Treatment equipment for effectively eliminating surface defects of metal bipolar plate

Abstract

The utility model provides processing equipment for effectively eliminating surface defects of a metal bipolar plate, which comprises a fixing frame and a cleaning device, the fixing frame is used for fixing and clamping the metal bipolar plate to be processed, and the cleaning device comprises an ultrasonic cleaning tank, a rinsing tank, a polishing tank and a drying tank which can be placed in the fixing frame. And carrying out ultrasonic cleaning, rinsing, polishing and drying treatment on the metal bipolar plate. The treatment equipment for effectively eliminating the surface defects of the metal bipolar plate can improve the quality of a subsequent coating process, so that the corrosion resistance of the bipolar plate is improved, and the service life of the bipolar plate is prolonged. The polishing device is suitable for workpieces with flow channels and complex shapes, and a non-mechanical contact method is adopted for polishing; different from traditional electrochemical and chemical polishing, the surface defect of the material can be effectively removed, and no new corrosion spot is introduced. The polishing treatment speed is high, neutral polishing liquid is adopted, the process is environmentally friendly, and the method is suitable for large-scale industrial production.

Description

Technical Field

[0001] The utility model relates to a fuel cell processing device, in particular to a processing device which can effectively eliminate surface defects of a metal bipolar plate. Background Art

[0002] With the development of fuel cells, application scenarios have put forward clear life and cost requirements for them. As one of the important technical routes, the metal bipolar plate stack has gradually occupied an increasing market share due to its high power density and large-scale production process that adapts to the modern industrial system. Since metal plate materials are easily corroded in the electrochemical environment of fuel cells, life is an important factor restricting its development. In order to solve the above problems, a conductive and corrosion-resistant coating is generally deposited on the surface of the metal bipolar, and the thickness of this coating is generally 50-500nm.

[0003] The manufacture of metal plates includes processes such as stamping, welding, and cleaning. In these processes, especially stamping, the friction between the mold and the surface of the metal plate material, as well as multiple forming processes, can easily cause surface cracking. Therefore, before the coating process, various defects such as scratches, cracks, and dark holes already exist on the surface of the metal plate, which greatly affect the growth of the corrosion-resistant layer. In order to eliminate the influence of surface defects on the film quality, cleaning, polishing and other methods are used to reduce or remove the defects. However, whether it is plasma cleaning or the addition of acid and alkali cleaning agents, it is difficult to eliminate micron-level damage and dark holes; mechanical polishing is difficult to handle complex workpieces with flow channels, and it is easy to introduce new scratches, while chemical polishing or traditional electrochemical polishing has problems such as being difficult to control and causing corrosion pits or corrosion points. Therefore, it is difficult for existing surface treatment methods to obtain a smooth and defect-free material surface. Utility Model Content

[0004] The utility model provides a processing device for effectively eliminating surface defects of metal bipolar plates, solving the problem of ultrasonic cleaning and surface polishing of metal bipolar plates. The technical solution is as follows:

[0005] A processing device for effectively eliminating surface defects of metal bipolar plates comprises a fixing frame and a cleaning device. The fixing frame is used to fix and clamp the metal bipolar plate to be processed. The cleaning device comprises an ultrasonic cleaning tank, a rinsing tank, a polishing tank and a drying tank, all of which can be placed in the fixing frame to perform ultrasonic cleaning, rinsing, polishing and drying on the metal bipolar plate.

[0006] The fixing frame includes a bipolar plate clamp and a bipolar plate bracket. The bottom of the metal bipolar plate to be processed is placed in the compartment of the bipolar plate bracket, and the top of the metal bipolar plate is inserted into the groove in the middle of the convex part of the bipolar plate clamp. A through hole is provided on the side of the groove for inserting a conductive bolt in contact with the metal bipolar plate.

[0007] The cleaning device comprises an ultrasonic cleaning tank, a first rinsing tank, a second rinsing tank, a polishing tank, a third rinsing tank, a fourth rinsing tank and a drying tank which are connected in sequence. The ultrasonic cleaning tank and the rinsing tank are both provided with a heating device and an ultrasonic vibrator.

[0008] The third rinsing tank and the fourth rinsing tank may not be provided with a heating device.

