Molten salt corrosion electrochemical testing system

Abstract

The utility model belongs to the field of molten salt corrosion, and particularly relates to a molten salt corrosion electrochemical testing system. The system comprises a crucible, an electrode system, a heating furnace and a gas control device, an insulating spacer is arranged at the bottom of an inner cavity of a furnace body of the heating furnace, and the crucible containing fused salt is placed on the insulating spacer of the inner cavity of the furnace body; an opening in the upper end of the furnace body is sealed through a flange, a gas inlet pipe and a gas outlet pipe are inserted into the flange, and an inlet in one end of the gas inlet pipe extends out of the furnace body and is connected with a gas control device. The electrode system is provided with a reference electrode, a working electrode and a counter electrode, the reference electrode is horizontally immersed in the fused salt and located in the center of the crucible, the working electrode is immersed in the fused salt and located at the circle center of the reference electrode, and the crucible serves as the counter electrode. According to the utility model, the problems of non-uniform power line distribution and non-uniform mass transfer on the surface of the electrode during the molten salt corrosion test can be solved, the stable control capability on key environmental parameters can be improved, and the test system has the advantages of high precision, good reproducibility and accurate regulation and control of the corrosion environment.

Description

Technical Field

[0001] This utility model belongs to the field of molten salt corrosion, specifically relating to an electrochemical testing system for molten salt corrosion. Background Technology

[0002] Electrochemical measurement of molten salt corrosion is an important method for studying the corrosion behavior of metallic materials in molten salt environments. It is primarily based on electrochemical principles, reflecting the corrosion status of metals in molten salt by measuring parameters such as electrode potential and current density. However, reliable measurement of molten salt corrosion electrochemistry is very difficult due to the challenges of high-temperature environments, the corrosiveness of molten salts, the complexity of molten salt composition, limitations in measurement techniques, and the difficulty of experimental operation. Therefore, developing a molten salt corrosion electrochemical testing system with low noise and precise environmental control has become one of the key aspects of molten salt corrosion research.

[0003] Chinese patent application CN 113237827 A discloses an electrochemical testing system for molten salt corrosion experiments. The working electrode, reference electrode, and counter electrode extend into the experimental crucible through electrode holes distributed on a furnace plug. The reference electrode is filamentous, and the counter electrode is filamentous, sheet-like, or rod-shaped. However, the relative positions of the electrodes in this invention cause severe uneven distribution of electric field lines between the counter electrode and the working electrode, and between the counter electrode and the reference electrode, thus affecting the accuracy of the electrochemical test results. Chinese patent application CN 221078413U discloses an electrochemical testing system for molten salt corrosion experiments, employing a three-electrode system placed parallel to each other, with a stirrer located on one side of the three-electrode system. This invention not only suffers from uneven distribution of electric field lines between the counter electrode and the working electrode, and between the counter electrode and the reference electrode, but also from differences in mass transfer on the electrode surface caused by uneven stirring, thus affecting the accuracy of the electrochemical test. Chinese patent application CN 112941567 A discloses an electrochemical method and apparatus for high-temperature molten salt electrolysis in a humid atmosphere, wherein the cathode (working electrode) is a metal oxide and the anode is a graphite crucible. Although this method can improve the uniformity of electric field distribution between electrodes, the invention is intended for electrochemical metallurgy and cannot be used to measure corrosion electrochemical signals.

