A supercritical water polarization curve test platinum wire quasi-reference electrode device

Abstract

The application belongs to the technical field of test electrode, and specifically discloses a supercritical water polarization curve test platinum wire quasi-reference electrode device, which comprises a reaction kettle, a kettle cover, an electrode system integrated on the kettle cover, an electric connection system, a temperature acquisition and compensation system and a water cooling system, the electrode system comprises a working electrode interface, a platinum sheet auxiliary electrode, a platinum wire quasi-reference electrode, a redundant platinum wire electrode, a detachable Ag / AgCl reference electrode and first and second thermocouples respectively arranged in correspondence with the platinum wire quasi-reference electrode and the redundant platinum wire electrode. The supercritical water polarization curve test platinum wire quasi-reference electrode device is used to solve the technical problems of the prior art, such as the inability to evaluate the stability of the reference electrode, the unreliable sealing structure, the lack of temperature compensation and the complex calibration process, and to realize high precision, high reliability and continuity of electrochemical testing in a supercritical water environment.

Description

Technical Field

[0001] This invention relates to the field of test electrode technology, and in particular to a platinum wire quasi-reference electrode device for testing supercritical water polarization curves. Background Technology

[0002] Supercritical water (temperature > 374℃, pressure > 22.1 MPa) is widely used in nuclear power, heavy oil thermal recovery, and other fields due to its unique physicochemical properties. Studying the corrosion behavior of metallic materials in supercritical water environments is crucial for ensuring the safe operation of equipment. Electrochemical testing techniques, due to their speed and sensitivity, have become an important tool in corrosion research.

[0003] However, the supercritical water environment presents significant challenges to electrochemical testing. Traditional reference electrodes, such as Ag / AgCl electrodes and saturated calomel electrodes, cannot operate stably under supercritical conditions due to issues such as the vaporization of the electrolyte solution at high temperatures and changes in the solubility of the reference substance. Platinum wire quasi-reference electrodes, with their advantages of chemical inertness and high-temperature stability, have become the preferred choice for supercritical water testing. However, existing solid-state quasi-reference technologies, represented by platinum wire quasi-reference electrodes, suffer from the following technical defects: Stability cannot be assessed: the potential of a single platinum wire electrode in a supercritical water environment drifts over time, but real-time monitoring methods are lacking, making it impossible to determine the reliability of the measurement data; Unreliable sealing structure: existing devices mostly employ a single sealing structure, which is prone to leakage under high-temperature and high-pressure alternating conditions, leading to test failure; Lack of temperature compensation for the quasi-reference electrode: existing quasi-reference electrodes cannot perform effective temperature compensation, affecting the accuracy of potential measurement; Complex calibration process: existing devices cannot achieve in-situ calibration, requiring electrode disassembly for low-temperature calibration, which is cumbersome and affects test continuity; Insufficient thermal expansion compensation: the difference in thermal expansion coefficients between the platinum wire and metal components leads to seal failure, and existing devices lack an effective thermal expansion compensation mechanism.

[0004] To address the aforementioned issues, those skilled in the art urgently need a platinum wire quasi-reference electrode device that can operate stably under supercritical water conditions, has real-time drift monitoring capabilities, is reliably sealed, and provides accurate temperature measurement. Summary of the Invention

[0005] The purpose of this invention is to provide a platinum wire quasi-reference electrode device for testing supercritical water polarization curves, which solves the technical problems in the prior art such as the inability to assess the stability of the reference electrode, unreliable sealing structure, lack of temperature compensation, and complex calibration process, and achieves high precision, high reliability and continuity of electrochemical testing in supercritical water environment.

[0006] To achieve the above objectives, this invention provides a platinum wire quasi-reference electrode device for supercritical water polarization curve testing, comprising a reaction vessel, a vessel lid, an electrode system integrated on the vessel lid, an electrical connection system, a temperature acquisition and compensation system, and a water cooling system. The vessel lid is connected to the reaction vessel by bolts, and a metal O-ring or metal sealing gasket is provided between the vessel lid and the reaction vessel. The vessel lid has multiple through-mounting interfaces. The electrode system includes a working electrode interface, a platinum sheet auxiliary electrode, a platinum wire quasi-reference electrode, a redundant platinum wire electrode, a detachable Ag / AgCl reference electrode, and a first thermocouple and a second thermocouple respectively corresponding to the platinum wire quasi-reference electrode and the redundant platinum wire electrode. The temperature acquisition and compensation system acquires the temperatures at the tips of the platinum wire quasi-reference electrode and the redundant platinum wire electrode in real time, and corrects the potential measured with the platinum wire quasi-reference electrode as a reference based on the low-temperature calibration data and the pre-established platinum wire electrode temperature correction relationship.

