JPS6261675B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing an electrode that exhibits low overvoltage and has sufficient durability and corrosion resistance. The present invention relates to a method of manufacturing the above-mentioned electrode by a plating method. The electrode obtained by the present invention is suitable for use as a variety of electrodes such as an electrode for hydrogen generation and an electrode for oxygen generation, but is particularly suitable for use as a cathode whose main reaction is a hydrogen generation reaction in an alkaline solution. . Conventionally, iron cathodes have been mainly used in water electrolysis or electrolysis of aqueous alkali chloride solutions in which hydrogen generation reaction is the main reaction at the cathode. Iron is inexpensive as a cathode material and exhibits a fairly low hydrogen overvoltage, but in recent years there has been a need to further improve this. In particular, with the development of cation exchange membrane salt electrolysis technology, a further reduction in hydrogen overvoltage is desired from the perspective of energy conservation, and due to the electrolytic conditions of high temperature and high alkali concentration, the corrosion resistance of iron is becoming a problem. . For this reason, there is a desire for a new cathode that exhibits lower hydrogen overvoltage than iron cathodes, is economical, and has sufficient durability and corrosion resistance. Various studies have been conducted in various places, and several methods have been proposed. has been done. Among these, nickel metals that provide a low hydrogen overvoltage that have been proposed in the process of development of conventional water electrolysis technology, for example, nickel metals containing sulfur (for example, nickel metals containing sulfur (for example, Japanese Patent Publication No. 25-2305, or "Electrochemistry" co-authored by Shiro Yoshizawa and Nobuyuki Watanabe) Water electrolysis chapter published by Kyoritsu Zensho Publishing,
P69) has been known for a long time and is attracting attention because it is cheaper than electrodes coated with platinum group metals, etc. The present inventors conducted a detailed study on the plating films obtained by the above method, and found that these plating films have several drawbacks, namely, poor adhesion to the base material, and poor surface coating. He discovered a method for manufacturing an electrolytic cathode that overcomes the disadvantages of being brittle and weak, and furthermore, that hydrogen overvoltage is still insufficiently reduced.
092295, 56-000305). However, since nickel plating containing sulfur has pinholes inside, the base material to which the plating is applied needs to exhibit durability and corrosion resistance under the conditions used as an electrode. For example, using iron as the base material,
When an electrode directly coated with sulfur-containing nickel plating is used as a cathode in ion-exchange membrane salt electrolysis, iron in the base material is removed during electrolysis or power cut due to the conditions of high temperature and high alkali concentration. Dissolution occurs. If the interface between the base material and the coating is eroded in this way, the gas generated by electrolysis may cause the coating to bulge or even peel off.
Further, the electrode performance deteriorates due to reasons such as iron ions eluted from the base material adhering to the electrode. Furthermore, iron ions eluted from the base material may deteriorate the membrane performance of the ion exchange membrane, and furthermore, there is a risk that the product quality of the resulting caustic soda may be reduced. In order to solve these problems, the surface of the base material to which sulfur-containing nickel plating is applied is required to exhibit corrosion resistance and durability under the conditions used as an electrode. In addition to conventional knowledge, the present inventors conducted several studies and found that, with the exception of expensive platinum group metals, the surface of a metal substrate has a surface composition of chromium, nickel, or an alloy phase containing these. It was confirmed that it exhibits superior corrosion resistance and durability compared to iron. For these reasons, the present inventors have conducted various studies on sulfur-containing nickel plating on the surface of metal substrates having surface compositions of chromium, nickel, or alloy phases containing these, and have found that these surfaces are not necessarily satisfactory. It was found that a film with good adhesion could not be obtained. The present inventors have previously discovered that nickel plating containing ammonium ions exhibits good adhesion as a base plating for sulfur-containing nickel plating, and has previously filed a patent application (Japanese Patent Application No.
