Electrochemical measuring device and electrochemical measuring method for metallic materials

Abstract

To provide an electrochemical measuring device which is used for evaluating corrosion resistance (corrosion characteristics) of a metal material in a specific solution and is capable of restraining contamination in the solution to a low level and precisely evaluating corrosion resistance of the metal material.SOLUTION: An electrochemical measuring device includes a cell 1 for housing solution, and a reference electrode 2 and a counter electrode 3 dipped into the solution within the cell 1, wherein the cell 1 is composed of fluororesin, the reference electrode 2 is made of a reversible hydrogen electrode, and preferably the outside of a cylinder made of glass as a base material is coated with fluororesin in a supporting tube of the reference electrode 2. In electrochemical measurement of a metal material in an acid aqueous solution containing an alkali aqueous solution or a fluoride ion (F-), contamination (boron (B), aluminum (Al), silicon (Si), nitride ion (Cl-), or the like) derived from glass in the solution and derived from an internal liquid in the reference electrode 2 can be reduced to an extremely low level.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electrochemical measuring device used to evaluate the corrosion resistance (corrosion properties) of a metal material in a specific solution, and more particularly to an electrochemical measuring device suitable for evaluating the corrosion resistance of metal materials used in fuel cells and water electrolysis devices (especially materials for separators). [Background technology]

[0002] In recent years, efforts have been made to develop social infrastructure for using hydrogen as fuel in order to achieve carbon neutrality. In particular, the spread of water electrolysis devices (such as polymer electrolyte water electrolysis devices and anion exchange membrane water electrolysis devices) that produce highly pure and valuable hydrogen gas by electrolyzing water, and fuel cells (such as polymer electrolyte fuel cells) that generate electricity using hydrogen gas as fuel, is progressing. The separators that make up water electrolysis devices (water electrolysis cells, especially water electrolysis cells in solid polymer water electrolysis devices) and fuel cells use various metal materials such as press-formable stainless steels like SUS304 and SUS316L, and titanium (Ti), which is more corrosion-resistant and lighter than stainless steel, and has been treated to have excellent electrical conductivity. Among these, it is expected that stainless steel will become the mainstream metal material in the future from an economic standpoint. In addition, the use of nickel, nickel alloys, and surface-treated stainless steel with excellent electrical conductivity is being considered for the water electrolysis cells of anion exchange membrane water electrolysis devices.

[0003] During water electrolysis in water electrolysis devices (especially polymer electrolyte water electrolysis devices) and during power generation in fuel cells (especially polymer electrolyte fuel cells), the perfluorosulfonic acid polymer membrane used as the proton-conducting membrane in the MEA (membrane-electrode assembly) deteriorates, leading to sulfate ions (SO4). 2- ) and fluoride ions (F -) ions are released. These ions concentrate at the interface of the separator / porous transport layer or the separator / gas diffusion layer, creating an acidic environment containing fluoride ions. Therefore, metal materials used in water electrolysis devices and fuel cells need to be corrosion resistant in such environments. For this reason, materials used in such environments must be treated in a simulated environment, i.e., fluoride ions (F - Electrochemical measurements are performed to evaluate corrosion resistance (corrosion properties) in acidic aqueous solutions containing ).

[0004] Furthermore, since water electrolysis devices (especially anion exchange membrane type water electrolysis devices) use alkaline aqueous solutions (generally aqueous solutions of potassium hydroxide, etc.) as the electrolyte, the separator is exposed to an alkaline environment, and therefore corrosion resistance in such an environment is required. For this reason, electrochemical measurements are performed to evaluate the corrosion resistance (corrosion characteristics) of materials used in such environments, i.e., in a simulated environment, i.e., an alkaline aqueous solution.

[0005] Generally, electrochemical measurements of metal materials used in water electrolyzers and fuel cells are performed under controlled conditions, where the potential between the metal material to be evaluated and a reference electrode is controlled. This electrochemical measurement is carried out using a three-electrode cell in which the metal material to be evaluated is the working electrode, and the working electrode, the counter electrode (platinum electrode), and the reference electrode (generally a silver / silver chloride electrode) that serves as the potential standard are immersed in the same test solution (an acidic aqueous solution containing fluoride ions or an alkaline aqueous solution (not containing fluoride ions)). The measurement is performed under heated conditions of approximately 60°C to 80°C (for example, Patent Document 1). Generally, glass is used as the material for the three-electrode cell. For example, Non-Patent Document 1 describes using a three-electrode cell to produce 1M H2SO4 + 2ppm F - Electrochemical measurements (anodic polarization test, potentiometer polarization test) were performed on various stainless steels in solution at 70°C, and the order of corrosion resistance in a polymer electrolyte fuel cell environment was clarified based on the magnitude of the measured current values. [Prior art documents] [Patent Documents]

[0006]

Patent Document 1

Non-Patent Document

[0007]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] However, as a result of repeated tests and studies by the present inventors, in the electrochemical measurement of the above-described metal materials, contamination occurred in the test solution (acidic aqueous solution or alkaline aqueous solution (excluding fluoride ions) containing fluoride ions (F - )), and it was found that this was affecting the accuracy of the corrosion resistance evaluation. Therefore, an object of the present invention is to provide an electrochemical measurement device that can suppress contamination in a solution to a low level and accurately evaluate the corrosion resistance of a metal material in an electrochemical measurement device used for evaluating the corrosion resistance (corrosion characteristics) of a metal material in a solution.

