A closed-loop dual-chamber electrochemical test device and test method

Abstract

This invention discloses a closed-loop dual-cavity electrochemical testing device and method, comprising a first electrolytic cell and a second electrolytic cell, both sealed and identical in structure, arranged opposite to each other; a sample mounting device is provided between the first and second electrolytic cells for mounting the porous metal material to be tested; the electrolyte in the first electrolytic cell flows through the porous metal material to the second electrolytic cell; the electrolyte in the second electrolytic cell flows back to the first electrolytic cell through a flexible tube connected to a peristaltic pump; and a temperature control device is also included. The first electrolytic cell contains a first reference electrode and a first auxiliary electrode, and the second electrolytic cell contains a second reference electrode and a second auxiliary electrode, with the porous metal material serving as a non-circular working electrode. This invention establishes a controllable flow rate electrolyte circulation, applies electrochemical excitation to the sample under isothermal conditions, and combines electrochemical response with corrosion product analysis to accurately evaluate the corrosion resistance of the material in a real service environment.

Description

Technical Field

[0001] This invention relates to the field of electrochemical corrosion testing technology, specifically to a closed-loop dual-cavity electrochemical testing device and method. Background Technology

[0002] Porous metallic materials, due to their high specific surface area, excellent electrical conductivity, good mechanical strength, and stable passivation films formed in strong acid and alkali environments, are widely used in electrochemical engineering fields such as proton exchange membrane water electrolysis for hydrogen production, fuel cell gas diffusion layers, electrocatalytic reactors, and electrochemical sensors. In these applications, the materials are exposed to highly corrosive electrolytes (such as H₂SO₄, KOH, or fluoride-containing ion media) for extended periods and are subjected to certain potential biases; therefore, their corrosion resistance directly determines the lifespan and safety of the devices.

[0003] To assess the service reliability of such materials, electrochemical testing methods (such as potentiodynamic polarization, electrochemical impedance spectroscopy, and potentiostatic polarization) have become important tools for studying corrosion behavior. However, existing standard electrochemical testing methods (such as ASTM G5 and G59) for dense metals (such as titanium plates and sheets) face significant technical bottlenecks when applied to three-dimensional porous materials: traditional electrochemical corrosion tests are mostly based on static immersion or flat electrode models, which cannot reflect the complex working conditions experienced by porous metal materials in actual applications (such as electrolyzers and fuel cells), such as forced convection of electrolyte, mass transfer within pores, pressure gradients, and dynamic interface renewal. Existing fixtures are difficult to integrate controlled flow with standard three-electrode measurements. In particular, in actual applications (such as PEM electrolyzer anodes), the electrolyte is forced to pass through the porous network at a certain flow rate, and its corrosion behavior is significantly affected by mass transfer within pores, pressure gradients, and interface renewal rates.

[0004] Currently, there is a lack of standardized electrochemical testing fixtures specifically designed for porous metal materials. Traditional single-cavity immersion testing cannot establish a flow path through the sample, resulting in corrosion data that deviates significantly from actual operating conditions. Furthermore, it faces the following insurmountable technical obstacles: 1) Difficulty in extracting the working electrode: Porous metal materials are generally conductive, but if spot welding or conductive adhesive is used for connection, the contact resistance is high and unstable, and galvanic corrosion and crevice corrosion are prone to occur during polarization; 2) Existing dual-cavity devices cannot simulate actual seepage conditions: In commercially available dual-cavity electrolytic cells, the solution does not flow between the two cavities, while in PEM electrolytic cells, the electrolyte is forced to flow through the porous electrodes at a certain flow rate. The corrosion electrochemical data measured under static conditions are significantly different from those under dynamic seepage conditions. Summary of the Invention

[0005] This invention addresses the problems existing in the prior art by providing a closed-loop dual-cavity electrochemical testing device and method.