027510). A more detailed study of this method revealed that ammonium ions with a pH in the neutral range (range from around PH4 to PH6) can be used on substrates with surface compositions such as chromium or alloys containing chromium, such as stainless steel. It has been found that the nickel plating contained therein causes a problem of poor adhesion and peeling of the plating. Furthermore, it has been found that even with a substrate having a surface composition of nickel or an alloy containing nickel, adhesion failure is not as extreme as with chromium or an alloy containing chromium, but sometimes sufficient adhesion cannot be obtained. Ta. This is because the surface of the metal substrate having the above surface composition forms a passive film. It is well known that surfaces such as chromium or alloys containing chromium, such as stainless steel, form a passive film, but nickel may also form a passive film. Therefore, plating with good adhesion cannot be obtained unless this passive film is removed. In order to solve these problems, the present inventors have continued to conduct detailed studies on the base plating in order to perform sulfur-containing nickel plating on the surface of the metal substrate having the above-mentioned composition. As a result of studying base plating baths and base plating methods that are economical from a viewpoint and suitable for reliable and continuous electrode manufacturing processes, the following two methods showed sufficient adhesion and resulted in good results. We succeeded in obtaining an electrode with excellent corrosion resistance and durability, as well as excellent properties. The electrode obtained according to the present invention can be manufactured by the following two methods. One method is to manufacture an electrode by performing base nickel plating on the surface of the substrate using a nickel plating bath containing ammonium ions and having a pH of 2.5 or less, and then applying nickel plating on top of that using a nickel plating bath containing sulfur. It is the law. As a result of various studies on the pH of the base nickel plating bath containing ammonium ions, the present inventors found that by setting the PH of the base nickel plating bath to an acidic region of 2.5 or less, the substrate surface, the base nickel plating, and the sulfur-containing nickel plating were We found that this method provides good adhesion and established this method. Another method is to perform the first base nickel plating on the surface of the substrate using a nickel plating bath containing no ammonium ions and containing hydrochloric acid with a pH of 1 or less, and then apply a second nickel plating bath on top of that using a nickel plating bath containing ammonium ions. In this method, an electrode is manufactured by applying nickel plating to the base layer, and then applying nickel plating thereon using a sulfur-containing nickel plating bath. A typical example of a hydrochloric acid acidic nickel plating bath for this first base nickel plating is a plating bath made of nickel chloride and hydrochloric acid called strike nickel. When plating the surface on which a passive film is to be formed, it is known to use strike nickel as the base plating. It is true that this strike nickel plating can produce a film that exhibits sufficient adhesion to the surface of a metal substrate having the above-mentioned surface composition, but according to the studies of the present inventors, it is possible to obtain a film that exhibits sufficient adhesion to the surface of the metal substrate having the above-mentioned surface composition. Adhesion is poor. As a result of various studies on this problem, the present inventors found that the second base nickel plating using the above-mentioned nickel plating bath containing ammonium ions:
The present method was established by discovering that it exhibits good adhesion to strike nickel and also to the upper layer of sulfur-containing nickel. Therefore, in the present invention, the surface of a metal substrate having a surface composition of chromium, nickel, or an alloy phase containing these is subjected to base nickel plating using a nickel plating bath that contains ammonium ions and has a pH of 2.5 or less, or A first base nickel plating is performed using a hydrochloric acid nickel plating bath that does not contain ions and has a pH of 1 or less, and then a second base nickel plating is applied thereon using a nickel plating bath containing ammonium ions, and then a sulfur-containing nickel plating bath is applied. This invention relates to a method for producing an electrode characterized by performing nickel plating using a nickel plating bath, and is characterized in that it provides an electrode that has particularly excellent corrosion resistance and durability, and maintains a low hydrogen overvoltage for a long period of time. be. In the present invention, the surface of a metal substrate having a surface composition of chromium, nickel, or an alloy phase containing these refers to the surface of a substrate material such as chromium, nickel, a chromium alloy, a nickel alloy, or an alloy containing chromium or nickel, such as stainless steel, Alternatively, it refers to the surface of a metal base material whose metal surface is densely coated with chromium, nickel, or an alloy containing these by plating, thermal spraying, vapor deposition, or the like. These base materials exhibit good corrosion resistance and durability when used as electrode base materials under conditions of high temperature and high alkali concentration, for example.
It is also an economical material. Furthermore, the shape of the substrate may be any shape such as a flat plate, mesh shape, porous shape, etc., but when used as a hydrogen generating electrode at high current density, the shape of the base material such as expanded metal, punched metal, wire mesh shape, etc. is particularly suitable. It is preferable to use The method for manufacturing an electrode of the present invention includes, on the surface of the substrate,
It is necessary to apply the base nickel plating using the two methods described above. The effects of these two methods are almost the same, and it is possible to select a convenient method in actual plating work.