[0004] To explore the molten salt corrosion behavior of materials under specific working conditions, the experimental testing system needs to be able to precisely control typical environmental parameters. Among these, minute differences in water and oxygen content can significantly affect the corrosion behavior of materials; therefore, precise control of water and oxygen content is crucial for the study of molten salt corrosion. Chinese patent application CN 103728353A proposes a sealed high-temperature electrochemical measuring device, where the gas inlet and outlet are sealed and integrated on the upper flange for the entry and exit of inert gas to reduce the residual water and oxygen content within the device. However, water and oxygen within the device cannot be completely removed by inert atmosphere alone. Chinese patent CN 205139075 U proposes an experimental device for molten salt electrochemical measurement, which first evacuates the heat-resistant steel crucible to a vacuum before introducing an inert atmosphere. While this method can further reduce the water and oxygen content in the device, even high-purity inert gas still contains trace amounts of water impurities, and this invention cannot remove the water impurities carried by the gas itself. Furthermore, because the saturated vapor pressure of high-temperature molten salts is generally high, the evaporated salt easily deposits at the outlet, blocking the airflow. In addition, even for flange sealing devices, trace amounts of gas leakage are still unavoidable, making it difficult for the equipment to achieve ultra-low water and oxygen content control. Utility Model Content

[0005] The purpose of this invention is to provide a molten salt corrosion electrochemical testing system with high precision, good reproducibility, and precise control of the corrosive environment, so as to carry out molten salt corrosion testing and research stably and reliably.

[0006] To achieve the above objectives, the technical solution of this utility model is as follows:

[0007] An electrochemical testing system for molten salt corrosion includes a crucible, an electrode system, a heating furnace, and a gas control device, with the following specific structure:

[0008] The bottom of the furnace body cavity of the heating furnace is equipped with an insulating gasket. The crucible containing molten salt is placed on the insulating gasket in the furnace body cavity. The crucible is made of graphite or inert metal. The opening at the top of the furnace body is sealed by a flange. An inlet pipe and an outlet pipe are inserted into the flange. One end of the inlet pipe extends out of the furnace body and is connected to the gas control device. The other end of the inlet pipe extends out to the middle and lower part of the furnace body cavity. One end of the outlet pipe extends to the upper part of the furnace body cavity, and the other end extends out of the furnace body cavity.

[0009] The electrode system includes a reference electrode, a working electrode, a counter electrode, an electrochemical workstation, and electrode leads. The reference electrode, working electrode, and counter electrode are connected to the electrochemical workstation outside the heating furnace via electrode leads. The reference electrode is ring-shaped, horizontally immersed in molten salt, and located in the center of the crucible. The working electrode is cylindrical, immersed in molten salt, and located at the center of the reference electrode. The crucible serves as the counter electrode, with its sidewall connected to the electrode leads. The electrode leads and contacts of the counter electrode are both above the surface of the molten salt.

[0010] The molten salt corrosion electrochemical testing system has two or more electrode leads connected to the upper edge of the side wall of the crucible, with each connection point symmetrically distributed along the upper edge of the side wall of the crucible.

[0011] The molten salt corrosion electrochemical testing system also has vertical insulating ceramic tubes inserted into the flange. Each insulating ceramic tube contains an electrode lead. One end of the insulating ceramic tube extends into the inner cavity of the furnace body, and the other end extends above the flange. The upper and lower open ends of the insulating ceramic tube are sealed with high-temperature resistant inorganic adhesive. The electrode leads of the working electrode, counter electrode, and reference electrode are exposed at the upper end of their respective insulating ceramic tubes.

[0012] In the molten salt corrosion electrochemical testing system, a horizontal baffle is suspended above the molten salt in the crucible cavity. The electrode lead of the working electrode and the insulating ceramic tube pass through the baffle. The insulating ceramic tube is fixed to the baffle by a connecting component. The electrode lead of the reference electrode and the insulating ceramic tube pass through the opening on the baffle.

[0013] The molten salt corrosion electrochemical testing system has a stirrer installed in the molten salt below the working electrode. The stirrer is installed at the lower end of a vertical connecting rod, which passes through a flange. The connecting rod and the flange are connected by a dynamic seal. The upper end of the connecting rod extends above the flange and is connected to the output end of the motor.

[0014] The molten salt corrosion electrochemical testing system described above uses a stirrer made of wear-resistant, corrosion-resistant, and thermal shock-resistant ceramic. The stirrer material includes, but is not limited to, BN, ZrB2, or BeO.