[0006] The technical solution adopted in this invention is: a closed-loop dual-cavity electrochemical testing device, comprising a first electrolytic cell and a second electrolytic cell that are relatively sealed and have the same structure; A sample mounting device is provided between the first electrolytic cell and the second electrolytic cell for mounting the porous metal material to be tested; the electrolyte in the first electrolytic cell flows through the porous metal material to the second electrolytic cell; the electrolyte in the second electrolytic cell flows back to the first electrolytic cell through a hose connected to a peristaltic pump. It also includes a temperature control device for adjusting the electrolyte temperature in the first and second electrolytic cells; The first electrolytic cell is equipped with a first reference electrode and a first auxiliary electrode, and the second electrolytic cell is equipped with a second reference electrode and a second auxiliary electrode. Porous metal material is used as an irregularly shaped working electrode. The first reference electrode, the first auxiliary electrode, the second reference electrode, the second auxiliary electrode, the irregular working electrode, the peristaltic pump, and the temperature control device are all connected to the control device.

[0007] Furthermore, a first base plate and a second base plate are respectively provided at the opposite ends of the first electrolytic cell and the second electrolytic cell; it also includes a connecting rod that passes through the first base plate and the second base plate in sequence; the first electrolytic cell and the second electrolytic cell press the sample mounting device together through the first base plate and the second base plate.

[0008] Furthermore, the sample mounting device includes a mounting boss connected to the second electrolytic cell and a mounting recess that cooperates with and is connected to the first electrolytic cell; an O-ring is provided between the mounting boss and the mounting recess for sealing.

[0009] Furthermore, the temperature control device includes a constant temperature water bath system. The first electrolytic cell has a double-layer structure, with an inner cavity for holding the electrolyte and an outer cavity surrounding it to form a water bath chamber. The water bath chamber is connected to the first circulating water inlet and the first circulating water outlet. The constant temperature water bath system controls the temperature of the inner cavity by injecting circulating water into the water bath chamber.

[0010] Furthermore, a first retaining plate is provided between the first electrolytic cell and the sample mounting device, and a second retaining plate is provided between the second electrolytic cell and the sample mounting device; The connecting rod passes through the first base plate, the first retaining plate, the second retaining plate, and the second base plate in sequence for fixation; There are four connecting rods, which are arranged in parallel and evenly distributed around the first and second electrolytic cells.

[0011] Furthermore, the mounting boss has an outer end face and an inner end face; the mounting recess includes an inner end face that mates with the outer end face of the boss and an outer end face that mates with the inner end face of the boss; a second O-ring is provided on the inner end face of the recess. The irregularly shaped working electrode includes an electrode body disposed between the inner end face of the concave platform and the inner end face of the convex platform, and a conductive handle extending outward to connect with the signal acquisition device. A first O-ring is provided at the connection between the inner end face of the boss and the outer end face of the concave platform.

[0012] Furthermore, the first electrolytic cell and the second electrolytic cell are respectively provided with a first reference electrode mounting hole and a second reference electrode mounting hole. It also includes two Luggin capillaries, which are inserted into the first electrolytic cell and the second electrolytic cell respectively through the first reference electrode mounting hole and the second reference electrode mounting hole; the tips of the two Luggin capillaries are close to the sample mounting device. The first and second reference electrodes are respectively disposed in two Lugin capillaries.

[0013] Furthermore, plugs are respectively provided at the corresponding positions of the first reference electrode mounting hole and the second reference electrode mounting hole; both the first electrolytic cell and the second electrolytic cell are made of transparent materials.

[0014] Furthermore, the first auxiliary electrode is disposed near the first base plate, and a first wire lead-out hole is disposed at a corresponding position on the first base plate; the second auxiliary electrode is disposed near the second base plate, and a second wire lead-out hole is disposed at a corresponding position on the second base plate.

[0015] A closed-loop dual-cavity electrochemical testing method includes the following steps: Step 1: Place the irregularly shaped working electrode in the sample mounting device; place the first reference electrode and the first auxiliary electrode in the first electrolytic cell; place the second reference electrode and the second auxiliary electrode in the second electrolytic cell; inject electrolyte into the first and second electrolytic cells. Step 2: Start the peristaltic pump to establish a closed-loop circulation of the electrolyte, and start the temperature control device to maintain the electrolyte temperature in the first and second electrolytic cells within the range of 20 to 90 ℃; Step 3: The control device acquires the signals measured by the first reference electrode, the first auxiliary electrode, the second reference electrode, the second auxiliary electrode, and the irregular working electrode.

