Method for testing high and low temperature cycle accelerated life of metal bipolar plate

Abstract

The invention relates to the technical field of metal bipolar plate detection, and discloses a metal bipolar plate high and low temperature rapid cycle accelerated life test technology. The method specifically comprises the following steps: (1) preparing a metal bipolar plate sample; (2) determining experimental working conditions of high-temperature and low-temperature circulation of the metal bipolar plate; (3) metal bipolar plate high and low temperature rapid cycle experiment; and (4) comparing and testing the accelerated life of the metal bipolar plate: comparing whether the accelerated life test results of the metal bipolar plate subjected to high and low temperature rapid circulation exist or not, and judging the high and low temperature resistance of the metal bipolar plate sample. According to the invention, a high-low temperature test box is used, an accelerated life test model is constructed, and various properties of the metal bipolar plate subjected to high-low temperature rapid circulation are compared, such as bonding strength, corrosion resistance, conductivity, electrochemical characteristics, internal stability, coating state morphology and thickness change of the metal bipolar plate with a flow channel, and the like. And the method is very important to the popularization and application evaluation work of the metal bipolar plate with the coating.

Description

Technical Field

[0001] The present invention relates to the field of proton exchange membrane fuel cells, and particularly to a high and low temperature rapid cycle accelerated life test technology for metal bipolar plates of proton exchange membrane fuel cells. Background Art

[0002] Proton Exchange Membrane Fuel Cell (PEMFC) is one of the most widely used fuel cells, which has the advantages of low operating temperature, pollution-free water emission, high specific power and high energy conversion rate.

[0003] The bipolar plate is a key component in the proton exchange membrane fuel cell, which has the functions of affecting the distribution and diffusion of reaction gases, the management of coolant, and providing interlayer support for the fuel cell stack. Among them, metal bipolar plates have been widely studied due to their better formability, stamping resistance, electrical and thermal conductivity, and lower gas permeability. To extend the service life of metal bipolar plates, corrosion-resistant conductive coatings need to be prepared, including carbon-based coatings, metal-based coatings, and polymer coatings, etc. These coatings provide protection for the metal substrate through barrier effects, cathodic protection, anodic protection, and active substance corrosion inhibition effects.

[0004] During the operation of PEMFC, there will be a harsh working environment, such as acidity, high humidity, high potential, and high and low temperature changes, etc. Especially in the high and low temperature rapid cycle of -40°C - 120°C, due to the different lattice structures of the corrosion-resistant conductive coating and the metal plate, deformation, coating cracking, and even coating peeling may occur after the high and low temperature rapid cycle. The lattice inside the coating may change, affecting the corrosion resistance, electrical conductivity, electrochemical performance, and internal stability of the coating. And the time cost required by the conventional method for testing the life of metal bipolar plates is relatively large. Therefore, it is crucial to study the high and low temperature rapid cycle accelerated life test technology for metal bipolar plates.

[0005] A Chinese invention patent with the publication number of CN113916760A discloses a method for evaluating the high and low temperature performance of a metal bipolar plate coating of a proton exchange membrane fuel cell, which sets a cyclic experiment from -40°C to 150°C with a high and low temperature stabilization time of 30 min, and after 48 h of the experiment, potentiodynamic and potentiostatic electrochemical tests are carried out to measure the change of corrosion resistance under the conditions of pH = 3 (H2SO4 + 0.01 ppm HF) and 80°C. Another Chinese invention patent with the publication number of CN114383931A discloses a method for evaluating the high and low temperature performance of a fuel cell metal bipolar plate, which proposes a cyclic test from -30°C to 90°C with a high and low temperature stabilization time of 20 min, 3 h for one cycle, and a total of 5 cycles, and the contact resistance of the sample after each cycle is tested.

