System and method for testing corrosion resistance of bipolar plate coating

Abstract

The invention relates to the technical field of corrosion resistance testing of bipolar plate coatings, in particular to a corrosion resistance testing system of a bipolar plate coating and a testing method of the corrosion resistance testing system. A corrosion resistance test system for a bipolar plate coating comprises: an electrolytic tank; the working electrode is in an L shape, one end of the working electrode is arranged in the containing cavity, and the working electrode penetrates through one mounting through hole and is arranged outside the containing cavity; a reference electrode; and an auxiliary electrode. The basic structure of the test system is optimized, and the structural form of the working electrode is adjusted to form an L-shaped structure, so that the mechanical pressure distribution and the contact corrosion environment of the bipolar plate in an actual electrolytic bath are simulated, and the test accuracy is improved by simulating the contact pressure, the temperature and the electrolyte environment of a real working condition. And the consistency of a test result and actual operation is remarkably improved, so that errors caused by neglecting contact corrosion and start-stop working conditions in a traditional method are avoided.

Description

Technical Field

[0001] The present application relates to the technical field of corrosion resistance testing of bipolar plate coatings, and in particular to a corrosion resistance testing system and a testing method for bipolar plate coatings. Background Art

[0002] In the AEM electrolyzer, the bipolar plate plays the role of transmitting electrons, mechanically supporting the membrane electrode, distributing the electrolyte, and discharging the reaction generated gas, which directly affects the performance of the electrolyzer. Currently, commercial AEM electrolyzers operate in an alkaline environment at a temperature of 60-80°C, which requires the bipolar plate to have good alkali corrosion resistance. Nickel-based bipolar plates have excellent alkali corrosion resistance, but the use of pure nickel materials will directly increase the manufacturing cost of the AEM electrolyzer; stainless steel materials have good alkali corrosion resistance and obvious price advantages, but they are easily oxidized in high-potential alkaline environments, accompanied by the dissolution of metal ions such as Fe, Cr, and Mo. Therefore, stainless steel nickel plating is an effective way to balance cost and alkali corrosion resistance.

[0003] To evaluate the alkali corrosion resistance of nickel-plated bipolar plates, existing methods usually use potentiodynamic polarization to obtain the corrosion current density of the sample. However, this method is quite different from the actual working conditions of the bipolar plate in the AEM electrolyzer and cannot accurately reflect its true alkali corrosion resistance. For example, in actual operation, the bipolar plate is in contact with the porous transport layer, and there is contact corrosion; in addition, the local oxygen-rich environment on the anode side and the ion dissolution of the anode catalyst may accelerate the corrosion of the bipolar plate. Therefore, a simple and easy test method that can reflect the actual working conditions is needed to accurately evaluate the alkali corrosion resistance of the nickel-plated coating of the bipolar plate. Summary of the invention

[0004] In order to improve the complex defects of the existing corrosion resistance testing method of nickel bipolar plates, the present application provides a corrosion resistance testing system and a testing method for a bipolar plate coating.

[0005] In the first aspect, the present application provides a corrosion resistance testing system for a bipolar plate coating, which adopts the following technical solutions: A corrosion resistance testing system for a bipolar plate coating, comprising: An electrolytic cell, wherein the electrolytic cell is provided with a containing chamber for adding electrolyte, an electrolytic cell cover is provided at an open end of the electrolytic cell, and the electrolytic cell cover is provided with a plurality of mounting through holes penetrating along the thickness direction thereof; A working electrode, the working electrode is formed into an L shape, one end of the working electrode is arranged in the accommodation chamber, and the working electrode passes through one of the mounting through holes and is arranged outside the accommodation chamber; A reference electrode, wherein the reference electrode is formed into a rod-shaped member and one end of the reference electrode is arranged in the accommodation chamber at a distance from one end of the working electrode, and the other end of the reference electrode passes through another of the mounting through holes and is arranged outside the accommodation chamber; The auxiliary electrode is formed as a rod-shaped member and one end of the auxiliary electrode is arranged in the accommodating chamber with a spacing from one end of the reference electrode, and the other end of the auxiliary electrode passes through another of the mounting through holes and is arranged outside the accommodating chamber.