Means for Solving the Problems

[0009] In order to solve the above problems, the present inventors investigated and studied the influence of contamination in the test solution on the accuracy of electrochemical measurement. As a result, it was found that the main components of the contamination are chloride ions (Cl - ) and other specific elemental components, and the following problems are caused by this contamination, resulting in a decrease in the accuracy of the corrosion resistance evaluation. (i) Chloride ions (Cl - ) accelerate the corrosion of the sample (working electrode) and reduce the measurement accuracy of the corrosion current. In particular, when stainless steel is used as the sample, even the incorporation of trace amounts of chloride ions (Cl - ) promotes the corrosion of the sample. (ii) When quantifying the eluted metal from the working electrode by inductively coupled plasma mass spectrometry (ICP-MS) or inductively coupled plasma atomic emission spectrometry (ICP-AES) for the test solution used in electrochemical measurement, contamination affects the analysis results. (iii) For the sample (test piece) used in the electrochemical test, a contact resistance measurement test is later performed, but the contact resistance increases due to contamination and high-precision measurement cannot be performed.

[0010] In the electrochemical measurement of the above-mentioned metal materials, when examining the components of the contamination generated in the test solution, the main components are chloride ions (Cl - ) and part of the glass components (boron (B), aluminum (Al), silicon (Si), etc.). Also, as the source of generation, the former is chloride ions (Cl - ) derived from the internal solution of the reference electrode (generally a silver / silver chloride electrode), and the latter is found to be components derived from the glass constituting the cell and reference electrode of the electrochemical measurement device.

[0011] In conventional electrochemical measurement devices, silver / silver chloride electrodes etc. are generally used as reference electrodes. However, it has been found that the internal solution (KCl solution) eluting from the liquid junction part into the test solution is the chloride ion source and is contained in the test solution as contamination. Also, in conventional electrochemical measurement devices, glass cells are used. However, in the electrochemical measurement of metal separator materials in solid polymer fuel cells and solid polymer water electrolysis cells, since the test solution temperature is relatively high at about 80°C, when the test solution is an acidic aqueous solution containing fluoride ions (F - ), the glass of the cell is affected by the fluoride ions (F -It was found that the test solution was contaminated by ( ), and some of the glass components leached into the test solution as contamination. Furthermore, it was found that the cylindrical body constituting the reference electrode was also made of glass, and some of the glass components leached into the test solution as contamination from this body as well. In addition, when the test solution is an alkaline aqueous solution, it goes without saying that the glass components of the cylindrical body constituting the cell and reference electrode dissolve into the test solution and become contamination.

[0012] Therefore, in this invention, as a measure against contamination as described above, a reversible hydrogen electrode whose internal solution does not contain chloride is used as the reference electrode, thereby eliminating the source of chloride ions and preventing contamination (chloride ions) originating from the internal solution of the reference electrode. Furthermore, the cell is constructed of fluororesin, and preferably the glass cylindrical body constituting the reference electrode is coated with fluororesin, thereby suppressing glass-derived contamination (boron (B), aluminum (Al), silicon (Si), etc.) to an extremely low level. In other words, the gist of the present invention for solving the above problems is as follows.

[0013] [1] An apparatus for performing electrochemical measurements of metallic materials in solution, The device comprises a cell (1) for containing a solution, and a reference electrode (2) and a counter electrode (3) immersed in the solution within the cell (1). An electrochemical measuring device characterized in that the cell (1) is made of fluororesin and the reference electrode (2) is a reversible hydrogen electrode. [2] An electrochemical measuring apparatus as described in [1] above, characterized in that the support tube for the reversible hydrogen electrode, which is the reference electrode (2), has a glass cylindrical body as the base material, on the outside of which is coated with fluororesin.

[0014] [3] An electrochemical measuring device according to [1] or [2] above, characterized in that the support tube of the reversible hydrogen electrode which is the reference electrode (2) has a liquid junction portion at its tip made of a ceramic porous material, and the porosity of the ceramic porous material is 40% or less. [4] An electrochemical measuring device in any of the above [1] to [3], characterized in that the lid (4) and connector (5) attached to the cell (1) are made of fluororesin.

[0015] [5] In any of the electrochemical measuring devices described in [1] to [4] above, an internal liquid temperature control mechanism (6) is provided to control the temperature of the internal liquid of the reversible hydrogen electrode by controlling the temperature of the hydrogen gas supplied to the reversible hydrogen electrode, which is the reference electrode (2). The electrochemical measuring device is characterized in that the internal liquid temperature control mechanism (6) comprises a heating means (60) for heating hydrogen gas supplied to the reversible hydrogen electrode, a temperature measuring means (61) for measuring the temperature of the internal liquid of the reversible hydrogen electrode, and a control means (62) for controlling the heating temperature of the hydrogen gas by the heating means (60) so that the temperature of the internal liquid of the reversible hydrogen electrode measured by the temperature measuring means (61) reaches a predetermined temperature. [6] An electrochemical measuring device as described in [5] above, wherein the internal liquid temperature control mechanism (6) further comprises a temperature measuring means (63) for measuring the temperature of the solution in the cell (1), and the control means (62) controls the heating temperature of hydrogen gas by the heating means (60) so that the temperature of the internal liquid of the reversible hydrogen electrode measured by the temperature measuring means (61) is within a predetermined range relative to the temperature of the solution in the cell (1) measured by the temperature measuring means (63).

[0016] [7] In any of the electrochemical measuring devices described in [1] to [4] above, an internal liquid temperature control mechanism (7) is provided, which controls the temperature of the internal liquid of the reversible hydrogen electrode by controlling the flow rate of hydrogen gas supplied to the reversible hydrogen electrode, which is the reference electrode (2). The electrochemical measuring device is characterized in that the internal liquid temperature control mechanism (7) comprises a flow rate adjustment means (70) for adjusting the flow rate of hydrogen supplied to the reversible hydrogen electrode, a temperature measuring means (71) for measuring the temperature of the internal liquid of the reversible hydrogen electrode, and a control means (72) for controlling the flow rate adjustment of hydrogen gas by the flow rate adjustment means (70) so that the temperature of the internal liquid of the reversible hydrogen electrode measured by the temperature measuring means (71) reaches a predetermined temperature. [8] An electrochemical measuring device as described in [7] above, wherein the internal liquid temperature control mechanism (7) further comprises a temperature measuring means (73) for measuring the temperature of the solution in the cell (1), and the control means (72) controls the flow rate adjustment of hydrogen gas by the flow rate adjustment means (70) so that the temperature of the internal liquid of the reversible hydrogen electrode measured by the temperature measuring means (71) is within a predetermined range relative to the temperature of the solution in the cell (1) measured by the temperature measuring means (73).