[0006] Although the above-mentioned existing invention patent documents can investigate the influence of rapid high and low temperature cycling on the performance of metal bipolar plates, there are still the following problems: 1) In actual operation, after cold start at low temperature or start at higher temperature, the actual operating temperature that the fuel cell stack can finally reach is 60-90 °C and is maintained for a certain period of time, while the above patents ignore the residence time at this temperature. 2) The humidity setting is less targeted for different temperatures. 3) Less attention is paid to the bonding strength of the coating, because in rapid high and low temperature cycling, the change in the bonding strength between the coating and the substrate will seriously affect the corrosion resistance of the coating, and in severe cases, the entire coating will peel off. 4) The electrochemical performance of the coating is ignored. The electrochemical performance is usually obtained by EIS testing. By applying a small alternating impedance on the coating surface and testing the changes in current and voltage, the self-protection ability of the coating, that is, the ability to resist external changes, can be analyzed. Generally speaking, the larger the impedance value, the stronger the self-protection ability of the coating. 5) The structural stability test of the coating is lacking. For the coatings commonly used in PEMFC, taking the carbon-based coating as an example, the proportion of C sp2 / C sp3 varies greatly and affects the corrosion resistance and conductivity of the coating. After the rapid high and low temperature cycling experiment, the performance of the coating will change due to the shedding of a small amount of large particles on the surface of the carbon-based coating. 6) It is ignored that the stress on the coating at different positions in the flow channel metal bipolar plate is different. Therefore, after rapid high and low temperature cycling and accelerated life testing, there may be a situation where the state of some coatings changes. 7) The above patents only involve the performance testing after high and low temperature cycling, and do not study the influence of high and low temperature cycling on the life of metal bipolar plates. Summary of the Invention

[0007] The purpose of the present invention is to provide a rapid high and low temperature cycling accelerated life test technology for metal bipolar plates, so as to solve one or more technical problems existing in the prior art and at least provide a beneficial choice or create conditions.

[0008] To achieve the above purpose, the present invention adopts the following technical solutions.

[0009] A method for high and low temperature rapid cycling accelerated life test of metal bipolar plates specifically includes the following steps: 1) Preparation of metal bipolar plate samples: Cut the metal bipolar plates deposited with corrosion-resistant conductive coatings into required sizes and wipe the surfaces; Prepare 6-8 metal bipolar plates with the same coating, divided into group A and group B; Then prepare 3-4 metal bipolar plates with flow channels and the same coating, which is group C. 2) Determine the experimental conditions for high and low temperature cycling of metal bipolar plates: According to the actual operating conditions of PEMFC, determine the highest temperature, lowest temperature, actual operating temperature of the fuel cell stack, stable time corresponding to each temperature, temperature change rate, humidity corresponding to each temperature, humidity stable time, and high and low temperature cycling times of the high and low temperature rapid cycling experiment. 3) High and low temperature rapid cycling experiment of metal bipolar plates: The samples in group A are used as the blank control group and are not placed in the high and low temperature test chamber. Put 3-4 metal bipolar plates with corrosion-resistant conductive coatings in group B and group C into the high and low temperature test chamber and make marks. Set the parameters of the high and low temperature test chamber according to the experimental conditions determined in step 2) and conduct the experiment. When the experiment completes the high and low temperature cycling times, the experiment stops automatically. Take out the metal bipolar plate samples and conduct accelerated life comparison tests. 4) Accelerated life comparison test of metal bipolar plates: 41) Determine the experimental conditions for the accelerated life test model: According to the actual operating conditions of PEMFC, set the voltage and residence time for starting and stopping electrochemical off-line testing, variable load and rated conditions, variable load rate, composition of the electrolyte, gas types and flow rates in electrochemical testing, total number of tolerance test cycles, test methods and parameters for adhesion, potentiodynamic test voltage range, frequency range for alternating current impedance (EIS) testing, test pressure for contact resistance, and wavelength range for Raman testing. 42) Conduct off-line start-stop, variable load and rated condition electrochemical tests on 3-4 metal bipolar plate samples in group A that have not undergone high and low temperature rapid cycling, 3-4 metal bipolar plate samples in group B that have undergone high and low temperature rapid cycling experiments, and 3-4 metal bipolar plate samples with flow channels in group C that have undergone high and low temperature rapid cycling experiments in sequence. According to the total number of tolerance test cycles, conduct adhesion, potentiodynamic and contact resistance tests and Raman tests on samples A and B every 20 times until the total number of tolerance test cycles is completed, then stop the test and conduct adhesion (bonding strength between the substrate and the coating), potentiodynamic (corrosion resistance of the coating), contact resistance (conductivity of the coating), EIS (electrochemical characteristics of the coating), and Raman tests (stability of the coating) on the samples; At the end of the accelerated life test, observe the coating state (whether there are cracks, peeling, deformation, etc.) at different positions of sample C and calculate its thickness change rate.