One method for performing base nickel plating is to perform base nickel plating using a nickel plating bath containing ammonium ions and having a pH of 2.5 or less. The nickel salt may be any soluble salt, and nickel chloride, nickel sulfate, nickel acetate, nickel sulfamate, etc. are used.The concentration is not particularly limited, but is usually used in the range of 0.05 molar to 2.0 molar. It will be done. Ammonium ions are added to the plating bath by soluble ammonium salts such as chloride, sulfate, or ammonium hydroxide or other ammonium salts. By adding ammonium ions, the adhesion between the base plating layer and the sulfur-containing nickel plating layer is significantly improved. The ammonium ion concentration added to the plating bath is 0.05 molar or more, and the upper limit is not particularly limited, and a saturation concentration is allowed. If the ammonium ion concentration is below the above concentration, the adhesion between the resulting nickel plating layer and the sulfur-containing nickel plating layer will be insufficient. The pH of the base nickel metal bath is limited to 2.5 or less. When the pH of the base nickel plating bath exceeds 2.5, the adhesion between the base nickel plating layer and the surface of the metal substrate having a surface composition of chromium, nickel, or an alloy phase containing these becomes insufficient. Adjustment of pH is easily carried out using acids such as hydrochloric acid and sulfuric acid.
In addition to the above-mentioned components, other soluble salts may be added to the plating bath for forming the base plating layer, as long as they do not cause any inconvenience to the resulting surface coating.
For example, a surfactant or a buffer such as boric acid used in ordinary nickel plating may be used. Further, the operating conditions for plating to form the base plating layer are not subject to any particular strict limitations, but are preferably within a temperature range of about 70°C from room temperature, and at a temperature of 0.1/
It is desirable to perform plating under stirring at a current density range of about 10 A/dm ² . Another method for performing base nickel plating is to perform the first base nickel plating using a hydrochloric acid nickel plating bath that does not contain ammonium ions and has a pH of 1 or less, and then to apply the second base nickel plating using a nickel plating bath containing ammonium ions. This is a method of performing nickel plating on the base. The composition of the first base nickel plating bath generally includes hydrochloric acid and nickel chloride. The concentration of nickel chloride is not particularly limited, but is generally used in a range of about 1 molar concentration. Furthermore, add hydrochloric acid to PH1
The PH is lowered to the following range, preferably PH0 or lower. Further, the operating conditions for this first base plating are not subject to any particular strict limitations, but it is generally carried out at room temperature and in a current density range of about several A/dm ² to 10 A/dm ² . For the second base nickel plating, it is necessary to use a nickel plating bath containing ammonium ions. Note that the pH of the plating bath in this case is not particularly limited, and is used within the range of PH 3.5 to 6 at the time of normal bath preparation. The nickel salt may be any soluble salt, and nickel chloride, nickel sulfate, nickel acetate, nickel sulfamate, etc. are used.The concentration is not particularly limited, but is usually in the range of 0.05 molar to 2.0 molar. It will be done. Ammonium ions are added to the plating bath by soluble ammonium salts such as chloride, sulfate, or ammonium hydroxide or other ammonium salts. By adding ammonium ions, the adhesion between the second base plating layer and the sulfur-containing nickel plating layer is significantly improved, and also shows good adhesion to the first base plating layer. The concentration of ammonium ions added to the plating bath is 0.05 molar or more, and the upper limit is not particularly limited, and a saturation concentration is allowed. If the ammonium ion concentration is below the above concentration, the adhesion between the resulting nickel plating layer and the sulfur-containing nickel plating layer will be insufficient. In addition to the above-mentioned components, other soluble salts may be added to the plating bath for forming the second base plating layer, as long as they do not make the resulting surface coating undesirable. For example, a surfactant or a buffer such as boric acid used in ordinary nickel plating may be used. Furthermore, the operating conditions for plating to form the base plating layer are not subject to any particular strict limitations, but preferably a temperature range of about 70°C from room temperature;