[0009] The polishing tank includes a tank body, a high-voltage pulse power supply and a stirring paddle. The tank body is grounded and electrically insulated from other parts of the cleaning device. The high-voltage pulse power supply is used to provide 0-500V pulse high voltage. A stirring paddle is installed at the bottom of the tank body. The tank body is provided with a mesh partition on the upper part of the stirring paddle for placing a bipolar plate bracket.

[0010] A liquid storage tank is arranged at the rear of the polishing tank, and the liquid storage tank is provided with a water pump and a radiator. The liquid storage tank draws the polishing liquid in the liquid storage tank into the polishing tank through a first pipeline, and the polishing liquid flows into the liquid storage tank from the bottom of the polishing tank through a unidirectional second pipeline.

[0011] The first pipeline is provided with a first one-way valve and a water pump, the second pipeline is provided with a second one-way valve, and a radiator is installed inside the side wall of the liquid storage tank for air cooling and heat dissipation of the polishing liquid.

[0012] The rinsing liquid of the first rinsing tank is industrial tap water, the rinsing liquids of the second rinsing tank and the fourth rinsing tank are deionized water, and the rinsing liquid of the third rinsing tank is clean water.

[0013] The ultrasonic cleaning frequency of the ultrasonic cleaning tank is 25-40kHz, and the heating temperature is 50-60°C.

[0014] The body of the ultrasonic cleaning tank is made of 304 or 316L stainless steel, and the body of the rinsing tank is made of 304 stainless steel.

[0015] The processing equipment for effectively eliminating surface defects of metal bipolar plates can improve the quality of subsequent coating processes, thereby improving the corrosion resistance of bipolar plates and extending their service life. The utility model is suitable for complex-shaped workpieces with flow channels, and is polished by a non-mechanical contact method; unlike traditional electrochemical and chemical polishing, it can effectively remove material surface defects and will not introduce new corrosion points. The polishing process has a high rate, uses a neutral polishing liquid, and is environmentally friendly, and is suitable for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic diagram of the support structure of the processing equipment for effectively eliminating surface defects of metal bipolar plates;

[0017] Figure 2It is a schematic diagram of the structure of the cleaning device of the processing equipment for effectively eliminating the surface defects of the metal bipolar plate;

[0018] Figure 3 It is a structural schematic diagram of the polishing groove. DETAILED DESCRIPTION

[0019] The processing equipment for effectively eliminating surface defects of metal bipolar plates includes a fixing frame and a cleaning device. The fixing frame is used to fix and clamp the metal bipolar plate to be processed. The cleaning device includes an ultrasonic cleaning tank, a rinsing tank, a polishing tank and a drying tank, all of which can be placed in the fixing frame to perform ultrasonic cleaning, rinsing, polishing and drying treatments on the metal bipolar plate.

[0020] like Figure 1 As shown, the fixing frame includes a bipolar plate fixture 101 and a bipolar plate support 103. The bottom of the metal bipolar plate 102 to be processed is placed on the bipolar plate support 103. The bipolar plate support 103 includes a plurality of partitions, and compartments are formed between adjacent partitions. Multiple compartments are realized by the partitions, and each compartment is used to place a metal bipolar plate. The upper end of the metal bipolar plate is fixed to the bipolar plate fixture 101 by a conductive bolt 104. The bipolar plate fixture 101 is provided with a plurality of protrusions, and a groove is provided in the middle of each protrusion. The groove is used to insert the top of the metal bipolar plate 102. The side of the protrusion is provided with a through hole for inserting the conductive bolt 104. The conductive bolt 104 is in contact with the metal bipolar plate 102 and is used to connect to a high-voltage power supply during polishing.

[0021] like Figure 2 As shown, the cleaning device includes an ultrasonic cleaning tank, a rinsing tank, a polishing tank and a drying tank, each of which is provided with a group, and the rinsing tank is provided with four groups, which include, from left to right, an ultrasonic cleaning tank 1, a first rinsing tank 2, a second rinsing tank 3, a polishing tank 4, a third rinsing tank 5, a fourth rinsing tank 6, and a drying tank 7. The ultrasonic cleaning tank and the rinsing tank are both provided with a heating device and an ultrasonic vibrator 9, and the heating device uses a heating rod 8, which is an electric heating device.