[0010] By comparing the accelerated life data of Group A samples and Group B samples, the high and low temperature resistance performance of the metal bipolar plates is judged. The bonding strength is measured by the scratch method. If the difference in bonding strength between the two groups of samples exceeds 15%; the difference in corrosion current density between the two groups of samples obtained by potentiodynamic testing exceeds 50%; for the contact resistance test, the difference between the two samples exceeds 50%; through EIS testing, it is found that the low-frequency impedance modulus values of the two samples show an order-of-magnitude change; Raman testing gives the I D / I G difference exceeding 15%. If any of the above situations occur, it is judged that the life change degrees of Group A and Group B of the metal bipolar plates are relatively large, indicating that the high and low temperature resistance performance of the metal bipolar plate samples is poor. Otherwise, it is considered that the life change degrees of Group A and Group B of the metal bipolar plates are relatively small, indicating that the high and low temperature resistance performance of the metal bipolar plate samples is good. At the end of the accelerated life test, for the coating state and its thickness change rate at different positions of Sample C, if the coating thickness change rate is lower than 10%, it is considered that the change is small, indicating that the internal stress generated during the coating preparation process, the external stress in the service environment, etc. are small, maintaining the stability and durability of the coating; if the change is large, it indicates that the stress of the metal bipolar plate is large and its high and low temperature rapid cycling accelerated life is poor.

[0011] It should be noted that the above-mentioned larger and smaller are judged by setting corresponding thresholds. As for the specific threshold values, they may vary depending on the product type and can be obtained through experiments or by taking empirical values.

[0012] Furthermore, the corrosion-resistant conductive coating in the metal bipolar plate sample with the deposited corrosion-resistant conductive coating described in step 1) includes: carbon-based coating, metal-based coating, and polymer coating.

[0013] Furthermore, the size of the metal bipolar plate described in step 1) should be greater than 5 cm × 5 cm; and the method of surface wiping is: select a special isopropyl alcohol wiping paper to gently remove the dust on the surface of the sample.

[0014] Furthermore, in step 2), the temperature change range of the high and low temperature rapid cycling experiment is -40°C - 120°C, that is, the low temperature stable point is -40°C, the stable time is 10 - 30 min, the high temperature stable point is 120°C, and the stable time is 10 - 30 min; the actual operating temperature of the stack, 60 - 90°C, is selected as the temperature stable point, and the stable time is 5 - 20 min; the temperature change rate is 1 - 5°C / min, and the temperature deviation ≤ 2°C. The number of high and low temperature cycles ≥ 10000 times.

[0015] The humidity setting range of the humidity stable point is 0 - 100% humidification, and the humidity deviation is controlled within ≤ 3%. The humidity temperature time is the same as the temperature stable time.

[0016] Further, the high and low temperature test chamber in step 3) can control various parameters and realize the program setting, automatic operation and stop of the humidity and temperature change conditions.

[0017] Further, in step 4), the accelerated life test condition is a method of electrochemical corrosion resistance, and its test conditions are: H2SO4 solution with pH = 0 and containing 2 ppm HF and 60 ppm H2O2, and H2O2 solution is injected at a rate of 1 mL / min during the test, the temperature is 80 °C, and saturated air is continuously introduced during the test.

[0018] Further, in step 4), the off-line start-stop, variable load and rated conditions are: the start-stop voltage of the electrochemical test is set to 2.0 V, the residence time is 1 s, the variable load voltage is 0.6 - 2.0 V, the variable load rate is 100 mV / s, the time is 2244 s, the rated voltage is 0.85 V, the residence time is 1345 s, and the start-stop condition is 2.0 V with a residence time of 1 s. The above off-line start-stop, variable load and rated conditions are one tolerance test cycle, and different tolerance test cycle numbers are tested, such as 20 times, 40 times, 60 times, 80 times and 100 times, etc., and the total number of tolerance test cycles ≥ 100 times.

[0019] Further, the adhesion test uses the scratch method and is tested with reference to the industry standard JB / T 8554-1997. A small part of sample A and sample B are respectively cut for testing. The scratch speed is 5 - 15 mm / min, the loading rate is 10 - 100 N / min, and the loading accuracy is 0.01 - 0.5 N.

[0020] The voltage range of the potentiodynamic test is -0.6 V - 1.4 V, and a platinum electrode is used; the frequency range of the EIS test is 0.01 Hz ~ 1000000 Hz, and the contact resistance test pressure is 1.4 MPa.

[0021] The wavelength range of the Raman test is 1000 cm -1 -2000 cm -1 。

[0022] Compared with the prior art, the present invention has at least the following beneficial effects.

[0023] First, the high and low temperature test chamber used in the high and low temperature rapid cycle accelerated life test technology of the metal bipolar plate provided by the present invention can simulate the temperature and humidity change conditions during the actual operation of PEMFC and can perform high and low temperature rapid cycle experiments.