It is desirable to perform plating under stirring at a current density range of about 0.1 to 10 A/dm ² . In order to provide the electrode of the present invention, it is necessary to form a sulfur-containing nickel plating layer on the base nickel plating layer applied by either of the above two methods. Nickel plating containing sulfur is provided by a nickel plating bath containing a soluble nickel salt and an appropriate amount of a soluble sulfur-containing compound. More preferably,
It is desirable to add an appropriate amount of ammonium ions to the Nickelmecki bath. Nickel salt can be any soluble salt, usually
It is desirable to use the concentration in the range of 0.1 molar to 2.0 molar. The soluble sulfur-containing compound used in the plating bath means a thiocyanate, a thiourea, or an oxoacid salt having a sulfur oxidation number of 5 or less, and is particularly effective in providing a plating film exhibiting a low hydrogen overvoltage. The oxoacid salt having a sulfur oxidation number of 5 or less means, for example, salts of sulfite, bisulfite, thiosulfite, dithionite, and the like. The concentration of thiocyanates and thiourea oxoacid salts with an oxidation number of sulfur of 5 or less to be added to the bath is 0.01 molar or more based on the amount of sulfur in the compound,
It is desirable to use it in a range of 1.0 molar or less, preferably 0.05 molar or more and 1 molar or less. If the concentration of the sulfur compound is less than 0.01 molar concentration, the hydrogen overvoltage on the resulting nickel plating surface will be insufficiently reduced, and if it exceeds 1.0 molar concentration, the adhesion between the base plating and the plating film will be poor. Furthermore, by adding an appropriate amount of ammonium ions to the nickel plating bath that provides the nickel plating containing sulfur, the adhesion of the resulting plating film is improved, and the covering power of the plating is also increased.
A coating surface with even stronger properties can be obtained. The concentration of ammonium ions added to the plating bath should be at least 0.5 times the molar concentration relative to the amount of sulfur in sulfur compounds such as thiocyanates, thioureas, and oxoacids with a sulfur oxidation number of 5 or less. Preferably, the upper limit is not particularly limited and is allowed up to saturation concentration. The pH of the plating bath is preferably 6 or less; when the pH exceeds 6, the resulting plating surface tends to become brittle and easily peel off. In addition to the above-mentioned components, the plating bath used to form the sulfur-containing nickel plating layer may contain surfactants and other soluble materials used in normal plating, as long as they do not make the resulting surface coating inconvenient. It is also permissible to add salt. For example, the use of a buffer such as boric acid, which is often used in nickel plating baths, may improve the properties of the nickel plating film used in the present invention, and may be added as a suitable component to the nickel plating bath used in the present invention. . Furthermore, the operating conditions for plating to form a sulfur-containing nickel plating layer are not subject to any particular strict limitations, but preferably a temperature range of about 70°C from room temperature and a current density range of about 0.1 to ¹⁰ A/dm2. It is desirable to perform plating under stirring. Furthermore, in order to provide the electrode of the present invention, appropriate heat treatment as a treatment after plating may improve the adhesion of the plating, and these treatments may be carried out to the extent that the characteristics of the surface coating are not lost. You may also do so. As described above, the surface of a metal substrate having a surface composition of chromium, nickel, or an alloy phase containing these is subjected to base nickel plating using a nickel plating bath that contains ammonium ions and has a pH of 2.5 or less, or is coated with ammonium ions. After performing the first base nickel plating using an acidic nickel plating bath containing no sulfur and having a pH of 1 or less, and then applying the second base nickel plating using a nickel plating bath containing ammonium ions, a nickel plating bath containing sulfur is applied. By performing nickel plating using nickel plating, it has excellent corrosion resistance and durability, and by maintaining particularly low hydrogen overvoltage over a long period of time, it is possible to provide an electrode with extremely high energy efficiency as a cathode for water electrolysis and salt electrolysis. can. Examples will be described below, but the present invention is not limited thereto. Example 1, Comparative Examples 1 to 3 A flat plate (3 mm x 5 mm) of stainless steel (SUS304), which is an alloy containing chromium, was used as the base material.
After normal pretreatment such as degreasing and pickling, base nickel plating is performed using the plating bath composition shown in Table 1.
On it he made a sulfur-containing nickel-meck. A well-known adhesion test was performed on these samples.