[0007] Preferably, both the platinum wire quasi-reference electrode and the redundant platinum wire electrode are made of platinum wire with a purity of not less than 99.95%, and the diameter of the platinum wire is 0.5 to 1.0 mm. The platinum wire is introduced into the reaction vessel through an insulating sleeve, and the effective exposure length of the platinum wire in the test medium is 5 to 20 mm.

[0008] Preferably, the platinum wire requires pretreatment before use. First, it is soaked in aqua regia for 5 minutes, then rinsed with deionized water, and annealed at 500°C for 2 hours under argon protection in a muffle furnace. After pretreatment, it is subjected to electrochemical passivation treatment: in 0.5M H2SO4, it is cyclically rotated 50 times between -0.3V and +1.5V at a scan rate of 100mV / s, fixed at +1.2V for 30 minutes to form a PtO layer, stabilized by slow scanning 20 times between +0.6V and +1.0V, rinsed with deionized water, and dried at 80°C for 2 hours.

[0009] Preferably, the platinum sheet auxiliary electrode uses a platinum sheet with a purity of not less than 99.95%, and its size can be 20mm × 10mm × 0.5mm, with an effective area of ​​2cm². 2 The working electrode interface is used to mount the metal sample to be tested. The sample is fixed by an insulating support and connected to the working electrode terminal outside the reactor by a high-temperature resistant conductive lead.

[0010] Preferably, the water cooling system includes a water cooling jacket, a cooling water circulation pipeline, and a flow regulating valve, with the cooling water flow rate controlled at 0.5-2L / min and the inlet and outlet temperature difference controlled within 5℃.

[0011] Preferably, the spatial arrangement of the electrode system on the vessel lid satisfies the following: with the working electrode interface as the center, the platinum wire quasi-reference electrode and redundant platinum wire electrodes are symmetrically arranged at a 60° angle with the working electrode as the center, and are 45-50 mm away from the working electrode; the detachable Ag / AgCl reference electrode is arranged at a 90° angle with the platinum wire quasi-reference electrode with the working electrode as the center, and is 10-15 mm away from the working electrode; the platinum sheet auxiliary electrode is arranged at a 60° angle with the detachable Ag / AgCl reference electrode with the working electrode as the center, and is 45-50 mm away from the working electrode.

[0012] Preferably, the distance between the measuring ends of the first thermocouple and the second thermocouple and the tips of the corresponding platinum wire quasi-reference electrode and redundant platinum wire electrode does not exceed 10 mm.

[0013] Preferably, the detachable Ag / AgCl reference electrode is installed on the reactor lid via a threaded connector or a sealed interface with a shut-off valve, and is used for in-situ calibration of the platinum wire quasi-reference electrode under conditions of 25–60°C. Before the reactor is heated to the high-temperature testing stage, the detachable Ag / AgCl reference electrode is removed from the reactor lid and sealed by a plug, or isolated from the reactor cavity by a shut-off valve.

[0014] Preferably, the electrical connection system includes external terminals that are respectively connected to the platinum wire quasi-reference electrode, the redundant platinum wire electrode, the detachable Ag / AgCl reference electrode, the platinum sheet auxiliary electrode, the working electrode interface, and the first thermocouple and the second thermocouple; in room temperature calibration mode, the platinum wire quasi-reference electrode and the Ag / AgCl reference electrode form a calibration circuit; in test mode, the working electrode interface, the platinum sheet auxiliary electrode, and the platinum wire quasi-reference electrode form a three-electrode test circuit, and the redundant platinum wire electrode is connected to the potential monitoring channel.