[0017] [9] A method for measuring the electrochemical properties of a metallic material, characterized by using any of the electrochemical measuring devices described in [1] to [8] above to perform electrochemical measurements of the metallic material used in a fuel cell or water electrolysis device.

[10] An electrochemical measurement method for metallic materials, characterized in that the temperature of the internal liquid in the reversible hydrogen electrode, which is the reference electrode (2), is within ±5°C of the temperature of the solution in the cell (1), in the electrochemical measurement method of [9] above.

[11] An electrochemical measurement method for metallic materials according to the electrochemical measurement method of [9] or

[10] above, characterized in that the temperature of the solution in cell (1) is 90°C or lower.

[12] In any of the electrochemical measurement methods described in [9] to

[11] above, the solution in cell (1) is an alkaline aqueous solution or a fluoride ion (F - A method for electrochemical measurement of a metallic material, characterized by being an acidic aqueous solution containing ). [Effects of the Invention]

[0018] The electrochemical measuring device of the present invention uses a reversible hydrogen electrode whose internal solution does not contain chlorides as the reference electrode, thereby eliminating the source of chloride ions and substantially eliminating contamination (chloride ions) originating from the internal solution of the reference electrode. Furthermore, by constructing the cell from fluororesin, and preferably coating the glass cylindrical body constituting the reference electrode with fluororesin, glass-derived contamination (boron (B), aluminum (Al), silicon (Si), etc.) can be suppressed to an extremely low level. As a result, contamination in the test solution is suppressed to an extremely low level, improving the accuracy of analysis of eluted metals in the test solution, the accuracy of measurement of contact resistance of the sample, and the accuracy of measurement of corrosion current, allowing for accurate evaluation of the corrosion resistance (corrosion characteristics) of metal materials. For this reason, the electrochemical measuring device of the present invention is particularly suitable as an electrochemical measuring device for evaluating the corrosion resistance of metal materials (especially materials for separators) used in fuel cells and water electrolysis devices. [Brief explanation of the drawing]

[0019] [Figure 1] A schematic diagram illustrating one embodiment of the electrochemical measuring device of the present invention. [Figure 2] Front view showing one embodiment of the reference electrode included in the electrochemical measuring device of the present invention. [Figure 3] Partially enlarged longitudinal section view of section A in Figure 2. [Figure 4] This shows another embodiment of the reference electrode included in the electrochemical measuring device of the present invention, a partially enlarged longitudinal cross-sectional view of the tip of the cylindrical body. [Figure 5] This is a schematic diagram illustrating one embodiment of the present invention, which includes an internal liquid temperature control mechanism for controlling the internal liquid temperature of a reversible hydrogen electrode (reference electrode). [Figure 6] This schematic diagram shows another embodiment of the apparatus of the present invention, which includes an internal liquid temperature control mechanism for controlling the internal liquid temperature of a reversible hydrogen electrode (reference electrode). [Modes for carrying out the invention]

[0020] The electrochemical measuring device of the present invention is used to evaluate the corrosion resistance (corrosion properties) of a metal material in a specific solution. This electrochemical measuring device is basically used to apply an electric potential to a test sample in a solution in a cell (hereinafter sometimes referred to as the "test solution") and measure its electrical response (corrosion current, etc.). Furthermore, it can also be used to perform quantitative analysis of metals eluted into the solution in the cell, and based on these measurement and analysis results, the corrosion resistance (corrosion properties) of the metal material can be evaluated. Here, a specific solution (test solution) for performing electrochemical measurements of a metal material may be, for example, a solution containing fluoride ions (F - Examples include "acidic aqueous solutions containing )" and "alkaline aqueous solutions."

[0021] Figure 1 schematically shows one embodiment of the electrochemical measuring device of the present invention, and is an explanatory diagram showing the device in use (an explanatory diagram showing the cell in a longitudinal cross-section). This electrochemical measuring device measures solutions (e.g., "fluoride ions (F)"). - The apparatus comprises a cell 1 (test tank) containing an acidic aqueous solution (containing ) or an alkaline aqueous solution (), a reference electrode 2 and a counter electrode 3 immersed in the solution y in cell 1, and when the apparatus is in use, the sample x (working electrode), which is the metal material to be tested, is also immersed in the solution y as shown in the figure. These configurations are the same as those of conventionally used and known measuring devices.

[0022] Cell 1 is a beaker-shaped container with an open top, and a lid 4 is fitted over the top opening. The lid 4 has multiple mounting holes 40 through it for attaching the reference electrode 2, counter electrode 3, etc. The reference electrode 2, counter electrode 3, and sample x are inserted into cell 1 through the mounting holes 40 and supported by the lid 4 via the connector 5. In other words, the connector 5 serves to support the reference electrode 2, counter electrode 3, and sample x on the lid 4. The connector 5 also serves to close the upper end of the mounting holes 40 to prevent evaporation of the solution y. Furthermore, the lid 4 may have a mounting hole (not shown) for attaching a thermometer. The thermometer is inserted into the cell 1 through the mounting hole. By inserting the thermometer, the liquid temperature can be accurately evaluated, for example, when trying to control the liquid temperature.

[0023] In the apparatus of the present invention, cell 1 is made of fluororesin. While the cells of conventional apparatuses are made of glass, as mentioned earlier, fluoride ions (F) are added to the glass cells. - It was found that when acidic or alkaline aqueous solutions containing fluoride ions (F) are added, glass components (boron (B), aluminum (Al), silicon (Si), etc.) dissolve and become contaminants. In contrast, the fluororesin cell 1 of the present invention contains fluoride ions (F) - It is stable in acidic and alkaline aqueous solutions containing ) and does not produce contamination such as glass-derived eluted components. Furthermore, although the lid 4 and connector 5 attached to cell 1 are not components that come into direct contact with the solution y, evaporated solution y will adhere to them, so it is preferable that these components also be made of fluororesin.

