Pretreatment method and system for surface microdefects of titanium alloy bipolar plate and bipolar plate

Abstract

The embodiment of the invention provides a pretreatment method and system for surface microdefects of a titanium alloy bipolar plate and the bipolar plate, and the pretreatment method comprises the following steps: sequentially putting a rolled titanium alloy bipolar plate with the thickness of 0.1-0.15 mm into an industrial degreasing agent for ultrasonic cleaning for 10-30 minutes through ultrasonic degreasing cleaning, and then performing ultrasonic rinsing in distilled water for 10-30 minutes; ultrasonic vibration assisted electrochemical composite polishing is conducted, the treated titanium alloy bipolar plate serves as an anode, a graphite plate or a titanium plate serves as a cathode, the titanium alloy bipolar plate and the graphite plate or the titanium plate are immersed in an electrochemical polishing solution containing H2SO4 and HF, ultrasonic vibration with the frequency of 20 kHz to 40 kHz is applied, and treatment is conducted for 5 s to 60 s under the conditions that the distance between the anode and the cathode is 30 mm to 50 mm, the voltage is 30 V to 60 V, and the temperature of the polishing solution is 10 DEG C to 25 DEG C; and performing ultrasonic rinsing on the polished bipolar plate with distilled water for 10-30 minutes, and performing vacuum drying at the temperature of 60-100 DEG C for 30-60 minutes. According to the technical scheme, the microdefects on the surface of the titanium metal bipolar plate can be rapidly eliminated or weakened, the titanium alloy bipolar plate surface which is flatter in surface and fewer in microdefects is obtained, and the comprehensive performance of a subsequent high-corrosion-resistance conductive functional coating is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal surface coatings, and in particular relates to a method and system for pretreating surface microscopic defects of a titanium alloy bipolar plate, and the bipolar plate. Background Art

[0002] Hydrogen fuel cells are power generation devices that use hydrogen as fuel and air or pure oxygen as an oxidant, converting chemical energy directly into electrical energy. They have attracted widespread attention from governments and research institutions worldwide due to their high efficiency, energy efficiency, safety, and environmental friendliness. Bipolar plates are the core component of hydrogen fuel cell stacks. Operating in a complex environment characterized by acid, heat, and electrochemical corrosion, they perform multiple functions, including current collection and conduction, heat dissipation, uniform dispersion of the reaction medium, and leakage prevention. Corrosion and damage to the bipolar plates will lead to hydrogen fuel cell failure, and therefore largely determine the performance, lifespan, and reliability of the fuel cell.

[0003] Common bipolar plate materials include graphite, metal, and composite materials. Metal bipolar plates are the main direction of future development due to their good mechanical strength, processing performance, and electrical conductivity, especially impact and vibration resistance. Metal bipolar plates are mainly divided into two categories: stainless steel and titanium alloy. Titanium alloy has the advantages of corrosion resistance, high temperature resistance, low density, high specific strength, non-magnetic properties, and no precipitation of heavy metal elements that are toxic to precious metal catalysts. It can significantly improve the performance, reliability, and life of hydrogen fuel cells, and reduce the overall weight of hydrogen fuel cells. It is an ideal material for the metal bipolar plate substrate of hydrogen fuel cells. However, the elongation of titanium alloy is only 25% to 30%, which is much lower than that of stainless steel (elongation of more than 40%). Therefore, many microscopic defects will inevitably appear on the surface of titanium alloy bipolar plates during the rolling and stamping process. These defects have a significant impact on the preparation process and performance of the bipolar plate coating.

