Traceless detection device and method for coating cracks of metal bipolar plate

Abstract

The invention provides a traceless detection device and method for coating cracks of a metal bipolar plate, the traceless detection device comprises an electrolyte box, the metal bipolar plate, a platinum sheet electrode, a temperature control element, an electrochemical workstation and a control terminal, electrolyte is injected into the electrolyte box, the platinum sheet electrode is fixed in the electrolyte box, the metal bipolar plate is fixed in the electrolyte box through a positioning piece, and the temperature control element is fixed in the electrochemical workstation. The platinum sheet electrode and the metal bipolar plate are immersed in the electrolyte, the top ends of the platinum sheet electrode and the metal bipolar plate extend out of a top cover of the electrolyte tank through an electrode clamp to be connected with the electrochemical workstation, the temperature control element is arranged at the bottom of the electrolyte tank, and the control terminal is electrically connected with the temperature control element and the electrochemical workstation. According to the invention, the metal bipolar plate with crack defects on the surface of the coating is detected by using the current density difference between the crack part and the crack-free part, and the crack condition on the surface of the coating of the bipolar plate can be rapidly detected.

Description

Technical Field

[0001] The present invention belongs to the technical field of nondestructive detection of cracks in metal bipolar plate coatings of fuel cells, and in particular relates to a traceless detection device and method for cracks in metal bipolar plate coatings. Background Art

[0002] The corrosion problem of metal bipolar plates has attracted more and more attention from researchers. Many studies have shown that metal bipolar plates hope to solve the corrosion problem through coating, but once cracks appear in the coating, corrosive solution ions will enter, and corrosion is very likely to occur in the working environment of the fuel cell.

[0003] Currently, the main research methods for coating cracks are optical microscopes, scanning electron microscopes, X-ray detection, ultrasonic detection, etc. Optical microscopes and scanning electron microscopes can be used to directly observe cracks and other defects on the coating surface. These technologies are intuitive and effective, but may not be able to detect micron-level or internal cracks; X-ray detection and ultrasonic detection methods are highly accurate and can detect crack information inside metal bipolar plates, but the detection equipment is expensive, the operation requirements are relatively high, and small cracks are difficult to detect.

[0004] These detection methods have their own advantages and disadvantages, and have many limitations. Therefore, there is an urgent need to develop new simple and feasible test methods and systems to detect defects on the surface of metal bipolar plate coatings. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a traceless detection method for cracks in the coating of metal bipolar plates in response to the above-mentioned problems, which uses the difference in current density between cracked and non-cracked areas to detect metal bipolar plates with crack defects on the coating surface.

[0006] The embodiment of the present application is implemented as follows: An embodiment of the present application provides a traceless detection device for cracks in a metal bipolar plate coating, which is characterized in that it includes an electrolyte tank, a metal bipolar plate, a platinum electrode, a temperature control element, an electrochemical workstation, and a control terminal. Electrolyte is injected into the electrolyte tank, the platinum electrode is fixed in the electrolyte tank, the metal bipolar plate is fixed in the electrolyte tank by a positioning piece, the platinum electrode and the metal bipolar plate are immersed in the electrolyte, and the top end extends out of the top cover of the electrolyte tank through an electrode clamp and is connected to the electrochemical workstation. The temperature control element is arranged at the bottom of the electrolyte tank, and the control terminal is electrically connected to the temperature control element and the electrochemical workstation.

[0007] In some optional embodiments, the temperature control element includes an electric heating wire and a thermocouple, the electric heating wire heats the electrolyte, and the thermocouple monitors the electrolyte temperature and transmits it to the control terminal.

[0008] In some optional embodiments, the positioning member is a positioning slot, both ends of the positioning slot are fixed to the inner wall of the electrolyte tank, and the bottom end of the metal bipolar plate is snapped into the positioning slot.

[0009] In some optional embodiments, the positioning slot is made of insulating material.

[0010] In some optional embodiments, the electrolyte is a NaCl solution.

[0011] A method for detecting cracks in a metal bipolar plate coating by a traceless detection device is characterized by comprising the following steps: Step a: add electrolyte to the electrolyte tank up to the baseline, insert an intact metal bipolar plate into the positioning slot so that the metal bipolar plate is completely immersed in the electrolyte, connect an external power supply to the electrode clamp at the top of the intact metal bipolar plate, set a constant voltage, and heat the electrolyte to an appropriate temperature using a temperature control element. Terminate the terminal to collect and record the current-time curve in real time, which is recorded as a standard comparison sample. Step b: insert the metal bipolar plate to be tested into the positioning card slot, connect the detection device, set the constant voltage and temperature, and collect and record the current-time curve in real time, which is recorded as the sample to be tested; Step c, comparing the data of the sample to be tested with the data of the standard reference sample. If the data matches the data of the standard reference sample, it is a "qualified sample"; if the data does not match the data of the standard reference sample, it is a "failed sample"; Step d: evaluating the surface crack condition of the sample coating according to the current data change curve obtained by detection and the sample surface morphology.