[0015] The molten salt corrosion electrochemical testing system includes a gas control device comprising a water vapor absorption unit connected to the inlet pipe, a tail gas treatment unit connected to the outlet pipe, and a furnace vacuum control unit connected to the outlet pipe. Gas valves are installed at the inlet and outlet pipes, and the tail gas treatment unit and the furnace vacuum control unit are switched at the outlet pipe via valves.

[0016] The molten salt corrosion electrochemical testing system is equipped with a molten salt filter at the inlet end of the gas outlet pipe and the exhaust gas treatment unit.

[0017] The molten salt corrosion electrochemical testing system has a secondary sealing device nested outside the heating furnace, and the secondary sealing device is sealed to the furnace body.

[0018] The molten salt corrosion electrochemical testing system described above uses a glove box as its secondary sealing device.

[0019] Compared with the prior art, the advantages and beneficial effects of this utility model are as follows:

[0020] 1. High accuracy in electrochemical measurement. Current molten salt corrosion electrochemical testing systems mainly employ a parallel placement of the working electrode, counter electrode, and reference electrode, resulting in uneven distribution of electric field lines between the counter and working electrodes, and between the counter and reference electrodes, thus affecting the accuracy of the test results. To address this issue, this invention significantly improves the uniformity of electric field line distribution on the electrode surface through electrode system design and structural optimization, thereby achieving reliable acquisition of electrochemical signals. Furthermore, current molten salt electrochemical systems have the stirrer located on one side of the electrode system, leading to uneven stirring and differences in mass transfer on the electrode surface. To address this issue, this invention achieves uniform stirring through the coordinated design and optimization of the electrode system and stirrer structure, further improving the accuracy of electrochemical testing.

[0021] 2. High-precision and stable control of key environmental parameters. To investigate the molten salt corrosion behavior of materials under specific working conditions, the experimental testing system needs to be able to precisely control key environmental parameters. Current molten salt corrosion electrochemical testing systems generally suffer from difficulties in controlling water and oxygen. To address this issue, this invention achieves precise and stable control of key environmental parameters such as water and oxygen by adding a two-stage sealing device, a water vapor absorption unit, a vacuum control unit, and a molten salt filter, thereby improving the laboratory simulation capability of molten salt corrosion conditions.

[0022] 3. Excellent reproducibility of measurement results. The electrochemical behavior of molten salt corrosion of materials is closely related to the corrosion environment. Even small changes in environmental parameters such as water and oxygen can significantly affect the corrosion rate and even the corrosion mechanism. This invention achieves precise control of key environmental parameters by adding a secondary sealing device and optimizing the gas control system. Furthermore, by optimizing the electrode system and stirring system, the distribution of electric field lines and mass transport on the electrode surface are made more uniform, thereby improving the reliability and reproducibility of the measurement results. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the molten salt corrosion electrochemical testing system prepared in Example 1.

[0024] Figure 2 A schematic diagram of the working electrode and its connection and packaging method for an electrochemical testing system for molten salt corrosion according to an embodiment of this application is shown.

[0025] Figure 3 The diagram shows the working electrode packaging in Examples 1 and 2.

[0026] Figure 4 This is a schematic diagram of the current density distribution of the improved three-electrode system of this utility model.

[0027] Figure 5 This is a schematic diagram of the electric field distribution of the improved three-electrode system of this utility model.

[0028] Figure 6 The figures show the electrochemical impedance spectroscopy (EIS) spectra of the alloy in the LiCl-KCl eutectic salt system at 550 °C for different corrosion times. In the figures, the horizontal axis Z... re The real part of the electrochemical impedance spectroscopy (Ω·cm) 2 ), ordinate Z im The imaginary part (Ω·cm) of the electrochemical impedance spectroscopy 2 ).

