Galvanic corrosion test method for metal bipolar plate coatings based on suppression voltage

Abstract

The present invention proposes a method for testing the corrosion of a metal bipolar plate coating using an inhibition voltage. In a prepared two-electrode system, an inert electrode is used as a working electrode, and a standard electrode with the most active element exposed on the coating surface is used as a counter electrode and connected to an electrochemical workstation. The inhibition voltage between the two elements is first measured, and the voltage value required for subsequent testing is determined based on the inhibition voltage to ensure that the lower ends of the electrodes are immersed in the electrolyte. At a determined voltage, the test is carried out over time, and the corrosion of the sample coating using the detected current changes and the surface state of the sample is evaluated. The present invention can monitor the reaction of the metal bipolar plate coating using an electrochemical fuel cell, and can also infer the degree of reaction based on the current numerical quantitative analysis, and evaluate the life of the metal bipolar plate coating.

Description

Technical Field

[0001] The present invention belongs to the technical field of fuel cells, and in particular relates to a method for testing the corrosion of a metal bipolar plate coating in a primary cell based on suppression voltage. Background Art

[0002] The corrosion of metal bipolar plates is a growing concern among researchers. Numerous studies have shown that metal bipolar plate coatings are susceptible to galvanic corrosion in the operating environment of fuel cells. During fuel cell operation, spontaneous galvanic corrosion occurs when the coating and substrate come into contact with each other in a humid environment due to differences in material.

[0003] Current research on coating corrosion primarily involves electrochemical polarization testing of bipolar plates under varying conditions, supplemented by surface morphology and composition analysis. However, these testing methods use the sample electrode as the working electrode and the inert electrode as the counter electrode. The measured data fail to reflect the galvanic corrosion reactions occurring within the sample itself. Consequently, existing testing methods differ from the actual corrosion conditions experienced by bipolar plates during fuel cell operation. Consequently, there is an urgent need to develop new methods that directly reflect the galvanic corrosion occurring within the coating. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a metal bipolar plate coating primary cell corrosion test method based on suppression voltage in response to the above-mentioned problems, which can quickly analyze the actual bipolar plate coating primary cell corrosion situation during the operation of the fuel cell.

[0005] The technical solution adopted by the present invention to solve the above technical problems is: a metal bipolar plate coating galvanic cell corrosion testing method based on suppression voltage, characterized by comprising the following steps:

[0006] Step a: Cut the coated bipolar plate of the sample to be tested into a suitable size, peel off the surface of one end of the copper wire to expose a portion of the wire, then wrap it around one end of the sample and secure it with phenolic resin. The sample electrode is also sealed with phenolic resin, leaving only the central area of ​​the coated surface exposed.

[0007] Step b: In the prepared two-electrode system, the inert electrode is used as the working electrode, and the standard electrode with the most active element exposed on the coating surface is used as the counter electrode. They are connected to the electrochemical workstation to ensure that the lower ends are immersed in the electrolyte. At the same time, a certain rate of air is introduced. The electrolytic cell is kept sealed and placed in a constant temperature water bath. The corrosion voltage, i.e., the inhibition voltage, is measured.

[0008] Step c, placing the sample electrode and the inert electrode in an electrolytic cell filled with electrolyte, ensuring that the lower ends are immersed in the electrolyte in the electrolytic cell, while air is introduced into the electrolyte at a certain rate, and the electrolytic cell is kept sealed and placed in a constant temperature water bath;

[0009] Step d: Use the inert electrode as the working electrode and the sample electrode as the counter electrode, connect them to the electrochemical workstation respectively, select the IT constant potential mode, set the voltage and time, and start the test. The voltage set in the IT constant potential mode is higher than the inhibition voltage and lower than the water electrolysis voltage. During the test, observe the current changes and take photos of the sample surface state;

[0010] Step e: Evaluate the galvanic cell corrosion of the sample coating based on the current data change curve obtained from the electrochemical test and the sample surface photograph.

[0011] According to the above scheme, the sample coating described in step a is a dual-component metal coating.

[0012] According to the above scheme, the inert electrode described in step c does not react with the electrolyte.

[0013] According to the above scheme, the electrolyte composition is a mixture of H2SO4 and HF, and the concentration is multiple times the DOE standard concentration. The DOE standard concentration is: PH = 3, F - The concentration is 0.1mg / L.

[0014] According to the above scheme, the voltage set in the IT constant potential mode described in step d is higher than the inhibition voltage and lower than the water electrolysis voltage.

[0015] According to the above scheme, the time set in the IT constant potential mode is the time required for the natural corrosion surface state of the sample to change significantly under the same environment.