[0024] In the apparatus of the present invention, the reference electrode 2 consists of a reversible hydrogen electrode (RHE). Although a minute amount of the internal liquid (ions) of the reference electrode 2 leaks into solution y from the liquid junction, the reversible hydrogen electrode does not contain chloride, so chloride ions (Cl) are not released into solution y. - This eliminates the contamination of ( ). Note that this reversible hydrogen electrode is typically a single-junction type electrode. Furthermore, in the apparatus of the present invention, in order to prevent contamination by eluted components derived from glass, or to suppress such contamination to an extremely low level, it is preferable that the support tube of the reversible hydrogen electrode, which is the reference electrode 2, has its outer surface coated with fluororesin on the glass cylindrical base material. Although it was considered to construct the support tube of the reversible hydrogen electrode itself from fluororesin, it was found that the difference in thermal expansion between the fluororesin cylindrical body (support tube) and the ceramic porous body constituting the liquid junction was large, causing a large amount of internal liquid to leak into the test solution, making it unsuitable for use. In contrast, the glass cylindrical body, which is the base material of the cylindrical body, has a thermal expansion coefficient close to that of the ceramic porous body, so such problems do not occur.

[0025] Figures 2 and 3 show one embodiment of the reference electrode 2 (reversible hydrogen electrode) of the apparatus of the present invention. Figure 2 is a front view, and Figure 3 is a partially enlarged longitudinal cross-sectional view of part A (the tip of the support tube) in Figure 2. The reversible hydrogen electrode, which is the reference electrode 2, consists of a support tube 20, a platinum electrode 21 (platinum-blackened electrode) placed inside the tip of the support tube 20, a platinum wire 22 connected to the platinum electrode 21, a hydrogen gas inlet tube 23 arranged along the inside of the support tube 20 and supplying hydrogen gas from the tip to the platinum electrode 21, a ceramic porous body 24 that forms the liquid junction at the tip of the support tube 20, and an internal liquid 25 filled inside the support tube 20. This internal liquid is an electrolyte (usually the same solution as solution y) with the same pH as solution y (test solution). Other components in Figure 2 include 230, the gas outlet at the tip of the gas inlet tube 23, 231, the gas inlet for supplying hydrogen gas to the gas inlet tube 23, and 26, the gas outlet for discharging hydrogen gas from inside the support tube 20. The configuration of the reference electrode 2 (reversible hydrogen electrode) as described above is the same as that of a known reversible hydrogen electrode in conventional use. Since the base material of the support tube 2 is made of transparent glass, the platinum electrode 21, platinum wire 22, hydrogen gas introduction tube 23, ceramic porous body 24, etc., which are arranged inside the support tube 2 are represented by solid lines in Figure 2.

[0026] The support tube 20 has a fluororesin coating layer 28 formed on the outside of a glass cylindrical body 27, which is the base material. From the viewpoint of minimizing the surface area of ​​the glass base material (cylindrical body 27) that comes into contact with the solution y, it is preferable that the fluororesin coating layer 28 be formed on at least the main part of the surface of the support tube 20 that comes into contact with the solution y (including the surface of the support tube 20 to which the evaporated solution y adheres). In this embodiment, a fluororesin coating layer 28 is formed on the entire circumferential surface (the area shown in Figure 2) of the support pipe (tube) portion below the gas inlet 231 (towards the tip), excluding the tip surface of the tube. Since the fluororesin coating layer 28 is formed by covering the cylindrical body 27 with a heat-shrinkable fluororesin tube and then heat-shrinking it, there is no fluororesin coating layer 28 on the tip surface of the cylindrical body 27, and the glass substrate comes into contact with the solution y in this area. However, the elution of glass components is negligible within this contact area and therefore does not pose a problem.

[0027] The fluororesin coating layer 28 can be formed by any method, such as covering the cylindrical body 27 with a heat-shrinkable tube made of fluororesin and then heat-shrinking it with a heat gun, or by painting the fluororesin (e.g., spray painting with liquid paint, powder coating). In the method of coating with fluororesin, a fluororesin coating layer 28 can also be formed on the tip surface of the cylindrical body 27. Figure 4 shows an embodiment in this case, and is a partially enlarged longitudinal cross-sectional view of the tip of the support pipe 20. In this embodiment, the fluororesin coating layer 28 is formed not only on the circumferential surface of the cylindrical body 27 but also on the tip surface of the cylindrical body 27.

[0028] There are no special restrictions on the type of fluororesin that constitutes cell 1 and the fluororesin coating layer 28 (and also the lid 4 and connector 5, etc.). Examples of usable fluororesins include polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE, CTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), and ethylene-chlorotrifluoroethylene copolymer (ECTFE), and one or more of these can be used.

[0029] As described above, the present invention eliminates the source of chloride ions by using a reversible hydrogen electrode in the reference electrode 2 whose internal solution does not contain chloride, and by having the cell 1 made of fluororesin, and more preferably by having the outside of the glass cylindrical body 27 which is the base material of the support tube 20 of the reference electrode 2 (reversible hydrogen electrode) coated with fluororesin, thereby preventing chloride ions (Cl) from entering the solution y. - This eliminates the inclusion of ) and suppresses the generation of glass-derived contaminants (boron (B), aluminum (Al), silicon (Si), etc.) to an extremely low level. In other words, chloride ions (Cl) contained in solution y are eliminated. - In the quantitative analysis of boron (B), aluminum (Al), and silicon (Si), chloride ions (Cl) in solution y are found to be present. - ), the quantitative analysis values ​​of boron (B), aluminum (Al), and silicon (Si) were measured at 0.1 mg / L. -1 It can be set to less than (limit of quantification).