[0004] Therefore, how to provide a pretreatment method, system and bipolar plate for micro defects on the surface of titanium alloy bipolar plates, so as to quickly eliminate or weaken the micro defects on the surface of titanium metal bipolar plates and obtain a titanium alloy bipolar plate surface with a smoother surface and fewer micro defects has become a technical problem that needs to be solved urgently. Summary of the Invention

[0005] The embodiments of the present invention provide a method, system, and bipolar plate for pretreating microscopic defects on the surface of a titanium alloy bipolar plate. By using ultrasonic vibration-assisted electrochemical polishing, microscopic defects on the surface of the titanium metal bipolar plate can be quickly eliminated or weakened, resulting in a titanium alloy bipolar plate surface with a smoother surface and fewer microscopic defects, thereby improving the comprehensive performance of subsequent high-corrosion-resistant conductive functional coatings.

[0006] In one embodiment of the present invention, a method for pre-processing the surface microscopic defects of a rolled titanium alloy bipolar plate is provided, comprising:

[0007] S101, ultrasonic degreasing and cleaning, placing the rolled titanium alloy bipolar plates with a thickness of 0.1 mm to 0.15 mm in an industrial degreasing agent for ultrasonic cleaning for 10 min to 30 min, and then ultrasonic rinsing in distilled water for 10 min to 30 min;

[0008] S102, ultrasonic vibration-assisted electrochemical composite polishing, using the titanium alloy bipolar plate treated as the anode and the graphite plate or titanium plate as the cathode, immersed in an electrochemical polishing solution containing H2SO4 and HF, while applying ultrasonic vibration at a frequency of 20kHz to 40kHz, and treating for 5s to 60s under the conditions of a cathode-cathode distance of 30mm to 50mm, a voltage of 30V to 60V, and a polishing solution temperature of 10°C to 25°C;

[0009] S103, ultrasonically rinsing the polished bipolar plate with distilled water for 10 minutes to 30 minutes, and then vacuum drying it at 60° C. to 100° C. for 30 minutes to 60 minutes.

[0010] Furthermore, the electrochemical polishing solution comprises the following components:

[0011] The H2SO4 concentration is 30g / L~60g / L, the HF concentration is 2g / L~10g / L, the methanol corrosion inhibitor concentration is 20g / L~40g / L, and the ultrasonic vibration power density is 0.5W / cm 2 ~2.0W / cm 2 .

[0012] Furthermore, the electrochemical polishing solution satisfies any of the following ratios:

[0013] H2SO4 concentration is 40g / L, HF concentration is 3g / L, and methanol corrosion inhibitor concentration is 20g / L;

[0014] The H2SO4 concentration is 60g / L, the HF concentration is 2g / L, and the methanol corrosion inhibitor concentration is 40g / L.

[0015] Furthermore, the distance between the anode and cathode is set to satisfy the relationship:

[0016] d=k×V

[0017] Where d is the inter-electrode distance, mm; V is the voltage, V; k is the adjustment coefficient, ranging from 0.8 to 1.2.

[0018] Furthermore, the ultrasonic vibration tank and the electrochemical polishing tank adopt a split nested structure, the medium in the ultrasonic vibration tank is water, and the medium in the electrochemical polishing tank is an acidic electrolyte.

[0019] Furthermore, the titanium alloy bipolar plate is made of TA1 alloy or TA2 alloy, and the depth of surface microscopic defects is reduced by ≥80% after ultrasonic vibration assisted electrochemical composite polishing treatment.

[0020] In another embodiment of the present invention, a system for pre-processing the surface micro-defects of a rolled titanium alloy bipolar plate is provided. The system is based on any one of the above methods for pre-processing the surface micro-defects of a rolled titanium alloy bipolar plate, and includes: an ultrasonic degreasing module, a composite polishing module, and a post-processing module.

[0021] The ultrasonic degreasing module is used for ultrasonic degreasing and cleaning. The rolled titanium alloy bipolar plates with a thickness of 0.1 mm to 0.15 mm are sequentially placed in an industrial degreasing agent for ultrasonic cleaning for 10 to 30 minutes, and then ultrasonically rinsed in distilled water for 10 to 30 minutes.