[0016] The beneficial effects of the present invention are: providing a metal bipolar plate coating galvanic corrosion test method based on inhibition voltage, which avoids the reaction between the sample electrode and the inert electrode by reversing the electrodes and applying inhibition voltage, so that only the galvanic corrosion reaction occurs in the sample itself. After the reaction, the change in the surface roughness of the sample brings about a change in the current, and the change in the current value reflects the galvanic corrosion reaction of the metal plate coating. This method can qualitatively and quantitatively analyze the galvanic corrosion of the coating, is convenient, fast and efficient, and has important research significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0018] Figure 1 Schematic diagram of a prepared sample according to an embodiment of the present invention.

[0019] Figure 2 Schematic diagram of test data and sample surface status photos according to an embodiment of the present invention. DETAILED DESCRIPTION

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Generally, the components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0021] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments in the present application without creative work are within the scope of protection of the present application.

[0022] The features and performance of the present application are further described in detail below with reference to the embodiments.

[0023] Galvanic corrosion test method for metal bipolar plate coatings based on inhibition voltage, including

[0024] Next steps:

[0025] Step a: Cut the coated bipolar plate of the sample to be tested into a suitable size, peel off the surface of one end of the copper wire to expose a portion of the wire, then wrap it around one end of the sample and secure it with phenolic resin. The sample electrode is also sealed with phenolic resin, leaving only the central area of ​​the coated surface exposed.

[0026] Step b: In the prepared two-electrode system, the inert electrode is used as the working electrode, and the standard electrode with the most active element exposed on the coating surface is used as the counter electrode. They are connected to the electrochemical workstation to ensure that the lower ends are immersed in the electrolyte. At the same time, a certain rate of air is introduced. The electrolytic cell is kept sealed and placed in a constant temperature water bath. The corrosion voltage, i.e., the inhibition voltage, is measured.

[0027] Step c, placing the sample electrode and the inert electrode in an electrolytic cell filled with electrolyte, ensuring that the lower ends are immersed in the electrolyte in the electrolytic cell, while air is introduced into the electrolyte at a certain rate, and the electrolytic cell is kept sealed and placed in a constant temperature water bath;

[0028] Step d: Use the inert electrode as the working electrode and the sample electrode as the counter electrode, connect them to the electrochemical workstation respectively, select the IT constant potential mode, set the voltage and time, and start the test. The voltage set in the IT constant potential mode is higher than the inhibition voltage and lower than the water electrolysis voltage. During the test, observe the current changes and take photos of the sample surface state;

[0029] Step e: Evaluate the galvanic cell corrosion of the sample coating based on the current data change curve obtained from the electrochemical test and the sample surface photograph.

[0030] The sample coating described in step a is a two-component metal coating.

[0031] The electrolyte composition is a mixture of H2SO4 and HF, and the concentration is multiple times the DOE standard concentration. The DOE standard concentration is: PH = 3, F - The concentration is 0.1mg / L.

[0032] The voltage set in the it constant potential mode is higher than the inhibition voltage and lower than the water electrolysis voltage; the time set in the it constant potential mode is the time required for the natural corrosion surface state of the sample to change significantly under the same environment.

[0033] Example 1

[0034] The galvanic corrosion test method for metal bipolar plate coating based on suppression voltage has the following specific steps:

[0035] 1) Cut the sample coated bipolar plate (titanium nano-gold coated bipolar plate, multi-serpentine flow channel) into a size of 1.5cm*2.0cm, cut a section of copper wire, tear off the skin to expose the wire, and then wrap it around the short end of the sample and fix it with phenolic resin. The sample is also sealed on all sides, leaving only a square area of ​​about 1cm2 where the coating is located. The prepared sample is as follows Figure 1 shown.

[0036] 2) In the prepared two-electrode system, a standard Au sheet electrode (size 10 mm × 10 mm × 0.1 mm, purity 99.99%) was used as the working electrode, and a standard Ti sheet electrode (size 10 mm × 10 mm × 0.1 mm, purity 99.99%) was used as the counter electrode. These electrodes were connected to the electrochemical workstation, ensuring that their lower ends were immersed in the electrolyte. Air was introduced at a certain rate. The electrolytic cell was kept sealed and placed in a constant temperature water bath at 80°C to measure the corrosion voltage, i.e., the inhibition voltage.

[0037] 3) Place the sample electrode and standard Au sheet electrode (size 10 mm × 10 mm × 0.1 mm, purity 99.99%) prepared in step 1) in a solution containing an electrolyte (1000 times the DOE standard concentration specified by the U.S. Department of Energy, with a composition of H2SO4 and a concentration of H + Concentration 1mol / L, F - The electrolytic cell was placed in an electrolytic solution with a concentration of 0.1 g / L, ensuring that the lower end was immersed in the electrolyte. Air was introduced at a certain rate. The electrolytic cell was kept sealed and placed in a constant temperature water bath at 80°C.