[0030] The liquid junction at the tip of the support tube of the reference electrode 2 is usually composed of a ceramic porous body 24 as in this embodiment. However, if the porosity of this ceramic porous body 24 is too large, a large amount of internal liquid may flow out, resulting in insufficient internal liquid in the support tube 20. For this reason, the porosity of the ceramic porous body 24 is preferably 40% or less, and more preferably 38% or less. Furthermore, in order to prevent a decrease in measurement accuracy due to changes in potential, it is desirable to maintain the internal solution in the reversible hydrogen electrode, which is the reference electrode 2, at a temperature within a predetermined range relative to the test solution (solution y), preferably within ±5°C, and more preferably within ±3°C, relative to the test solution (solution y). Here, although hydrogen gas is passed through the reversible hydrogen electrode, if dry room temperature gas is passed through, the temperature of the internal solution in the reversible hydrogen electrode will decrease, and it may become impossible to maintain the temperature of the internal solution within a predetermined range relative to the test solution (preferably within ±5°C, more preferably within ±3°C). Therefore, it is preferable that the apparatus of the present invention includes an internal liquid temperature control mechanism for controlling the temperature of the internal liquid of the reversible hydrogen electrode, which is the reference electrode 2.

[0031] Figure 5 schematically shows one embodiment of the present invention apparatus equipped with an internal liquid temperature control mechanism for controlling the internal liquid temperature of a reversible hydrogen electrode (reference electrode). This embodiment shows an apparatus equipped with an internal liquid temperature control mechanism 6 (means) that controls the temperature of the internal liquid of the reversible hydrogen electrode (reference electrode 2) by controlling the temperature of the hydrogen gas supplied to the reversible hydrogen electrode (reference electrode 2). In this embodiment, hydrogen gas is supplied from a hydrogen cylinder 8 to a reversible hydrogen electrode (reference electrode 2) through a gas pipe 9. The gas pipe 9 is equipped with a flow rate adjustment means 10 (flow rate regulator) and a regulator 11, and the flow rate (supply amount) of hydrogen gas is adjusted by the flow rate adjustment means 10. In addition, a heater 12 is attached along the outer surface of the cell 1, and the solution (test solution) inside the cell 1 is heated by this heater 12. As described later, the gas piping 9 is heated by a heater during transport, so it is preferable to use a metal with high thermal conductivity (for example, stainless steel). The flow rate adjustment means 10 can be, for example, a flow meter or a mass flow controller (MFC), but is not limited to these.

[0032] The internal liquid temperature control mechanism 6 consists of a heating means 60 for heating the hydrogen gas supplied to the reversible hydrogen electrode (reference electrode 2), a temperature measuring means 61 for measuring the temperature of the internal liquid of the reversible hydrogen electrode, and a control means 62 (controller) for controlling the heating temperature of the hydrogen gas by the heating means 60 so that the temperature of the internal liquid of the reversible hydrogen electrode, as measured by the temperature measuring means 61, reaches a predetermined temperature. The configuration of the heating means 60 is not particularly limited, but in this embodiment it is composed of a heater (such as an electric heater) provided along the longitudinal direction of the gas pipe 9 so as to cover it. The heating means 60 may also be composed of, for example, a heating device provided in the middle of the gas pipe 9, in which case it is preferable to have a heat-insulating structure for the gas pipe 9 downstream of the heating device. The temperature measuring means 61 is typically composed of a thermocouple inserted into a reversible hydrogen electrode (reference electrode 2).

[0033] The internal liquid temperature control mechanism 6 of this embodiment further includes a temperature measuring means 63 for measuring the temperature of the solution in the cell 1, and a temperature measuring means 64 for measuring the temperature of the hydrogen gas (hydrogen gas in the gas piping 9) immediately before it is heated by the heating means 60 and introduced into the reversible hydrogen electrode. Although the temperature measuring means 64 is not essential, it is preferable to include it for more accurate temperature control. The temperature measuring means 63 and 64 are typically composed of thermocouples. A fluororesin coating layer 65 is formed on the outside of the thermocouple that constitutes the temperature measuring means 63. The type of fluororesin that constitutes this fluororesin coating layer 65 is the same as that of the fluororesin coating layer 28 described earlier. The thermocouples constituting the temperature measuring means 61, 63, and 64 are contact-type temperature sensors that are placed within the object to be measured to directly measure the temperature. However, the temperature measuring means 61, 63, and 64 may be composed of non-contact type temperature sensors instead of such contact-type temperature sensors. The temperature information measured by the temperature measuring means 61, 63, and 64 is input to the control means 62, and the control means 62 controls the heating temperature of the hydrogen gas by the heating means 60 based on this temperature information.

[0034] Specifically, the temperature of the internal liquid of the reversible hydrogen electrode is measured by the temperature measuring means 61, and this temperature information is input to the control means 62. Based on this temperature information, the control means 62 controls the heating temperature of the hydrogen gas by the heating means 60 so that the internal liquid of the reversible hydrogen electrode reaches a predetermined temperature. In this embodiment, the temperature of the solution in cell 1 is measured by the temperature measuring means 63, and this temperature information is input to the control means 62. Based on this temperature information and the temperature information of the internal solution of the reversible hydrogen electrode measured by the temperature measuring means 61, the control means 62 controls the heating temperature of the hydrogen gas by the heating means 60 so that the temperature of the internal solution of the reversible hydrogen electrode measured by the temperature measuring means 61 is within a predetermined range of the temperature of the solution in cell 1 measured by the temperature measuring means 63, preferably within ±5°C (more preferably within ±3°C). Furthermore, in this embodiment, in order for the control means 62 to more accurately control the heating temperature of the hydrogen gas by the heating means 60, the temperature measuring means 64 measures the temperature of the hydrogen gas (hydrogen gas in the gas pipe 9) immediately before it is heated by the heating means 60 and introduced into the reversible hydrogen electrode. This temperature information is input to the control means 62, and the control means 62 controls the heating temperature of the hydrogen gas by the heating means 60 based on this temperature information.