[0022] The composite polishing module is used for ultrasonic vibration-assisted electrochemical composite polishing. The titanium alloy bipolar plate treated as above is used as the anode, and the graphite plate or titanium plate is used as the cathode. They are immersed in an electrochemical polishing solution containing H2SO4 and HF, and ultrasonic vibration with a frequency of 20kHz to 40kHz is applied at the same time. The treatment is carried out for 5s to 60s under the conditions of a cathode-anode distance of 30mm to 50mm, a voltage of 30V to 60V, and a polishing solution temperature of 10°C to 25°C.

[0023] The post-processing module is used to ultrasonically rinse the polished bipolar plate with distilled water for 10 minutes to 30 minutes, and then vacuum dry it at 60° C. to 100° C. for 30 minutes to 60 minutes.

[0024] In another embodiment of the present invention, a titanium metal bipolar plate for a hydrogen fuel cell is provided. The bipolar plate is produced by a method for pre-treating the surface micro-defects of a rolled titanium alloy bipolar plate as described in any one of the above items, and has no work-hardening layer on its surface and a coating bonding strength ≥18 MPa.

[0025] The beneficial effects brought about by the present invention are as follows:

[0026] It can be seen from the above scheme that the embodiment of the present invention provides a pretreatment method, system and bipolar plate for microscopic defects on the surface of a titanium alloy bipolar plate. By ultrasonic degreasing and cleaning, a rolled titanium alloy bipolar plate with a thickness of 0.1mm to 0.15mm is placed in an industrial degreasing agent for ultrasonic cleaning for 10min to 30min, and then ultrasonically rinsed in distilled water for 10min to 30min; ultrasonic vibration assisted electrochemical composite polishing, the titanium alloy bipolar plate treated as above is used as the anode, and the graphite plate or titanium plate is used as the cathode, immersed in an electrochemical polishing solution containing H2SO4 and HF, and ultrasonic vibration with a frequency of 20kHz to 40kHz is applied at the same time. The treatment is carried out for 5s to 60s under the conditions of a cathode-anode distance of 30mm to 50mm, a voltage of 30V to 60V, and a polishing liquid temperature of 10℃ to 25℃; the polished bipolar plate is ultrasonically rinsed with distilled water for 10min to 30min, and then vacuum dried at 60℃ to 100℃ for 30min to 60min. The technical solution of the present invention, through ultrasonic vibration-assisted electrochemical polishing, can quickly eliminate or weaken the microscopic defects on the surface of the titanium metal bipolar plate, obtain a titanium alloy bipolar plate surface with a smoother surface and fewer microscopic defects, and improve the comprehensive performance of the subsequent high-corrosion-resistant conductive functional coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a flow chart of a method for pre-processing the surface micro defects of a rolled titanium alloy bipolar plate according to an embodiment of the present invention. DETAILED DESCRIPTION

[0028] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0029] Currently, common methods for pre-finishing micro-defects include mechanical grinding and polishing, as well as chemical polishing. Since the thickness of titanium alloy plates after rolling is typically less than 0.15mm, mechanical grinding and polishing can easily cause deformation. Furthermore, improper temperature control during the grinding process can also result in the formation of an oxidized surface layer. Due to the excellent corrosion resistance of titanium alloys, chemical polishing only uses chemical reagents such as hydrofluoric acid, which poses significant safety and environmental risks, and is also inefficient.

[0030] like Figure 1 As shown, Figure 1 This is a flow chart of a method for pre-processing the surface micro defects of a rolled titanium alloy bipolar plate according to an embodiment of the present invention.

