Electrolytic treatment device and electrolytic treatment method for metal

Abstract

To provide a device and a method by which an electrode is hardly consumed when a metal is electrolytically treated by applying an AC voltage to the electrode.SOLUTION: An electrolytic treatment device 1 includes a pair of electrodes 3 facing each other. The pair of electrodes 3 includes electrodes 11 and 12. At least one of the electrodes 11 and 12 has: a first electrode portion having a noble metal oxide, a compound containing a noble metal oxide, or a mixture containing a noble metal oxide on its surface; and a second electrode portion having a valve metal on its surface. With the first electrode portion and the second electrode portion connected to one terminal of an AC power source 4, an AC voltage or an AC current is applied from the AC power source 4 to the electrodes 11 and 12.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an electrolytic treatment apparatus and a method for electrolytic treatment of metals using alternating current electrolysis. [Background technology]

[0002] Conventionally, graphite has been widely used as an electrode when metals are electrolytically treated by applying an AC voltage or current to the electrode. Graphite has resistance to acid and corrosion in electrolytes, but its electrical conductivity is lower than that of metals, so the electrode is made thicker and its density is increased to increase its electrical conductivity. Graphite is also more brittle than metals, and has a lower degree of freedom in terms of shape.

[0003] In order to solve the above problems, Patent Document 1 proposes an electrode for use in AC electrolytic treatment of metals, in which a coating containing an oxide of ruthenium, iridium, rhodium, or the like is provided on a metal substrate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 63-277799 Summary of the Invention [Problem to be solved by the invention]

[0005] The electrode described in Patent Document 1 was originally developed as an anode for DC electrolysis, and this paper proposes converting this electrode to AC electrolysis. When the electrode described in Patent Document 1 is used as a cathode for DC electrolysis, the coating on the metal substrate is reduced and consumed. Therefore, when the electrode described in Patent Document 1 is used as an electrode for AC electrolysis, the coating on the metal substrate is reduced and consumed when the electrode is a cathode. In addition, the lower the frequency of the AC current, the easier it is for the electrolytic treatment of the metal to proceed, but the lower the frequency, the longer the time the electrode is continuously a cathode, and the easier it is for the electrode to be consumed.

[0006] An object of the present invention is to make electrodes less susceptible to wear when metals are electrolytically treated by applying an AC voltage or an AC current to the electrodes. [Means for solving the problem]

[0007] The electrolytic treatment apparatus disclosed in this specification is an electrolytic treatment apparatus that includes a pair of opposing electrodes and performs AC electrolytic treatment on a metal placed between the pair of electrodes by applying an AC voltage or AC current from an AC power source to the pair of electrodes, and the surface of at least one of the pair of electrodes includes a first electrode portion having a precious metal oxide, a compound containing a precious metal oxide, or a mixture containing a precious metal oxide, and a second electrode portion having a valve metal.

[0008] The method for electrolytic treatment of metals disclosed in this specification is a method for electrolytic treatment of metals, which involves applying an AC voltage or an AC current from an AC power source to a pair of opposing electrodes, thereby subjecting a metal placed between the pair of electrodes to AC electrolytic treatment, wherein the surface of at least one of the pair of electrodes comprises a first electrode portion having a precious metal oxide, a compound containing a precious metal oxide, or a mixture containing a precious metal oxide, and a second electrode portion having a valve metal, and an AC voltage or an AC current is applied to the pair of electrodes.