[0016] The beneficial effects of this invention are: This invention's testing device realistically simulates the percolation mass flow environment: horizontal percolation + closed-loop circulation, more closely resembling the actual electrolyte flow in an electrolytic cell. It employs highly reliable sealing with double O-rings on the sample edges and independent sealing of all electrolyte interfaces to prevent leakage. The uniquely shaped working electrode is a one-piece structure, molded from a single piece of porous metal material. There is no welding or bonding interface between the electrode body and the conductive handle, ensuring uniform current distribution, extremely low contact resistance, and excellent durability. With no heat-affected zone or adhesive layer, the pore structure is intact, and the percolation path remains undisturbed. This design solves the problems of galvanic corrosion and crevice corrosion caused by heterogeneous connection methods such as welding and bonding, thus avoiding interference with test data.

[0017] The testing device employs a double-layer water bath jacket and transparent material settings to achieve high-precision temperature control and visualization of bubbles / deposits. It boasts strong sample compatibility, suitable for various porous metal materials such as sintered titanium felt, nickel foam, and metal fiber mesh, and supports multiple corrosive media and electrochemical testing modes. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure of the testing device of the present invention.

[0019] Figure 2 This is an axial cross-sectional view of the first electrolytic cell in this invention.

[0020] Figure 3 This is a schematic diagram of the first base plate structure in this invention.

[0021] Figure 4 This is a schematic diagram of the irregularly shaped working electrode in this invention.

[0022] Figure 5 This is a schematic diagram of the mounting recess structure in this invention.

[0023] Figure 6 This is a schematic diagram of the second O-ring seal structure in this invention.

[0024] Figure 7 This is a schematic diagram of the mounting boss structure in this invention.

[0025] Figure 8 This is a schematic diagram of the first O-ring seal structure in this invention.

[0026] Figure 9 This is a schematic diagram of the installation of the Lujin capillary tube in this invention.

[0027] Figure 10 This is the electrochemical impedance spectrum obtained in Example 1 of this invention.

[0028] Figure 11 This is a potentiodynamic polarization curve obtained in Example 1 of the present invention.

[0029] In the diagram: 1-First base plate, 2-First wire lead-out hole, 3-First circulating water outlet, 4-First electrolyte injection port, 5-First reference electrode mounting hole, 6-First retaining plate, 7-Irregularly shaped working electrode, 8-Second retaining plate, 9-Second reference electrode mounting hole, 10-Reference electrode plug, 11-Second electrolyte injection port, 12-Second electrolyte injection port plug, 13-Second circulating water outlet, 14-Second wire lead-out hole, 15-Second base plate, 16-Connecting rod, 17-Second electrolyte outlet, 18-Hose, 19-Second circulating water inlet, 20-Mounting boss, 21-First O 22-Mounting recess, 23-Peristaltic pump connection point, 24-First circulating water inlet, 25-First electrolyte inlet, 26-Second electrolytic cell, 27-Outer wall of first water bath chamber, 28-First water bath chamber, 29-Outer wall of electrolyte chamber of first electrolytic cell, 30-First electrolytic cell, 31-Conductive handle slot, 32-Inner end face of recess, 33-Second O-ring seal, 34-Outer end face of recess, 35-First opening, 36-First auxiliary electrode slot, 37-Connecting rod opening, 38-Conductive handle, 39-Electrode body, 40-Outer end face of boss, 41-Inner end face of boss, 42-Lugin capillary tube. Detailed Implementation

[0030] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0031] like Figure 1 As shown, a closed-loop dual-cavity electrochemical testing device includes a first electrolytic cell 30 and a second electrolytic cell 26, which are relatively enclosed and structurally identical. The second electrolytic cell 26 and the first electrolytic cell 30 have the same structure; only the specific structure of the first electrolytic cell 30 will be described below, including the installation position and method of the auxiliary electrode. The electrolyte is an acidic solution (0.1~1M H2SO4), an alkaline solution (0.5~5 M KOH), or a corrosive medium containing halide ions.

[0032] A sample mounting device is provided between the first electrolytic cell 30 and the second electrolytic cell 26 for mounting the porous metal material to be tested. The electrolyte in the first electrolytic cell 30 permeates through the porous metal material to the second electrolytic cell 26. The electrolyte in the second electrolytic cell 26 flows back to the first electrolytic cell 30 through a flexible tube 18, which is connected to a peristaltic pump, forming a closed-loop electrolyte circulation circuit, allowing the electrolyte to flow back from the second electrolytic cell 26 to the first electrolytic cell 30. The porous metal material sample is sintered metal felt, sintered foam metal, metal mesh, etc., with a thickness of 0.3~3.0 mm and a porosity of 40%~90%. The peristaltic pump hose is connected to the peristaltic pump to adjust the permeation rate, ranging from 0.1~50 mL / min.