[0006] Through the above technical solution, this application optimizes the basic structure of the test system, and adjusts the structural morphology of the working electrode to form an L-shaped structure, thereby simulating the mechanical pressure distribution and contact corrosion environment (such as contact with the porous transport layer) of the bipolar plate in the actual electrolytic cell, and then maintains the electrolyte at 60~80℃ through a heating device to accelerate the corrosion reaction to shorten the test cycle. Finally, through a three-electrode system, the reference electrode and the auxiliary electrode are used to construct an electrochemical test environment to accurately control the potential and current. Therefore, by simulating the contact pressure, temperature and electrolyte environment of the real working conditions, the consistency between the test results and the actual operation is significantly improved, thereby avoiding the errors caused by the traditional method due to ignoring the contact corrosion and start-stop conditions.

[0007] Furthermore, the working electrode comprises: A fixing rod, the fixing rod is formed as a rod-shaped member and at least a portion of which is disposed in the accommodating chamber; A test terminal, the test terminal is vertically fixedly connected to the fixing rod, one end of the test terminal away from the fixing rod is provided with a circular accommodating cavity for accommodating a test electrode, and the outer peripheral surface of the test terminal is provided with an external thread; A bipolar plate, the bipolar plate is disposed in the circular accommodation cavity of the test end and is formed in a circular shape; an anode electrode, the anode electrode being formed into a circle having the same size as the bipolar plate and being arranged on a side of the bipolar plate away from the fixed plate; A fixed end cover is formed as a cylindrical part with openings at both ends, the inner wall surface of the fixed end cover is provided with an internal thread matching the outer peripheral surface of the test end head, one end of the fixed end cover is provided with a test through hole passing through along its axial direction, and the diameter of the test through hole is not greater than the size of the anode electrode.

[0008] Through the above technical scheme, the present application further defines the composition structure of the working electrode, and simulates the actual contact pressure between the bipolar plate and the anode electrode by threaded connection between the fixed end cap and the test end, thereby ensuring the constant contact area between the bipolar plate and the anode electrode and avoiding the edge effect from interfering with the test results. On this basis, a test through hole is set on the fixed end cap to limit the exposed area of ​​the anode electrode, thereby preventing the electrolyte from infiltrating and causing contact resistance measurement errors, thereby further improving the accuracy and convenience of the overall test scheme. By simplifying the electrode packaging process and using mechanical pressure to simulate real contact corrosion conditions, the corrosion resistance degradation of the bipolar plate coating under dynamic conditions can be accurately reflected.

[0009] Furthermore, an annular concave sealing groove is provided on the outer periphery of the circular accommodating cavity of the test terminal so as to embed an annular sealing member between the fixed end cover and the test terminal.

[0010] Through the above technical scheme, the present application adds an annular seal between the fixed end cover and the test end head and uses it in conjunction with an annular concave sealing groove to prevent the electrolyte from penetrating into the contact interface between the bipolar plate and the anode electrode, thereby ensuring the stability of the contact resistance between the bipolar plate and the anode electrode during the test, improving the accuracy of the corrosion current density calculation, and further extending the service life of the electrode tooling to avoid test interruption due to seal failure.

[0011] In a second aspect, the present application provides a method for testing the corrosion resistance of a bipolar plate coating, comprising the following steps: Take the bipolar plate with metal coating to be tested, wash and dry it, and then package it with the anode electrode in the circular receiving cavity of the test end of the working electrode in sequence, extend one end of the working electrode into the receiving cavity of the electrolytic cell, and then inject electrolyte into the receiving cavity and heat it; Take the reference electrode and the auxiliary electrode, use an electrochemical workstation to perform activation treatment in a three-electrode system, and after the activation is completed, perform an open circuit potential test, perform a linear potential scan on the sample, and after the linear potential scan is completed, perform Tafel fitting to obtain the corrosion current density; After the open circuit potential test is completed, the bipolar plate is taken out for cleaning and drying, and its contact resistance is tested. The changes in surface morphology and composition before and after the test are compared by means of surface analysis methods such as SEM detection, XRF detection and XRD test.

