A test method for hydrogen permeation of metals considering the effect of stray current corrosion

Abstract

The present invention relates to metal hydrogen permeation technology, and aims to provide a metal hydrogen permeation test method that takes into account the corrosion effect of stray current. The method comprises: building a combined device comprising an autoclave, a soil box and an electrolytic cell box, and connecting the inner cavities of the three with metal specimens at the same time, and adding hydrogen-containing gas, soil and hydrogen evolution solution respectively. A waveform generator is used as a signal source, and different parameter outputs are achieved through a converter to realistically simulate the generation of stray current and the transmission process in the pipeline, taking into account the influence of stray current on the hydrogen permeation behavior of buried metal. The present invention can obtain metal hydrogen diffusion rate test results that take into account the corrosion effect of stray current, and the hydrogen diffusion coefficient obtained by the test is closer to the actual situation of buried metal. The device used has a simple structure and a reasonable design, and can scientifically study the hydrogen permeation behavior law under the coupling effect of stray current and impurity gas in the soil environment, providing a reference for the anti-hydrogen embrittlement design of buried pipelines.

Description

Technical Field

[0001] The invention relates to a metal hydrogen permeation technology, in particular to a metal hydrogen permeation testing method taking into account the corrosion effect of stray current. Background Art

[0002] Hydrogen, due to its abundant resources, pollution-free nature, high calorific value, and renewable nature, has become one of the most promising secondary energy sources. It is a key tool for achieving global energy transformation, and developing clean hydrogen utilization is a crucial component of energy strategy. Within the hydrogen energy industry chain, hydrogen storage and transportation are crucial links. Utilizing existing natural gas pipelines to transport hydrogen is a key solution for achieving large-scale hydrogen application.

[0003] The primary challenge in transporting hydrogen through existing natural gas pipelines is hydrogen embrittlement of the pipes. Hydrogen embrittlement of metallic materials occurs when hydrogen atoms enter the metal, causing degradation of material properties, inducing cracks, or causing delayed fracture. Hydrogen-induced failure generally requires hydrogen permeation, and hydrogen permeation testing is an effective method for studying and assessing the susceptibility of metallic materials to hydrogen embrittlement.

[0004] Currently, the most commonly used method for studying hydrogen permeation through metals is the DS dual-electrolytic cell electrochemical hydrogen permeation method. This method uses an electrolyte solution to generate hydrogen atoms through an electrochemical reaction. Driven by the concentration difference, the hydrogen atoms adsorbed on the metal surface diffuse to the other side of the sample, generating a polarization current. However, this method cannot accurately simulate the high-pressure hydrogen-blended natural gas environment within the pipeline and also changes the surface state of the sample. While the gas-phase hydrogen permeation method can avoid these problems, it generally only studies the influence of a single factor on the hydrogen permeation behavior of metals.

[0005] Furthermore, buried natural gas pipelines are often subject to interference from stray currents during actual service. Under the influence of stray currents, hydrogen evolution occurs on the metal surface, and the resulting hydrogen atoms can affect hydrogen permeation within the pipeline. Current methods for measuring hydrogen permeation do not account for the presence of stray currents.

[0006] Therefore, conducting metal hydrogen permeation tests under the action of stray current and studying the laws of metal hydrogen permeation under the coupling of stray current and impurity gas can deepen the understanding of pipeline hydrogen embrittlement and provide a basis for the anti-hydrogen embrittlement design of buried pipelines. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to propose a metal hydrogen permeation test method taking into account the corrosion effect of stray current in order to overcome the shortcomings of the existing technology.

[0008] In order to solve the above technical problems, the solution provided by the present invention is:

[0009] A method for testing hydrogen permeation of metals taking into account the effects of stray current corrosion is provided, comprising the following steps:

[0010] (1) Build the test apparatus as follows:

[0011] The first autoclave is sequentially connected to a pressure reducing valve and a second autoclave via pipelines. The first autoclave is provided with an air inlet, and the second autoclave is provided with an air outlet. The air inlet is connected to multiple gas cylinders via pipelines. The second autoclave, the soil box, and the electrolytic cell box each have a mounting hole connected to their inner cavities. The three mounting holes are close to each other, and metal specimens can be simultaneously embedded in different locations in the three mounting holes.