[0031] Figure 1 A method for pre-processing the surface micro defects of a rolled titanium alloy bipolar plate comprises:

[0032] S101, ultrasonic degreasing and cleaning, placing the rolled titanium alloy bipolar plates with a thickness of 0.1 mm to 0.15 mm in an industrial degreasing agent for ultrasonic cleaning for 10 min to 30 min, and then ultrasonic rinsing in distilled water for 10 min to 30 min;

[0033] S102, ultrasonic vibration-assisted electrochemical composite polishing, using the titanium alloy bipolar plate treated as the anode and the graphite plate or titanium plate as the cathode, immersed in an electrochemical polishing solution containing H2SO4 and HF, while applying ultrasonic vibration at a frequency of 20kHz to 40kHz, and treating for 5s to 60s under the conditions of a cathode-cathode distance of 30mm to 50mm, a voltage of 30V to 60V, and a polishing solution temperature of 10°C to 25°C;

[0034] S103, ultrasonically rinsing the polished bipolar plate with distilled water for 10 minutes to 30 minutes, and then vacuum drying it at 60° C. to 100° C. for 30 minutes to 60 minutes.

[0035] In an embodiment of the present invention, a method for pre-processing the surface microscopic defects of a rolled titanium alloy bipolar plate is provided. A DC regulated power supply is used for electrochemical polishing. The bipolar plate is connected to the positive pole of the power supply, and a flat titanium plate or graphite plate is connected to the negative pole of the power supply. The titanium alloy bipolar plate and the cathode plate are placed in an electrochemical polishing tank at the same time. During the electrochemical polishing process, the bipolar plate and the cathode plate are ensured to be in a facing position, and the distance between the anode and cathode is 30 mm to 50 mm to avoid direct contact.

[0036] The surface microscopic defects of rolled titanium alloy bipolar plates are significantly reduced, which can improve the overall performance of subsequent highly corrosion-resistant and conductive functional coatings. The electrochemical polishing solution of the present invention has simple composition and stable performance, making it suitable for large-scale production applications. The present invention offers advantages such as high efficiency, high precision, low labor intensity, low processing costs, and the absence of a work-hardened layer on the polished surface. It is also highly compatible with pre-vacuum coating cleaning processes.

[0037] In one embodiment of the present invention, the electrochemical polishing solution comprises the following components:

[0038] The H2SO4 concentration is 30g / L~60g / L, the HF concentration is 2g / L~10g / L, the methanol corrosion inhibitor concentration is 20g / L~40g / L, and the ultrasonic vibration power density is 0.5W / cm 2 ~2.0W / cm 2 .

[0039] In one embodiment of the present invention, the electrochemical polishing solution satisfies any of the following ratios:

[0040] H2SO4 concentration is 40g / L, HF concentration is 3g / L, and methanol corrosion inhibitor concentration is 20g / L;

[0041] The H2SO4 concentration is 60g / L, the HF concentration is 2g / L, and the methanol corrosion inhibitor concentration is 40g / L.

[0042] In one embodiment of the present invention, the distance between the anode and cathode is set to satisfy the relationship:

[0043] d=k×V

[0044] Where d is the inter-electrode distance, mm; V is the voltage, V; k is the adjustment coefficient, ranging from 0.8 to 1.2.

[0045] In one embodiment of the present invention, the ultrasonic vibration tank and the electrochemical polishing tank adopt a split nested structure, the medium in the ultrasonic vibration tank is water, and the medium in the electrochemical polishing tank is an acidic electrolyte.

[0046] In one embodiment of the present invention, the titanium alloy bipolar plate is made of TA1 alloy or TA2 alloy, and the depth of surface micro defects is reduced by ≥80% after ultrasonic vibration assisted electrochemical composite polishing.

[0047] In another embodiment of the present invention, a system for pre-processing the surface micro-defects of a rolled titanium alloy bipolar plate is provided. The system is based on any one of the above methods for pre-processing the surface micro-defects of a rolled titanium alloy bipolar plate, and includes: an ultrasonic degreasing module, a composite polishing module, and a post-processing module.

[0048] The ultrasonic degreasing module is used for ultrasonic degreasing and cleaning. The rolled titanium alloy bipolar plates with a thickness of 0.1 mm to 0.15 mm are sequentially placed in an industrial degreasing agent for ultrasonic cleaning for 10 to 30 minutes, and then ultrasonically rinsed in distilled water for 10 to 30 minutes.