[0024] II. A high and low temperature rapid cycling accelerated life test technology for metal bipolar plates provided by the present invention can quickly obtain the values of bonding force, dynamic potential corrosion current density, EIS, contact resistance, and Raman test, as well as the coating state and thickness change of the metal bipolar plate with flow channels under the same test conditions and accelerated life for different metal bipolar plate samples, so as to know the influence degree of high and low temperature rapid cycling on the life of metal bipolar plates, reduce the R & D cost, and can be widely applied.

[0025] Additional aspects and some advantages of the present invention will be given in part in the following description, become apparent in part from the following description, or be understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The flowchart of a high and low temperature rapid cycling accelerated life test method for metal bipolar plates in the present invention is shown.

[0027] Figure 2 The temperature working condition diagram of the metal bipolar plate resistant to high and low temperature rapid cycling is shown.

[0028] Figure 3 The humidity working condition diagram of the metal bipolar plate resistant to high and low temperature rapid cycling is shown.

[0029] Figure 4 The voltage working condition diagram of the metal bipolar plate accelerated life test is shown.

[0030] Figure 5 The test result diagram of the bonding force of the samples in Group A and Group B is shown.

[0031] Figure 6 The test result diagram of the dynamic potential of the samples in Group A and Group B is shown.

[0032] Figure 7 The test result diagram of the EIS of the samples in Group A and Group B is shown.

[0033] Figure 8 The test result diagram of the contact resistance of the samples in Group A and Group B is shown.

[0034] Figure 9 The schematic diagram of the thickness change of the samples in Group C is shown. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] The following further describes the specific embodiments of the present invention in conjunction with the drawings of the specification, making the technical solutions and their beneficial effects of the present invention clearer and more definite. The embodiments described below by referring to the drawings are exemplary and are intended to explain the present invention, but should not be construed as limiting the present invention.

[0036] The additional aspects and advantages of the present invention will become apparent in part in the following description, or be understood through the practice of the present invention.

[0037] The present invention provides a high and low temperature rapid cycling accelerated life test technology for metal bipolar plates, which specifically includes the following steps: 1) Preparation of metal bipolar plate samples: Cut the metal bipolar plates deposited with corrosion-resistant conductive coatings into required sizes and wipe the surfaces; Prepare 6 - 8 metal bipolar plates with the same coating, divide them into group A and group B, and then prepare 3 - 4 metal bipolar plates with flow channels and the same coating, which is group C.

[0038] 2) Determine the experimental conditions for high and low temperature cycling of metal bipolar plates: According to the actual operating conditions of PEMFC, determine the highest temperature, lowest temperature, actual operating temperature of the stack, stable time corresponding to each temperature, temperature change rate, humidity corresponding to each temperature, humidity stable time, and high and low temperature cycling times in the high and low temperature rapid cycling experiment. Generally, it is considered that the high and low temperature cycling times ≥ 10000 times.

[0039] 3) High and low temperature rapid cycling experiment for metal bipolar plates: The samples in group A are used as the blank control group and are not placed in the high and low temperature test chamber. Put 3 - 4 metal bipolar plates with corrosion-resistant conductive coatings in group B and group C into the high and low temperature test chamber and make marks. Set the parameters of the high and low temperature test chamber according to the experimental conditions determined in step (2) and conduct the experiment. When the experiment completes the high and low temperature cycling times, the experiment automatically stops. Take out the metal bipolar plate samples and conduct accelerated life comparison tests.

[0040] 4) Accelerated life comparison test for metal bipolar plates: 41) Determine the experimental conditions for the accelerated life test model: According to the actual operating conditions of PEMFC, set the start and stop of electrochemical off-line testing, voltages and residence times under variable load and rated conditions, variable load rate, composition of the electrolyte, gas types and flow rates in electrochemical testing, total number of cycles in tolerance testing, test methods and parameters for bonding force, voltage range for potentiodynamic testing, frequency range for alternating current impedance (EIS) testing, test pressure for contact resistance, and wavelength range for Raman testing. Generally, it is considered that the total number of cycles in tolerance testing ≥ 100 times. 42) Conduct electrochemical tests on 3 - 4 metal bipolar plate samples in group A that have not undergone high and low temperature rapid cycling, 3 - 4 metal bipolar plate samples in group B that have undergone high and low temperature rapid cycling experiments, and 3 - 4 metal bipolar plate samples with flow channels in group C that have undergone high and low temperature rapid cycling experiments in sequence for off-line start and stop, variable load, and rated condition tests. According to the total number of cycles in tolerance testing, conduct bonding force testing, potentiodynamic testing, contact resistance testing, and Raman testing on samples A and B every 20 times until the total number of cycles in tolerance testing is completed, then stop the testing and conduct bonding force, potentiodynamic, contact resistance, EIS, and Raman tests on the samples. At the end of the accelerated life test, observe the coating status (such as whether there are cracks, peeling, deformation, etc.) at different positions of sample C and calculate its thickness change rate.