[0029] The reference numerals in the figure are as follows: 1 is the furnace lining; 2 is the heating wire; 3 is the furnace body; 4 is the electrode lead; 5 is the insulating ceramic tube; 6 is the insulating gasket; 7 is the crucible; 8 is the molten salt; 9 is the reference electrode; 10 is the working electrode; 11 is the baffle; 12 is the connecting component; 13 is the flange; 14 is the inlet pipe; 15 is the outlet pipe; 16 is the stirrer; 17 is the connecting rod; 18 is the dynamic seal; 19 is the glove box; 20 is the weld point; 21 is the high-temperature resistant inorganic adhesive. Detailed Implementation

[0030] like Figure 1 As shown, this utility model proposes a molten salt corrosion electrochemical testing system, which consists of a crucible, an electrode system, a well-type heating furnace, and a gas control device. Its basic structure includes a furnace lining 1, a heating wire 2, a furnace body 3, electrode leads 4, an insulating ceramic tube 5, an insulating gasket 6, a crucible 7, molten salt 8, a reference electrode 9, a working electrode 10, a baffle 11, a connecting component 12, a flange 13, an inlet pipe 14, and an outlet pipe 15. The specific structure is as follows:

[0031] The well-type heating furnace includes a furnace lining 1, heating wires 2, and a furnace body 3. Heating wires 2 are installed in the side wall of the furnace lining 1. The furnace body 3 is installed inside the furnace lining 1, which has an open top. An insulating gasket 6 is installed at the bottom of the inner cavity of the furnace body 3. A crucible 7 containing molten salt 8 is placed on the insulating gasket 6 in the inner cavity of the furnace body 3. The upper opening of the furnace body 3 is sealed by a flange 13. An inlet pipe 14 and an outlet pipe 15 are inserted into the flange 13. One end of the inlet pipe 14 extends to the outside of the furnace body 3 and is connected to a gas control device. The other end of the inlet pipe 14 extends to the lower middle part of the inner cavity of the furnace body 3. Inert gas flows into the inlet pipe 14 from the gas control device and is then introduced into the lower middle part of the inner cavity of the furnace body 3 through the inlet pipe 14. One end of the outlet pipe 15 extends to the upper part of the inner cavity of the furnace body 3, and the other end extends to the outside of the furnace body 3. A vertical insulating ceramic tube 5 is also inserted on the flange 13. Each insulating ceramic tube 5 is equipped with an electrode lead 4. One end of the insulating ceramic tube 5 extends into the inner cavity of the furnace body 3, and the other end of the insulating ceramic tube 5 extends above the flange 13.

[0032] The electrode system includes a reference electrode 9, a working electrode 10, a counter electrode, an electrochemical workstation, and electrode leads 4. The reference electrode 9 is annular, horizontally immersed in molten salt 8 and located at the center of crucible 7. The working electrode 10 is cylindrical, immersed in molten salt 8 and located at the center of the reference electrode 9. The crucible 7 serves as the counter electrode, with its sidewall connected to electrode leads 4. Both the electrode leads 4 and the contact points of the counter electrode are above the surface of the molten salt 8. The reference electrode 9, working electrode 10, and counter electrode are connected to the electrochemical workstation outside the pit-type furnace via electrode leads 4.

[0033] A horizontal baffle 11 is suspended above the molten salt 8 inside the crucible 7. The electrode lead 4 of the working electrode 10 and the insulating ceramic tube 5 pass through the baffle 11. The insulating ceramic tube 5 is fixed to the baffle 11 by a connecting component 12. The electrode lead 4 of the reference electrode 9 and the insulating ceramic tube 5 pass through the opening on the baffle 11.