[0049] The composite polishing module is used for ultrasonic vibration-assisted electrochemical composite polishing. The titanium alloy bipolar plate treated as above is used as the anode, and the graphite plate or titanium plate is used as the cathode. They are immersed in an electrochemical polishing solution containing H2SO4 and HF, and ultrasonic vibration with a frequency of 20kHz to 40kHz is applied at the same time. The treatment is carried out for 5s to 60s under the conditions of a cathode-anode distance of 30mm to 50mm, a voltage of 30V to 60V, and a polishing solution temperature of 10°C to 25°C.

[0050] The post-processing module is used to ultrasonically rinse the polished bipolar plate with distilled water for 10 minutes to 30 minutes, and then vacuum dry it at 60° C. to 100° C. for 30 minutes to 60 minutes.

[0051] In another embodiment of the present invention, a titanium metal bipolar plate for a hydrogen fuel cell is provided. The bipolar plate is produced by a method for pre-treating the surface micro-defects of a rolled titanium alloy bipolar plate as described in any one of the above items, and has no work-hardening layer on its surface and a coating bonding strength ≥18 MPa.

[0052] Example 1

[0053] (1) Place the TA2 titanium bipolar plate with an original thickness of 0.1 mm in an ultrasonic degreasing cleaning device. First, use LT-T4030 industrial degreasing agent for ultrasonic degreasing cleaning for 10 minutes, and then use distilled water for ultrasonic rinsing for 10 minutes to ensure that the surface of the titanium alloy bipolar plate is clean and free of oil stains that may affect the next process.

[0054] (2) Prepare electrochemical polishing solution. The solution composition is H2SO4 30g / L + HF 5g / L + methanol 20g / L. According to the solute concentration of the mother liquor used, the solution volume is converted to the corresponding solution volume, added to a certain amount of distilled water, stirred and mixed evenly, and then injected into the electrochemical polishing tank.

[0055] (3) Connect the TA2 titanium bipolar plate to the positive pole of the DC power supply and the graphite cathode plate to the negative pole of the power supply. The cathode plate and the titanium bipolar plate are in a facing position, with a distance of 30 mm between the cathode and the anode. Completely immerse the bipolar plate in the polishing solution. Turn on the ultrasonic generator and connect the electrochemical polishing power supply. Adjust the power supply voltage to 50 V, the polishing solution temperature to 25°C, and the polishing time to 30 seconds.

[0056] (4) After polishing, the TA2 titanium bipolar plate is placed in a distilled water tank for ultrasonic rinsing for 10 minutes. After rinsing, it is placed in a vacuum drying oven for drying for 60 minutes.

[0057] Example 2

[0058] (1) Place the TA2 titanium bipolar plate with an original thickness of 0.1 mm in an ultrasonic degreasing cleaning device. First, use LT-T4030 industrial degreasing agent for ultrasonic degreasing cleaning for 15 minutes, and then use distilled water for ultrasonic rinsing for 15 minutes to ensure that the surface of the titanium alloy bipolar plate is clean and free of oil stains that may affect the next process.

[0059] (2) Prepare electrochemical polishing solution. The solution composition is H2SO4 60g / L + HF 2g / L + methanol 40g / L. According to the solute concentration of the mother liquor used, the solution volume is converted to the corresponding solution volume, added to a certain amount of distilled water, stirred and mixed evenly, and then injected into the electrochemical polishing tank.

[0060] (3) Connect the TA2 titanium bipolar plate to the positive pole of the DC power supply and the graphite cathode plate to the negative pole of the power supply. The cathode plate and the titanium bipolar plate are in a facing position, with a distance of 50 mm between the cathode and the anode. Completely immerse the bipolar plate in the polishing solution. Turn on the ultrasonic generator and connect the electrochemical polishing power supply. Adjust the power supply voltage to 30 V, the polishing solution temperature to 25°C, and the polishing time to 20 seconds.