[0009] The oxides of precious metals such as ruthenium, iridium, or rhodium disclosed in Patent Document 1 are excellent as anodes, but when used as cathodes, they are consumed by reduction reactions and the like. In contrast, according to the present invention, the electrode surface is provided with a valve metal that allows current to flow in one direction but does not easily flow in the reverse direction, in addition to a first electrode portion having a precious metal oxide, a compound containing a precious metal oxide, or a mixture containing a precious metal oxide. When an AC voltage or AC current is applied to this electrode, when it is an anode, a current flows through the first electrode portion having a precious metal oxide, a compound containing a precious metal oxide, or a mixture containing a precious metal oxide, which is resistant to oxidation reactions, and almost no current flows through the second electrode portion, which is a protective electrode. On the other hand, when it is a cathode, the current is shunted to the protective electrode (second electrode portion) which is resistant to reduction reactions, and a large amount of current flows through the protective electrode (second electrode portion). As a result, the current flowing through the first electrode portion having a precious metal oxide, a compound containing a precious metal oxide, or a mixture containing a precious metal oxide is reduced, so that when it is a cathode, the precious metal oxide, a compound containing a precious metal oxide, or a mixture containing a precious metal oxide is less likely to be consumed. In other words, the second electrode portion functions as a protective electrode portion when it is a cathode. As a result, when metals are subjected to AC electrolysis, the electrodes are less likely to wear out whether they are used as an anode or a cathode, and the life of the electrodes can be made longer than in the past.

[0010] In the above-mentioned electrolytic treatment device, at least one of the pair of electrodes is a metal plate coated at multiple locations with a precious metal oxide, a compound containing a precious metal oxide, or a mixture containing a precious metal oxide, the metal plate contains a valve metal, the portion coated with the precious metal oxide, the compound containing a precious metal oxide, or the mixture containing a precious metal oxide is the first electrode portion, the portion of the metal plate not coated with the precious metal oxide, the compound containing a precious metal oxide, or the mixture containing a precious metal oxide is the second electrode portion, and the multiple first electrode portions may be present apart from each other.

[0011] According to the above configuration, the electrodes can be made less likely to be worn by simply coating a part of the metal plate containing a valve metal with a precious metal oxide, a compound containing a precious metal oxide, or a mixture containing a precious metal oxide. In addition, since the multiple first electrode parts are present apart from each other, the first electrode parts and the second electrode parts are easily dispersed. This makes it easy for a current to flow from one electrode to the opposing other electrode in the electrolyte. Therefore, the metal placed between the pair of electrodes is efficiently electrolytically treated.

[0012] In the above, the frequency of the AC electrolysis may be 20 Hz or less. By setting the frequency to a low frequency of 20 Hz or less, the timing at which the direction of the current is switched is delayed. In other words, the time until the direction of the current is switched (the time when the electrode is an anode or the time when the electrode is a cathode) is longer. Therefore, the electrolysis of the metal is likely to proceed. However, when the electrode described in the conventional example is used, the electrode is likely to be worn out when the electrode is a cathode. In contrast, according to the above configuration, when the electrode is a cathode, the current is diverted to the second electrode part that is resistant to reduction reactions, and the current flowing to the first electrode part having a precious metal oxide, a compound containing a precious metal oxide, or a mixture containing a precious metal oxide is reduced. Therefore, the electrode is not likely to be worn out even if the electrode is a cathode for a long time. Therefore, the electrode is not likely to be worn out even if the AC electrolysis is performed under conditions under which the conventional electrode is likely to be worn out.

[0013] In the above-mentioned metal electrolytic treatment method and electrolytic treatment device, the noble metal oxide may be an oxide containing at least one of ruthenium, iridium and rhodium. The above-mentioned effects can be obtained when the noble metal oxide, the compound containing the noble metal oxide, or the mixture containing the noble metal oxide used in the electrode is used.

[0014] In the above-mentioned metal electrolytic treatment method and electrolytic treatment device, the valve metal preferably contains at least one of titanium, tantalum, niobium and tungsten. The above-mentioned effect can be obtained even when using the above-mentioned valve metals that are widely used. Effect of the Invention

[0015] When metals are subjected to AC electrolysis by applying an AC voltage or an AC current, the electrodes are less likely to be worn out. [Brief description of the drawings]