[0038] 4) In the two-electrode system prepared in step 3), connect the standard Au sheet electrode as the working electrode and the sample electrode as the counter electrode to the electrochemical workstation. Select the it constant potential mode and set the voltage to 0.6 V. After a set time, start the test. During the test, observe and photograph the sample surface condition;

[0039] 5) Based on the current data change curve obtained from the electrochemical test in step 4) and the sample surface photos, evaluate the galvanic corrosion of the sample coating. Test data and sample surface status photos (see Figure 2 ), as can be seen from the figure, under the condition of 0.6V constant potential, as time goes on, the current value has a significant change at the 15th hour, and continues to increase to the 20th hour. At the same time, it can be observed that the surface state of the sample changes from smooth and intact to slightly wrinkled to obvious surface gold shedding to large-area gold leakage from the black Ti substrate. From this, it can be concluded that in the 1000-fold accelerated electrolyte environment, Au and Ti begin to undergo a galvanic cell reaction at the 15th hour, which then lasts for 5 hours and causes the coating to fail. Under the condition of 0.8V constant potential, as time goes on, the current value has a significant change at the 10th hour. At the same time, it can be observed that as the reaction progresses, the surface state of the sample changes from smooth and intact to slightly wrinkled to obvious surface gold shedding. From this, it can be concluded that in the 1000-fold accelerated electrolyte environment, Au and Ti begin to undergo a galvanic cell reaction at the 10th hour, which then lasts for 10 hours and causes the coating to fail.

[0040] Compared with the existing test methods, the corrosion time of this test method is closer to the time in actual application. Therefore, it can be seen that the data measured by this test method can better reflect the situation of the galvanic cell corrosion reaction inside the sample itself than the data measured by the existing test method.

[0041] The above description is merely a preferred embodiment of the present invention; however, the scope of protection of the present invention is not limited thereto. Any person skilled in the art who, within the technical scope disclosed by the present invention, makes equivalent substitutions or modifications based on the technical solutions and improved concepts of the present invention shall be covered by the scope of protection of the present invention.

Claims

1. A method for testing the corrosion of metal bipolar plate coatings using a galvanic cell based on suppression voltage, characterized in that: The steps include: Step a: Cut the coated bipolar plate of the sample to be tested into a suitable size, peel off the surface of one end of the copper wire to expose a portion of the wire, then wrap it around one end of the sample and secure it with phenolic resin. The sample electrode is also sealed with phenolic resin, leaving only the central area of ​​the coated surface exposed. Step b: In the prepared two-electrode system, an inert electrode is used as a working electrode, and a standard electrode with the most active element exposed on the coating surface is used as a counter electrode. The two electrodes are connected to an electrochemical workstation, ensuring that the lower ends are immersed in the electrolyte. Air is introduced at a certain rate. The electrolytic cell is kept sealed and placed in a constant temperature water bath. The corrosion voltage, i.e., the inhibition voltage, is measured. Step c, placing the sample electrode and the inert electrode in an electrolytic cell filled with electrolyte, ensuring that the lower ends are immersed in the electrolyte in the electrolytic cell, while air is introduced into the electrolyte at a certain rate, and the electrolytic cell is kept sealed and placed in a constant temperature water bath; Step d: Use the inert electrode as the working electrode and the sample electrode as the counter electrode, connect them to the electrochemical workstation respectively, select the IT constant potential mode, set the voltage and time, and start the test. The voltage set in the IT constant potential mode is higher than the inhibition voltage and lower than the water electrolysis voltage. During the test, observe the current changes and take photos of the sample surface state; Step e: Evaluate the galvanic cell corrosion of the sample coating based on the current data change curve obtained from the electrochemical test and the sample surface photograph.

2. The method for testing the corrosion of a metal bipolar plate coating using a galvanic cell based on suppression voltage according to claim 1, wherein: The sample coating described in step a is a two-component metal coating.

3. The method for testing the corrosion of a metal bipolar plate coating using a galvanic cell based on suppression voltage according to claim 1 or 2, wherein: The inert electrode in step c does not react with the electrolyte.

4. The method for testing the corrosion of a metal bipolar plate coating using a galvanic cell based on suppression voltage according to claim 3, wherein: The electrolyte composition is a mixture of H2SO4 and HF, and the concentration is multiple times the concentration of the standard electrolyte of the U.S. Department of Energy. The standard electrolyte concentration of the U.S. Department of Energy is: PH=3, F - The concentration is 0.1 mg / L.

5. The method for testing the corrosion of a metal bipolar plate coating using a galvanic cell based on suppression voltage according to claim 1 or 4, wherein: The time set in the IT constant potential mode is the time required for the natural corrosion surface state of the sample to change significantly under the same environment.

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