Table 1 also shows the measurement results of the 90° bending test. As is clear from the table, Example 1 of the present invention using a base nickel plating bath containing ammonium ions and having a pH of 2.5 or less shows good adhesion. On the other hand, Comparative Example 3 in which base plating was not performed, Comparative Example 2 in which ammonium ions were not included in the base nickel plating bath, and Comparative Example 1 in which the PH in the base nickel plating bath exceeded 2.5 all had poor adhesion. I understand that. Next, the sample of Example 1 was used as a cathode in a 30 wt % NaOH solution using platinum as an anode under electrolytic conditions of 90° C. and 15 A/dm ² for 100 days, and the cathode potential was measured.

[Table] Cathode potential was measured using the Luggin capillary method using a mercury oxide electrode. During this measurement, the cathode potential showed a nearly constant value of -1.07 to -1.09V vs. Hg/HgO, and there was no problem of peeling, and the adhesion was good. The cathode potential of the stainless steel plate used as the base material was -1.42V vs. Hg/HgO under the same conditions.
It can be seen that the sample of Example 1 of the present invention exhibits a hydrogen overpotential that is about 340 mV lower than that of the base material. As described above, it can be seen that Example 1 of the present invention maintains an extremely low hydrogen overvoltage for a long period of time and exhibits excellent durability and corrosion resistance. Example 2, Comparative Example 4 Using the base material shown in Example 1, after normal pretreatment such as degreasing and pickling, base nickel plating was performed using the plating bath composition shown in Table 2, and then the plating was carried out on top of that. Nickel plating containing sulfur was carried out with the same bath composition as in Example 1. Table 2 also shows the measurement results of a 90° bending test, which is a well-known adhesion test, for these samples. As is clear from the table, the first base plating was performed using a hydrochloric acid acidic nickel plating bath with a pH of 0 or less,
Example 2 of the present invention, in which a second base plating was then performed using a nickel plating bath containing ammonium ions, and a nickel plating containing sulfur was further applied thereon, had good adhesion. On the other hand, Comparative Example 4 in which the first base plating was performed, the second base plating was not performed, and nickel plating containing sulfur was directly applied.
It can be seen that the adhesion is poor.

【table】

[Table] Next, the sample of Example 2 was used as a cathode for 50 days under the same conditions as Example 1, and the cathode potential was measured. During this measurement, the cathode potential is −1.08~
Almost the same results as in Example 1 were shown at 1.10V vs. Hg/HgO. As described above, it can be seen that Example 2 of the present invention maintains an extremely low hydrogen overvoltage and exhibits excellent durability and corrosion resistance. Example 3, Comparative Example 5 The following samples were prepared using a steel plate (5 cm x 3 cm) as a base material, which was coated with dense electroless nickel plating using Kanigen's Blue Schumer solution. did. That is, in Example 3, base nickel plating was performed using the nickel plating bath shown in Table 3 under the conditions shown in Table 4. Table 3 Nickel plating bath composition Nickel chloride 0.5M / Ammonium chloride 0.5M / Hydrochloric acid (36%) 2ml / PH approx. 1.5 Table 4 Nickel plating conditions Temperature 40℃ Current density 2A/dm ² hours 10 minutes After that, the nickel plating bath shown in Table 5 was applied. Nickel plating containing sulfur was performed under the conditions shown in Table 6. Table 5 Nickel plating bath composition Nickel chloride 0.5M / Sodium thiocyanate 0.2M / Ammonium chloride 1.0M / Boric acid 0.49M / Table 6 Nickel plating condition temperature 60℃ Current density 1A/dm ² Plating time 2 hours On the other hand, in Comparative Example 5 , without performing base nickel plating on the electroless nickel plated sample,
Directly using the same plating bath and plating conditions as in Example 3,
They performed nickel-metal removal containing sulfur. These samples were used as cathodes under the conditions shown in Example 1 for 10 days. Table 7 shows the measurement results of the cathode potential of each example and the surface condition after 10 days. In addition,
The cathode potential of the sample used as a base material and subjected to electroless nickel plating was -1.48V vs. Hg/HgO.