[0016] [Figure 1] 1 is a schematic diagram showing an example of an electrolytic processing apparatus according to an embodiment of the present invention; [Diagram 2] FIG. 13 is a diagram showing a current waveform when an AC voltage is applied to the electrodes in Experiment 1. [Diagram 3] 1 is a graph showing the sample electrode potential (E [V]) of the embodiment (electrode A) and the conventional example when the electrolysis current density (effective value) is 0.7 A rms / cm2. [Figure 4] 1 is a graph showing the sample electrode potential (E [V]) of the embodiment (electrode A) and the conventional example when the electrolysis current density (effective value) is 1.0 A rms / cm2. [Diagram 5] 1 is a graph showing the current value (Current [mA / cm2]) split into the protected electrode of the embodiment. [Figure 6] 1 is a graph showing the current value (Current [mA / cm2]) shunted to the protected electrode in Experiment 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

[0018] As shown in FIG. 1, the electrolytic treatment device 1 includes a pair of electrodes 3 disposed in an electrolytic cell 2. The pair of electrodes 3 includes an electrode 11 and an electrode 12. The electrodes 11 and 12 face each other. The electrodes 11 and 12 are connected to an AC power source 4. A metal 100 to be subjected to AC electrolysis is disposed between the electrodes 11 and 12. In the electrolytic cell 2, the electrodes 11 and 12 and the metal 100 are immersed in an electrolytic solution 5.

[0019] At least one surface of the electrodes 11 and 12 includes a first electrode portion having a precious metal oxide, a compound containing a precious metal oxide, or a mixture containing a precious metal oxide, and a second electrode portion having a valve metal. The electrode 11 is connected to one terminal of an AC power source 4, and the electrode 12 is connected to the other terminal of the AC power source 4. The waveform of the AC electrolysis treatment may be a sine wave or a pulse wave.

[0020] The noble metal is at least one selected from the group consisting of gold (Au), silver (Ag), platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), ruthenium (Ru) and osmium (Os). The noble metal oxide is at least one oxide selected from the group consisting of gold (Au), silver (Ag), platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), ruthenium (Ru) and osmium (Os). Among these, at least one oxide of rhodium, iridium and ruthenium is widely used as an electrode.

[0021] The compound containing a precious metal oxide is, for example, a composite oxide of a precious metal and another metal, or an oxyhalide salt of a precious metal. Examples of the composite oxide of a precious metal and another metal include composite oxides of a precious metal and magnesium, calcium, lithium, potassium, zinc, tantalum, zirconium, titanium, etc. Examples of the oxyhalide salt of a precious metal include oxyhalide salts of a precious metal in which part of the oxygen in the precious metal oxide is replaced with chlorine or fluorine.

[0022] Furthermore, the mixture containing a precious metal oxide may be a mixture of a precious metal oxide or a compound containing a precious metal oxide with other substances, for example, a mixture of a precious metal oxide or a compound containing a precious metal oxide with tantalum oxide, niobium oxide, aluminum oxide, zirconium oxide, or the like, or with a binder such as p-phenylenediamine, 4-butylaniline, melamine, or m-xylylenediamine.

[0023] The valve metal in this embodiment is a metal that has the property of passing electric current in one direction but hardly passing electric current in the opposite direction, and in particular, is a metal that easily passes electric current when it is a cathode, but hardly passes electric current when it is an anode because an oxide film is formed. Examples of such metals include titanium, tantalum, niobium, tungsten, aluminum, molybdenum, vanadium, bismuth, zirconium, hafnium, and silicon. Among these, titanium, tantalum, niobium, and tungsten are widely used, and when used as the second electrode part (protective electrode), they easily pass electric current when it is a cathode, but hardly pass electric current when it is an anode.

[0024] There is no particular limitation on the configuration in which the first electrode portion and the second electrode portion are present in electrode 11 and / or electrode 12. Examples of the configuration in which the first electrode portion and the second electrode portion are present include the following configurations.