[0012] In some optional embodiments, the constant voltage in step a is 0.6-0.8V, and the suitable temperature is 60-80°C.

[0013] In some optional embodiments, a corrosion inhibitor is added to the electrolyte described in step a.

[0014] The beneficial effects of the present application are: 1. The present application provides a traceless detection method for cracks in the coating of a metal bipolar plate, which realizes rapid and quantitative detection through the difference in current density at the crack in the electrolyte environment, facilitating the detection and screening of cracks that are invisible to the naked eye; 2. The use of a neutral electrolyte, rather than the acidic environment under conventional electrochemical testing, will not cause corrosion and damage to the metal bipolar plate. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] 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.

[0016] Figure 1 This is a schematic diagram of a traceless detection device in an embodiment of the present application; Figure 2 This is an IT test curve diagram at a potential of 0.8V in the embodiment of this application. DETAILED DESCRIPTION

[0017] 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.

[0018] 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.

[0019] It should be understood that the size of the serial numbers of the steps in the embodiment does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present application.

[0020] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0021] The features and performance of the present application are further described in detail below with reference to the embodiments.

[0022] like Figure 1As shown, the present invention provides a traceless detection device for cracks in a metal bipolar plate coating, comprising an electrolyte tank 1, a metal bipolar plate 2, a platinum electrode 3, a temperature control element 4, an electrochemical workstation 5 and a control terminal 6. Electrolyte is injected into the electrolyte tank, the platinum electrode is fixed in the electrolyte tank, the metal bipolar plate is fixed in the electrolyte tank by a positioning member 7, the platinum electrode and the metal bipolar plate are immersed in the electrolyte, and the top end extends out of the top cover of the electrolyte tank through an electrode clamp 8 and is connected to the electrochemical workstation. The temperature control element is arranged at the bottom of the electrolyte tank, and the control terminal is electrically connected to the temperature control element and the electrochemical workstation. The electrochemical workstation provides the working voltage of the fuel cell to the detection device by simulating the working potential of the fuel cell.

[0023] The temperature control element includes a heating wire 41 and a thermocouple 42. The heating wire heats the electrolyte to control the constant temperature of the electrolyte inside the tank. The thermocouple monitors the electrolyte temperature and transmits it to the control terminal so that the test temperature of the electrolyte can be adjusted as needed.

[0024] Furthermore, the positioning member is a positioning slot, with both ends fixed to the inner wall of the electrolyte tank. The bottom end of the metal bipolar plate snaps into the positioning slot, which is made of insulating material. Positioning slots of different sizes can be replaced to accommodate metal bipolar plates of different sizes, ensuring the universal applicability of the detection device.

[0025] Furthermore, the electrolyte is a NaCl solution, which is a neutral electrolyte. It is not an acidic environment under conventional electrochemical testing and will not cause corrosion and damage to the metal bipolar plates.

[0026] The experimental principle of the present invention is that the cracked metal bipolar plate substrate will be exposed, and a reaction will occur between the active elements of the substrate material and the inert electrode (platinum electrode). The increased conductivity and enhanced reaction activity caused by the reaction will make the current higher than that of the crack-free metal bipolar plate.

[0027] The detection method using the above-mentioned traceless detection device includes the following steps: 1. Add electrolyte to the electrolyte tank up to the baseline, insert the intact metal bipolar plate into the positioning slot so that the metal bipolar plate is completely immersed in the electrolyte, connect the external power supply to the electrode clamp on the top of the intact metal bipolar plate, set a constant voltage, and heat the electrolyte to the appropriate temperature through the temperature control element. Stop the terminal to collect and record the current-time curve in real time, and record it as a standard comparison sample.

[0028] 2. Insert the metal bipolar plate to be tested into the positioning card slot, connect the detection device, set the constant voltage and temperature, and collect and record the current-time curve in real time, which is recorded as the sample to be tested.

[0029] 3. Compare the data of the sample to be tested with the data of the standard reference sample. If it matches the data of the standard reference sample, it is a "qualified sample"; if it does not match the data of the standard reference sample, it is a "failed sample".

[0030] 4. Evaluate the surface crack condition of the sample coating based on the current data change curve obtained from the test and the sample surface morphology.

[0031] In some optional embodiments, the constant voltage is 0.6-0.8V and the suitable temperature is 60-80°C.