[0012] Through the above technical scheme, the present application further discloses the specific steps of the test method, and comprehensively evaluates the corrosion resistance of the coating by combining dynamic operating condition simulation with electrochemical testing. First, the bipolar plate and the anode electrode are encapsulated into an L-shaped electrode and immersed in a heated KOH electrolyte to simulate the actual operating environment of the electrolytic cell; then, periodic start-stop activation is performed to accelerate the growth and rupture process of the passivation film on the surface of the bipolar plate through high current density; the open circuit potential test is used to confirm the steady state of the system, and the linear potential scan obtains the complete polarization curve, and the corrosion current density is calculated by combining Tafel fitting; finally, the reliability of the electrochemical test results is verified by contact resistance and surface morphology analysis. This method integrates dynamic operating conditions (start-stop, contact pressure, temperature) with standardized electrochemical tests for the first time, solving the limitations of traditional single static tests (such as dynamic potential polarization). In addition, the correlation analysis between contact resistance and corrosion current density provides a new dimension for the study of coating failure mechanisms.

[0013] Further, the activation treatment comprises the following steps: At 1A / cm 2One cycle is to run the machine at a constant current density for 1 hour and then stop the machine for 1 hour, and a total of 50 cycles are run to complete the activation treatment step.

[0014] Through the above technical solution, the present application defines the activation conditions, 1A / cm 2 The current density is much higher than the conventional test value, which is designed to induce the bipolar plate surface to reach a high potential in a short period of time, accelerate the oxidation and dissolution of the nickel plating and the rupture of the passivation film of the stainless steel substrate. The periodic start-stop simulates the sudden changes in temperature and potential caused by the frequent start-stop of the electrolytic cell, which induces thermomechanical stress and chemical-mechanical corrosion at the coating / substrate interface. This parameter combination can simulate the aging effect of the actual operation of the electrolytic cell for about 2000 hours within 100 hours, greatly shortening the test cycle.

[0015] Further, the open circuit potential test comprises the following steps: When the potential change did not exceed 5 mV within 2 min, it was considered stable. Then, a linear potential scan was performed on the bipolar plate with a scan rate of 0.5 mV / s and a scan potential range of -0.5 V to 0.2 V relative to the reference electrode.

[0016] Through the above technical solution, this application adjusts the open circuit potential stability condition based on the electrochemical steady-state criterion and low-speed scanning optimization, and ensures that the bipolar plate surface is in a quasi-steady state by stabilizing the open circuit potential, avoiding the interference of transient processes on the corrosion current density calculation. The low scan speed design of 0.5mV / s can reduce the influence of the double-layer capacitance current and improve the linearity of the polarization curve in the Tafel zone, which is especially suitable for low corrosion rate materials.

[0017] Furthermore, the reference electrode is a Hg / HgO reference electrode.

[0018] Furthermore, the auxiliary electrode is a platinum sheet auxiliary electrode.

[0019] Furthermore, the electrolyte includes 0.5-1.5 mol / L KOH electrolyte.

[0020] Through the above technical solution, this application defines the reference electrode as Hg / HgO, the auxiliary electrode as platinum sheet, and the electrolyte as 0.1-1.5M KOH. Accurately match the actual operating environment of the AEM electrolytic cell. The Hg / HgO reference electrode has a stable potential in a concentrated alkaline solution and does not contain Cl⁻; the platinum sheet auxiliary electrode can ensure uniform distribution of polarization current due to its high conductivity and inertness; the 0.1-1.5M KOH concentration range covers the typical electrolyte conditions of commercial AEM electrolytic cells, avoiding the problem of corrosion rate distortion due to too low concentration or over-passivation of nickel caused by too high concentration.