[0041] By comparing the accelerated life data of Group A samples and Group B samples, the high and low temperature resistance performance of the metal bipolar plate is judged. The bonding strength is measured by the scratch method. If the difference in bonding strength between the two groups of samples exceeds 15%; the difference in corrosion current density between the two groups of samples obtained by potentiodynamic testing exceeds 50%; the difference in contact resistance between the two samples exceeds 50%; through EIS testing, it is found that the low-frequency impedance modulus values of the two samples show an order-of-magnitude change; Raman testing gives the I D / I G The difference exceeds 15%. If any of the above situations occur, it is judged that the change in the life of Group A and Group B of the metal bipolar plate is relatively large, indicating that the high and low temperature resistance performance of the metal bipolar plate sample is poor. Otherwise, it is considered that the change in the life of Group A and Group B of the metal bipolar plate is relatively small, indicating that the high and low temperature resistance performance of the metal bipolar plate sample is good. At the end of the accelerated life test, for the coating state and its thickness change rate at different positions of Sample C, if the coating thickness change rate is less than 10%, it is considered that the change is small, indicating that the internal stress generated during the coating preparation process, the external stress in the service environment, etc. are small, maintaining the stability and durability of the coating; if the change is large, it indicates that the stress of the metal bipolar plate is large and its high and low temperature rapid cycling accelerated life is poor.

[0042] Further, in step 1), the corrosion-resistant conductive coating on the metal bipolar plate sample includes: a carbon-based coating, a metal-based coating, and a polymer coating.

[0043] Further, in step 1), the size of the metal bipolar plate should be greater than 5 cm × 5 cm; and the method of surface wiping is: select a special isopropyl alcohol wiping paper to gently remove the dust on the surface of the sample.

[0044] Further, in step 2), the temperature change range of the high and low temperature rapid cycling experiment is -40°C - 120°C, that is, the low temperature stable point is -40°C, the stable time is 10 - 30 min, the high temperature stable point is 120°C, and the stable time is 10 - 30 min; select the actual operating temperature of the stack 60 - 90°C as the temperature stable point, and the stable time is 5 - 20 min; the temperature change rate is 1 - 5°C / min, and the temperature deviation ≤ 2°C. The number of high and low temperature cycles ≥ 10000 times.

[0045] The humidity setting range of the humidity stable point is 0 - 100% humidification, and the humidity deviation is controlled within ≤ 3%. The humidity temperature time is the same as the temperature stable time.

[0046] Further, in step 3), the high and low temperature test chamber can realize the control of each parameter and realize the program setting, automatic operation and stop of the humidity and temperature change working conditions.

[0047] Further, in step 4), the accelerated life test is an electrochemical method, and its test conditions are: H2SO4 solution with pH = 0, containing 2 ppm HF and 60 ppm H2O2, injecting H2O2 solution at a rate of 1 mL / min during the test, the temperature is 80 °C, and saturated air is continuously introduced during the test.

[0048] Further, in step 4), the off-line start-stop, load change, and rated conditions are as follows: Set the start-stop voltage of the electrochemical test to 2.0 V, the residence time to 1 s, the load change voltage to 0.6 - 2.0 V, the load change rate to 100 mV / s, the time to 2244 s, the rated voltage to 0.85 V, the residence time to 1345 s, and the start-stop condition to 2.0 V with a residence time of 1 s. Taking the above off-line start-stop, load change, and rated conditions as one cycle number, test the total number of different tolerance cycles, such as 20 times, 40 times, 60 times, 80 times, and 100 times, etc., and the cycle number ≥ 100 times.

[0049] Further, the adhesion test uses the scratch method and is tested with reference to the industry standard JB / T 8554 - 1997. Cut a small part of sample A and sample B respectively for testing. The scratch speed is 5 - 15 mm / min, the loading rate is 10 - 100 N / min, and the loading accuracy is 0.01 - 0.5 N.