[0034] like Figure 2As shown, this utility model proposes another electrochemical testing system for molten salt corrosion. Its improved structure includes a stirrer 16, a connecting rod 17, a dynamic seal 18, and a glove box 19. The stirrer 16 is installed in the molten salt 8 below the working electrode 10. The stirrer 16 is mounted on the lower end of the vertical connecting rod 17, which passes through a flange 13. The connecting rod 17 and flange 13 are connected by a dynamic seal 18. The upper end of the connecting rod 17 extends above the flange 13 and connects to the output end of the motor. The connecting rod 17 passes through an opening on the baffle 11. The stirrer 16 is made of wear-resistant, corrosion-resistant, and thermally shock-resistant ceramic, including but not limited to BN, ZrB2, or BeO. The furnace lining 1 and furnace body 3 of the pit-type heating furnace are nested in a glove box 19 equipped with a water and oxygen purification system, and are sealed to the top of the lower chamber of the glove box 19 via a flange at the upper opening of the furnace body 3. The gas control device includes a water vapor absorption unit connected to the inlet pipe 14, a tail gas treatment unit connected to the outlet pipe 15, and a furnace body vacuum control unit connected to the outlet pipe 15. Gas valves are installed at the inlet pipe 14 and the outlet pipe 15. The tail gas treatment unit and the furnace body vacuum control unit can be switched at the outlet pipe 15 by the valve. A molten salt filter is installed between the outlet pipe 15 and the inlet end of the tail gas treatment unit.

[0035] like Figure 3 As shown, the working electrode 10 and the electrode lead 4 are connected by solder joint 20. The electrode lead 4 is nested in an insulating ceramic tube 5. Both ends of the insulating ceramic tube 5 are sealed with high-temperature resistant inorganic adhesive 21. The electrode leads of the working electrode 10, the counter electrode (crucible 7), and the reference electrode 9 are exposed at the upper end of their respective insulating ceramic tubes 5.

[0036] The present invention will be further illustrated by way of embodiments below, but the present invention is not limited to the scope of the embodiments described herein.

[0037] Example 1

[0038] The electrochemical properties of iron-based alloy samples in LiCl-KCl molten salt were tested using a molten salt corrosion electrochemical testing system. The material preparation included the following steps:

[0039] (1) Preparation and drying of molten salt: Weigh LiCl and KCl according to the eutectic ratio, grind and mix them evenly in a mortar, and place them in a graphite crucible. Place the furnace lining and furnace body of the well-type heating furnace in a glove box. After completing the water and oxygen purification, place the graphite crucible on the insulating gasket at the bottom of the furnace body cavity, seal the flange, evacuate, introduce Ar gas, raise the temperature to 200℃, heat for 24 hours, cool to room temperature, and place it in a glove box for later use.

[0040] (2) Preparation of working electrode: The iron-based alloy sample was polished with sandpaper, welded to the molybdenum wire electrode lead by argon arc welding, ultrasonically cleaned with alcohol and dried, nested in a corundum tube, and sealed at both ends of the corundum tube with high-temperature resistant inorganic adhesive. After standing for 24 hours, it was heated and cured at 100℃ and 200℃ for 2 hours respectively, and then polished with a file until smooth and flat.

[0041] (3) Preparation of reference electrode: The ring platinum wire and the molybdenum wire electrode lead are welded together, ultrasonically cleaned with alcohol and dried. The molybdenum wire electrode lead is nested in the corundum tube, and the corundum tube also wraps the weld point. High temperature resistant inorganic adhesive is prepared and sealed at both ends of the corundum tube. After standing for 24 hours, it is heated and cured at 100℃ and 200℃ for 2 hours respectively. It is then polished with a file until smooth and flat.

[0042] (4) Preparation of the electrode: Drill holes along the side wall of the graphite crucible, pass molybdenum wire electrode leads through, rinse with alcohol and dry, put into a glove box, purify with water and oxygen, and then transfer the dried mixed salt to the crucible.

[0043] Instructions for use: Place the crucible containing the mixed salt on the insulating gasket at the bottom of the furnace cavity. Then, place the BN stirrer, reference electrode, and working electrode in sequence. Secure the working electrode by attaching the baffle and connecting parts, ensuring it is centered on the annular reference electrode. Next, cover with the flange and tighten the bolts to seal. Connect the electrode leads to the electrochemical workstation. Evacuate the system and introduce high-purity argon gas (99.999% volume purity) until a slight positive pressure (0.12 MPa) is reached. Open the outlet pipe and heat to 600°C. After the salt melts and the system stabilizes, begin electrochemical testing.