[0035] Figure 6 schematically shows another embodiment of the present invention apparatus equipped with an internal liquid temperature control mechanism for controlling the internal liquid temperature of a reversible hydrogen electrode (reference electrode). This embodiment shows an apparatus equipped with an internal liquid temperature control mechanism 7 (means) that controls the temperature of the internal liquid of a reversible hydrogen electrode (reference electrode 2) by controlling the flow rate of hydrogen gas supplied to the reversible hydrogen electrode. Here, the temperature of the internal liquid of the reversible hydrogen electrode can be adjusted by the flow rate of hydrogen gas supplied into the electrode, and the temperature of the internal liquid decreases as the flow rate of hydrogen gas increases. In this embodiment of the apparatus, hydrogen gas is supplied from the hydrogen cylinder 8 to the reversible hydrogen electrode (reference electrode 2) through the gas piping 9. The gas piping 9 is equipped with a flow rate adjustment means 70 (flow rate regulator) and a regulator 11, and the flow rate (supply amount) of hydrogen gas is adjusted by the flow rate adjustment means 70. In addition, a heater 12 is attached along the outer surface of the cell 1, and the solution (test solution) inside the cell 1 is heated by this heater 12.

[0036] The internal liquid temperature control mechanism 7 consists of a flow rate adjustment means 70 that adjusts the flow rate of hydrogen supplied to the reversible hydrogen electrode (reference electrode 2), a temperature measuring means 71 that measures the temperature of the internal liquid of the reversible hydrogen electrode, and a control means 72 (controller) that controls the flow rate adjustment of hydrogen gas by the flow rate adjustment means 70 so that the temperature of the internal liquid of the reversible hydrogen electrode measured by the temperature measuring means 71 reaches a predetermined temperature. The flow rate adjustment means 70 can be, for example, a flow meter or a mass flow controller (MFC), but is not limited to these. The temperature measuring means 71 is typically composed of a thermocouple inserted into a reversible hydrogen electrode (reference electrode 2). The internal liquid temperature control mechanism 7 of this embodiment further includes a temperature measuring means 73 for measuring the temperature of the solution in the cell 1. This temperature measuring means 73 is also typically composed of a thermocouple. A fluororesin coating layer 74 is formed on the outside of the thermocouple that constitutes the temperature measuring means 73. The type of fluororesin that constitutes this fluororesin coating layer 74 is the same as that of the fluororesin coating layer 28 described earlier. The thermocouples constituting the temperature measuring means 71 and 73 are contact-type temperature sensors that are placed within the object to be measured to directly measure the temperature. However, the temperature measuring means 71 and 73 may be composed of non-contact type temperature sensors instead of such contact-type temperature sensors.

[0037] The temperature information measured by the temperature measuring means 71 and 73 is input to the control means 72, and the control means 72 controls the flow rate adjustment of hydrogen gas by the flow rate adjustment means 70 based on this temperature information. Specifically, the temperature of the internal liquid of the reversible hydrogen electrode is measured by the temperature measuring means 71, and this temperature information is input to the control means 72. Based on this temperature information, the control means 72 controls the flow rate of hydrogen gas by the flow rate adjustment means 70 so that the internal liquid of the reversible hydrogen electrode reaches a predetermined temperature. That is, the flow rate of hydrogen gas is increased when it is desired to lower the temperature of the internal liquid, and decreased when it is desired to raise the temperature of the internal liquid. The relationship between the hydrogen gas flow rate and the temperature of the internal liquid is determined in advance and stored (set) in the control means 72, and the control means 72 controls the flow rate of hydrogen gas by the flow rate adjustment means 70 based on this relationship. In this embodiment, the temperature of the solution in cell 1 is measured by the temperature measuring means 73, and this temperature information is input to the control means 72. Based on this temperature information and the temperature information of the internal solution of the reversible hydrogen electrode measured by the temperature measuring means 71, the control means 72 controls the flow rate adjustment of the hydrogen gas by the flow rate adjustment means 70 so that the temperature of the internal solution of the reversible hydrogen electrode measured by the temperature measuring means 71 is within a predetermined range of the temperature of the solution in cell 1 measured by the temperature measuring means 73, preferably within ±5°C (more preferably within ±3°C).

[0038] Next, preferred operating conditions for the apparatus of the present invention and an electrochemical measurement method using the apparatus of the present invention will be described. When using the apparatus of the present invention, if the test temperature is too high (for example, 100°C or higher), the test solution may boil, which could increase the internal pressure inside the cell. For this reason, the test temperature, i.e., the temperature of the test solution (solution y), should be 90°C or lower, more preferably 80°C or lower. Furthermore, the lower limit of the temperature of the test solution (solution y) should be 0°C or higher, which is the temperature at which the solution does not freeze. In addition to heating with a heater attached to cell 1 as shown in the embodiments of Figures 5 and 6, the temperature of the test solution may also be controlled by heating in a constant temperature bath. Furthermore, as mentioned above, in order to prevent a decrease in measurement accuracy due to changes in potential, it is preferable to keep the internal liquid in the reversible hydrogen electrode, which is the reference electrode 2, at a temperature within a predetermined range relative to the test solution, preferably within ±5°C relative to the test solution, and more preferably within ±3°C. The temperature of the internal liquid in the reversible hydrogen electrode can be controlled by, for example, an internal liquid temperature control mechanism as shown in the embodiments of Figures 5 and 6.