[0032] Example 1 1) First, add 0.1M NaCl solution to the electrolyte tank to the baseline, and add As a corrosion inhibitor, this not only provides an ion conductive pathway but also prevents the metal plate substrate from being corroded during the detection process; 2) Insert the intact metal bipolar plate into the positioning slot, turn on the power switch of the electrochemical workstation, set the constant voltage to 0.8V on the computer, set the temperature of the temperature control element to 80℃, wait for the temperature to rise to 80℃, and then start the test. Obtain the IT curve of the metal bipolar plate under the normal operating conditions of the simulated fuel cell and save it in the computer database as a standard comparison sample; 3) As in step 2), after connecting the detection device, set the constant voltage to 0.8V and the temperature to 80°C on the computer. After the temperature reaches 80°C, insert the metal bipolar plate to be tested into the positioning card slot, start the test, obtain the corresponding IT curve, and save it in the computer database; 4) Compare the test data of the sample obtained in step 3) with the data of the standard reference sample (see Figure 2 ), if it matches the standard comparison sample, it is a "qualified sample"; if it does not match the standard comparison sample, it is a "failed sample" and the system will alarm at the same time; 5) Based on the current difference between the sample to be tested and the standard reference sample, the crack depth and other information can be evaluated. The deeper the crack, the more exposed the substrate is, and the greater the current value will be.

[0033] The present invention can not only be used to detect surface cracks in metal bipolar plate coatings, but also to collect current signals from the metal bipolar plates and infer the extent of the cracks based on quantitative analysis of the current values. This has important scientific significance for the life evaluation of metal bipolar plate coatings under actual battery operating conditions, and provides theoretical guidance for the further development and application of metal bipolar plate coatings.

Claims

1. A traceless detection device for cracks in a metal bipolar plate coating, characterized in that: It includes an electrolyte tank, a metal bipolar plate, a platinum electrode, a temperature control element, an electrochemical workstation and a control terminal. The electrolyte tank is injected with electrolyte, the platinum electrode is fixed in the electrolyte tank, and the metal bipolar plate is fixed in the electrolyte tank through a positioning piece. The platinum electrode and the metal bipolar plate are immersed in the electrolyte, and the top end extends out of the top cover of the electrolyte tank through the electrode clamp and is connected to the electrochemical workstation. The temperature control element is arranged at the bottom of the electrolyte tank, and the control terminal is electrically connected to the temperature control element and the electrochemical workstation.

2. The traceless detection device for cracks in a metal bipolar plate coating according to claim 1, characterized in that: The temperature control element includes an electric heating wire and a thermocouple. The electric heating wire heats the electrolyte, and the thermocouple monitors the electrolyte temperature and transmits it to the control terminal.

3. A traceless detection device for cracks in a metal bipolar plate coating according to claim 1 or 2, characterized in that: The positioning member is a positioning slot, both ends of which are fixed on the inner wall of the electrolyte box, and the bottom end of the metal bipolar plate is snapped into the positioning slot.

4. The traceless detection device for cracks in a metal bipolar plate coating according to claim 3, characterized in that: The positioning slot is made of insulating material.

5. The traceless detection device for cracks in a metal bipolar plate coating according to claim 4, characterized in that: The electrolyte is NaCl solution.

6. A detection method using the traceless detection device for metal bipolar plate coating cracks according to claim 5, characterized in that: The steps include: Step a: add electrolyte to the electrolyte tank up to the baseline, insert an intact metal bipolar plate into the positioning slot so that the metal bipolar plate is completely immersed in the electrolyte, connect an external power supply to the electrode clamp at the top of the intact metal bipolar plate, set a constant voltage, and heat the electrolyte to an appropriate temperature using a temperature control element. Terminate the terminal to collect and record the current-time curve in real time, which is recorded as a standard comparison sample. Step b: insert the metal bipolar plate to be tested into the positioning card slot, connect the detection device, set the constant voltage and temperature, and collect and record the current-time curve in real time, which is recorded as the sample to be tested; Step c: compare the data of the sample to be tested with the data of the standard reference sample. If the data matches the standard reference sample, it is considered a "qualified sample"; If it does not match the standard comparison sample, it is considered a "failed sample"; Step d: evaluating the surface crack condition of the sample coating according to the current data change curve obtained by detection and the sample surface morphology.

7. The method for seamlessly detecting cracks in a metal bipolar plate coating according to claim 6, characterized in that: The constant voltage in step a is 0.6-0.8V, and the suitable temperature is 60-80°C.

8. The method for seamlessly detecting cracks in a metal bipolar plate coating according to claim 7, characterized in that: Add a corrosion inhibitor to the electrolyte described in step a.

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