[0012] A soil box is filled with soil, and a platinum electrode is inserted into the soil; the platinum electrode is connected to an ammeter, a waveform generator, and a metal sample via a wire to form a closed circuit; an auxiliary electrode and a reference electrode are provided in the electrolytic cell box, both of which are connected to an electrochemical workstation via wires, and the electrochemical workstation is connected to the metal sample via wires;

[0013] (2) Wrap a resistance wire around the surface of the metal sample, and then connect the resistance wire to a heating controller, which is connected to an external power supply via a wire; weld two wires on the surface of the metal sample, one of which is used to connect to the electrochemical workstation, and the other is used to form a closed loop with the platinum electrode; embed the metal sample into the three mounting holes, ensuring that the metal sample is sealed with the second autoclave and the electrolytic cell box, and can fit tightly against the soil;

[0014] (3) preparing pressurized hydrogen-containing gas using different gas cylinders and a first autoclave according to the components or proportions designed in the experimental plan; adding hydrogen evolution solution to the electrolytic cell box until the auxiliary electrode and the reference electrode are immersed;

[0015] (4) applying a constant potential to the metal sample using an electrochemical workstation, and first passivating the sample surface; after the background current stabilizes, introducing hydrogen-containing gas into the second autoclave through a pressure reducing valve and maintaining the pressure; at this time, the metal sample is located in three mounting holes, and its surface is in contact with the pressurized hydrogen-containing gas in the second autoclave, the soil in the soil box, and the hydrogen evolution solution in the electrolytic cell box, respectively;

[0016] (5) Turn on the heating controller to increase the hydrogen permeation rate on the sample surface, and observe the changes in the hydrogen permeation current in the electrolytic cell displayed on the electrochemical workstation; after the current reaches a stable state, record the steady-state current I1 under the action of hydrogen-containing gas displayed on the electrochemical workstation; then turn on the waveform generator, and after the hydrogen permeation current reaches a stable state again, record the steady-state hydrogen permeation current I3 under the combined action of hydrogen-containing gas and stray current;

[0017] (6) Release the gas in the second autoclave and purge it with nitrogen several times; turn off the electrochemical workstation and only turn on the waveform generator; after the current displayed on the ammeter reaches a stable state, record the steady-state current I2 under the action of stray current; compare the sizes of I1+I2 and I3, and summarize the laws of hydrogen permeation behavior of metal materials under the coupling of hydrogen-containing gas and stray current.

[0018] As a preferred embodiment of the present invention, the method further includes step (7): replacing metal samples of different materials, changing the partial pressure ratio or gas composition of the hydrogen-containing gas, changing the magnitude and waveform of the stray current, repeating the experiment under the conditions of adjusting the influencing factors, and summarizing the laws of hydrogen permeation behavior of metal materials under different influencing factors.

[0019] As a preferred embodiment of the present invention, it is characterized in that during the test, the first autoclave is used to continuously replenish the test gas to the second autoclave to maintain the pressure in the second autoclave constant.

[0020] As a preferred solution of the present invention, it is characterized in that before the metal sample is installed, the surface used for contact with the hydrogen-containing gas is first nickel-plated to reduce the background current density during the hydrogen permeation test.

[0021] As a preferred embodiment of the present invention, it is characterized in that the gas cylinders include hydrogen cylinders, oxygen cylinders, carbon dioxide cylinders, inert gas cylinders and natural gas cylinders.

[0022] As a preferred solution of the present invention, it is characterized in that pressure gauges are respectively provided on the end covers of the first autoclave and the second autoclave.