[0022] The ultrasonic cleaning tank 1 is provided with a heating rod 8 at the bottom, which is physically isolated from the bipolar plate support by a partition. The heating rod 8 is used to heat the cleaning agent aqueous solution. The tank body of the ultrasonic cleaning tank 1 is made of 304 or 316L stainless steel, which is resistant to corrosion by weak acid or weak alkaline cleaning agents. When the ultrasonic cleaning tank 1 is working, a group of metal bipolar plates to be treated are placed vertically on the bipolar plate support 103 without using the bipolar plate fixture 101. The bipolar plate support 103 and the metal bipolar plate 102 are placed together in the ultrasonic cleaning tank 1, and the liquid level of the cleaning liquid in the tank is above the metal plate. The concentration and type of the cleaning agent need to be determined according to the oil and impurities remaining in the metal plate manufacturing process. Usually, a neutral stainless steel degreasing cleaning agent can be selected, followed by a weak alkaline cleaning agent. The ultrasonic cleaning frequency is 25-40kHz, the heating temperature is maintained at 50-60°C, and the ultrasonic cleaning time is 5-10min.

[0023] When the first rinsing tank 2 and the second rinsing tank 3 are working, after the ultrasonic cleaning is completed, the bipolar plate support 103 and the metal bipolar plate 102 are transferred to the first rinsing tank 2 together. The first rinsing tank 2 can use industrial tap water, and the ultrasonic frequency and heating temperature can be consistent with the ultrasonic cleaning steps, and the ultrasonic time is 5 minutes. After the first rinsing tank 2 is completed, the bipolar plate support 103 and the metal bipolar plate 102 are transferred to the second rinsing tank 3, and the rinsing liquid is deionized water. Other conditions are consistent with the first rinsing tank 2.

[0024] When the polishing tank 4 is working, after the second rinsing tank 3 is rinsed, the bipolar plate holder 103 and the metal bipolar plate 102 are taken out from the second rinsing tank 3, and after the water is drained, the bipolar plate fixture 101 is fixed on the metal bipolar plate 102. Figure 1 As shown. The surfaces of the bipolar plate fixture 101 and the conductive bolt 104 are treated with rust prevention or insulation, except for a small amount of exposed conductive surface in contact with the metal bipolar plate 102. The metal bipolar plate 102 is immersed in the polishing liquid in the polishing tank 4, leaving only the upper part of the bipolar plate fixture 101 unimmersed. The polishing liquid is selected to have a concentration of 4% ammonium sulfate aqueous solution, the high-voltage power supply selects a constant voltage working mode, the positive electrode is connected to the metal bipolar plate to be treated, and the negative electrode is a stainless steel plate of the same material. The polishing conditions can be preferentially selected as: voltage 300V, frequency 2.5kHz, pulse width 0.2ms. The polishing time lasts for 2min.

[0025] When the third rinsing tank 5 and the fourth rinsing tank 6 are working, after the polishing process is completed, the bipolar plate fixture 101 is removed, the bipolar plate bracket 103 and the metal bipolar plate 102 are transferred to the rinsing tank 3, and ultrasonically rinsed with clean water for 5 minutes, and then the last rinsing process is carried out in the fourth rinsing tank 6 with deionized water.

[0026] The first rinsing tank 2 and the second rinsing tank 3 are provided with a heating device at the bottom to heat tap water or deionized water. The third rinsing tank 5 and the fourth rinsing tank 6 are used to rinse and remove the residual polishing liquid on the surface of the bipolar plate after polishing, and no heating device is required at the bottom. The rinsing tank body is made of 304 stainless steel, and the metal bipolar plate is placed on the bipolar plate holder. When transferring, the bipolar plate holder is transferred together with the metal bipolar plate.

[0027] When the drying tank 7 is working, after the fourth rinsing tank 6 is completed, the metal bipolar plate 102 is dried in the drying tank 7 at a temperature of 70-80°C until there is no obvious water droplets on the surface. The surface of the metal bipolar plate polished by the above surface treatment method is clean and bright, and the surface defects are effectively removed, and it can be directly used for coating treatment.