[0050] Further, the dynamic potential test voltage range is -0.6 V - 1.4 V, and a platinum electrode is used; the frequency range of the EIS test is 0.01 Hz ~ 1000000 Hz, the contact resistance test pressure is 1.4 MPa; the Raman test wavelength range is 1000 cm -1 -2000 cm -1 。

[0051] The high and low temperature test chamber used in the present invention can simulate the temperature and humidity change conditions during the actual operation of PEMFC and can conduct high and low temperature rapid cycle experiments; and the accelerated life test technology can quickly obtain the values of adhesion, corrosion current density, EIS, contact resistance, and Raman analysis of different metal bipolar plate samples under the same test conditions and accelerated life, as well as the changes in the state and thickness of the flow channel - carrying metal bipolar plate coating, thereby knowing the influence degree of high and low temperature rapid cycling on the life of the metal bipolar plate, reducing the R & D cost, and can be widely applied. Example 1

[0052] Refer to Figure 1 As shown, a method for high and low temperature rapid cycle accelerated life test of a metal bipolar plate specifically includes the following steps:

[0053] 1) Preparation of metal bipolar plate samples: Cut the metal bipolar plates with deposited carbon-based coatings into 5 cm × 5 cm sizes, and use special isopropyl alcohol wiping paper to remove the dust on the surface; there are a total of 6 samples, with 3 samples in each group, divided into Group A and Group B. Then prepare 3 metal bipolar plates with flow channels and the same coating as Group C. Each group of samples is numbered as A1, A2, A3, B1, B2, B3, and C1, C2, C3 respectively.

[0054] 2) Determine the experimental conditions for the high and low temperature cycling of metal bipolar plates: According to the actual operating conditions of PEMFC, set the relevant parameters for the high and low temperature rapid cycling experiment. Among them, the low temperature stable point is -40 °C, the high temperature stable point is 120 °C, the stable time at high and low temperatures is 10 min, the stable point of the actual operating temperature of the stack is 80 °C, the stable time of the actual operating temperature of the stack is 5 min, and the temperature change rate is 4 °C / min. The temperature conditions are as Figure 2 shown; when the temperature is stable at low temperature, set the humidity to 30%, when the actual operating temperature of the stack, the humidity is 75%, and when the high temperature stable point, the humidity is set to 90%. The humidity conditions are as Figure 3 shown. One cycle of high and low temperature rapid cycling is 110 min, and the number of high and low temperature cycles is 10,000 times.

[0055] 3) High and low temperature rapid cycling experiment of metal bipolar plates: The metal bipolar plate samples of A1, A2, and A3 with carbon-based coatings are used as the blank control group and are not placed in the high and low temperature test chamber. Mark the metal bipolar plates of B1, B2, and B3 with the same carbon-based coating and the metal bipolar plates of C1, C2, and C3 with flow channels and the same carbon-based coating, and place them in the high and low temperature test chamber. Set the parameters of the high and low temperature test chamber and conduct the experiment. When the experiment completes 10,000 times of high and low temperature cycles, the experiment will automatically stop. Take out the metal bipolar plate samples and conduct an accelerated life comparison test.

[0056] 4) Accelerated life comparison test of metal bipolar plates.

[0057] 41) Determine the experimental conditions for the accelerated life test model: According to the actual operating conditions of PEMFC, set the start and stop voltage of the electrochemical test to 2.0 V, the residence time to 1 s, the variable load voltage to 0.6 - 2.0 V, the variable load rate to 100 mV / s, the time to 2244 s, the rated voltage to 0.85 V, the residence time to 1345 s, the start and stop conditions to 2.0 V, the residence time to 1 s. The test voltage conditions are as Figure 4As shown. The test conditions for electrochemical corrosion resistance are as follows: an H2SO4 solution with pH = 0, containing 2 ppm HF and 60 ppm H2O2, with the H2O2 solution being injected at a rate of 1 mL / min during the test, the temperature being 80 °C, and saturated air being continuously introduced during the test at a flow rate of 10 mL / min. It is determined that one tolerance test is 1 h, and the total number of tolerance test cycles is 100 times. The speed for measuring the bonding strength by the scratch method is 10 mm / min, the loading rate is 20 N / min, the loading accuracy is 0.03 N, the potential range for the potentiodynamic test is -0.6 - 1.4 V, the test frequency for the alternating current impedance (EIS) is 0.01 Hz - 1000000 Hz, the test pressure for the contact resistance is 1.4 MPa, and the Raman test wavelength range is 1000 cm -1 -1800 cm -1 .

[0058] 42) Electrochemical tests of off-line start-stop, variable load, and rated conditions are sequentially performed on 3 metal bipolar plate samples in Group A that have not undergone rapid high-low temperature cycling and 3 metal bipolar plate samples in Group B that have undergone rapid high-low temperature cycling experiments. According to the total number of tolerance test cycles being 100 times, the bonding strength, potentiodynamic, contact resistance, and Raman tests are performed on the samples every 20 times until 100 times are reached, at which point the test is stopped, and the bonding strength, potentiodynamic, contact resistance, alternating current impedance (EIS) test, and Raman test are performed on the samples. At the end of the accelerated life test, the coating state (such as whether there are cracks, peeling, deformation, etc.) at different positions of sample C is observed, and its thickness change rate is calculated.