[0039] The apparatus of the present invention can be used for electrochemical measurements to evaluate the corrosion resistance (corrosion properties) of various metal materials, but is particularly suitable as an electrochemical measurement apparatus for evaluating the corrosion resistance (corrosion properties) of metal separator materials used in fuel cells (especially polymer electrolyte fuel cells) and water electrolysis devices (especially polymer electrolyte water electrolysis devices and anion exchange membrane water electrolysis devices). In this case (see Figure 1), solution y is subjected to a predetermined simulated environment, i.e., a predetermined concentration of fluoride ions (F - Acidic aqueous solution or alkaline aqueous solution containing fluoride ions (F - Assuming that (and not containing) ) the metal separator material (candidate material) is used as sample x for electrochemical measurements, the corrosion resistance (corrosion properties) of the test metal material is evaluated based on the results, such as the corrosion current and the analysis of the metals dissolved in solution y. [Examples]

[0040] Using electrochemical measuring devices of the inventive example and comparative example having the structure shown in Figure 1, we conducted elution tests of the components of the cell and reference electrode (including seepage of the internal solution of the reference electrode). The apparatus configurations of inventive examples 1 and 2 and comparative examples 1 and 2 are as follows. • Example of Invention 1 Cell 1 is made of fluororesin (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer; PFA), and the lid 4 and connector 5 are also made of fluororesin (polytetrafluoroethylene; PTFE). Furthermore, the support tube 20 of the single-junction type reversible hydrogen electrode, which is the reference electrode 2, has a fluororesin coating layer 28 on the outside of the glass cylindrical body 27, which is the base material, as shown in Figures 2 and 3. This fluororesin coating layer 28 was formed by covering the glass cylindrical body 27 with a heat-shrinkable tube of fluororesin (PTFE) and then heat-shrinking it. The ceramic porous body 24 at the tip of the reference electrode 2 has a wire diameter of 0.4 mm and a porosity of 30%. • Invention Example 2 Cell 1 is made of fluororesin (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer; PFA), and the lid 4 and connector 5 are also made of fluororesin (polytetrafluoroethylene; PTFE). The support tube 20 for the single-junction type reversible hydrogen electrode, which is the reference electrode 2, is made of glass. The ceramic porous body 24 at the tip of the reference electrode 2 has a wire diameter of 0.4 mm and a porosity of 30%.

[0041] • Comparative Example 1 The cell and lid were configured in the same way as in the inventive example, and the reference electrode was a double-junction type saturated KCl silver / silver chloride electrode made of glass tube. The outer cylinder of this reference electrode had a fluororesin coating layer on the outside of the glass tube base material, similar to that in the inventive example. The ceramic porous body 24 at the tip of the reference electrode 2 had a wire diameter of 2.2 mm and a porosity of 42%. • Comparative Example 2 The conventional apparatus consisted of a cell and lid made of glass, and the reference electrode was a double-junction type saturated KCl silver / silver chloride electrode made of glass tube. As it was a conventional apparatus, the outer cylinder of this reference electrode did not have a fluororesin coating layer like in Comparative Example 1. The ceramic porous body 24 at the tip of the reference electrode 2 had a wire diameter of 2.2 mm and a porosity of 42%. In both the inventive example and the comparative example, the areas in the cell lid where the working electrode and counter electrode are inserted were sealed with polytetrafluoroethylene (PTFE) rods to prevent evaporation of the test solution.

[0042] As the test solution used for the dissolution test, sulfuric acid is mixed with fluoride ions (F - NaF powder was added in reagent form to achieve a concentration of 2 ppm, and an aqueous solution was prepared by adjusting the pH to 3 with sulfuric acid. 400 mL of this test solution was poured into a cell, and the test solution was heated in a constant temperature water bath to 353 K (80°C). The dissolution test was then performed at this temperature for one week. After the dissolution test, the components contaminating the test solution were analyzed by ICP-AES for glass-derived components such as boron (B), aluminum (Al), and silicon (Si), and chloride ions (Cl). - Quantitative analysis of each component was performed using ion chromatography. For comparison, the test solution before the dissolution test was also analyzed in the same manner. The results of the quantitative analysis are shown in Table 1. Furthermore, the quantification limits for boron (B), aluminum (Al), and silicon (Si) by ICP-AES, and the quantification limit for chloride ions (Cl) by ion chromatography are <0.1 mgL, respectively. -1 The amount of boron (B), aluminum (Al), and silicon (Si) leached from glass was 0.5 mg / L. -1 Those below a certain level are considered "passing," and chloride ions (Cl - ) is 0.1 mg L -1 Anything below a certain level was considered a "pass," and ultimately, an overall evaluation of "pass" was given only when all of these evaluation criteria were satisfied.

[0043] According to Table 1, in Invention Example 1, boron (B), aluminum (Al), silicon (Si), and chloride ions (Cl) are added to the test solution. - The amount of elution for each was 0.1 mgL. -1 It was below the required level. Therefore, the overall evaluation was "Pass". Furthermore, in Invention Example 2, boron (B), aluminum (Al), and chloride ions (Cl) are added to the test solution. - The amount of elution for each was 0.1 mgL.-1 It was less than [amount missing]. Furthermore, the amount of silicon (Si) eluted was 0.5 mg / L. -1 It was below the required level. Therefore, the overall evaluation was "Pass". In contrast, in Comparative Example 1, the elution amounts of boron (B), aluminum (Al), and silicon (Si) into the test solution were all 0.1 mgL. -1 Although it was less than the chloride ion (Cl - The amount of elution is 13.1 mgL. -1 Therefore, the overall evaluation was "Fail." In Comparative Example 2, the amounts of boron (B), aluminum (Al), and silicon (Si) eluted into the test solution were, respectively, B: 0.3 mgL. -1 Al: 0.2 mg L -1 Si: 1.3 mg L -1 It was. Also, chloride ions (Cl - The amount of elution is 13.1 mgL. -1 Therefore, the overall evaluation was "Fail." Based on the above test results, in the example of the invention, boron (B), aluminum (Al), silicon (Si), and chloride ions (Cl) are added to the test solution. - It was found that the amount of ) leached out met the required level.