[Table] As shown in the above table, Example 3 of the present invention exhibits good adhesion and maintains an extremely low hydrogen overvoltage. On the other hand, in Comparative Example 5, the adhesion was poor, the plating film peeled off, and the electrode performance deteriorated. Furthermore, when the sample of Example 3 was subjected to an electrolytic test under the same conditions for 100 consecutive days,
The cathode potential was almost constant, and there was no problem of peeling of the plating layer. As described above, it can be seen that Example 3 of the present invention maintains an extremely low hydrogen overvoltage for a long period of time and provides an electrode exhibiting excellent corrosion resistance and durability. Example 4 A chrome flat plate (3 mm x 5 mm) was used as the base material, and after normal pretreatment such as degreasing and pickling, the first and second bases were plated with nickel using the same plating bath and plating conditions as in Example 2. Then, using the nickel plating bath shown in Table 8, nickel plating containing sulfur was carried out under the conditions shown in Table 9. Table 8 Nickel plating bath composition Nickel sulfate 0.57M / Sodium thiocyanate 0.20M / Ammonium chloride 0.50M / Boric acid 0.24M / Table 9 Nickel plating conditions Temperature 50℃ Current density 1A/dm ² Plating time 2 hours This sample was used in Example 1 It was used as a cathode for 30 days under the conditions shown in , and the cathode potential was measured. During this measurement, the cathode potential was approximately constant at -1.09 to -1.10V vs. Hg/HgO, and there was no problem of peeling of the plating layer. Note that the cathode potential of chromium used as the base material was -1.49V vs. Hg/HgO. As described above, it can be seen that Example 4 of the present invention maintains an extremely low hydrogen overvoltage and provides an electrode exhibiting excellent corrosion resistance and durability. Example 5, Comparative Example 6 Half-inch expanded metal made of nickel and measuring 14 cm x 14 cm (minor diameter 7.0
mm, major axis 12.7 mm), Table 10 is used as Example 5.
First base plating was performed using the nickel plating bath shown in Table 11 under the conditions shown in Table 11, and second base plating was performed using the nickel plating bath shown in Table 12 under the conditions shown in Table 13. Then, using the nickel plating bath shown in Table 14, nickel plating containing sulfur was applied under the conditions shown in Table 15. Table 10 Nickel plating bath composition Nickel chloride 1.2M / Hydrochloric acid 120ml / PH 0 or less Table 11 Nickel plating condition temperature 25℃ Current density 2A/dm ² plating time 10 minutes Table 12 Nickel plating bath composition Nickel sulfate 0.91M / Nickel chloride 0.19M / Boric acid 0.49M / Ammonium chloride 0.15M / Table 13 Nickel plating condition temperature 40℃ Current density 1A/dm ² plating time 1 hour Table 14 Nickel plating bath composition Nickel sulfate 0.91M / Nickel chloride 0.19M / Thiourea 0.10M / Boric acid 0.49M/ Table 15 Nickel plating condition Temperature 50℃ Current density 0.5A/dm ² Plating time 4 hours On the other hand, as Comparative Example 6, ammonium chloride was extracted from the bath composition of the second base nickel plating bath, that is, the nickel plating bath composition shown in Table 12. The first base nickel plating, the second base nickel plating, and the sulfur-containing nickel plating were applied in the same manner as in Example 5, except that a plating bath other than .
These samples were used as cathodes in a 30wt% NaOH solution, and a nickel electrode with the same substrate shape was used as an anode.
Water electrolysis was performed for 100 days at a temperature of 90° C. and a current density of 20 A/dm ² relative to the peripheral area of the sample. Table 16 shows the measurement results of the cathode potential of each example and the surface condition after 100 days. The cathode potential of the nickel electrode used as the base material was -1.30V vs. Hg/HgO.

【table】

[Table] As described above, Example 5 of the present invention maintained an extremely low hydrogen overvoltage for 100 days, although there was slight deterioration, and exhibited good adhesion without any problem of peeling of the plating layer. It can be seen that it has excellent corrosion resistance and durability. On the other hand, in Comparative Example 6, the electrode potential was clearly shifted toward the base direction, and the electrode performance was significantly deteriorated. After 100 days, this electrode had peeled off from the end, and all the plating peeled off when rubbed a little. As described above, it can be seen that Example 5 of the present invention maintains an extremely low hydrogen overvoltage and exhibits excellent corrosion resistance and durability. Example 6 A half-inch expanded metal made of SUS304 and measuring 14 cm x 14 cm (minor axis 7.0 mm, major axis 12.7 mm) was used as the electrode base material, and the base material was nickel plated and sulfur coated using the method shown in Example 1. I performed a nickel-metuki including. The nickel plating containing sulfur was used for 4 hours. A cation exchange membrane was used with this sample as the cathode, and a RuO ₂ -TiO ₂ film was used on Ti as the anode.