[0015] Preferably, the interfaces of the platinum wire quasi-reference electrode, redundant platinum wire electrode, platinum sheet auxiliary electrode, and working electrode all penetrate the reactor lid through an insulating sealing assembly. The insulating sealing assembly includes a metal outer tube, a ceramic insulating sleeve, a graphite-metal composite sealing ring, an alloy clamping nut, and an elastic clamping element. The metal outer tube penetrates the reactor lid, the elastic clamping element is located inside the metal outer tube, and the metal outer tube is fitted outside the ceramic insulating sleeve. The metal outer tube is connected to the reactor lid through the alloy clamping nut, and a graphite-metal composite sealing ring is provided between the alloy clamping nut and the reactor lid.

[0016] The advantages and beneficial effects of the present invention using the above-mentioned supercritical water polarization curve testing platinum wire quasi-reference electrode device are as follows: 1. The electrode device of the present invention includes two independent platinum wire quasi-reference electrodes. By monitoring the potential difference between the two electrodes in real time, it is possible to quickly determine whether the electrodes have drifted or failed, providing a basis for potential compensation and avoiding erroneous measurements caused by the failure of a single electrode.

[0017] 2. The device of this invention integrates a detachable Ag / AgCl reference electrode, which allows for absolute potential calibration of the platinum wire quasi-reference electrode before testing (room temperature to 60°C) without the need to open the reactor or change the solution, thus realizing a streamlined calibration-testing process. Furthermore, it is detachable before heating to prevent damage from high temperatures.

[0018] 3. Each platinum wire quasi-reference electrode in this invention is equipped with an independent thermocouple. The temperature measuring point is very close to the electrode tip, which can accurately reflect the temperature at the electrode location, provide accurate input for the temperature compensation algorithm, and significantly improve the accuracy of potential measurement at high temperatures.

[0019] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the arrangement of electrodes and thermocouples on the reactor lid in a platinum wire quasi-reference electrode device for testing supercritical water polarization curves according to the present invention. Figure 2 This is a schematic diagram of the insulating and sealing components in a platinum wire quasi-reference electrode device for testing supercritical water polarization curves according to the present invention. Figure 3 This is a schematic diagram of the overall structure of a platinum wire quasi-reference electrode device for testing supercritical water polarization curves according to the present invention.

[0021] Figure Labels 1. Reactor lid; 2. Platinum wire quasi-reference electrode; 3. Redundant platinum wire electrode; 4. Ag / AgCl reference electrode; 5. Platinum sheet auxiliary electrode; 6. Working electrode interface; 7. First thermocouple; 8. Second thermocouple; 9. Ceramic insulating sleeve; 10. Alloy clamping nut; 11. Graphite-metal composite sealing ring; 12. Elastic clamping component; 13. Metal outer sleeve; 14. Water-cooled jacket; 15. Cooling water circulation pipeline; 16. Flow regulating valve; 17. Electrical connection terminal; 18. Temperature acquisition and compensation system; 19. Electrochemical workstation; 20. Reactor. Detailed Implementation

[0022] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0023] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0024] The following examples are not intended to limit the invention, but are only for illustration. Unless otherwise specified, the experimental methods used in the following examples are generally performed under conventional conditions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0025] Example 1 A platinum wire quasi-reference electrode 2 device for supercritical water polarization curve testing includes a high-temperature and high-pressure reactor 20, a reactor lid 1, an electrode system integrated on the reactor lid 1, an electrical connection system, a temperature acquisition and compensation system 18, and a water cooling system. The reactor lid 1 is provided with multiple through-mounting interfaces for installing related components.

[0026] The lid 1 of the high-temperature and high-pressure reactor 20 is forged from Hastelloy C-276. The lid 1 is connected to the reactor 20 by high-strength bolts, and a rigid sealing structure with a metal O-ring is set between the two. The lid 1 is equipped with a working electrode interface 6, a platinum sheet auxiliary electrode 5 mounting interface, a platinum wire quasi-reference electrode 2 mounting interface, a redundant platinum wire electrode 3 mounting interface, a detachable Ag / AgCl reference electrode 4 mounting interface, a first thermocouple 7, a second thermocouple 8 mounting hole, and necessary interfaces for liquid inlet, gas inlet, pressure measurement, and internal medium temperature measurement.

[0027] The electrode system includes a working electrode interface 6, a platinum sheet auxiliary electrode 5, a platinum wire quasi-reference electrode 2, a redundant platinum wire electrode 3, a detachable Ag / AgCl reference electrode 4, a first thermocouple 7, and a second thermocouple 8.