[0021] In summary, the present application includes at least one of the following beneficial technical effects: 1. This application realizes for the first time a multi-dimensional simulation of the real working conditions of the bipolar plates in the AEM electrolyzer by combining the L-shaped electrode tooling with dynamic test conditions. The traditional potentiodynamic polarization method only focuses on static electrochemical parameters, ignoring the influence of mechanical pressure, contact corrosion and start-stop cycles on the corrosion resistance of the coating in actual operation. The present invention simulates the assembly clamping force of the bipolar plate in the electrolyzer through the threaded fixing structure of the L-shaped electrode, which is closer to the actual failure mode than the traditional loose contact test. In addition, the periodic start-stop activation runs at a high current density of 1A / cm² for 1h / stops for 1h, simulating the passivation film rupture and re-passivation process caused by frequent start-stop of the electrolyzer, accelerating the exposure of coating defects.

[0022] 2. This application integrates standardized electrode tooling and accelerated aging methods to significantly shorten the test cycle and reduce equipment investment costs. The traditional method requires disassembly and evaluation after thousands of hours of actual operation in the AEM electrolyzer, which is time-consuming and costly; while this test system only takes 100 hours to simulate 2000 hours of actual operation, which is 20 times more efficient.

[0023] 3. This application significantly improves the reliability and engineering application value of test data through high-precision electrochemical parameter control and multi-dimensional data analysis. The traditional potentiodynamic polarization method ignores the change in contact interface resistance, resulting in high error in corrosion current density measurement; while this method blocks electrolyte leakage through seal design, further improving the stability of contact resistance measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the structure of the corrosion resistance testing system of the bipolar plate coating in the embodiment of the technical solution of the present application; Figure 2 An exploded view of a working electrode in an embodiment of the technical solution of this application; Figure 3 This is a surface SEM image of a sample stainless steel material that has not been electroplated and was tested in the corrosion resistance test system of the bipolar plate coating in the embodiment of the present application; Figure 4 This is a surface SEM image of a stainless steel bipolar plate containing a nickel-plated layer, which was not subjected to a corrosion resistance test, and is a sample tested in the corrosion resistance test system of the bipolar plate coating in the embodiment of the present application; Figure 5 This is a surface SEM image of a stainless steel bipolar plate containing a nickel-plated layer after the corrosion resistance test of the sample tested in the corrosion resistance test system of the bipolar plate coating in the embodiment of the present application; Figure 6 This is the XRD diffraction pattern of the sample tested in the corrosion resistance test system of the bipolar plate coating in the embodiment of the present application.

[0025] Description of the drawings: 1. electrolytic cell; 2. working electrode; 21. fixed rod; 22. test terminal; 23. bipolar plate; 24. anode electrode; 25. seal; 26. fixed end cap; 3. reference electrode; 4. auxiliary electrode. DETAILED DESCRIPTION

[0026] The present application is further described in detail below with reference to the embodiments.

[0027] like Figure 1-Figure 2 As shown, the present application discloses a corrosion resistance testing system for a bipolar plate coating, including an electrolytic cell 1, wherein the electrolytic cell 1 is provided with a containing chamber for containing an electrolyte, an electrolytic cell cover is provided at an open end of the electrolytic cell 1, and the electrolytic cell cover is provided with three mounting through holes penetrating along the thickness direction thereof.

[0028] It should be noted that, during actual use, the electrolytic cell 1 used in the technical solution of the present application can be placed in an oil bath heating device for oil bath heating treatment.

[0029] A working electrode 2 is inserted and installed in the first mounting through hole, and the working electrode 2 includes a fixed rod 21 formed as a rod-shaped part and a test terminal 22 vertically connected to the fixed rod 21, wherein the test terminal 22 is partially arranged in the accommodating chamber, and a part of the fixed rod 21 extends out of the accommodating chamber from the first mounting through hole, and a circular accommodating chamber for accommodating the test electrode plate is provided at the end of the test terminal 22 away from the fixed rod 21, and a bipolar plate 23 is provided on one side of the circular accommodating chamber close to the fixed rod 21, and an anode electrode 24 is abutted against the other side of the bipolar plate 23, wherein the bipolar plate 23 and the anode electrode 24 are both circular plate-shaped parts with the same size and structure, and the bipolar plate 23 and the anode electrode 24 are encapsulated in the circular accommodating chamber through a fixed end cover 26.