[0033] At opposite ends of the first electrolytic cell 30 and the second electrolytic cell 26, a first base plate 1 and a second base plate 15 are respectively provided; the device also includes a connecting rod 16 that passes through the first base plate 1 and the second base plate 15 in sequence; the first electrolytic cell 30 and the second electrolytic cell 26 press the sample mounting device together through the first base plate 1 and the second base plate 15. The structure of the first base plate 1 is as follows: Figure 3 As shown.

[0034] A first retaining plate 6 is provided between the first electrolytic cell 30 and the sample mounting device, and a second retaining plate 8 is provided between the second electrolytic cell 26 and the sample mounting device; The connecting rod 16 passes through the first base plate 1, the first retaining plate 6, the second retaining plate 8, and the second base plate 15 in sequence for fixation; There are four connecting rods 16, which are arranged in parallel and evenly distributed around the first electrolytic cell 30 and the second electrolytic cell 26.

[0035] The sample mounting device includes a mounting boss 20 connected to the second electrolytic cell 26 and a mounting recess 22 that mates with it and is connected to the first electrolytic cell 30; the mounting boss structure is as follows: Figure 7 As shown, the mounting recess structure is as follows Figure 5 As shown, an O-ring is provided between the mounting boss 20 and the mounting recess 22 for sealing. This is used to limit the effective test area of ​​the working electrode in the clamped state and to prevent electrolyte bypass leakage.

[0036] The mounting boss 20 includes an outer end face 40 and an inner end face 41; the mounting recess 22 includes an inner end face 32 that mates with the outer end face 40 of the boss and an outer end face 34 that mates with the inner end face 41 of the boss; a second O-ring 33 is provided on the inner end face 32 of the recess; the thickness of the second O-ring 33 is slightly greater than the height difference between the outer end face 34 and the inner end face 32 of the recess. The structure of the second O-ring 33 is as follows: Figure 6 As shown, the structure of the first O-ring 21 is as follows: Figure 8 As shown.

[0037] The irregular working electrode 7 includes an electrode body 39 disposed between the inner end face 32 of the concave platform and the inner end face 41 of the convex platform, and a conductive handle 38 extending outward to connect with the signal acquisition device. A first O-ring 21 is provided at the connection between the inner end face 41 of the boss and the outer end face 34 of the concave platform. The first O-ring 21 and the second O-ring 33, along with the end faces of the concave and boss platforms, fit tightly together to form a double sealing structure. Under the pressure of the connecting rod (which can use bolts), the two O-rings undergo elastic deformation, achieving a liquid-tight seal at the lead-out point of the conductive handle and the edge of the sample.

[0038] It also includes a temperature control device for adjusting the electrolyte temperature in the first electrolytic cell 30 and the second electrolytic cell 26; the temperature control device includes a constant temperature water bath system, the first electrolytic cell 30 has a double-layer structure, the inner cavity is used to hold the electrolyte, and the outer cavity surrounds and forms the first water bath chamber 28, as shown in the figure. Figure 2 As shown. The first water bath chamber 28 is connected to the first circulating water inlet 24 and the first circulating water outlet 3. The constant temperature water bath system controls the internal temperature by injecting circulating water into the first water bath chamber 28. The structure of the second electrolytic cell 26 is the same as that of the first electrolytic cell 30. The second electrolytic cell 26 is also a double-layer structure. The second water bath chamber is connected to the second circulating water inlet 19 and the second circulating water outlet 13. The constant temperature water bath system uses an existing constant temperature water bath system, with a temperature control range of 20~90 ℃.

[0039] The first electrolytic cell 30 is equipped with a first reference electrode and a first auxiliary electrode, and the second electrolytic cell 26 is equipped with a second reference electrode and a second auxiliary electrode. A porous metal material serves as the irregularly shaped working electrode 7; the irregularly shaped working electrode 7 has the following structure... Figure 4 As shown, it includes a circular electrode body 39 and a conductive handle 38.