[0028] The platinum wire quasi-reference electrode 2 and the redundant platinum wire electrode 3 constitute a redundant quasi-reference electrode unit. The two platinum wire electrodes are independent of each other, have the same structure, and are in the same test medium environment. During the corrosion polarization curve test, the platinum wire quasi-reference electrode 2 serves as the main reference electrode, and the redundant platinum wire electrode 3 serves as the potential monitoring electrode to evaluate the drift state of the main reference electrode in real time.

[0029] like Figure 1 As shown, the working electrode is located in the center of the vessel lid 1. The platinum wire quasi-reference electrode 2 and redundant platinum wire electrode 3 are symmetrically arranged at a 60° angle with the working electrode as the center, 45-50 mm away from the working electrode. The Ag / AgCl reference electrode 4 is arranged at a 90° angle with the platinum wire quasi-reference electrode 2 with the working electrode as the center, 10-15 mm away from the working electrode. The auxiliary electrode is arranged at a 60° angle with the Ag / AgCl reference electrode with the working electrode as the center, 45-50 mm away from the working electrode. This arrangement can effectively reduce the ohmic drop during quasi-reference potential calibration and corrosion polarization curve measurement. Thermocouple temperature measuring devices are equipped around the platinum wire quasi-reference electrode 2 and redundant platinum wire electrode 3 to calculate the quasi-reference electrode temperature compensation.

[0030] The water cooling system includes a water cooling jacket 14, a cooling water circulation pipeline 15, and a flow regulating valve 16. The cooling water flow rate is controlled at 0.5-2L / min, and the inlet and outlet temperature difference is controlled within 5℃.

[0031] The platinum wire quasi-reference electrode 2 and redundant platinum wire electrode 3 are made of high-purity platinum wire with a purity of 99.95% and a diameter of [missing information]. 0.8mm, 10mm immersion portion, total length 120mm.

[0032] The platinum wire quasi-reference electrode 2 and redundant platinum wire electrode 3 were pretreated by first soaking in aqua regia for 5 minutes, then rinsing with deionized water, and annealing in a muffle furnace at 500°C for 2 hours (argon protection).

[0033] After pretreatment, electrochemical passivation was performed: in 0.5MH2SO4, the PtO layer was formed by 50 cycles at a scan rate of 100mV / s between -0.3V and +1.5V, fixed at +1.2V for 30 min, stabilized by 20 cycles at +0.6V to +1.0V, rinsed with deionized water, and dried at 80℃ for 2 hours.

[0034] The platinum wire quasi-reference electrode 2, redundant platinum wire electrode 3, platinum sheet auxiliary electrode 5, and working electrode interface 6 all penetrate the vessel lid 1 through a high-temperature and high-pressure resistant insulating sealing assembly. The insulating sealing assembly includes a metal outer tube 13, a ceramic insulating sleeve 9, a graphite-metal composite sealing ring 11, an alloy clamping nut 10, and an elastic clamping element 12. The metal outer tube 13 penetrates the vessel lid 1, the elastic clamping element 12 is located inside the metal outer tube 13, and the metal outer tube 13 is fitted over the ceramic insulating sleeve 9. The metal outer tube 13 is connected to the vessel lid 1 via the alloy clamping nut, and a graphite-metal composite sealing ring 11 is provided between the alloy clamping nut 10 and the vessel lid 1. The ceramic insulating sleeve 9 is used to achieve electrical insulation between the conductive components and the vessel lid 1, the graphite-metal composite sealing ring 11 is used to form a high-temperature and high-pressure resistant seal, and the elastic clamping element 12 is used to compensate for the thermal expansion difference between the conductive components and the metal outer tube 13 during heating and cooling.

[0035] The measuring end of the first thermocouple 7 is adjacent to the effective exposed section of the platinum wire quasi-reference electrode 2, and the measuring end of the second thermocouple 8 is adjacent to the effective exposed section of the redundant platinum wire electrode 3. The distance between the measuring end and the corresponding tip of the platinum wire electrode is no more than 10 mm, preferably no more than 8 mm. The temperature acquisition and compensation system 18 acquires the temperatures at the two locations in real time and corrects the potential measured with the platinum wire quasi-reference electrode 2 as a reference based on the low-temperature calibration data and the pre-established platinum wire electrode temperature correction relationship.