[0023] As a preferred solution of the present invention, it is characterized in that the metal sample is cylindrical and the surface in contact with the soil is not wrapped with resistance wire; the area of the resistance wire wrapped on the metal sample is greater than 2 / 3 of the area of the sample side wall.

[0024] As a preferred embodiment of the present invention, it is characterized in that the side wall of the second high-pressure autoclave is provided with a through-going variable-diameter countersunk hole, and the countersunk hole is used as a mounting hole position; the soil box body includes a box-shaped main body and a cover plate, and the side edges of the cover plate and the adjacent box body side walls have notches; the electrolytic cell box body is made of organic glass and is placed on the upper side of the soil box body, and has a notch in the lower part of its side wall; the notches in the electrolytic cell box body and the soil box body together constitute a mounting hole position adapted to the shape of the end of the metal sample.

[0025] As a preferred embodiment of the present invention, it is characterized in that the composition of the hydrogen evolution solution is 0.2 mol / L NaOH + 2 mL / L Na2S.

[0026] Description of the invention principle:

[0027] To solve the problems of leakage and gas pressure reduction over time in traditional gas-phase hydrogen permeation tests, the present invention provides two autoclaves with different gas pressures and volumes, interconnecting them. A pressure reducing valve is provided on the pipeline after the first autoclave to replenish the test gas to the second autoclave in a timely manner, so that the test gas is in direct contact with the metal sample.

[0028] The heating controller and resistance wire together form the heating assembly. By adjusting the current through the heating controller, the specimen is uniformly heated, increasing the hydrogen permeation rate, shortening test time, and improving work efficiency. The side ends of the metal specimen do not need to be wrapped with resistance wire, which increases the effective contact area between the specimen and the soil.

[0029] The electrochemical hydrogen evolution assembly consists of an electrolytic cell housing, hydrogen evolution solution, electrochemical workstation, auxiliary electrode, and reference electrode. The electrolytic cell housing contains the hydrogen evolution solution. Hydrogen atoms escaping from the metal sample surface enter the hydrogen evolution solution, where they are oxidized to form hydrogen ions and generate current. Parameters such as hydrogen diffusion rate and adsorbed hydrogen concentration are obtained through the signal current. Both the auxiliary electrode and the reference electrode are placed in the hydrogen evolution solution.

[0030] The waveform generator, ammeter and platinum electrode constitute a waveform generating assembly, which is used to simulate, among other things, the platinum electrode is located in the soil, and the output end of the waveform generator is connected to and respectively connected to the metal sample and the platinum electrode through a second wire. When building the device, the soil box needs to be filled with soil, and the metal sample must be in full contact with the soil. The ammeter can be used to confirm whether a closed loop is formed. During the test, after the power is turned on, the stray current enters the metal sample through the wire, and then flows from the sample into the soil, simulating the stray current corrosion of the buried pipeline. Suitable test soil can be selected according to different environments, and the soil humidity, salinity, temperature and other conditions can be designed according to the test plan.

[0031] This invention utilizes a waveform generator as a signal source, which, through a converter, can output different parameters, including voltage, current, waveform, and frequency. This realistically simulates the generation and transmission of stray currents in pipelines, taking into account their impact on hydrogen permeation through buried metals. An autoclave assembly is connected to a gas cylinder assembly via a gas pipeline. Hydrogen, natural gas, and impurity gases (such as CO2 and O2) enter the autoclave assembly through the gas pipeline. This allows for the study of hydrogen permeation patterns in metal pipelines under the coupled effects of stray currents and impurity gases. A heating assembly accelerates the hydrogen permeation rate, and an electrochemical hydrogen evolution assembly measures the signal current generated by the hydrogen evolution reaction.

[0032] The present invention takes into account the influence of stray current in hydrogen permeation test research. The device used has a simple structure and reasonable design. It can scientifically study the hydrogen permeation behavior law under the coupling effect of stray current and impurity gas in the soil environment, and provide a reference for the anti-hydrogen embrittlement design of buried pipelines.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. Compared with existing testing schemes that can only realize single-factor hydrogen permeation testing, the service environment of actual structures often includes the coupling effects of many influencing factors; the testing method proposed in this invention can obtain metal hydrogen diffusion rate test results that take into account the effect of stray current corrosion.