[0025] The electrode 11 and / or the electrode 12 may be a metal plate containing a valve metal coated with a precious metal oxide, a compound containing a precious metal oxide, or a mixture containing a precious metal oxide. In this case, the part coated with the precious metal oxide, the compound containing a precious metal oxide, or the mixture containing a precious metal oxide is the first electrode part, and the part of the metal plate where the valve metal is exposed on the surface and is not coated with the precious metal oxide, the compound containing a precious metal oxide, or the mixture containing a precious metal oxide is the second electrode part. The precious metal oxide, the compound containing a precious metal oxide, or the mixture containing a precious metal oxide may be coated at only one place, or may be coated at multiple places. By coating the precious metal oxide, the compound containing a precious metal oxide, or the mixture containing a precious metal oxide at multiple places while being spaced apart from each other, multiple first electrode parts are present at a distance from each other. This makes it easier for the first electrode part and the second electrode part to be dispersed.

[0026] In addition, the electrode 11 and / or the electrode 12 may be a metal plate having a portion (first electrode portion) coated with a precious metal oxide, a compound containing a precious metal oxide, or a mixture containing a precious metal oxide, and a portion (second electrode portion) coated with a valve metal. The material of the metal plate is not particularly limited, and may be, for example, a valve metal different from that of the second electrode portion, or a metal that is not a valve metal. The precious metal oxide, the compound containing a precious metal oxide, or the mixture containing a precious metal oxide may be coated only at one place, or may be coated at multiple places. The valve metal may be coated only at one place, or may be coated at multiple places. By coating the "precious metal oxide, the compound containing a precious metal oxide, or the mixture containing a precious metal oxide" and / or the "valve metal" at multiple places while being spaced apart from each other, multiple first electrode portions and / or multiple second electrode portions are present at a distance from each other. This makes it easier for the first electrode portion and the second electrode portion to be dispersed in the electrode.

[0027] When the metal plate is coated with "a noble metal oxide, a compound containing a noble metal oxide, or a mixture containing a noble metal oxide" and / or "a valve metal", there are no particular limitations on the location of the coating, the shape of the coated portion, the thickness of the coating, etc. The first electrode portion and the second electrode portion may be present alternately in a stripe or lattice pattern, for example.

[0028] Alternatively, electrode 11 and / or electrode 12 may be a metal plate having a valve metal on its surface, one side of which is coated with a precious metal oxide, a compound containing a precious metal oxide, or a mixture containing a precious metal oxide. In this case, the one side coated with a precious metal oxide, a compound containing a precious metal oxide, or a mixture containing a precious metal oxide is the first electrode portion, and the other side having a valve metal on its surface that is not coated with a precious metal oxide, a compound containing a precious metal oxide, or a mixture containing a precious metal oxide is the second electrode portion.

[0029] Alternatively, electrode 11 and / or electrode 12 may be a metal plate having one surface coated with a precious metal oxide, a compound containing a precious metal oxide, or a mixture containing a precious metal oxide, and the other surface coated with a valve metal. In this case, the one surface coated with the precious metal oxide, the compound containing a precious metal oxide, or the mixture containing a precious metal oxide is the first electrode portion, and the other surface coated with the valve metal is the second electrode portion.

[0030] Furthermore, electrode 11 and / or electrode 12 may have an electrode (first electrode portion) containing a precious metal oxide, a compound containing a precious metal oxide, or a mixture containing a precious metal oxide on its surface, and an electrode (second electrode portion) containing a valve metal. The electrode portion (first electrode portion) containing a precious metal oxide, a compound containing a precious metal oxide, or a mixture containing a precious metal oxide, and the electrode portion (second electrode portion) containing a valve metal may be disposed adjacent to each other or may be disposed with a gap therebetween.

[0031] The configuration of electrode 11 and the configuration of electrode 12 may be the same or different. One of electrode 11 and electrode 12 may include a first electrode portion and a second electrode portion, or both of electrode 11 and electrode 12 may include a first electrode portion and a second electrode portion.