[0036] The detachable Ag / AgCl reference electrode 4 is installed on the reactor lid 1 via a threaded connector, a sealed joint, or an interface with a shut-off valve. It is used only in the low-temperature stage (25–60°C) for in-situ calibration of the platinum wire quasi-reference electrode 2 and / or the redundant platinum wire electrode 3. Before the reactor 20 enters the high-temperature heating stage, the Ag / AgCl reference electrode 4 is removed and the interface is sealed with a high-temperature and high-pressure resistant plug, or the shut-off valve is closed to isolate it from the high-temperature medium inside the reactor, thereby preventing damage to the Ag / AgCl reference electrode 4 under high-temperature conditions.

[0037] Example 2 A platinum wire quasi-reference electrode device for testing supercritical water polarization curves, including the structure of the main electrode device.

[0038] like Figure 1 As shown, the electrode device includes a high-temperature, high-pressure reactor 20 and a reactor cover 1. The reactor cover 1 is forged from Hastelloy C-276 and connected to the reactor 20 by high-strength bolts. A metal O-ring or metal gasket is provided between the reactor cover 1 and the reactor 20 to meet the pressure sealing requirements under supercritical water conditions. The reactor cover 1 has multiple through-mounting interfaces for mounting a platinum wire quasi-reference electrode 2, a redundant platinum wire electrode 3, an Ag / AgCl reference electrode 4, a platinum sheet auxiliary electrode 5, a working electrode interface 6, a first thermocouple 7, and a second thermocouple 8.

[0039] Both the platinum wire quasi-reference electrode 2 and the redundant platinum wire electrode 3 are made of platinum wire with a purity of not less than 99.95% and a diameter of 0.8 mm. The platinum wire is introduced into the reaction vessel 20 through an insulating sleeve, and the effective exposed length of the platinum wire in the test medium is 10 mm. The horizontal distance between the two platinum wire electrodes is 50 ± 2 mm, and they are both arranged in an area 650 mm away from the working electrode interface, so that the two platinum wire electrodes are in a nearly uniform temperature field and chemical environment during the test.

[0040] The platinum sheet auxiliary electrode 5 uses a platinum sheet with a purity of not less than 99.95%, and its size can be 20mm × 10mm × 0.5mm, with an effective area of ​​approximately 2cm². 2 The working electrode interface 6 is used to mount the metal sample to be tested. The sample is fixed by an insulating support and connected to the electrical connection terminal 17 of the working electrode outside the reactor via a high-temperature resistant conductive lead.

[0041] The Ag / AgCl reference electrode 4 is installed on the reactor lid 1 via a detachable threaded sealing connector. This electrode is used only in the low-temperature stage when the reactor 20 is at room temperature to 60°C to calibrate the temperature coefficient of the platinum wire quasi-reference electrode 2 relative to the Ag / AgCl reference system. After calibration, before the reactor 20 is heated to the high-temperature testing stage, the Ag / AgCl reference electrode 4 is removed, and the interface is sealed with a high-temperature and high-pressure resistant plug.

[0042] The first thermocouple 7 and the second thermocouple 8 can be type K or type N armored thermocouples with an outer diameter of 0.5 to 1.5 mm. The measuring end of the first thermocouple 7 is 8 mm away from the tip of the platinum wire quasi-reference electrode 22, and the measuring end of the second thermocouple 8 is 8 mm away from the tip of the redundant platinum wire electrode 3, used to collect the real-time temperature near the two platinum wire electrodes respectively.

[0043] Example 3 like Figure 2 As shown, the platinum wire quasi-reference electrode 2 and the redundant platinum wire electrode 3 pass through the vessel cover 1 through a high-temperature and high-pressure resistant insulating sealing assembly. The insulating sealing assembly includes a metal outer sleeve 13, a ceramic insulating sleeve 9, a graphite-metal composite sealing ring 11, an alloy clamping nut 10, and an elastic clamping element 12. The metal outer sleeve 13 and the vessel cover 1 can be mechanically fixed by threaded connection, welding, or integrated processing; the ceramic insulating sleeve 9 is placed between the platinum wire and the metal outer sleeve 13 to maintain electrical insulation; the graphite-metal composite sealing ring 11 is axially compressed under the action of the alloy clamping nut 10 to achieve high-temperature and high-pressure sealing.