[0035] 2. When testing the metal hydrogen diffusion rate, the present invention takes into account the combined effects of stray current and impurity gases, so the hydrogen diffusion coefficient obtained from the test is closer to the actual situation of buried metal. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The present invention will be further described below with reference to the accompanying drawings and embodiments;

[0037] Figure 1 A schematic diagram of the device used in the present invention;

[0038] Figure 2 Schematic diagram of the connection between the metal sample and the heating component.

[0039] In the figure: pressure gauge 1, air inlet 2, first autoclave 3, hydrogen-containing gas 4, pressure reducing valve 5, second autoclave 6, pressure gauge 7, air outlet 8, metal sample 9, heating controller 10, ammeter 11, electrochemical workstation 12, waveform generator 13, electrolytic cell box 14, auxiliary electrode 15, reference electrode 16, hydrogen evolution solution 17, cover 18, platinum electrode 19, soil box 20, soil 21. DETAILED DESCRIPTION

[0040] The serial numbers assigned to the components in this application, such as "first", "second", etc., are only used to distinguish the objects described and do not have any order or technical meaning. The "connection" and "coupling" mentioned in this application, unless otherwise specified, include direct and indirect connections (couplings). In the description of this application, it should be understood that the orientation or position relationship indicated by the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", etc. are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to this application.

[0041] In this application, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0042] In the present invention, the first autoclave, the pressure reducing valve and the second autoclave connected in sequence together constitute an autoclave group; as an example, the working pressure of the first autoclave is between 15 and 20 MPa, and the working pressure of the second autoclave is between 12 and 15 MPa.

[0043] The metal hydrogen permeation test method of the present invention is implemented based on the following test device, the structure of which is as follows: Figure 1 shown.

[0044] The device includes a first autoclave 3, a second autoclave 6, a metal sample 9, a heating controller 10, an ammeter 11, an electrochemical workstation 12, a waveform generator 13, an electrolytic cell box 14, a cover 18, a platinum electrode 19 and a soil box 20.

[0045] A first autoclave 3 is provided with a pressure gauge 1 and an air inlet 2. The air inlet 2 is connected to multiple gas cylinders via pipelines, one of which is a hydrogen cylinder. The other gas cylinders include hydrogen cylinders, oxygen cylinders, carbon dioxide cylinders, inert gas cylinders, and natural gas cylinders (used for doping and compatibility to form hydrogen-containing gas 4). A second autoclave 6 is connected to a pressure reducing valve 5 and the first autoclave 3 via pipelines. The second autoclave 6 is provided with an air outlet 8 and a pressure gauge 7.

[0046] The second autoclave 6, the electrolytic cell housing 14, and the soil housing 20 each have a mounting hole connected to their respective inner cavities. The three mounting holes are located adjacent to one another, and the metal sample 9 is embedded simultaneously in different locations within each of the three mounting holes. The metal sample 9 is hermetically sealed against the mounting holes of the second autoclave 6 and the electrolytic cell housing 14, and closely adheres to the soil 21 within the soil housing 20. Specifically, the surfaces of each embedded portion are in contact with the pressurized hydrogen-containing gas 4 within the second autoclave 6, the soil 21 within the soil housing 20, and the hydrogen evolution solution 17 within the electrolytic cell housing 14.

[0047] A platinum electrode 19 inserted into the soil 21 is provided in the soil box 20. The platinum electrode 19 is connected to the waveform generator 13, the ammeter 11 and the metal sample 9 through a wire to form a closed loop. An auxiliary electrode 15 and a reference electrode 16 immersed in the hydrogen evolution solution 17 are provided in the electrolytic cell box 14. Both are connected to the electrochemical workstation 12 through wires, and the latter is connected to the metal sample through a wire. A resistance wire is wound around the surface of the metal sample 9. The resistance wire is connected to the heating controller 10 through a wire, and the latter is connected to an external power supply (not shown). The metal sample 9 can be optionally cylindrical, and the winding area of the resistance wire on the surface of the metal sample is larger than 2 / 3 of the side surface of the sample (such as Figure 2 shown).