[0044] Example 2

[0045] The electrochemical properties of nickel-based alloy samples in NaCl-KCl molten salt were tested using a molten salt corrosion electrochemical testing system. The material preparation included the following steps:

[0046] (1) Preparation and drying of molten salt: Weigh NaCl and KCl according to the eutectic ratio, grind and mix them evenly in a mortar, and place them in a graphite crucible. Place the furnace lining and furnace body of the well-type heating furnace in a glove box. After completing the water and oxygen purification, place the graphite crucible on the insulating gasket at the bottom of the furnace body cavity, seal the flange, evacuate, introduce Ar gas, raise the temperature to 300℃, heat for 24 hours, cool to room temperature, and place it in a glove box for later use.

[0047] (2) Preparation of working electrode: The nickel-based alloy sample was polished with sandpaper, welded to stainless steel wire electrode lead by argon arc welding, ultrasonically cleaned with alcohol and dried, nested in a corundum tube, and sealed at both ends of the corundum tube with high temperature resistant inorganic glue. After standing for 24 hours, it was heated and cured at 100℃ and 200℃ for 2 hours respectively, and then polished with a file until smooth and flat.

[0048] (3) Preparation of reference electrode: The ring graphite is welded to the stainless steel wire electrode lead, ultrasonically cleaned with alcohol and dried, and the weld point and stainless steel wire electrode lead are nested in the corundum tube. High temperature resistant inorganic glue is prepared and sealed at both ends of the corundum tube. After standing for 24 hours, it is heated and cured at 100℃ and 200℃ for 2 hours respectively, and then polished with a file until smooth and flat.

[0049] (4) Preparation of the electrode: Drill holes along the side wall of the graphite crucible, pass stainless steel wire electrode leads through, rinse with alcohol and dry, put into a glove box, purify with water and oxygen, and then transfer the dried mixed salt to the crucible.

[0050] Instructions for use: Place the crucible containing the mixed salt on the insulating gasket at the bottom of the furnace cavity. Then, place the ZrB2 stirrer, reference electrode, and working electrode in sequence. Secure the baffle and connecting parts in place, cover with the flange, and tighten the bolts to seal. Connect the electrode leads to the electrochemical workstation. Evacuate the system and introduce high-purity argon gas (99.999% volume purity) until a slight positive pressure (0.12 MPa) is reached. Open the vent pipe and heat to 800°C. After the salt melts and the system stabilizes, begin electrochemical testing.

[0051] Example 3

[0052] The electrochemical properties of nickel-based alloy samples in LiCl-KCl-CeCl3 molten salt were tested using a molten salt corrosion electrochemical testing system. The material preparation included the following steps:

[0053] (1) Preparation and drying of molten salt: Weigh LiCl and KCl according to the eutectic ratio, add CeCl3 with a mass fraction of 5%, grind and mix evenly in a mortar, and place it in a tungsten metal crucible. Place the furnace lining and furnace body of the pit-type heating furnace in a glove box. After completing the water and oxygen purification, place the graphite crucible on the insulating gasket at the bottom of the furnace body cavity, seal the flange, evacuate, introduce nitrogen, heat to 250℃, heat for 40h, cool to room temperature, and place in a glove box for later use.

[0054] (2) Preparation of working electrode: The nickel-based alloy sample was polished with sandpaper, welded to the molybdenum wire electrode lead by argon arc welding, ultrasonically cleaned with alcohol and dried, nested in a corundum tube, and sealed at both ends of the corundum tube with high-temperature resistant inorganic adhesive. After standing for 24 hours, it was heated and cured at 100℃ and 200℃ for 2 hours respectively, and then polished with a file until smooth and flat.