[0044] The elastic clamping element 12 can be an Inconel 718 alloy spring, located inside the alloy clamping nut 10 or at the upper connection point of the electrode. During assembly, the elastic clamping element 12 has a pre-compression of 2–4 mm, preferably 3 ± 0.5 mm. During heating, the elastic clamping element 12 compensates for the relative displacement caused by the difference in thermal expansion coefficients between the platinum wire, the ceramic insulating sleeve 9, and the metal outer sleeve 13, maintaining the stability of the sealing ring clamping force and the effective exposed length of the platinum wire.

[0045] Example 4 like Figure 3 As shown, the electrical connection system includes multiple electrical connection terminals 17 disposed on the outside of the vessel lid 1. A platinum wire quasi-reference electrode 2, a redundant platinum wire electrode 3, an Ag / AgCl reference electrode 4, a platinum sheet auxiliary electrode 5, and a working electrode interface 6 are each connected to an independent electrical connection terminal 17. A first thermocouple 7 and a second thermocouple 8 are connected to a temperature acquisition and compensation system 18.

[0046] In low-temperature calibration mode, Ag / AgCl reference electrode 4 is used as the standard reference electrode, and platinum wire quasi-reference electrode 2 is connected to electrochemical workstation 19 to record its stable potential relative to Ag / AgCl reference electrode 4.

[0047] In the high-temperature polarization curve testing mode, the Ag / AgCl reference electrode 4 is removed or isolated. The working electrode interface 6, the platinum sheet auxiliary electrode 5, and the platinum wire quasi-reference electrode 2 are connected to the working electrode, auxiliary electrode, and reference electrode channels of the electrochemical workstation 19, respectively, forming a three-electrode testing circuit. The redundant platinum wire electrode 3 is connected to the auxiliary potential monitoring channel or the independent high-resistance potential acquisition channel of the electrochemical workstation 19 for real-time monitoring of the potential difference between it and the platinum wire quasi-reference electrode 2.

[0048] Example 5 To improve the consistency of the platinum wire surface condition, the platinum wire quasi-reference electrode 2 and redundant platinum wire electrode 3 can be pretreated as follows before assembly: first, soak in aqua regia for about min, then rinse thoroughly with deionized water and ultrasonically clean for about 10 min; then anneal at 500℃ for 2 hours under an argon protective atmosphere; then, in a 0.5 mol / L H2SO4 solution, cyclically scan at a scan rate of 100 mV / s within the range of -0.3V to +1.5V for about 50 cycles, and hold at +1.2V for about 30 min to form a stable platinum oxide surface layer; finally, slowly scan within the range of +0.6V to +1.0V for about 20 cycles, rinse with deionized water, and dry at 80℃ for about 2 hours. The above parameters can be adjusted appropriately according to the medium type and test requirements.

[0049] Example 6 During the test, the temperature acquisition module collects the temperatures T1 and T2 of the first thermocouple 7 and the second thermocouple 8 in real time. T1 can be taken as the local temperature of the main reference electrode, or the average of T1 and T2 can be taken as the representative temperature of the platinum wire quasi-reference electrode 2 unit when the difference between T1 and T2 is less than a preset temperature difference threshold. The electrochemical workstation 19 simultaneously records the potential E1 of the platinum wire quasi-reference electrode 2 and the potential E2 of the redundant platinum wire electrode 3, and calculates ΔE = E1 - E2 or |E1 - E2|. When |ΔE| exceeds the preset threshold, it is determined that the quasi-reference electrode has drift, contamination, abnormal contact, or local environmental disturbance, and the system prompts to discard, mark, or retest the data for that time period. The preset threshold can be set to 3-10mV according to the test accuracy requirements, preferably 3mV.

[0050] During temperature compensation, the potential of the platinum wire quasi-reference electrode 2 relative to the Ag / AgCl reference electrode 4, obtained from low-temperature in-situ calibration, can be used as the initial calibration value. Combined with the pre-established platinum wire electrode temperature correction relationship f(T), the working electrode potential measured using the platinum wire quasi-reference electrode 2 as a reference during the high-temperature testing phase can be converted. The specific functional form can be obtained from calibration experiments under the same medium system.