Salt water was electrolyzed using DSA type expanded metal under the following conditions. For comparison, electrolysis was performed under the same conditions using an expanded metal made of SUS304 as a cathode. Electrolysis conditions: Temperature: 90°C Current density: 30 A/dm ² (electrode peripheral area) Cathode chamber NaOH concentration: 32 to 33 wt% Table 17 shows the cathode potential at the beginning of energization for the case of the SUS304 cathode used as the base material and the cathode of the present invention. The value, the cathode potential value after one year, and the bath voltage value are shown.

【table】

[Table] As described above, Example 6 of the present invention exhibited excellent durability and corrosion resistance, and maintained an extremely low hydrogen overvoltage for a long period of 300 mV compared to the comparative SUS304 cathode.
It can be seen that this is an excellent cathode with low hydrogen overvoltage and bath voltage, and high energy efficiency. Example 7 The expanded nickel metal used in Example 5 as an electrode base material (half-inch size, 14 cm x 14
cm square), and placed it in a cathode chamber made of SUS304, and applied the first base plating, second base plating, and sulfur-containing nickel plating to the entire surface of the cathode chamber and the electrode section as shown in Example 2. did. Incidentally, the nickel removal containing sulfur was carried out for 4 hours. Using this sample as a cathode, saline solution was electrolyzed under the same conditions as in Example 6. Table 18 shows the cathode potential value at the initial stage of energization, the cathode potential value after one year, and the bath voltage value for the cathode made of nickel and the cathode of the present invention.

[Table] As described above, Example 7 of the present invention exhibited excellent durability and corrosion resistance, maintained an extremely low hydrogen overvoltage for a long period of time, and was superior to the comparative nickel cathode.
It shows a low hydrogen overvoltage and bath voltage of about 250mV to 300mV, indicating that it is an excellent cathode with high energy efficiency.

Claims (1)

[Scope of Claims] 1. Nickel plating is applied to the surface of a metal substrate having a surface composition of chromium, nickel, or an alloy phase containing these, using a nickel plating bath containing ammonium ions and a pH of 2.5 or less, and then containing sulfur. A method for manufacturing an electrode characterized by applying nickel plating using a nickel plating bath. 2. The method for producing an electrode according to claim 1, wherein nickel plating is performed using a nickel plating bath containing ammonium ions at a concentration of 0.05 molar or more. 3. The sulfur-containing nickel metal bath contains at least one sulfur-containing compound selected from the group consisting of (a) nickel salts and (b) thioureas, thiocyanates, and oxoacid salts with a sulfur oxidation number of 5 or less. A method for manufacturing an electrode according to claim 1 or 2. 4. The sulfur-containing nickel metal bath contains at least one sulfur-containing compound selected from the group consisting of (a) nickel salts, (b) thioureas, thiocyanates, and oxoacid salts with a sulfur oxidation number of 5 or less, and ( c) A method for producing an electrode according to any one of claims 1 to 3, which contains ammonium ions. 5. On the surface of a metal substrate having a surface composition of chromium, nickel, or an alloy phase containing these, nickel plating is performed as a first base using a hydrochloric acid acidic nickel bath with a pH of 1 or less, and then a nickel plating bath containing ammonium ions is applied on top of that. 1. A method for producing an electrode, which comprises applying a second base nickel plating using a sulfur-containing nickel plating bath, and then applying nickel plating using a sulfur-containing nickel plating bath. 6. The sulfur-containing nickel metal bath contains at least one sulfur-containing compound selected from the group consisting of (a) nickel salts and (b) thioureas, thiocyanates, and oxoacid salts with a sulfur oxidation number of 5 or less. A method for manufacturing an electrode according to claim 5. 7. The sulfur-containing nickel metal bath contains at least one sulfur-containing compound selected from the group consisting of (a) nickel salts, (b) thioureas, thiocyanates, and oxoacid salts with a sulfur oxidation number of 5 or less, and ( c) A method for producing an electrode according to claim 5 or 6, which contains ammonium ions.