[0040] The first reference electrode, the first auxiliary electrode, the second reference electrode, the second auxiliary electrode, and the irregular working electrode 7, the peristaltic pump, and the temperature control device are all connected to the control device.

[0041] The first electrolytic cell 30 and the second electrolytic cell 26 are respectively provided with a first reference electrode mounting hole 5 and a second reference electrode mounting hole 9; It also includes two Luggin capillaries 42, which are inserted into the first electrolytic cell 30 and the second electrolytic cell 26 respectively through the first reference electrode mounting hole 5 and the second reference electrode mounting hole 9; the tips of both Luggin capillaries 42 are close to the sample mounting device; the distance between the tips of the Luggin capillaries and the surface of the porous metal material sample is 0.5~2.0 mm. The mounting structure is as follows: Figure 9 As shown.

[0042] The first and second reference electrodes are respectively disposed in two Lugin capillaries.

[0043] A plug is provided at the corresponding position of the first reference electrode mounting hole 5 and the second reference electrode mounting hole 9; both the first electrolytic cell 30 and the second electrolytic cell 26 are made of transparent materials. Polycarbonate (PC), polysulfone (PSU), polymethylpentene (TPX) and quartz glass can be selected to facilitate in-situ observation of bubble generation or corrosion product formation.

[0044] The first auxiliary electrode is disposed near the first base plate 1, and a first wire lead-out hole 2 is provided on the first base plate 1 at a corresponding position. The second auxiliary electrode is disposed near the second base plate 15, and a second wire lead-out hole 14 is provided on the second base plate 15 at a corresponding position. The first electrolytic cell 30 has a first opening 35 corresponding to the position of the first base 1, and a first auxiliary electrode slot 36 is provided on the first opening 35 corresponding to the position of the first base 1 for mounting the first auxiliary electrode. The second auxiliary electrode is mounted in the same position as the first auxiliary electrode.

[0045] The device of this invention includes a first electrolytic cell and a second electrolytic cell arranged opposite each other, with a porous metal material sample serving as the working electrode sandwiched between them. This forces the electrolyte to flow horizontally from the first electrolytic cell through the internal pores of the sample to the second electrolytic cell, thereby accurately replicating the forced convection mass transfer environment in actual service. The first and second electrolytic cells have a double-layer structure, with an inner electrolyte chamber and an outer water bath chamber for precise temperature control of the electrolyte.

[0046] The base plates on both sides are equipped with auxiliary electrode slots for mounting auxiliary electrodes. These electrodes extend directly into the electrolyte chamber through openings, forming effective electrical contact with the electrolyte and avoiding the leakage risks associated with traditional through-wall wiring. The first and second electrolytic cells are connected via a peristaltic pump and piping, forming a closed-loop electrolyte circulation circuit, allowing the electrolyte to flow back from the second electrolytic cell to the first. The reference electrode is inserted through a sealed reference electrode opening, with its Luggin capillary tip close to the downstream surface of the sample. The porous metal sample employs an irregular structure, including a circular porous electrode body and a conductive handle extending radially from its edge. The conductive handle is led out through a conductive handle slot on the mounting platform and uses an O-ring for electrical connection and edge sealing. All functional interfaces, including the reference electrode opening, the injection port, and the auxiliary electrode mounting hole, are equipped with detachable sealing components to ensure good sealing performance under high temperature, pressure, and long-term operation conditions.

[0047] This invention establishes a controllable electrolyte circulation, applies electrochemical excitation to the sample under isothermal conditions, and combines electrochemical response with corrosion product analysis to accurately evaluate the corrosion resistance of materials in real service environments.

[0048] Example The following explanation uses the percolation corrosion behavior of sintered titanium felt in acidic electrolyte as an example.

[0049] A testing method for a closed-loop dual-cavity electrochemical testing device includes the following steps: Step 1: First, take a sintered titanium felt with a thickness of 1.0 mm and a porosity of 70% as a porous metal material sample. Laser cut or precision punch it into a 20 mm diameter conductive handle 38 with a cross-section of 2 mm × 2 mm and a length of 25 mm, forming an irregularly shaped working electrode 7. The structure is as follows: Figure 4 As shown, this structure ensures that the electrode body 39 maintains an intact porous network.