[0032] Metal is subjected to AC electrolysis using the above-mentioned electrolysis treatment device 1. When an AC voltage or AC current is applied to electrode 11 and electrode 12, the following events occur in the electrodes having the first electrode portion and the protected electrode (second electrode portion). When in an anode state, an anode current flows to the first electrode portion having a precious metal oxide, a compound containing a precious metal oxide, or a mixture containing a precious metal oxide, which is resistant to oxidation reactions, and almost no anode current flows to the protected electrode side (second electrode portion). On the other hand, when in a cathode state, a cathode current is diverted to the protected electrode (second electrode portion), which is resistant to reduction reactions, and a large amount of cathode current flows to the protected electrode (second electrode portion). Since the cathode current flowing to the electrode portion (first electrode portion) having a precious metal oxide, a compound containing a precious metal oxide, or a mixture containing a precious metal oxide is reduced, the precious metal oxide, the compound containing a precious metal oxide, or the mixture containing a precious metal oxide is less likely to be consumed when in a cathode state. When metals are electrolytically treated with alternating current as described above, the electrodes are less likely to wear out whether they are used as an anode or a cathode, and therefore the electrodes have a longer life than conventional electrodes.

[0033] An electrode having a first electrode portion and a second electrode portion on its surface is less likely to wear out and has a longer life than an electrode that is easily worn out when used as a conventional cathode. When both electrode 11 and electrode 12 have a first electrode portion and a second electrode portion, both electrode 11 and electrode 12 are less likely to wear out and have a longer life than a conventional electrode.

[0034] The frequency of the AC electrolysis is not particularly limited. For example, it may be the frequency of a commercial power supply (60 Hz or 50 Hz), or may be any other frequency. By using a low frequency, the timing at which the direction of the current is switched is delayed. In other words, the time until the direction of the current is switched (the time when the electrode is an anode or the time when the electrode is a cathode) is longer. Therefore, the electrolysis of the metal is likely to proceed. However, when a conventional electrode that is easily consumed when used as a cathode is used, the electrode is likely to be consumed. According to the configuration of this embodiment, when used as a cathode, the current is diverted to a protective electrode (second electrode portion) that is resistant to reduction reactions, and the current flowing to the first electrode portion having a precious metal oxide, a compound containing a precious metal oxide, or a mixture containing a precious metal oxide is reduced. Therefore, the electrode is not likely to be consumed even if the time when the electrode is a cathode is long. Therefore, the electrode is not likely to be consumed even if the AC electrolysis is performed under conditions that would easily consume a conventional electrode. For example, the electrode is not likely to be consumed even at a low frequency of 20 Hz or less. Furthermore, research by the present inventors has revealed that the lower the frequency, the greater the current diversion effect to the protective electrode (second electrode portion) when in cathode mode, and that even at low frequencies of 20 Hz or less, the current diversion effect to the protective electrode (second electrode portion) when in cathode mode is high (see the Examples described below).

[0035] The ratio of the first electrode part to the second electrode part on the electrode surface is not particularly limited. For example, the ratio of the first electrode part: the second electrode part may be 1:1. Either the first electrode part or the second electrode part may be more. For example, as in the experiment described later, the ratio of the first electrode part: the second electrode part may be 4:1, or the ratio of the first electrode part: the second electrode part may be 1:10 to 10:1.

[0036] There is no particular limitation on the method of connecting the first electrode unit and the second electrode unit to an AC power source. In addition, there is no particular limitation on the electrolyte used in the AC electrolytic treatment of metals. For example, the electrolyte may contain an acid component such as hydrochloric acid, nitric acid, sulfuric acid, or phosphoric acid, or may contain an alkaline component such as potassium hydroxide or sodium hydroxide. The electrolyte may be one in which these are dissolved in water or the like. The electrolyte may be changed depending on the metal to be electrolytically treated, the contents of the electrolytic treatment, and the like.

[0037] By using the electrolytic processing apparatus 1 and the method for AC electrolytic processing of metal described above, for example, etching of aluminum can be carried out, but the AC electrolytic processing of metal is not limited to this.

[0038] 1 shows one electrolytic treatment device 1, the metal may be AC ​​electrolytically treated by only one electrolytic treatment device 1, or by two or more electrolytic treatment devices 1. For example, a plurality of electrolytic treatment devices 1 may be lined up, and the metal 100 may pass between the pair of electrodes 3 of each electrolytic treatment device 1 in turn.