[0028] like Figure 3 As shown, the polishing tank includes a tank body, a high-voltage pulse power supply 10 and a stirring paddle 11. The tank body is used for electrochemically polishing the surface of the bipolar plate. Since it is connected to the high-voltage pulse power supply 10 during operation, the tank body is grounded and electrically insulated from other parts of the equipment. The high-voltage pulse power supply can provide 0-500V pulse high voltage, with adjustable frequency and pulse width, and has corresponding safety protection functions such as overvoltage, short circuit, open circuit, overcurrent, etc. A stirring paddle 11 is installed at the bottom of the polishing tank to make the temperature and concentration of the polishing liquid uniform. A mesh partition is arranged on the upper part of the stirring paddle, and the bipolar plate bracket 103 can be placed on the partition.

[0029] There is a liquid reservoir 15 at the rear of the polishing tank, which contains the same amount of polishing liquid as the polishing tank. The liquid reservoir 15 is provided with a water pump 12 and a radiator 16. The polishing liquid in the liquid reservoir 15 is extracted into the polishing tank through a first pipeline provided with a water pump 12. A one-way second pipeline is provided at the bottom of the polishing tank. The polishing liquid flows into the liquid reservoir 15 from the bottom. The temperature of the reaction zone is reduced by the circulation of the polishing liquid, heat is taken away, and fresh polishing liquid is replenished in time. A radiator 16 is installed inside the side wall of the liquid reservoir 15 to cool the polishing liquid with air. The first pipeline is provided with a first one-way valve 14, and the second pipeline is provided with a second one-way valve 13 to achieve one-way flow of the polishing liquid.

[0030] In a certain embodiment of the present invention, the formed or welded metal bipolar plates 102 are fixed in batches on the bipolar plate fixture 101, the plane of the metal bipolar plates 102 is perpendicular to the bottom of the cleaning device tank, the bipolar plates are arranged in parallel, and maintain good electrical contact with the bipolar plate fixture 101.

[0031] The workpiece 100 with the metal bipolar plate 102 is placed in an ultrasonic cleaning tank 1, and ultrasound of a certain power and frequency is applied. The cleaning liquid in the tank is composed of clean water with a certain proportion of neutral degreasing cleaning agent, and the cleaning liquid is heated by a heating device to maintain a temperature of 50-65°C, preferably, the temperature is selected between 55-60°C. After the cleaning is completed, the tooling is taken out and dried for several minutes.

[0032] The workpiece 100 after ultrasonic cleaning is placed in the first rinsing tank 2 and the second rinsing tank 3 respectively, rinsed with clean tap water and deionized water for several minutes respectively, and the workpiece is taken out and drained.

[0033] Place the dried workpiece 100 in the polishing tank 4, and the polishing liquid level exceeds the top of the metal plate. The polishing liquid is composed of a 0.1%-10% ammonium sulfate aqueous solution, and preferably, the ammonium sulfate concentration is selected to be between 2% and 4%. Turn on the high-voltage pulse power supply, the positive electrode is connected to the metal bipolar plate 102, and the negative electrode is connected to the stainless steel plate of the same material. Use constant voltage mode, the voltage is selected between 200-400V, preferably, the voltage value is selected between 280-300V. Set the high-voltage pulse frequency value between 1.0-2.5kHz, the pulse width is 0.1-1ms, and preferably between 0.15-0.2ms.

[0034] The surface polishing process is characterized in that, under the applied voltage condition, a large number of steam bubbles are generated on the metal plate, the anode is continuously wrapped by bubbles to form a foam layer, the oxygen plasma generated by ionization reacts with the matrix metal ions to generate an oxidized layer, and then a uniform glow discharge is formed in the isolation foam layer. When glow discharge occurs, it means that the polishing reaction is proceeding stably, and the rough protrusions and cracks on the surface of the metal plate are gradually eliminated and dissolved under the action of the microjet pressure generated by plasma discharge and bubble collapse. The above-mentioned polishing process lasts for 2-20 minutes, and the duration is related to the roughness of the metal plate surface. The greater the roughness, the longer the duration. After the polishing process is completed, the metal plate workpiece is taken out and placed in the third rinse tank 5 and the fourth rinse tank 6 respectively, and rinsed with clean water and deionized water; the workpiece is taken out and placed in a drying tank for drying.