[0050] The first substrate base 1 is provided with a connecting rod opening 37 for installing connecting rods (parallel bolts are used in this embodiment). Four parallel connecting rods pass through the through holes on the first retaining plate 6, the second retaining plate 8, and the second substrate base, respectively, and are fastened with bolts to fix the first electrolytic cell between the first substrate base and the first retaining plate 6; similarly, the second electrolytic cell is fixed between the second retaining plate and the second base plate. The four connecting rods can simultaneously ensure the stability of the overall device structure and the concentricity of the mounting recess 22 and the mounting boss 20, ensuring sealing.

[0051] The irregularly shaped working electrode 7 is placed inside the sample mounting device. A conductive handle slot 31 is provided on the mounting recess 22 for mounting and fixing the conductive handle 38 of the irregularly shaped working electrode 7. A circular electrode body 39 is placed on the first O-ring 33. The first O-ring 33 on the inner end face 32 of the recess is made of fluororubber. The thickness of the second O-ring 33 and the total thickness of the sample are slightly greater than the height difference between the outer end face 34 and the inner end face 32 of the recess. Under pressure and elastic deformation, this ensures a good seal on the left side of the conductive handle slot 31 and the conductive handle.

[0052] The outer end face 40 of the boss directly contacts the second O-ring seal 33, which is used to press the sample and the second O-ring seal together. The inner end face of the boss is equipped with the first O-ring seal 21, and the thickness of the first O-ring seal 21 is slightly greater than the height difference between the outer end face 40 and the inner end face 41 of the sample mounting boss. Under pressure and elastic deformation, the sealing effect on the right side of the notch-type groove and the conductive handle can be guaranteed.

[0053] Tighten the connecting rod to ensure that the sample mounting recess, mounting boss, irregular working electrode, and O-ring are tightly fitted together, forming a double seal and effectively preventing electrolyte leakage from the sample circumference bypass.

[0054] Insert the first and second reference electrodes into the hollowed-out portion of the cap, tighten the cap, and then insert them into the first and second electrolytic cells respectively through the openings of the first and second reference electrodes. This achieves high sealing performance and facilitates electrode replacement.

[0055] The first electrolytic cell is equipped with a first electrolyte injection port, and the second electrolytic cell is equipped with a second electrolyte injection port, both located at the top of the cavity and having external threads. After electrolyte injection is completed, the injection port caps are immediately tightened to achieve a seal.

[0056] The wire lead-out holes on the base plate are integrated with conductive sealing joints, which not only ensure electrical connection, but also achieve liquid tightness through radial compression sealing rings; all seals are made of corrosion-resistant materials (such as PTFE, FFKM perfluoroether rubber or Viton fluororubber), which are suitable for strong acid, strong alkali and high temperature environments.

[0057] Taking the first electrolytic cell as an example, the platinum sheet (mesh) auxiliary electrode is inserted into the first auxiliary electrode slot 36 of the first base plate 1, with the auxiliary electrode facing the first opening 30. The auxiliary electrode wire is led out through the first wire lead-out hole 2 and connected to the electrochemical workstation. The second auxiliary electrode on the right is installed in the same way.

[0058] Insert the reference electrode into the Lugin capillary 42 inside the second electrolytic cell through the second reference electrode mounting hole 9, ensuring that the tip of the Lugin capillary 42 is less than 1.0 mm from the right side surface of the irregular working electrode 7.

[0059] The left-side reference electrode is an optional configuration: when the irregularly shaped working electrode 7 is considered a homogeneous material, only the reference electrode needs to be placed on the right side, and no components need to be installed in the left-side reference electrode mounting hole; however, when it is necessary to monitor the potential on both sides of the sample simultaneously (e.g., when there is a difference in surface conditions on the left and right sides of the irregularly shaped working electrode 7), a cap with a reference electrode should be installed in the left-side reference electrode mounting hole. In this case, the distance between the left-side reference electrode and the working electrode should be the same as that on the right side.

[0060] After injecting electrolyte through the injection port, seal immediately and connect the hose. The second electrolyte outlet 17 → hose 18 → first electrolyte inlet 25 forms a stable seepage flow.

[0061] The first water bath chamber 28 is connected to the constant temperature water bath circulation system through the first circulating water inlet 19, the second circulating water inlet 25, the first circulating water outlet 3, and the second circulating water outlet 13.

[0062] Electrochemical impedance spectroscopy and potentiodynamic polarization tests were performed on sintered titanium felt samples using the above structure.