[0030] It should be noted that the fixed end cover 26 is a cylindrical member with openings at both ends, and the inner wall surface of the fixed end cover 26 is provided with an internal thread matching the outer peripheral surface of the test end 22, and one end of the fixed end cover 26 is provided with a test through hole passing through along its axial direction, and the diameter of the test through hole is not larger than the size of the anode electrode 24.

[0031] At the same time, an annular concave sealing groove is provided between the fixed end cover 26 and the test terminal 22, and a rubber seal 25 of an annular structure is provided in the concave sealing groove to prevent the electrolyte from penetrating into the circular accommodating cavity through the test through hole of the fixed end cover 26.

[0032] Recombination Figure 2It can be seen that on the right side of the test electrode, there is also a reference electrode 3, which is a rod-shaped member made of Hg / HgO material, one end of which is arranged in the accommodating chamber, and the other end extends to the outside of the accommodating chamber through the mounting through hole; on the right side of the reference electrode 3, there is also a platinum sheet auxiliary electrode 4, which is also a rod-shaped member and one end of which is arranged in the accommodating chamber at an interval with one end of the reference electrode 3, and the other end passes through another mounting through hole and is arranged outside the accommodating chamber.

[0033] Example A method for testing a corrosion resistance test system for a bipolar plate coating comprises the following steps: Take the stainless steel bipolar plate with a 60 μm thick nickel-plated layer to be tested, clean it with ethanol, dry it in a vacuum drying oven at 60°C, and package it with the anode electrode in sequence into the circular receiving cavity of the test end of the working electrode. After adding 1 mol / L KOH electrolyte to the electrolytic cell, heat the electrolytic cell in an oil bath to heat the receiving cavity to 60°C; Take the Hg / HgO reference electrode and the platinum auxiliary electrode, and use the electrochemical workstation to activate the three-electrode system. The activation condition is 1A / cm 2 The constant current density was run for 1 hour and then stopped for 1 hour as one cycle, and a total of 50 cycles were run. After activation was completed, the open circuit potential test was performed after the AEM electrolysis simulation test was completed. If the potential change did not exceed 5 mV within 2 minutes, it was considered to be stable. Then the sample was subjected to a linear potential scan at a scan rate of 0.5 mV / s and a scanning potential range of -0.5 V to 0.2 V (relative to the Hg / HgO reference electrode). After the linear potential scan was completed, Tafel fitting was performed to obtain a corrosion current density of 4.56 × 10 −8 A / cm 2 ; After the electrochemical test is completed, the bipolar plate is taken out for cleaning and drying, and its contact resistance is tested to be 6mΩ·cm 2 , using SEM, XRF and other surface analysis methods to compare the changes in surface morphology and composition before and after the test. The specific SEM test results are shown in Figure 3 As shown, XRF is shown in Table 1.

[0034] It should be noted that in the technical solution of this application, the contact resistance ranges from 5–20 mΩ·cm 2 , corrosion current density is less than 3.7×10 -6 A / cm 2 After the corrosion resistance test, the surface morphology showed no corrosion or shedding phenomenon compared with that before the test, and in the XRF component analysis, the element mass percentage of Ni exceeded 97%, with no significant change compared with that before the test, which proves that the stainless steel containing the nickel-plated layer has good corrosion resistance.