[0035] The processing equipment for effectively eliminating surface defects of metal bipolar plates can improve the quality of subsequent coating processes, thereby improving the corrosion resistance of bipolar plates and extending their service life. The utility model is suitable for complex-shaped workpieces with flow channels, and is polished by a non-mechanical contact method; unlike traditional electrochemical and chemical polishing, it can effectively remove material surface defects and will not introduce new corrosion points. The polishing process has a high rate, uses a neutral polishing liquid, and is environmentally friendly, and is suitable for large-scale industrial production.

Claims

1. A treatment device for effectively eliminating surface defects of metal bipolar plates, characterized in that: It includes a fixing frame and a cleaning device. The fixing frame is used to fix and clamp the metal bipolar plate to be processed. The cleaning device includes an ultrasonic cleaning tank, a rinsing tank, a polishing tank and a drying tank, all of which can be placed in the fixing frame to perform ultrasonic cleaning, rinsing, polishing and drying on the metal bipolar plate.

2. The processing equipment for effectively eliminating surface defects of metal bipolar plates according to claim 1, characterized in that: The fixing frame includes a bipolar plate clamp and a bipolar plate bracket. The bottom of the metal bipolar plate to be processed is placed in the compartment of the bipolar plate bracket, and the top of the metal bipolar plate is inserted into the groove in the middle of the convex part of the bipolar plate clamp. A through hole is provided on the side of the groove for inserting a conductive bolt in contact with the metal bipolar plate.

3. The processing equipment for effectively eliminating surface defects of metal bipolar plates according to claim 1, characterized in that: The cleaning device comprises an ultrasonic cleaning tank, a first rinsing tank, a second rinsing tank, a polishing tank, a third rinsing tank, a fourth rinsing tank and a drying tank which are connected in sequence. The ultrasonic cleaning tank and the rinsing tank are both provided with a heating device and an ultrasonic vibrator.

4. The processing equipment for effectively eliminating surface defects of metal bipolar plates according to claim 3 is characterized in that: The third rinsing tank and the fourth rinsing tank are not provided with a heating device.

5. The processing equipment for effectively eliminating surface defects of metal bipolar plates according to claim 1, characterized in that: The polishing tank includes a tank body, a high-voltage pulse power supply and a stirring paddle. The tank body is grounded. The high-voltage pulse power supply is used to provide 0-500 V pulse high voltage. A stirring paddle is installed at the bottom of the tank body. The tank body is provided with a mesh partition on the upper part of the stirring paddle for placing a bipolar plate bracket.

6. The processing equipment for effectively eliminating surface defects of metal bipolar plates according to claim 1, characterized in that: A liquid storage tank is arranged at the rear of the polishing tank, and the liquid storage tank is provided with a water pump and a radiator. The liquid storage tank draws the polishing liquid in the liquid storage tank into the polishing tank through a first pipeline, and the polishing liquid flows into the liquid storage tank from the bottom of the polishing tank through a unidirectional second pipeline.

7. The processing equipment for effectively eliminating surface defects of metal bipolar plates according to claim 6, characterized in that: The first pipeline is provided with a first one-way valve and a water pump, the second pipeline is provided with a second one-way valve, and a radiator is installed inside the side wall of the liquid storage tank for air cooling and heat dissipation of the polishing liquid.

8. The processing equipment for effectively eliminating surface defects of metal bipolar plates according to claim 3 is characterized in that: The rinsing liquid of the first rinsing tank is industrial tap water, the rinsing liquids of the second rinsing tank and the fourth rinsing tank are deionized water, and the rinsing liquid of the third rinsing tank is clean water.

9. The processing equipment for effectively eliminating surface defects of metal bipolar plates according to claim 1, characterized in that: The ultrasonic cleaning frequency of the ultrasonic cleaning tank is 25-40 kHz, and the heating temperature is 50-60°C.

10. The processing equipment for effectively eliminating surface defects of metal bipolar plates according to claim 1, characterized in that: The body of the ultrasonic cleaning tank is made of 304 or 316L stainless steel, and the body of the rinsing tank is made of 304 stainless steel.

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