[0059] By comparing the bonding strength test results, potentiodynamic test results, alternating current impedance (EIS) test results, contact resistance test results, and Raman analysis results of the samples in Group A and Group B, the differences in the data of each group of samples are calculated. From Figures 5 - 9 and Table 1, it can be calculated that for measuring the bonding strength by the scratch method, if the difference in the bonding strength between the two groups of samples is less than 15%; for the potentiodynamic test, the difference in the corrosion current density between the two groups of samples is less than 50%; for the contact resistance test, the difference between the two samples is less than 50%; through the EIS test, it is found that there is no order-of-magnitude change in the low-frequency impedance modulus values of the two samples; for the Raman test, the I D / I G difference between the two samples is less than 15%. Therefore, it can be considered that the metal bipolar plates with carbon-based coatings that have undergone rapid high-low temperature cycling and accelerated life tests have good high-low temperature resistance and good coating stability. The TEM observation results of sample C at the end of the accelerated life test show that there are no obvious changes in the coating state, no cracks, peeling, deformation, etc. The thickness change rate of this coating is about 5%, indicating that the internal stress generated during the coating preparation process, the external stress in the service environment, etc. are small, maintaining the stability and durability of the coating.

[0060] Table 1. Raman test results of samples in Group A and Group B Time (h) <![CDATA[Inside I of Coating A D / I G > <![CDATA[Inside the B coating I D / I G > 0 0.583 0.525 20 0.568 0.510 40 0.551 0.498 60 0.536 0.484 80 0.514 0.477 100 0.508 0.463 。

[0061] Through the description of the above structure and principle, those skilled in the art should understand that the present invention is not limited to the above specific embodiments. Improvements and substitutions using well-known technologies in the art based on the present invention fall within the protection scope of the present invention. The protection scope of the present invention shall be defined by each claim item and its equivalent. The parts not described in the specific embodiments are all prior art or common general knowledge.

[0062] English abbreviation.

[0063] PEMFC, the English abbreviation of Proton Exchange Membrane Fuel Cell, proton exchange membrane fuel cell.

Claims

1. A method for high and low temperature cycle accelerated life test of a metal bipolar plate, characterized in that, Including the following steps: 1) Preparation of metal bipolar plate samples: Cut the metal bipolar plates deposited with corrosion-resistant conductive coatings into required sizes and wipe the surfaces; The metal bipolar plates with the same coatings are divided into Group A and Group B; Then prepare the metal bipolar plates with flow channels and the same coatings as Group C; 2) Determine the experimental conditions of high and low temperature cycling of metal bipolar plates: According to the actual operating conditions of PEMFC, determine the highest temperature, lowest temperature, actual operating temperature of the stack, stable time corresponding to each temperature, temperature change rate, humidity corresponding to each temperature, humidity stable time and number of high and low temperature cycles in the high and low temperature rapid cycling experiment; 3) High and low temperature cycling experiment of metal bipolar plates: Group A is used as a blank control group and is not placed in the high and low temperature test chamber; Put the metal bipolar plates with corrosion-resistant conductive coatings in Group B and Group C into the high and low temperature test chamber and make marks; Set the parameters of the high and low temperature test chamber according to the experimental conditions determined in step 2) and conduct the experiment. After the experiment completes the number of high and low temperature cycles, take out the metal bipolar plate samples and conduct accelerated life comparison tests; 4) Accelerated life comparison test of metal bipolar plates: 41) Determine the experimental conditions of the accelerated life test model: According to the actual operating conditions of PEMFC, set the start and stop of electrochemical off-line testing, voltages and residence times under variable load and rated conditions, variable load rate, composition of the electrolyte, types and flow rates of gases in electrochemical testing, total number of tolerance test cycles, test methods and parameters of bonding strength, voltage range of potentiodynamic testing, frequency range of AC impedance testing, test pressure of contact resistance and wavelength range of Raman testing; 42) Conduct electrochemical tests of off-line start and stop, variable load and rated conditions on the metal bipolar plate samples in Group A without high and low temperature cycling experiments, the metal bipolar plate samples in Group B with high and low temperature cycling experiments, and the metal bipolar plate samples with flow channels in Group C with high and low temperature cycling experiments in sequence. Conduct bonding strength tests, potentiodynamic tests, contact resistance tests, AC impedance tests and Raman tests on the samples in Group A and Group B at certain intervals according to the total number of tolerance test cycles; Observe the samples in Group C after the accelerated life test, obtain the coating states at different positions of the samples and calculate their thickness change rates; 5) Judgment of high and low temperature resistance performance of the coating: Compare the bonding strength test data, potentiodynamic test data, contact resistance test data, AC impedance test data and Raman test data of the samples in Group A and Group B to judge the degree of change in the life of the metal bipolar plates. If the degree of change in life is small, it indicates that the metal bipolar plates have good high and low temperature resistance performance; If the degree of change in life is large, it indicates that the metal bipolar plates have poor high and low temperature resistance performance; Compare the coating states at different positions of the samples in Group C and their thickness change rates. If the changes are small, it indicates that the internal stress generated during the coating preparation process and the external stress in the service environment are small, maintaining the stability and durability of the coating; If the changes are large, it indicates that the metal bipolar plates have large stress and poor high and low temperature cycling accelerated life.