[0039] 1, a pair of electrodes 3 is disposed in the electrolytic cell 2, but two or more pairs of electrodes 3 may be disposed in the electrolytic cell 2. When two or more pairs of electrodes 3 are disposed in the electrolytic cell 2, the metal 100 may pass between the electrodes 3 in the electrolytic cell 2. EXAMPLES

[0040] The present invention will be described in more detail below with reference to examples. However, the following examples do not limit the present invention, and all modifications and variations within the scope of the present invention are included in the technical scope of the present invention.

[0041] [Experiment 1] The following experiment was conducted to compare an embodiment using an electrode having a first electrode portion (sample electrode) having a precious metal oxide on its surface and a second electrode portion (protected electrode) having a valve metal on its surface with a conventional example using an electrode having a first electrode portion (sample electrode) but no second electrode portion (protected electrode).

[0042] (Example) A pair of opposing electrodes was fitted with a sample electrode (facing area 8 cm) made of a metal plate (material: titanium (Ti)) coated with iridium oxide (IrO2) as a precious metal oxide. 2 ) was used as the first electrode (sample electrode), and a protected electrode (facing area 2 cm) containing titanium (Ti) as a valve metal was used. 2 Electrode A was used, with 1st electrode part (sample electrode) as the second electrode part (protected electrode). Each electrode A was connected to an AC power source so that the first electrode part (sample electrode) and the second electrode part (protected electrode) were connected in parallel. A reference electrode (silver (Ag) wire) was placed immediately adjacent to electrode A.

[0043] (Conventional example) A pair of opposing electrodes was fitted with a sample electrode (facing area 10 cm) made of a metal plate (material: titanium (Ti)) with the entire surface covered with iridium oxide (IrO2). 2 ) was used as electrode B. Each electrode B was connected to an AC power source. A reference electrode (silver (Ag) wire) was placed immediately adjacent to electrode B. The rest was the same as in the example.

[0044] The electrolysis conditions for the examples and the conventional example were as follows. Electrolyte: Aqueous solution mainly composed of hydrochloric acid AC electrolysis waveform: sine wave, frequency (between a pair of opposing electrodes) is 1Hz, 3Hz, 7Hz Electrolytic current density (root mean square value): 0.7A rms / cm 2 or 1.0A rms / cm 2

[0045] AC electrolysis experiments were carried out using six types of current waveforms with different frequencies (1 Hz, 3 Hz, 7 Hz) and current densities, as shown in Figure 2. The electrolysis current density (effective value, root mean square value) was calculated using the following formula. Electrolysis current density (effective value, root mean square value) = Maximum current shown in Figure 2 × 1 / √2

[0046] The sample electrode potential of the example having a protected electrode (electrode A) and the sample electrode potential of the conventional example having no protected electrode (electrode B) (both compared to a reference electrode) were measured as waveform data using a potentiometer (see Figs. 3 and 4 described below). The protected electrode potential of the example having a protected electrode (electrode A) was also measured as waveform data using a potentiometer (both compared to a reference electrode). The current value shunted to the protected electrode of the example having a protected electrode (electrode A) was measured as waveform data using a zero-resistance ammeter (see Fig. 5 described below).

[0047] 3 and 4 show graphs comparing the sample electrode potential (E [V]) of the embodiment (electrode A) with the sample electrode potential (E [V]) of the conventional example (electrode B). In Fig. 3, the electrolysis current density (effective value) is 0.7 A rms / cm 2 The graph in Fig. 4 shows the results when the electrolysis current density (effective value) is 1.0A rms / cm 2 3 and 4, a positive potential (E [V]) (positive direction on the vertical axis of the graph) indicates an anodic cycle, and a negative potential (E [V]) (negative direction on the vertical axis of the graph) indicates a cathodic cycle.