[0048] Figure 1 In the embodiment, a through-going variable diameter countersunk hole is provided on the side wall of the second autoclave 6, and the countersunk hole is used as a mounting hole. The soil box body 20 includes a box-shaped main body and a cover plate 18. The side edges of the cover plate 17 and the adjacent side walls of the box body have notches and constitute mounting holes. The electrolytic cell box body 14 is made of organic glass and is placed on the upper side of the soil box body 20. The lower part of its side wall has a notch and constitutes a mounting hole. The two notches on the lower part of the side wall of the electrolytic cell box body 14 and the upper part of the side wall of the soil box body 20 together form a mounting hole that adapts to the shape of the end of the metal sample 9. In order to adapt to the installation of the metal sample 9, the second autoclave 6, the electrolytic cell box body 14 and the soil box body 20 can also have other various combination and matching relationships. For example, the three containers are placed flat and arranged relative to each other with their respective mounting holes. The specific selection can be arranged according to actual conditions.

[0049] The electrolytic cell housing 14 is filled with a hydrogen evolution solution 17, the composition of which can be prepared according to methods described in existing literature. Hydrogen atoms escaping from the surface of the metal sample 9 enter the hydrogen evolution solution, where they are oxidized to form hydrogen ions, generating a signal current. This signal current can be used to calculate parameters such as the hydrogen diffusion rate and the adsorbed hydrogen concentration.

[0050] Specific application examples:

[0051] The application method of the present invention is described in detail below with reference to a specific test example:

[0052] (1) Use an electric spark wire cutting machine to cut the metal material into a cylindrical specimen with a diameter of 30 mm and a thickness of 10 mm. Polish its surface with water-abrasive paper of No. 200 to No. 1200 until it is smooth.

[0053] (2) Before installation, the metal sample 9 needs to be nickel-plated on the hydrogen-measuring side to reduce the background current density during the hydrogen permeation test. The nickel plating solution composition can be prepared according to the published literature, for example, 250g / L NiSO4·7H2O + 45g / L NiCl2·6H2O + 45g / L H3BO3. The current density during nickel plating is 2.8mA / cm2 , nickel plating time is 40s.

[0054] (3) Fill soil box 20 with soil 21 and insert platinum electrode 19 into soil 21. Connect platinum electrode 19 to waveform generator 13 and ammeter 11 via a wire. The other end of ammeter 11 is welded to metal specimen 9 via a wire. Turn on waveform generator 13, observe ammeter 11, and confirm that a closed circuit has been established. Then, turn off waveform generator 13.

[0055] (4) The cover plate 18 is placed on the upper portion of the soil box 20. The electrolytic cell box 14 is placed on the cover plate 18.

[0056] One end of the metal sample 9 is encapsulated in the mounting hole of the second autoclave 6. The area of the metal sample 9 that directly contacts the hydrogen-containing gas 4 is the circular end with a diameter of 24 mm. The soil box 20 and the electrolytic cell box 14 are then placed against the second autoclave 6, with the other end of the metal sample 9 extending into the mounting hole of the soil box 20 and the electrolytic cell box 14, and the lower surface of this end in close contact with the soil 21. During assembly, ensure a tight seal between the metal sample 9 and the mounting holes of the second autoclave 6 and the electrolytic cell box 14 to prevent leakage of the hydrogen-containing gas 4 or hydrogen evolution solution 17.

[0057] (5) Open the pressure reducing valve and purge the autoclave group with 1MPa nitrogen three times to exhaust the air in the autoclave. To ensure the stability of the internal environment of the autoclave group, the autoclave group must be tested for airtightness before the test. 15MPa nitrogen is introduced into the autoclave group to ensure that the pressure drops within 0.02MPa within 24 hours before the metal hydrogen permeation test can be carried out.