[0061] (4) After polishing, the TA2 titanium bipolar plate is placed in a distilled water tank for ultrasonic rinsing for 15 minutes. After rinsing, it is placed in a vacuum drying oven for drying for 60 minutes.

[0062] Example 3

[0063] (1) Place the TA1 titanium bipolar plate with an original thickness of 0.15 mm in an ultrasonic degreasing cleaning device. First, use LT-T4030 industrial degreasing agent for ultrasonic degreasing cleaning for 15 minutes, and then use distilled water for ultrasonic rinsing for 15 minutes to ensure that the surface of the titanium alloy bipolar plate is clean and free of oil stains that may affect the next process.

[0064] (2) Prepare electrochemical polishing solution. The solution composition is H2SO4 40g / L + HF 3g / L + methanol 20g / L. According to the solute concentration of the mother liquor used, the solution volume is converted to the corresponding solution volume, added to a certain amount of distilled water, stirred and mixed evenly, and then injected into the electrochemical polishing tank.

[0065] (3) Connect the TA1 titanium bipolar plate to the positive pole of the DC power supply and the graphite cathode plate to the negative pole of the power supply. The cathode plate and the titanium bipolar plate are in a facing position, with a distance of 40 mm between the cathode and the anode. Completely immerse the bipolar plate in the polishing solution. Turn on the ultrasonic generator and connect the electrochemical polishing power supply. Adjust the power supply voltage to 60 V, the polishing solution temperature to 25°C, and the polishing time to 20 seconds.

[0066] (4) After polishing, the TA1 titanium bipolar plate was placed in a distilled water tank for ultrasonic rinsing for 15 minutes. After rinsing, it was placed in a vacuum drying oven for drying for 45 minutes.

[0067] An embodiment of the present invention provides a method, system, and bipolar plate for pretreating surface micro defects of a titanium alloy bipolar plate. The method comprises the following steps: ultrasonic degreasing and cleaning are performed, and a rolled titanium alloy bipolar plate with a thickness of 0.1 mm to 0.15 mm is sequentially placed in an industrial degreasing agent for ultrasonic cleaning for 10 to 30 minutes, and then ultrasonically rinsed in distilled water for 10 to 30 minutes; ultrasonic vibration-assisted electrochemical composite polishing is performed, and the titanium alloy bipolar plate treated as the anode and a graphite plate or a titanium plate as the cathode are immersed in an electrochemical polishing solution containing H2SO4 and HF, and ultrasonic vibration with a frequency of 20 kHz to 40 kHz is applied simultaneously. The process is performed for 5 to 60 seconds under the conditions of a cathode-anode distance of 30 mm to 50 mm, a voltage of 30 V to 60 V, and a polishing solution temperature of 10°C to 25°C; the polished bipolar plate is ultrasonically rinsed with distilled water for 10 to 30 minutes, and then vacuum dried at 60°C to 100°C for 30 to 60 minutes.

[0068] The technical solution of the present invention, through ultrasonic vibration-assisted electrochemical polishing, can quickly eliminate or weaken the microscopic defects on the surface of the titanium metal bipolar plate, obtain a titanium alloy bipolar plate surface with a smoother surface and fewer microscopic defects, and improve the comprehensive performance of the subsequent high-corrosion-resistant conductive functional coating.

[0069] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for pretreating microscopic defects on the surface of titanium alloy bipolar plates, characterized in that: The method comprises: S101, ultrasonic degreasing and cleaning, placing the rolled titanium alloy bipolar plates with a thickness of 0.1 mm to 0.15 mm in an industrial degreasing agent for ultrasonic cleaning for 10 min to 30 min, and then ultrasonic rinsing in distilled water for 10 min to 30 min; S102, ultrasonic vibration-assisted electrochemical composite polishing, using the titanium alloy bipolar plate treated as the anode and the graphite plate or titanium plate as the cathode, immersed in an electrochemical polishing solution containing H2SO4 and HF, while applying ultrasonic vibration at a frequency of 20kHz to 40kHz, and treating for 5s to 60s under the conditions of a cathode-cathode distance of 30mm to 50mm, a voltage of 30V to 60V, and a polishing solution temperature of 10°C to 25°C; S103, ultrasonically rinsing the polished bipolar plate with distilled water for 10 minutes to 30 minutes, and then vacuum drying it at 60° C. to 100° C. for 30 minutes to 60 minutes.