[0048] 3 and 4, in the embodiment with a protected electrode, the fluctuation in the sample electrode potential is approximately 0.3 V less at maximum than in the conventional example without a protected electrode. By using a protected electrode in addition to the sample electrode, a current of the same density can be passed at a lower voltage than when only the sample electrode is used, making it easier for the current to flow. This tendency is particularly noticeable during the cathodic cycle. From the above, it was confirmed that the use of a protected electrode in addition to the sample electrode makes it less likely for cathodic reduction and wear of the sample electrode to occur in terms of potential.

[0049] FIG. 5 shows the current value (Current [mA / cm 2 In FIG. 5, a graph of positive current (Current[mA / cm 2 ]) indicates the anodic cycle, and negative current (Current[mA / cm 2 ]) indicates the cathode cycle.

[0050] The following was learned from Figure 5. In the anodic cycle, almost no current flows through the protected electrode, but in the cathodic cycle, current flows through the protected electrode. This shows that titanium (Ti), used as the protected electrode in the examples, has a valve action that prevents the flow of anodic current (positive direction on the vertical axis of the graph) but allows the flow of cathodic current (negative direction on the vertical axis of the graph). This shows that there is a half-wave rectifying anodic oxide film on titanium (Ti), which is a valve metal. In the anodic cycle, most of the current flows through the sample electrode and is not diverted to the protected electrode.

[0051] In addition, the current density (effective value) is 0.7 A / cm 2 Current value (Current [mA / cm 2 ]), the cathode current (negative direction on the vertical axis of the graph) at a frequency of 7 Hz is about 3% of the total current, but as the frequency decreases, the proportion of the cathode current (negative direction on the vertical axis of the graph) increases, and at 1 Hz the cathode current (negative direction on the vertical axis of the graph) rises to about 5-10% of the total current. 2 However, there is a tendency for the proportion of cathode current (negative direction on the vertical axis of the graph) to increase as the frequency decreases.

[0052] In addition, the current density (effective value) is set to 0.7 A / cm 2 to 1.0A / cm 2 When the frequency is 7 Hz, the change (increase) in the current shunted to the protected electrode is small when the frequency is 7 Hz, but increases as the frequency decreases, becoming 2 to 5 times higher at 3 Hz and 1 Hz.

[0053] From the above, it was found that the current shunting effect to the protected electrode in the cathode cycle is greater as the frequency is lower and as the current density is higher.

[0054] [Experiment 2] In Experiment 1, titanium (Ti), which is widely used for electrodes in electrolytic processes, was used as the valve metal for the protected electrode, but it was investigated whether other metals could be used as the valve metal for the protected electrode.

[0055] The protective electrode was made of any one of titanium (Ti), tantalum (Ta), niobium (Nb), tungsten (W), zirconium (Zr) and molybdenum (Mo). Other than this, the same conditions were as in the example of Experiment 1, the frequency was 7 Hz, and the current density (effective value) was 0.7 A / cm 2 An AC voltage was applied as the

[0056] Figure 6 shows the current value (Current [mA / cm 2 6 shows a graph of the current (Current [mA / cm 2 ]) at the positive electrode and the negative electrode. The data shown in FIG. 6 is the current value shunted to the protected electrode, measured as waveform data using a zero resistance ammeter. In FIG. 6, 2 ]) indicates the anodic cycle, and negative current (Current[mA / cm 2 ]) indicates the cathode cycle.

[0057] As can be seen from Figure 6, when titanium (Ti), tantalum (Ta), niobium (Nb) or tungsten (W) was used as the protective electrode, little current flowed through the protective electrode in the anodic cycle, but a lot of current flowed through the protective electrode in the cathodic cycle. However, when zirconium (Zr) or molybdenum (Mo) was used as the protective electrode, a lot of current flowed through the protective electrode in both the anodic and cathodic cycles. A valve action that makes it difficult for anodic current to flow was confirmed for titanium (Ti), tantalum (Ta), niobium (Nb) and tungsten (W), but no valve action that makes it difficult for anodic current to flow was observed for zirconium (Zr) or molybdenum (Mo).