[0051] Example 7 Electrode device testing procedure: (1) Constructing the electrode system: the metal sample to be tested, the quasi-reference electrode unit, the platinum auxiliary electrode 5, and the Ag / AgCl reference electrode (in-situ calibration function).

[0052] (2) The quasi-reference electrode was calibrated at room temperature. An electrochemical testing environment and solution medium were established. The potential of the platinum wire quasi-reference electrode 2 was calibrated at room temperature using an Ag\AgCl reference electrode.

[0053] (3) Calculation of the temperature coefficient of the quasi-reference electrode: The solution medium is slowly raised from room temperature to 60°C, the open circuit potential of the quasi-reference electrode relative to the Ag / AgCl reference electrode 4 is measured, a temperature-open circuit potential curve is established, and the temperature coefficient of the quasi-reference electrode is calculated.

[0054] (4) Increase the temperature and pressure to the target value, use the metal sample to be tested as the working electrode, increase the temperature and pressure of the electrochemical test environment to the target value, and monitor the temperature and pressure changes.

[0055] (5) Test the open circuit potential of the test sample. Measure the open circuit potential and monitor the fluctuation. When the open circuit potential fluctuation is ≤3mV, record the open circuit potential OCP.

[0056] (6) Monitor the potential difference between the quasi-reference electrode and the redundant quasi-reference electrode. After stabilization, measure and monitor the potential difference of the double platinum wire in real time. When <3mV, perform Tafel testing. When ≥3mV, automatically update the thermoelectric potential compensation.

[0057] (7) Using the updated potential as the potential reference, perform Tafel polarization curve measurements according to the standard electrochemical testing method. The potential coordinates of the polarization curve are directly converted to the standard hydrogen electrode (SHE) reference.

[0058] (8) Calculate the corrosion electrochemical parameters.

[0059] Through the above structure and process, the present invention can realize in-situ calibration, real-time drift monitoring and temperature compensation of platinum wire quasi-reference electrode 2 in high temperature and high pressure corrosive media such as supercritical water, thereby improving the accuracy, continuity and reliability of the test results of corrosion polarization curve of metal materials.

[0060] Therefore, the present invention employs the aforementioned platinum wire quasi-reference electrode device for supercritical water polarization curve testing, which solves the technical problems in the prior art such as the inability to assess the stability of the reference electrode, unreliable sealing structure, lack of temperature compensation, and complex calibration process, thereby achieving high precision, high reliability, and continuity in electrochemical testing in supercritical water environments.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A platinum wire quasi-reference electrode device for testing supercritical water polarization curves, characterized in that: The system includes a reactor, a reactor lid, an electrode system integrated on the lid, an electrical connection system, a temperature acquisition and compensation system, and a water cooling system. The lid is connected to the reactor by bolts, and a metal O-ring or metal sealing gasket is installed between the lid and the reactor. The lid has multiple through-mount interfaces. The electrode system includes a working electrode interface, a platinum sheet auxiliary electrode, a platinum wire quasi-reference electrode, a redundant platinum wire electrode, a detachable Ag / AgCl reference electrode, and a first thermocouple and a second thermocouple corresponding to the platinum wire quasi-reference electrode and the redundant platinum wire electrode, respectively. The temperature acquisition and compensation system acquires the temperatures at the tips of the platinum wire quasi-reference electrode and the redundant platinum wire electrode in real time, and corrects the potential measured with the platinum wire quasi-reference electrode as a reference based on the low-temperature calibration data and the pre-established platinum wire electrode temperature correction relationship.

2. The platinum wire quasi-reference electrode device for testing supercritical water polarization curves according to claim 1, characterized in that: Both the platinum wire quasi-reference electrode and the redundant platinum wire electrode are made of platinum wire with a purity of not less than 99.95%. The diameter of the platinum wire is 0.5 to 1.0 mm. The platinum wire is introduced into the reaction vessel through an insulating sleeve, and the effective exposure length in the test medium is 5 to 20 mm.