2. A method for testing the high and low temperature cycle accelerated life of a metal bipolar plate according to claim 1, characterized in that, The deposited corrosion-resistant conductive coating is a carbon-based coating, a metal-based coating or a polymer coating.

3. A method for high and low temperature cycle accelerated life test of a metal bipolar plate according to claim 1, characterized in that The method of surface wiping is as follows: Select isopropyl alcohol wiping paper to wipe the surface of the sample to remove the dust on the surface of the sample.

4. A method for testing the high and low temperature cycle accelerated life of a metal bipolar plate according to claim 1, characterized in that, The temperature change range of the high and low temperature cycle test is -40°C - 120°C, the low temperature stable point is -40°C, the stable time is 10 - 30 min, the high temperature stable point is 120°C, and the stable time is 10 - 30 min; and select an intermediate temperature stable point between the actual operating temperature of the stack of 60 - 90°C, and the stable time is 5 - 20 min; the temperature change rate is 1 - 5°C / min, and the temperature deviation ≤ 2°C; the number of high and low temperature cycles ≥ 10000 times; The humidity setting range of the humidity stable point is 0 - 100% humidification, and the humidity deviation is controlled within ≤ 3%, and the humidity stable time is the same as the temperature stable time.

5. A method for high and low temperature cycle accelerated life test of a metal bipolar plate according to claim 1, characterized in that, The potentiodynamic test conditions are as follows: Use an H2SO4 solution with pH = 0 and containing 2 ppm HF and 60 ppm H2O2, inject the H2O2 solution at a speed of 1 mL / min during the test, the temperature is 80°C, and continuously introduce saturated air during the test.

6. A method for high and low temperature cycle accelerated life test of a metal bipolar plate according to claim 1, characterized in that, The off-line start-stop, variable load and rated conditions are as follows: Set the start-stop voltage of the electrochemical test to 2.0 V, the residence time is 1 s, the variable load voltage is 0.6 - 2.0 V, the variable load rate is 100 mV / s, the time is 2244 s, the rated voltage is 0.85 V, the residence time is 1345 s, the start-stop condition is 2.0 V, and the residence time is 1 s; Conducting an off-line start-stop, variable load and rated condition tolerance test cycle is counted as one time, and the total number of tolerance test cycles ≥ 100 times.

7. A method for high and low temperature cycle accelerated life test of a metal bipolar plate, according to claim 1 or 6, characterized in that Perform adhesion test, potentiodynamic test, contact resistance test, AC impedance test and Raman test on Group A samples and Group B samples every 20 times.

8. A method for testing the high and low temperature cycle accelerated life of a metal bipolar plate according to claim 1, characterized in that, The number of high and low temperature cycles is not less than 10000 times.

9. A method for high and low temperature cycling accelerated life test of a metal bipolar plate according to claim 1, characterized in that, When observing the coating state of Group C coating at different positions, observe whether there are cracks, peeling and deformation of the coating.

10. The method for high and low temperature cycle accelerated life test of a metal bipolar plate according to claim 1, characterized in that, The adhesion force was tested by the scratch method, with a scratch speed of 5 - 15 mm / min, a loading rate of 10 - 100 N / min, and a loading accuracy of 0.01 - 0.5 N; the potentiodynamic test voltage range was -0.6 V - 1.4 V, using a platinum electrode; the frequency range of the AC impedance test was 0.01 Hz to 1000000 Hz; the pressure for the contact resistance test was 1.4 Mpa; the wavelength range of the Raman test was 1000 cm -1 -2000 cm -1 .

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