature is preferably in the range of 350°C to 400°C. Among these, the firing temperature for electrodes that do not decompose organic substances until the end of their life is approximately 350℃ to 380℃.
It was concluded that ℃ is optimal. (c) Regarding the thickness of the mixed oxide layer of iridium and tantalum In the above experimental example, the mixed oxide layer was approximately 1 μm thick.
It was formed to have a layer thickness of m. If this layer thickness is made too thin, a problem arises in that a non-conductive oxide film is formed on the surface of the titanium plate, which is the base of the fired product, and the electrical resistance increases. On the other hand, the inventor of the present invention has confirmed that the above-mentioned effects can be obtained even when the mixed oxide film has a layer thickness of about 10 μm, but when the thickness exceeds about 50 μm, the fired product exhibits electrical semiconductor characteristics. Therefore, a problem arises in that conduction resistance increases. FIG. 3 is a graph showing characteristics related to electrode potential and current density of a conventional platinum electrode and the present electrode. The vertical axis of the graph is the current density, and the horizontal axis is the electrode potential, and a gold plating bath with a bath temperature of 65°C is used. After energizing 600 clones under these conditions, with respect to the conventional electrode,
When the generated carbon dioxide gas and oxygen gas were collected and the amounts generated were measured, the following Table 2 and measurement results were obtained.

[Table] As is clear from Figure 3, the electrode potential of the present electrode shown by line 15 (mixing ratio of iridium and tantalum is 4:6 and firing temperature of 350°C) is significantly higher than that of the conventional example (line 16). It is confirmed that it is low. Furthermore, when comparing the amount of carbon dioxide gas generated, in this case it was reduced to about 18.2% of the conventional example, which shows that deterioration of the electrolyte solution is suppressed to that extent. Furthermore, when the total amount of generated gas measured as shown in Table 2 above is converted into oxygen gas, carbon dioxide gas in the generated gas is generated by a two-electron reaction in the conventional platinum electrode, and the present case It has been confirmed that the gas is generated by a one-electron reaction at the electrode, so in the conventional example, 12 + 11/2 = 17.5 cc...(4) is obtained, and the gas generated by this electrode is equivalent to 37 c. c. Therefore, when the platinum electrode of the conventional example and the present electrode are used, the degree of oxidation reaction of ions in the electrolytic bath to multivalent ions as shown by the above first equation is (38-17.5) in the conventional example. /38×100=54%...(5), and for the present electrode, it is calculated to be (38-37)/38×100=2.6%...(6). Therefore, regarding this point as well, by using the electrode of the present invention, the electrical energy loss explained with reference to the second equation above can be reduced to about 4.8% of the conventional example. As described above, according to this example, the degree of oxidation of gold ions into multivalent ions during gold plating can be reduced to about 1/25, and the degree of decomposition of organic matter can be reduced to about 1/5. can. Furthermore, the electrode potential can be reduced to about 1/2, and the power cost can be reduced to about 2/3. () Second experimental example In this experimental example, zinc sulfate (ZnSO ₄ 7H ₂ O)
300g/and sodium sulfate (Na ₂ SO ₄ ) 100
g/ and adjust the hydrogen ion concentration to PH1.2 with sulfuric acid (H ₂ SO ₄ ). While maintaining such a plating bath at a liquid temperature of 60℃, the current density is 0~
Power is applied under the condition of 20A/ ^dm2 . FIG. 4 is a graph showing the anode potential when a conventional platinum anode and several types of electrodes of the present invention are used as anodes for galvanizing performed in this manner. The vertical axis of the graph is the current density, and the horizontal axis is the anode potential. Line 117 corresponds to the case of the conventional platinum anode, and lines 118 to 120 correspond to the present anode, and the blending ratio of iridium and tantalum and firing. The combination with temperature (8:2, 500℃),
(9:1, 350°C) and (4:6, 350°C) respectively. In this experimental example as well, as is clear from FIG. 4, it is understood that the electrode manufactured under the manufacturing conditions indicated by line 120 obtained the most suitable results. Effects As described above, according to the present invention, an alcoholic solution of each chloride of iridium (Ir) and tantalum (Ta) is applied onto a titanium base material, dried, and then heated at 350°C to 400°C in an oxidizing atmosphere. Heat. At this time, the mixing ratio of each chloride of iridium and tantalum is such that the weight ratio of iridium and tantalum is 1:1.5 to 1:
Choose a range of 4. Electrodes manufactured in this manner can reduce the required applied voltage even when obtaining an electrolysis rate equivalent to that of the prior art. In addition, unnecessary oxidation of cations in the processing liquid in which such an electrode is immersed into multivalent ions is suppressed, thereby significantly reducing energy consumption. Further, such an electrode is suppressed from changing into a passive state, and can have a long life as an electrode. In particular, if the processing liquid contains various organic substances, it will not be decomposed, and therefore the processing liquid will be kept clean, making it easier to operate a manufacturing line that includes manufacturing processes using such electrodes. There is no need for processing operations such as stopping and purifying the processing liquid. This greatly improves work efficiency.

[Brief explanation of drawings]

FIG. 1 to FIG. 4 are graphs each explaining the characteristics of the present electrode.

Claims (1)

[Claims] 1. A mixture of iridium oxide (IrO ₂ ) and tantalum oxide (Ta ₂ O ₅ ), such that the weight ratio of iridium to tantalum is selected in the range of 1:1.5 to 1:4. 1. An electrode characterized in that a film made of a mixture is formed on a titanium (Ti) base material. 2 Alcohol solutions of iridium (Ir) and tantalum (Ta) chlorides were applied onto a titanium substrate, dried at approximately 120°C, and the application and drying processes were repeated multiple times in an oxidizing atmosphere. , a method for producing an electrode, characterized by heating at 350°C to 400°C for 20 minutes.