3. The platinum wire quasi-reference electrode device for testing supercritical water polarization curves according to claim 1, characterized in that: Before use, the platinum wire quasi-reference electrode and redundant platinum wire electrode need to be pretreated by soaking in aqua regia for 5 minutes, followed by rinsing with deionized water, annealing at 500°C for 2 hours under argon protection in a muffle furnace, and then undergoing electrochemical passivation treatment: in 0.5M H2SO4, 50 cycles are performed between -0.3V and +1.5V at a scan rate of 100mV / s, then fixed at +1.2V for 30 minutes to form a PtO layer, followed by 20 slow scans between +0.6V and +1.0V for stabilization, rinsing with deionized water, and drying at 80°C for 2 hours.

4. The platinum wire quasi-reference electrode device for testing supercritical water polarization curves according to claim 1, characterized in that: The platinum sheet auxiliary electrode uses a platinum sheet with a purity of not less than 99.95%, and its size can be 20mm × 10mm × 0.5mm, with an effective area of ​​2cm². 2 .

5. The platinum wire quasi-reference electrode device for testing supercritical water polarization curves according to claim 1, characterized in that: The water cooling system includes a water cooling jacket, cooling water circulation pipeline, and flow regulating valve. The cooling water flow rate is controlled at 0.5-2L / min, and the inlet and outlet temperature difference is controlled within 5℃.

6. The platinum wire quasi-reference electrode device for testing supercritical water polarization curves according to claim 1, characterized in that: The spatial arrangement of the electrode system on the vessel lid satisfies the following: with the working electrode interface as the center, the platinum wire quasi-reference electrode and redundant platinum wire electrodes are arranged symmetrically at a 60° angle with the working electrode as the center, and are 45-50 mm away from the working electrode; the Ag / AgCl reference electrode is arranged at a 90° angle with the platinum wire quasi-reference electrode with the working electrode as the center, and is 10-15 mm away from the working electrode; the platinum sheet auxiliary electrode is arranged at a 60° angle with the Ag / AgCl reference electrode with the working electrode as the center, and is 45-50 mm away from the working electrode.

7. The platinum wire quasi-reference electrode device for testing supercritical water polarization curves according to claim 1, characterized in that: The measuring ends of the first and second thermocouples are no more than 10 mm away from the tips of the corresponding platinum wire quasi-reference electrodes and redundant platinum wire electrodes.

8. The platinum wire quasi-reference electrode device for testing supercritical water polarization curves according to claim 1, characterized in that: The Ag / AgCl reference electrode is installed on the reactor lid via a threaded connector or a sealed interface with a shut-off valve. It is used for in-situ calibration of the platinum wire reference electrode at 25–60°C. Before the reactor is heated to the high-temperature testing stage, the Ag / AgCl reference electrode is removed from the reactor lid and sealed with a plug, or isolated from the reactor cavity by a shut-off valve.

9. The platinum wire quasi-reference electrode device for testing supercritical water polarization curves according to claim 1, characterized in that: The electrical connection system includes external electrical connection terminals that are respectively connected to the platinum wire quasi-reference electrode, redundant platinum wire electrode, Ag / AgCl reference electrode, platinum sheet auxiliary electrode, working electrode interface, and the first and second thermocouples. In room temperature calibration mode, the platinum wire quasi-reference electrode and the Ag / AgCl reference electrode form a calibration circuit. In test mode, the working electrode interface, platinum sheet auxiliary electrode, and platinum wire quasi-reference electrode form a three-electrode test circuit, and the redundant platinum wire electrode is connected to the potential monitoring channel.

10. The platinum wire quasi-reference electrode device for testing supercritical water polarization curves according to claim 1, characterized in that: The interfaces of the platinum wire quasi-reference electrode, redundant platinum wire electrode, platinum sheet auxiliary electrode, and working electrode all penetrate the reactor lid through an insulating sealing assembly. The insulating sealing assembly includes a metal outer tube, a ceramic insulating sleeve, a graphite-metal composite sealing ring, an alloy clamping nut, and an elastic clamping component. The metal outer tube penetrates the reactor lid, the elastic clamping component is located inside the metal outer tube, and the metal outer tube is fitted outside the ceramic insulating sleeve. The metal outer tube is connected to the reactor lid through the alloy clamping nut, and a graphite-metal composite sealing ring is provided between the alloy clamping nut and the reactor lid.

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