[0058] According to the experimental plan, high-pressure hydrogen-containing gas 4 is prepared in the first autoclave 3 using different gases in a plurality of gas cylinders.

[0059] (6) Add hydrogen evolution solution 17 to the electrolytic cell housing 14, the composition of which is 0.2 mol / L NaOH + 2 mL / L Na2S. Among them, Na2S acts as a poisoning agent to prevent hydrogen atoms from recombining into hydrogen molecules and escaping. At the same time, an auxiliary electrode 15 and a reference electrode 16 are placed in the solution, and the electrodes are connected to the electrochemical workstation 13 through wires. The other end of the electrochemical workstation 13 is connected to the metal sample 9 through a wire, and the connection point on the sample is welded; a polarization potential of a constant potential of 300 mV (relative to the reference electrode 16) is applied to passivate the nickel plating layer on the surface of the sample. The background current is less than 1 μA / cm 2 And then charge hydrogen after it becomes stable;

[0060] (7) When the background current value meets the requirements, introduce 15 MPa of hydrogen-containing gas 4 into the first autoclave 3 and maintain the pressure. It is worth noting that the ventilation time must be long enough (to maintain the pressure constant). Turn on the heating controller 10 and record the changes in the hydrogen permeation current displayed by the electrochemical workstation 12;

[0061] (8) After the current reaches a stable state, record the steady-state current I1 under the action of the hydrogen-containing gas 4. Turn on the waveform generator 13, and after the hydrogen permeation current reaches a stable state again, record the steady-state hydrogen permeation current I3 under the combined action of the hydrogen-containing gas 4 and the stray current.

[0062] (9) Slowly discharge the gas in the autoclave group and purge the autoclave group with 1MPa nitrogen for 3 times to ensure that there is no impurity gas in the autoclave. Turn off the electrochemical workstation 12 and turn on the waveform generator 13 separately. After the current reaches a stable state, record the steady-state current I2 under the action of stray current. Compare the sizes of I1+I2 and I3 to explore the hydrogen permeation behavior of buried metal materials under the coupling of hydrogen-containing gas and stray current. After the hydrogen permeation test is completed, remove the test electrode;

[0063] (10) Change the metal sample 9 to a new material, change the partial pressure ratio or impurity gas composition of the hydrogen-containing gas 4 in the autoclave, or change the magnitude and type of the stray current, and repeat (1) to (9). By changing various relevant factors in the test process, its impact on the test results can be tested.

[0064] As described above, using the test device proposed in this invention to conduct hydrogen permeation testing on buried metals can obtain metal hydrogen permeation parameters that account for the effects of stray current corrosion. Compared to existing testing methods that only measure hydrogen permeation under a single factor, the actual pipeline service environment often involves the coupled effects of multiple influencing factors. This invention can obtain the hydrogen diffusion coefficient under the combined effects of stray current and impurity gases, which is closer to the actual conditions of buried metals.