[0055] (3) Preparation of reference electrode: The lower end of the platinum wire is rolled into a ring, and the rest is used as the electrode lead. After ultrasonic cleaning with alcohol, it is dried. The electrode lead is nested in a corundum tube. High-temperature resistant inorganic glue is prepared and sealed at both ends of the corundum tube. After standing for 24 hours, it is heated and cured at 80℃ and 200℃ for 2 hours respectively. It is then polished with a file until smooth and flat.

[0056] (4) Preparation of the electrode: Drill holes along the side wall of the graphite crucible, pass molybdenum wire electrode leads through, rinse with alcohol and dry, put into a glove box, purify with water and oxygen, and then transfer the dried mixed salt to the crucible.

[0057] Instructions for use: Place the crucible containing the mixed salt on the insulating gasket at the bottom of the furnace cavity. Then, place the BeO stirrer, reference electrode, and working electrode in sequence. Secure the baffle and connecting parts in place, cover with the flange, and tighten the bolts to seal. Connect the electrode leads to the electrochemical workstation. Evacuate the system and introduce high-purity argon gas (99.999% volume purity) until a slight positive pressure (0.12 MPa) is reached. Open the vent pipe and heat to 600°C. After the salt melts and the system stabilizes, begin electrochemical testing.

[0058] Application examples

[0059] The current density and electric field distribution of conventional parallel-placed, equidistantly placed three-electrode systems and the improved three-electrode system of this invention were analyzed using COMSOL Multiphysics simulation software. The specific results are as follows:

[0060] (1) For a conventional parallel three-electrode system (working electrode, reference electrode, and crucible as counter electrode), the current density on the left side of the working electrode and the right side of the reference electrode is significantly higher than that in other areas, and the potential is distributed in an elliptical radial pattern. In electrochemical testing, the difference in current density on the left and right sides of the working electrode and the unequal potential distribution will cause differences in the corrosion of different parts of the test sample, thus affecting the accuracy of the test results.

[0061] (2) For a conventional three-electrode system with equidistant placement (working electrode, reference electrode, and crucible as counter electrode), the current density on the outer side of the three electrodes is significantly higher than that on the inner side, and the potential is distributed in a triangular radial pattern. In electrochemical testing, the difference in current density on different sides of each electrode and the unequal potential distribution will cause differences in the corrosion of different parts of the test sample, thus affecting the accuracy of the test results.

[0062] (3) Figure 4 , Figure 5 As shown, for the improved three-electrode system of this utility model (working electrode 10, reference electrode 9, and crucible 7 as counter electrode), the current density of the outer counter electrode is slightly lower than that of the working electrode 10 and the reference electrode 9, but there is no directional difference in the current density of each electrode, and the electrode potential distribution is uniform, the electric field lines are uniformly distributed, and there is no directional difference.

[0063] like Figure 2As shown, 200g of a LiCl-KCl mixed salt with a mass ratio of 45:55 was weighed and mixed evenly in a mortar. The mixture was then placed in a graphite crucible, which was placed in a well-type furnace within a glove box. A vacuum was drawn, and high-purity Ar gas (99.999% volume purity) was introduced. The mixture was heated to 200℃ and dried for 24 hours, then cooled. The resulting product was transferred to a graphite crucible connected to electrode lead 4 and placed back into the well-type furnace. A stirrer 16, a reference electrode 9, a working electrode 10, a baffle 11, and a connecting component 12 were then placed in sequence. The iron-based alloy served as the working electrode, the platinum mesh as the reference electrode, the graphite crucible as the counter electrode, and the molybdenum wire as the electrode lead. The well-type furnace was sealed, and the electrode leads were connected sequentially to the interface of a Gamry Interference 1000E electrochemical workstation. A vacuum was drawn, high-purity Ar gas was introduced, and the temperature was raised to 550℃ for electrochemical testing. Figure 6 As shown, the electrochemical impedance spectroscopy of the alloy in the LiCl-KCl eutectic salt system at 550℃ for different corrosion times demonstrates that the electrochemical testing system for molten salt corrosion has excellent stability.