[0044] [Table 1] [Explanation of Symbols]

[0045] 1 cell 2 Reference electrode 3. Opposite 4. Lid 5 Connectors 6,7 Internal liquid temperature control mechanism 8. Hydrogen cylinder 9 Gas piping 10 Flow rate adjustment means 11 Regulator 12 Heaters 20 Support tube 21 Platinum electrode 22 Platinum conductor wire 23 Hydrogen gas inlet pipe 24. Ceramic porous material 25 Internal fluid 26 Gas outlet 27 Cylinder 28 Fluororesin coating layer 230 Gas outlet 231 Gas inlet 60 Heating means 61,63,64 Temperature measurement means 62 Control means 65 Fluororesin coating layer 70 Flow rate adjustment means 71,73 Temperature measurement means 72 Control means 74 Fluororesin coating layer x sample y solution

Claims

1. An apparatus for performing electrochemical measurements of a metallic material in a solution, The device comprises a cell (1) for containing a solution, and a reference electrode (2) and a counter electrode (3) immersed in the solution within the cell (1). The cell (1) is made of fluororesin, and the reference electrode (2) is made of a reversible hydrogen electrode. An electrochemical measuring device characterized in that the support tube for the reversible hydrogen electrode, which is the reference electrode (2), has a glass cylindrical base material on the outside coated with fluororesin.

2. The electrochemical measuring device according to Claim 1, characterized in that the lid (4) and connector (5) attached to the cell (1) are made of fluororesin.

3. An apparatus for performing electrochemical measurements of a metallic material in a solution, The device comprises a cell (1) for containing a solution, and a reference electrode (2) and a counter electrode (3) immersed in the solution within the cell (1). The cell (1) is made of fluororesin, and the reference electrode (2) is made of a reversible hydrogen electrode. An electrochemical measuring device characterized in that the support tube for the reversible hydrogen electrode, which is the reference electrode (2), has a liquid junction at its tip made of a ceramic porous material, and the porosity of the ceramic porous material is 40% or less.

4. The electrochemical measuring device according to claim 3, characterized in that the lid (4) and connector (5) attached to the cell (1) are made of fluororesin.

5. An apparatus for performing electrochemical measurements of a metallic material in a solution, The device comprises a cell (1) for containing a solution, and a reference electrode (2) and a counter electrode (3) immersed in the solution within the cell (1). The cell (1) is made of fluororesin, and the reference electrode (2) is made of a reversible hydrogen electrode. Furthermore, it is equipped with an internal liquid temperature control mechanism (6) that controls the temperature of the internal liquid of the reversible hydrogen electrode by controlling the temperature of the hydrogen gas supplied to the reversible hydrogen electrode, which is the reference electrode (2). The electrochemical measuring device is characterized by comprising an internal liquid temperature control mechanism (6) that includes a heating means (60) for heating hydrogen gas supplied to the reversible hydrogen electrode, a temperature measuring means (61) for measuring the temperature of the internal liquid of the reversible hydrogen electrode, and a control means (62) for controlling the heating temperature of the hydrogen gas by the heating means (60) so that the temperature of the internal liquid of the reversible hydrogen electrode measured by the temperature measuring means (61) reaches a predetermined temperature.

6. The electrochemical measuring apparatus according to claim 5, characterized in that the internal liquid temperature control mechanism (6) further comprises a temperature measuring means (63) for measuring the temperature of the solution in the cell (1), and the control means (62) controls the heating temperature of hydrogen gas by the heating means (60) so that the temperature of the internal liquid of the reversible hydrogen electrode measured by the temperature measuring means (61) is within a predetermined range relative to the temperature of the solution in the cell (1) measured by the temperature measuring means (63).

7. An apparatus for performing electrochemical measurements of a metallic material in a solution, The device comprises a cell (1) for containing a solution, and a reference electrode (2) and a counter electrode (3) immersed in the solution within the cell (1). The cell (1) is made of fluororesin, and the reference electrode (2) is made of a reversible hydrogen electrode. Furthermore, it is equipped with an internal liquid temperature control mechanism (7) that controls the temperature of the internal liquid of the reversible hydrogen electrode by controlling the flow rate of hydrogen gas supplied to the reversible hydrogen electrode, which is the reference electrode (2). The electrochemical measuring device is characterized in that the internal liquid temperature control mechanism (7) comprises a flow rate adjustment means (70) for adjusting the flow rate of hydrogen supplied to the reversible hydrogen electrode, a temperature measuring means (71) for measuring the temperature of the internal liquid of the reversible hydrogen electrode, and a control means (72) for controlling the flow rate adjustment of hydrogen gas by the flow rate adjustment means (70) so that the temperature of the internal liquid of the reversible hydrogen electrode measured by the temperature measuring means (71) reaches a predetermined temperature.

8. The electrochemical measuring device according to claim 7, further comprising an internal liquid temperature control mechanism (7) for measuring the temperature of the solution in the cell (1), and a control means (72) for controlling the flow rate adjustment of hydrogen gas by a flow rate adjustment means (70) so that the temperature of the internal liquid of the reversible hydrogen electrode measured by the temperature measuring means (71) is within a predetermined range relative to the temperature of the solution in the cell (1) measured by the temperature measuring means (73).

9. A method for measuring the electrochemical properties of a metallic material, characterized by using an electrochemical measuring device according to any one of claims 1 to 8 to perform electrochemical measurements of a metallic material used in a fuel cell or water electrolysis device.

10. The electrochemical measurement method for a metallic material according to claim 9, characterized in that the temperature of the internal liquid in the reversible hydrogen electrode, which is the reference electrode (2), is within ±5°C of the temperature of the solution in the cell (1).

11. The electrochemical measurement method for a metallic material according to claim 9, characterized in that the temperature of the solution in cell (1) is 90°C or lower.

12. The solution in cell (1) is an alkaline aqueous solution or a fluoride ion (F － The electrochemical measurement method for a metallic material according to claim 9, characterized in that it is an acidic aqueous solution containing ).

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