[0058] The effect of the shielding electrode is considered to be tungsten (W) > tantalum (Ta) ≒ niobium (Nb) > titanium (Ti) based on the value of the cathode current shunted to the shielding electrode. Since almost no anodic current (positive direction on the vertical axis) flows through tantalum (Ta), it is believed to have extremely high resistance to dissolution when used as an anode.

[0059] In the above experiment, a protected electrode (second electrode portion) was used for both of a pair of electrodes as an example, but the same effect of the protected electrode as described above can be obtained even when a protected electrode (second electrode portion) is used for one electrode and no protected electrode is used for the other electrode.

[0060] In the above experiment, the frequency was set to 7 Hz or less. Since the protective electrode (second electrode portion) was effective even at low frequencies, it can be said that the protective electrode (second electrode portion) is also effective at higher frequencies.

[0061] In the above experiment, the current density (effective value) was 0.7 A / cm 2 or 1.0A / cm 2 However, the current density is not limited to these.

[0062] In the above experiments, a precious metal oxide was used for the sample electrode (first electrode part). However, similar effects can be obtained when a mixture of a precious metal oxide with tantalum oxide, niobium oxide, aluminum oxide, zirconium oxide, etc., or a binder such as p-phenylenediamine, 4-butylaniline, melamine, or m-xylylenediamine is used, when a composite oxide of a precious metal with another metal is used, or when an oxyhalide salt of a precious metal in which some of the oxygen in the precious metal oxide is replaced with chlorine or fluorine is used. [Explanation of symbols]

[0063] 1. Electrolytic treatment equipment 2 Electrolytic cell 3 Pair of electrodes 4 AC power supply 5 Electrolyte 11, 12 electrodes 100 metal 13 Separator 21, 22 Lead terminal

Claims

1. An electrolytic treatment apparatus comprising a pair of opposing electrodes, and applying an AC voltage or an AC current from an AC power source to the pair of electrodes to perform AC electrolytic treatment on a metal placed between the pair of electrodes, An electrolytic treatment apparatus characterized in that the surface of at least one of the pair of electrodes comprises a first electrode portion having a precious metal oxide, a compound containing a precious metal oxide, or a mixture containing a precious metal oxide, and a second electrode portion having a valve metal.

2. At least one of the pair of electrodes is a metal plate coated at multiple locations with a precious metal oxide, a compound containing a precious metal oxide, or a mixture containing a precious metal oxide; the metal plate comprises a valve metal; a portion coated with the precious metal oxide, the compound containing a precious metal oxide, or the mixture containing a precious metal oxide is the first electrode portion, a portion of the metal plate that is not covered with the precious metal oxide, the compound containing a precious metal oxide, or the mixture containing a precious metal oxide is the second electrode portion; The electrolytic processing apparatus according to claim 1 , wherein a plurality of the first electrode portions are present at intervals from each other.

3. 3. The electrolytic processing apparatus according to claim 1, wherein the noble metal oxide is an oxide containing at least one of rhodium, iridium and ruthenium.

4. 3. The electrolytic processing apparatus according to claim 1, wherein the valve metal includes at least one of titanium, tantalum, niobium, and tungsten.

5. A method for electrolytically treating a metal, comprising: applying an AC voltage or an AC current from an AC power source to a pair of opposing electrodes to subject a metal disposed between the pair of electrodes to AC electrolytic treatment, At least one of the pair of electrodes has a surface including a first electrode portion having a precious metal oxide, a compound containing a precious metal oxide, or a mixture containing a precious metal oxide, and a second electrode portion having a valve metal; A method for electrolytically treating a metal, comprising applying an AC voltage or an AC current to the pair of electrodes.

6. 6. The method for electrolytic treatment of metals according to claim 5, wherein the frequency of the AC electrolytic treatment is 20 Hz or less.

7. 6. The method for electrolytically treating metals according to claim 5, wherein the noble metal oxide is an oxide containing at least one of ruthenium, iridium and rhodium.

8. 6. The method for electrolytically treating metals according to claim 5, wherein the valve metal includes at least one of titanium, tantalum, niobium, and tungsten.

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