[0063] A sintered titanium felt with a diameter of 20 mm, a thickness of 1.0 mm, and a porosity of 70% was used as the working electrode. A conductive handle of the same material with a cross-section of 2 mm × 2 mm and a length of 25 mm was retained at the edge. This electrode was clamped between the sample mounting recess and the boss. The effective area (3.14 cm²) was limited by O-rings on both sides, a notch-type groove, and the outer end face of the boss. 2 ) and edge seal.

[0064] The conductive handle 38 extends through the conductive handle slot 31 and connects to the electrochemical workstation; a platinum mesh auxiliary electrode is inserted into the second base plate, and the Ag / AgCl reference electrode is introduced through the reference electrode opening. The tip of the Lugin capillary is 1.0 mm from the downstream surface of the sample. 30 mL of 0.5 M H2SO4 + 5 ppm NaF solution is injected into the system, the device is slightly tilted to expel air bubbles, and the sealing plug is tightened. The constant temperature water bath temperature is set to 70 °C, the peristaltic pump is started, and the horizontal percolation circulation is set at a flow rate of 15 mL / min. For comparison, another set of static test conditions is set: all other parameters remain the same, but the peristaltic pump is not started, that is, the electrolyte is in a static state and there is no forced percolation.

[0065] Electrochemical testing: Monitor the open-circuit potential. After the open-circuit potential stabilizes, perform electrochemical impedance spectroscopy at the open-circuit potential (frequency range 10). 5 ~10 -2 Hz, disturbance amplitude 10 mV), the results are as follows Figure 10 As shown, the Nyquist plot under static conditions shows two capacitive arcs, indicating insufficient interfacial stability; while at a flow rate of 15 mL / min, the Nyquist plot shows a single capacitive arc, indicating that the flow state promotes the formation of a passivation film. Subsequently, a potentiodynamic polarization test was performed (-0.3 V). vs OCP ~2.5 V Ag / AgCl (Scan rate 1 mV / s), the measured potentiodynamic polarization curve is as follows: Figure 11 As shown, the results indicate that the samples maintain a stable passivation state above -0.17 V under both conditions; the passivation current densities at 1 V at static and 15 mL / min flow rates are 129.2 and 101.3 μA / cm, respectively. 2 This indicates that the seepage environment improves the corrosion resistance of the titanium felt.

[0066] This invention can realistically simulate the electrochemical corrosion behavior of porous metal materials under dynamic seepage conditions, solving the corrosion assessment biases caused by static immersion, poor contact, sealing failure, and mass transfer distortion in existing technologies. By establishing a controllable electrolyte circulation and applying electrochemical excitation to the sample under isothermal conditions, combined with electrochemical response and corrosion product analysis, the corrosion resistance of the material in real service environments can be accurately evaluated.

Claims

1. A closed-loop dual-cavity electrochemical testing device, characterized in that, It includes a first electrolytic cell (30) and a second electrolytic cell (26) that are both relatively sealed and have the same structure. A sample mounting device is provided between the first electrolytic cell (30) and the second electrolytic cell (26) for mounting the porous metal material to be tested; the electrolyte in the first electrolytic cell (30) permeates through the porous metal material to the second electrolytic cell (26); the electrolyte in the second electrolytic cell (26) flows back to the first electrolytic cell (3) through the hose (18), and the hose (18) is connected to a peristaltic pump; It also includes a temperature control device for adjusting the electrolyte temperature in the first electrolytic cell (30) and the second electrolytic cell (26); The first electrolytic cell (30) is provided with a first reference electrode and a first auxiliary electrode, and the second electrolytic cell (26) is provided with a second reference electrode and a second auxiliary electrode. The porous metal material is used as the irregular working electrode (7). The first reference electrode, the first auxiliary electrode, the second reference electrode, the second auxiliary electrode, and the irregular working electrode (7), the peristaltic pump, and the temperature control device are all connected to the control device.

2. The closed-loop dual-cavity electrochemical testing device according to claim 1, characterized in that, The first electrolytic cell (30) and the second electrolytic cell (26) are respectively provided with a first base plate (1) and a second base plate (15); and also include a connecting rod (16) that passes through the first base plate (1) and the second base plate (15) in sequence; the first electrolytic cell (30) and the second electrolytic cell (26) press the sample mounting device together through the first base plate (1) and the second base plate (15).