2. The method for pretreating surface micro defects of a titanium alloy bipolar plate according to claim 1, characterized in that: The electrochemical polishing solution comprises the following components: The H2SO4 concentration is 30g / L~60g / L, the HF concentration is 2g / L~10g / L, the methanol corrosion inhibitor concentration is 20g / L~40g / L, and the ultrasonic vibration power density is 0.5W / cm 2 ~2.0W / cm 2 .

3. The method for pretreating surface micro defects of a titanium alloy bipolar plate according to claim 2, characterized in that: The electrochemical polishing solution satisfies any of the following ratios: H2SO4 concentration is 40g / L, HF concentration is 3g / L, and methanol corrosion inhibitor concentration is 20g / L; The H2SO4 concentration is 60g / L, the HF concentration is 2g / L, and the methanol corrosion inhibitor concentration is 40g / L.

4. The method for pretreating surface micro defects of a titanium alloy bipolar plate according to claim 1, characterized in that: The distance between the anode and cathode is set to satisfy the relationship: d=k×V Where d is the inter-electrode distance, mm; V is the voltage, V; k is the adjustment coefficient, ranging from 0.8 to 1.

2.

5. The method for pretreating surface micro defects of a titanium alloy bipolar plate according to claim 4, characterized in that: The ultrasonic vibration tank and the electrochemical polishing tank adopt a split nested structure. The medium in the ultrasonic vibration tank is water, and the medium in the electrochemical polishing tank is an acidic electrolyte.

6. The method for pretreating surface micro defects of a titanium alloy bipolar plate according to claim 1, characterized in that: The titanium alloy bipolar plate is made of TA1 alloy or TA2 alloy, and the depth of surface microscopic defects is reduced by ≥80% after ultrasonic vibration-assisted electrochemical composite polishing.

7. A system for pretreating microscopic defects on the surface of a titanium alloy bipolar plate, based on a method for pretreating microscopic defects on the surface of a titanium alloy bipolar plate according to any one of claims 1 to 6, characterized in that: The system includes: an ultrasonic degreasing module, a composite polishing module and a post-processing module; The ultrasonic degreasing module is used for ultrasonic degreasing and cleaning. The rolled titanium alloy bipolar plates with a thickness of 0.1 mm to 0.15 mm are sequentially placed in an industrial degreasing agent for ultrasonic cleaning for 10 to 30 minutes, and then ultrasonically rinsed in distilled water for 10 to 30 minutes. The composite polishing module is used for ultrasonic vibration-assisted electrochemical composite polishing. The titanium alloy bipolar plate treated as above is used as the anode, and the graphite plate or titanium plate is used as the cathode. They are immersed in an electrochemical polishing solution containing H2SO4 and HF, and ultrasonic vibration with a frequency of 20kHz to 40kHz is applied at the same time. The treatment is carried out for 5s to 60s under the conditions of a cathode-anode distance of 30mm to 50mm, a voltage of 30V to 60V, and a polishing solution temperature of 10°C to 25°C. The post-processing module is used to ultrasonically rinse the polished bipolar plate with distilled water for 10 minutes to 30 minutes, and then vacuum dry it at 60° C. to 100° C. for 30 minutes to 60 minutes.

8. A titanium bipolar plate for a hydrogen fuel cell, characterized in that: The bipolar plate is produced by the pretreatment method for surface micro defects of a titanium alloy bipolar plate according to any one of claims 1 to 6, has no work hardening layer on its surface and has a coating bonding strength of ≥18 MPa.

Images