[0064] The results show that this invention can solve the problems of uneven distribution of electric field lines and uneven mass transfer on the electrode surface during molten salt corrosion testing, and can improve the stable control of key environmental parameters. The testing system has the advantages of high precision, good reproducibility, and precise control of the corrosion environment.

Claims

1. A molten salt corrosion electrochemical test system characterized by, The system includes a crucible, an electrode system, a heating furnace, and a gas control device, with the following specific structure: The bottom of the furnace body cavity of the heating furnace is equipped with an insulating gasket. The crucible containing molten salt is placed on the insulating gasket in the furnace body cavity. The crucible is made of graphite or inert metal. The opening at the top of the furnace body is sealed by a flange. An inlet pipe and an outlet pipe are inserted into the flange. One end of the inlet pipe extends out of the furnace body and is connected to the gas control device. The other end of the inlet pipe extends out to the middle and lower part of the furnace body cavity. One end of the outlet pipe extends to the upper part of the furnace body cavity, and the other end extends out of the furnace body cavity. The electrode system includes a reference electrode, a working electrode, a counter electrode, an electrochemical workstation, and electrode leads. The reference electrode, working electrode, and counter electrode are connected to the electrochemical workstation outside the heating furnace via electrode leads. The reference electrode is ring-shaped, horizontally immersed in molten salt, and located in the center of the crucible. The working electrode is cylindrical, immersed in molten salt, and located at the center of the reference electrode. The crucible serves as the counter electrode, with its sidewall connected to the electrode leads. The electrode leads and contacts of the counter electrode are both above the surface of the molten salt.

2. The molten salt corrosion electrochemical test system of claim 1, wherein, Two or more electrode leads are connected to the upper edge of the side wall of the crucible, and the connection points are symmetrically distributed along the upper edge of the side wall of the crucible.

3. The molten salt corrosion electrochemical testing system according to claim 1, characterized in that, Vertical insulating ceramic tubes are also inserted into the flange. Each insulating ceramic tube contains an electrode lead. One end of the insulating ceramic tube extends into the inner cavity of the furnace body, and the other end extends above the flange. The upper and lower open ends of the insulating ceramic tube are sealed with high-temperature resistant inorganic adhesive. The electrode leads of the working electrode, the counter electrode, and the reference electrode are exposed at the upper end of their respective insulating ceramic tubes.

4. The molten salt corrosion electrochemical test system of claim 1, wherein, A horizontal baffle is suspended above the molten salt inside the crucible. The electrode lead of the working electrode and the insulating ceramic tube pass through the baffle. The insulating ceramic tube is fixed to the baffle by a connecting component. The electrode lead of the reference electrode and the insulating ceramic tube pass through the opening on the baffle.

5. The molten salt corrosion electrochemical test system according to claim 1 or 4, characterized in that, A stirrer is installed in the molten salt below the working electrode. The stirrer is installed at the lower end of a vertical connecting rod. The connecting rod passes through a flange and is connected to the flange by a dynamic seal. The upper end of the connecting rod extends above the flange and is connected to the output end of the motor.

6. The molten salt corrosion electrochemical test system of claim 1, wherein, The gas control device includes a water vapor absorption unit connected to the inlet pipe, a tail gas treatment unit connected to the outlet pipe, and a furnace body vacuum control unit connected to the outlet pipe. Gas valves are installed at the inlet pipe and the outlet pipe, and the tail gas treatment unit and the furnace body vacuum control unit are switched at the outlet pipe via valves.

7. The molten salt corrosion electrochemical test system of claim 6, wherein, Molten salt filters are installed at the inlet end of the exhaust pipe and the exhaust gas treatment unit.

8. The molten salt corrosion electrochemical test system of claim 1, wherein, The heating furnace is nested within a secondary sealing device, which is sealed to the furnace body.

9. The molten salt corrosion electrochemical test system of claim 1, wherein, The secondary sealing device is the glove box.

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