[0035] Performance Testing The surface analysis of the stainless steel bipolar plate containing the nickel-plated layer in the sample of the embodiment was respectively carried out by SEM test, and the surface of the stainless steel bipolar plate before nickel plating was also carried out by SEM test; In this embodiment, the stainless steel bipolar plates containing nickel-plated layers were tested by SEM detection, XRF detection and XRD test before and after the test. The SEM detection results are as follows: Figure 3 , Figure 4 , Figure 5 As shown, XRF test is shown in Table 1-3, and XRD test diagram is as follows Figure 6 As shown; The XRF test results of the stainless steel bipolar plate before nickel plating, the stainless steel bipolar plate after nickel plating, and the stainless steel bipolar plate after nickel plating are shown in the following table: Table 1 Stainless steel XRF

[0036] Table 2 XRF of stainless steel with nickel plating before testing

[0037] Table 3 XRF of stainless steel with nickel plating after testing

[0038] Combination Figure 3-6 Analyze with Table 1-3: Figure 3 , Figure 4 and Figure 5 It can be seen that the surface of the stainless steel bipolar plate before nickel plating is dense, defect-free and flat, with only nanoscale fluctuations ( Figure 3 ).

[0039] Combination Figure 4 It can be seen that the surface of the stainless steel bipolar plate after nickel plating is also dense and defect-free. Compared with the surface of the stainless steel bipolar plate, its surface roughness is slightly improved to severe roughness, but the surface structure is uniform overall; Finally, combine Figure 3 , Figure 4 and Figure 5 ,from Figure 5 It can be clearly seen that the surface roughness of the stainless steel containing the nickel plating layer is significantly improved after the corrosion resistance test, which further illustrates that the present application can effectively characterize the corrosion resistance of the stainless steel nickel plating layer through the corrosion resistance test, and combined with the corresponding corrosion current density and contact resistance, it can well quantify the corrosion resistance of the existing stainless steel material containing the nickel plating layer.

[0040] It can be seen from Tables 1-3 that after the test of the present application, the content of stainless steel (Ni) containing a nickel-plated layer slightly decreased, indicating that corrosion occurred in the nickel-plated layer in the technical solution of the present application. The change in the content of nickel element is used to further verify and quantify the corrosion resistance of the existing stainless steel material containing a nickel-plated layer.

[0041] At the same time, combined Figure 6 It can be seen that the XRD spectrum of the stainless steel sample is consistent with that of 316L stainless steel. The original diffraction peak disappears after nickel plating, and a new sharp diffraction peak corresponding to metallic nickel appears at 51.9°, indicating that the surface of the nickel plating layer is dense and complete, with high crystallinity. The diffraction peak of the stainless steel nickel plating layer has no obvious change after the test, indicating that the crystal structure of the nickel plating layer has not changed, and no new phase has been generated.

[0042] The present invention has been described in detail above in conjunction with specific implementations and exemplary examples, but these descriptions cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, a variety of equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its implementation methods, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be subject to the attached claims.

[0043] All publications, patent applications, patents and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings conventionally understood by those skilled in the art. In the event of a conflict, the definition in this specification shall prevail.

[0044] When this specification uses the prefix "well-known to those skilled in the art", "prior art" or similar terms to introduce materials, substances, methods, steps, devices or components, etc., the objects introduced by the prefix cover those commonly used in the art when this application is filed, but also include those that are not commonly used at present but will become recognized in the art as being suitable for similar purposes.

[0045] In the context of the present specification, any matters or items not mentioned are directly applicable to those known in the art without any changes except those explicitly stated.