3. The closed-loop dual-cavity electrochemical testing device according to claim 2, characterized in that, The sample mounting device includes a mounting boss (20) connected to the second electrolytic cell (26) and a mounting recess (22) that cooperates with and is connected to the first electrolytic cell (30); an O-ring is provided between the mounting boss (20) and the mounting recess (22) for sealing.

4. The closed-loop dual-cavity electrochemical testing device according to claim 1, characterized in that, The temperature control device includes a constant temperature water bath system. The first electrolytic cell (30) has a double-layer structure. The inner cavity is used to place the electrolyte, and the outer cavity surrounds and forms the first water bath chamber (28). The first water bath chamber (28) is connected to the first circulating water inlet (24) and the first circulating water outlet (3). The constant temperature water bath system controls the temperature of the inner cavity by injecting circulating water into the first water bath chamber (28).

5. A closed-loop dual-cavity electrochemical testing device according to claim 2, characterized in that, A first retaining plate (6) is provided between the first electrolytic cell (30) and the sample mounting device, and a second retaining plate (8) is provided between the second electrolytic cell (26) and the sample mounting device. The connecting rod (16) passes through the first base plate (1), the first retaining plate (6), the second retaining plate (8), and the second base plate (15) in sequence for fixation; There are four connecting rods (16), which are arranged in parallel and evenly distributed around the first electrolytic cell (30) and the second electrolytic cell (26).

6. The closed-loop dual-cavity electrochemical testing device according to claim 3, characterized in that, The mounting boss (20) has an outer end face (40) and an inner end face (41); the mounting recess (22) includes an inner end face (32) that structurally mates with the outer end face (40) and an outer end face (34) that structurally mates with the inner end face (41); the inner end face (32) is provided with a second O-ring seal (33). The irregular working electrode (7) includes an electrode body (39) disposed between the inner end face (32) of the concave platform and the inner end face (41) of the convex platform, and a conductive handle (38) extending outward to connect with the signal acquisition device. A first O-ring (21) is provided at the connection between the inner end face (41) of the boss and the outer end face (34) of the concave platform.

7. The closed-loop dual-cavity electrochemical testing device according to claim 1, characterized in that, The first electrolytic cell (30) and the second electrolytic cell (26) are respectively provided with a first reference electrode mounting hole (5) and a second reference electrode mounting hole (9); It also includes two Lugin capillary tubes (42), which are inserted into the first electrolytic cell (30) and the second electrolytic cell (26) through the first reference electrode mounting hole (5) and the second reference electrode mounting hole (9), respectively; the tips of the two Lugin capillary tubes (42) are close to the sample mounting device. The first and second reference electrodes are respectively disposed in two Lugin capillaries.

8. The closed-loop dual-cavity electrochemical testing device according to claim 7, characterized in that, The first reference electrode mounting hole (5) and the second reference electrode mounting hole (9) are respectively provided with plugs at corresponding positions; the first electrolytic cell (30) and the second electrolytic cell (26) are both made of transparent material.

9. A closed-loop dual-cavity electrochemical testing device according to claim 2, characterized in that, The first auxiliary electrode is disposed near the first base plate (1), and a first wire lead-out hole (2) is provided on the first base plate (1) at a corresponding position; the second auxiliary electrode is disposed near the second base plate (15), and a second wire lead-out hole (14) is provided on the second base plate (15) at a corresponding position.

10. A testing method using any one of the closed-loop dual-cavity electrochemical testing devices as described in claims 1 to 9, characterized in that, Includes the following steps: Step 1: Place the irregular working electrode (7) in the sample mounting device, place the first reference electrode and the first auxiliary electrode in the first electrolytic cell (30); place the second reference electrode and the second auxiliary electrode in the second electrolytic cell (26); inject electrolyte into the first electrolytic cell (30) and the second electrolytic cell (26); Step 2: Start the peristaltic pump to establish a closed-loop circulation of electrolyte, start the temperature control device, and maintain the electrolyte temperature in the first electrolytic cell (30) and the second electrolytic cell (26) within the range of 20 to 90 °C; Step 3: The control device acquires the signals measured by the first reference electrode, the first auxiliary electrode, the second reference electrode, the second auxiliary electrode and the irregular working electrode (7).

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