Claims

1. A method for testing metal hydrogen permeation taking into account the effect of stray current corrosion, characterized in that: The following steps are involved: (1) Build the test apparatus as follows: The first autoclave is sequentially connected to a pressure reducing valve and a second autoclave via pipelines. The first autoclave is provided with an air inlet, and the second autoclave is provided with an air outlet. The air inlet is connected to multiple gas cylinders via pipelines. The second autoclave, the soil box, and the electrolytic cell box each have a mounting hole connected to their respective inner cavities. The three mounting holes are close to each other, and different parts of the metal sample can be simultaneously embedded in the three mounting holes. A soil box is filled with soil, and a platinum electrode is inserted into the soil; the platinum electrode is connected to an ammeter, a waveform generator, and a metal sample via a wire to form a closed circuit; an auxiliary electrode and a reference electrode are provided in the electrolytic cell box, and both are connected to an electrochemical workstation via wires, and the electrochemical workstation is connected to the metal sample via wires; (2) Wrap the surface of the metal sample with a resistance wire, then connect the resistance wire to the heating controller, which is connected to an external power supply via a wire; weld two wires on the surface of the metal sample, one of which is used to connect to the electrochemical workstation, and the other is used to connect to the waveform generator and form a closed loop with the platinum electrode; embed the metal sample into the three mounting holes to ensure that the metal sample is sealed with the second autoclave and the electrolytic cell box, and can fit tightly against the soil; (3) Prepare pressurized hydrogen-containing gas using different gas cylinders and the first autoclave according to the components or proportions designed in the experimental plan; add hydrogen evolution solution into the electrolytic cell box until the auxiliary electrode and reference electrode are immersed; (4) Using an electrochemical workstation, a constant potential is applied to the metal sample, and the sample surface is first passivated. After the background current stabilizes, hydrogen-containing gas is introduced into the second autoclave through a pressure reducing valve and the pressure is maintained. At this time, the metal sample is located in three mounting holes, and its surface is in contact with the pressurized hydrogen-containing gas in the second autoclave, the soil in the soil box, and the hydrogen evolution solution in the electrolytic cell box, respectively. (5) Turn on the heating controller to increase the hydrogen permeation rate on the sample surface, and observe the changes in the hydrogen permeation current in the electrolytic cell displayed on the electrochemical workstation; after the current reaches a stable state, record the steady-state current I1 under the action of hydrogen-containing gas displayed on the electrochemical workstation; then turn on the waveform generator, and after the hydrogen permeation current reaches a stable state again, record the steady-state hydrogen permeation current I3 under the combined action of hydrogen-containing gas and stray current; (6) Release the gas in the second autoclave and purge it with nitrogen several times; turn off the electrochemical workstation and only turn on the waveform generator; after the current displayed by the ammeter reaches a stable state, record the steady-state current I2 under the action of stray current; compare the sizes of I1+I2 and I3, and summarize the laws of hydrogen permeation behavior of metal materials under the coupling of hydrogen-containing gas and stray current.

2. The method according to claim 1 further comprises step (7): replacing metal samples of different materials, changing the partial pressure ratio or gas composition of the hydrogen-containing gas, or changing the magnitude and waveform of the stray current, adjusting the conditions of the influencing factors and repeating the test, and summarizing the laws of the hydrogen permeation behavior of metal materials under different influencing factors.

3. The method according to claim 1, characterized in that During the test, the first autoclave was used to continuously supply the test gas to the second autoclave to maintain the pressure in the second autoclave constant.

4. The method according to claim 1, wherein Before mounting the metal specimen, the surface in contact with the hydrogen-containing gas was nickel-plated to reduce the background current density during the hydrogen permeation test.

5. The method according to claim 1, wherein The gas cylinders include hydrogen cylinders, oxygen cylinders, carbon dioxide cylinders, inert gas cylinders and natural gas cylinders.

6. The method according to claim 1, characterized in that Pressure gauges are respectively provided on the end covers of the first autoclave and the second autoclave.

7. The method according to claim 1, characterized in that The metal sample is cylindrical, and the surface in contact with the soil is not wound with resistance wire; the winding area of the resistance wire on the metal sample is larger than 2 / 3 of the area of the side wall of the sample.

8. The method according to claim 1, characterized in that The side wall of the second high-pressure autoclave is provided with a through-going variable-diameter countersunk hole, which is used as an installation hole; the soil box body includes a box-shaped main body and a cover plate, and the side edges of the cover plate and the adjacent box side walls have notches; the electrolytic cell box body is made of organic glass and is placed on the upper side of the soil box body, and has a notch in the lower part of its side wall; the notches in the electrolytic cell box body and the soil box body together constitute an installation hole that adapts to the shape of the end of the metal sample.

9. The method according to claim 1, characterized in that The composition of the hydrogen evolution solution is 0.2 mol / L NaOH+2 mL / L Na2S.

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