Claims

1. A corrosion resistance testing system for a bipolar plate coating, characterized in that: include: An electrolytic cell (1), wherein the electrolytic cell (1) is provided with a containing chamber for adding electrolyte, an electrolytic cell cover is provided at an open end of the electrolytic cell (1), and the electrolytic cell cover is provided with a plurality of mounting through holes penetrating along the thickness direction thereof; A working electrode (2), the working electrode (2) is formed into an L shape, one end of the working electrode (2) is arranged in the accommodating chamber, and the working electrode (2) passes through one of the mounting through holes and is arranged outside the accommodating chamber; A reference electrode (3), the reference electrode (3) being formed into a rod-shaped member and having one end thereof spaced apart from one end of the working electrode (2) and arranged in the accommodation chamber, and the other end of the reference electrode (3) passing through another of the mounting through holes and arranged outside the accommodation chamber; an auxiliary electrode (4), the auxiliary electrode (4) being formed as a rod-shaped member and having one end thereof spaced apart from one end of the reference electrode (3) and arranged in the accommodating chamber, and the other end of the auxiliary electrode (4) passing through another of the mounting through holes and being arranged outside the accommodating chamber; The working electrode (2) comprises: A fixing rod (21), the fixing rod (21) being formed as a rod-shaped member and at least a portion of which is disposed in the accommodating chamber; A test terminal (22), the test terminal (22) being vertically fixedly connected to the fixing rod (21), a circular accommodating cavity for accommodating a test electrode being provided at one end of the test terminal (22) away from the fixing rod (21), and an external thread being provided on an outer peripheral surface of the test terminal (22); A bipolar plate (23), the bipolar plate (23) being arranged in the circular accommodation cavity of the test end head (22) and formed in a circular shape; an anode electrode (24), the anode electrode (24) being formed into a circle having the same size as the bipolar plate (23) and being arranged on a side of the bipolar plate (23) away from the fixed plate; A fixed end cover (26), wherein the fixed end cover (26) is formed as a columnar member with openings at both ends, the inner wall surface of the fixed end cover (26) is provided with an internal thread matching the outer peripheral surface of the test end head (22), and one end of the fixed end cover (26) is provided with a test through hole extending through the fixed end cover along its axial direction, and the size of the test through hole is not larger than the size of the anode electrode (24).

2. A corrosion resistance testing system for bipolar plate coating according to claim 1, characterized in that: An annular concave sealing groove is also provided on the outer periphery of the circular accommodating cavity of the test terminal (22) so as to embed an annular sealing member (25) between the fixed end cover (26) and the test terminal (22).

3. A method for testing the corrosion resistance test system of the bipolar plate coating according to any one of claims 1 to 2, comprising the following steps: A sample of a bipolar plate (23) containing a metal coating to be tested is washed and dried, and then packaged in sequence with an anode electrode (24) into a circular receiving cavity of a test terminal (22) of a working electrode (2), and one end of the working electrode (2) is inserted into the receiving cavity of an electrolytic cell (1), and then an electrolyte is injected into the receiving cavity and heated; A reference electrode (3) and an auxiliary electrode (4) are first activated using an electrochemical workstation in a three-electrode system, and after the activation is completed, an open circuit potential test is performed, a linear potential scan is performed on the sample, and after the linear potential scan is completed, Tafel fitting is performed to obtain the corrosion current density; After the open circuit potential test is completed, the bipolar plate (23) is taken out for cleaning and drying, and its contact resistance is tested. The surface morphology and composition changes before and after the test are compared by means of surface analysis methods such as SEM detection, XRF detection and XRD test.

4. The testing method of a corrosion resistance testing system for a bipolar plate coating according to claim 3, characterized in that: The activation treatment comprises the following steps: At 1A / cm 2 One cycle is one hour of operation at a constant current density followed by one hour of shutdown, and a total of 50 cycles are performed to complete the activation treatment step.

5. The testing method of a corrosion resistance testing system for a bipolar plate coating according to claim 3, characterized in that: The open circuit potential test comprises the following steps: When the potential change within 2 minutes does not exceed 5 mV, it is considered to be stable, and the bipolar plate (23) is subjected to linear potential scanning at a scanning rate of 0.5 mV / s, and the scanning potential range relative to the reference electrode (3) is -0.5V~0.2V.

6. The testing method of a corrosion resistance testing system for a bipolar plate coating according to claim 3, characterized in that: The reference electrode (3) is a Hg / HgO reference electrode (3).

7. The testing method of a corrosion resistance testing system for a bipolar plate coating according to claim 3, characterized in that: The auxiliary electrode (4) is a platinum sheet auxiliary electrode (4).

8. The testing method of a corrosion resistance testing system for a bipolar plate coating according to claim 3, characterized in that: The electrolyte includes 0.1-1.5 mol / L KOH electrolyte.

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