A test device for metal hydrogen permeation considering stray current corrosion

Abstract

The present invention relates to metal hydrogen permeation technology, and aims to provide a test device for metal hydrogen permeation that takes into account the effects of stray current corrosion. The device comprises an autoclave, a soil box, and an electrolytic cell box. A metal sample is embedded in the three devices simultaneously, and its surface is in contact with pressurized hydrogen-containing gas, soil, and hydrogen evolution solution, respectively. The platinum electrode in the soil box forms a closed circuit with an ammeter, a waveform generator, and the metal sample. In the electrolytic cell box, the auxiliary electrode and reference electrode immersed in the hydrogen evolution solution are connected to an electrochemical workstation, which is connected to the metal sample via a wire. The resistance wire wrapped around the surface of the metal sample is connected to a heating controller, which is connected to an external power supply. Using the test device of the present invention, the metal hydrogen diffusion rate can be tested taking into account the effects of stray current corrosion. During the test, the combined effects of stray current and impurity gases can be taken into account, and the hydrogen diffusion coefficient obtained by the test is closer to the actual condition of the buried metal.

Description

Technical Field

[0001] The invention relates to a metal hydrogen permeation technology, in particular to a metal hydrogen permeation test device 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 device 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 metal hydrogen permeation test device that takes into account the effects of stray current corrosion is provided. The device includes an autoclave, a soil box, and an electrolytic cell box. Each of the three has a mounting hole connected to its inner cavity. The three mounting holes are close to each other, and a metal sample is embedded in the three mounting holes at different locations simultaneously. The surfaces of the embedded parts are in contact with the pressurized hydrogen-containing gas in the autoclave, the soil in the soil box, and the hydrogen evolution solution in the electrolytic cell box, respectively.

[0010] A platinum electrode inserted into the soil is provided in the soil box, and the platinum electrode is connected to an ammeter, a waveform generator and a metal sample through a wire to form a closed circuit; an auxiliary electrode and a reference electrode immersed in the hydrogen evolution solution are provided in the electrolytic cell box, and both are connected to an electrochemical workstation through wires, and the latter is connected to the metal sample through wires; a resistance wire is wound around the surface of the metal sample, and the resistance wire is connected to a heating controller through a wire, and the latter is connected to an external power supply.

[0011] As a preferred embodiment of the present invention, the autoclave includes a first autoclave and a second autoclave, wherein the first autoclave is connected to the pressure reducing valve and the second autoclave in sequence through a pipeline; an air inlet is provided on the first autoclave, and an air outlet and a mounting hole are provided on the second autoclave.

[0012] As a preferred embodiment of the present invention, the gas inlet is connected to a plurality of gas cylinders through pipelines, and the gas cylinders include hydrogen cylinders, oxygen cylinders, carbon dioxide cylinders, inert gas cylinders and natural gas cylinders.

[0013] As a preferred embodiment of the present invention, pressure gauges are respectively provided on the end covers of the first autoclave and the second autoclave.

[0014] As a preferred embodiment of the present invention, the metal sample is cylindrical, the resistance wire is wound around the side wall surface of the metal sample, and the winding area is greater than 2 / 3 of the side surface of the sample.

[0015] As a preferred embodiment of the present invention, the metal sample is sealed against the mounting holes of the autoclave and the electrolytic cell box, and the metal sample is tightly fitted against the soil in the soil box.

[0016] As a preferred solution of the present invention, a through-going countersunk hole with a variable diameter is provided on the side wall of the autoclave, and the countersunk hole is used as the installation hole.

[0017] As a preferred solution of the present invention, the soil box includes a box-shaped main body and a cover plate, and the side edges of the cover plate and the adjacent side walls of the box are provided with notches that together constitute mounting holes.

[0018] As a preferred solution of the present invention, the electrolytic cell box is made of organic glass plate, and the lower part of the side wall thereof has a notch forming a mounting hole.

[0019] As a preferred solution of the present invention, the electrolytic cell box is placed on the soil box, and the lower side wall of the electrolytic cell box and the upper side wall of the soil box have notches respectively, and the two notches together constitute an installation hole that adapts to the shape of the end of the metal sample.

[0020] Description of the invention principle:

[0021] To address the issues of leakage and decreased gas pressure over time in traditional gas-phase hydrogen permeation testing, this device incorporates two autoclaves. These two autoclaves, each with different pressures and volumes, are interconnected. A pressure-reducing valve is installed in the pipeline following the first autoclave to replenish test gas to the second autoclave in a timely manner, ensuring direct contact between the test gas and the metal specimen.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] The experimental device of the present invention utilizes a waveform generator as a signal source. Through a converter, it can output different parameters, including voltage, current, waveform, and frequency. This realistically simulates the generation and transmission of stray current in pipelines, and considers the impact of stray current on hydrogen permeation in buried metals. The autoclave assembly is connected to the gas cylinder assembly via a gas pipeline. Hydrogen and impurity gases (such as CO2 and O2) enter the autoclave assembly through the gas pipeline, allowing for the study of hydrogen permeation patterns in metal pipelines under the coupled effects of stray current 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.

[0026] The present invention takes into account the influence of stray current in hydrogen permeation test research. The device 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.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. Compared with existing testing schemes that can only realize single-factor hydrogen permeation tests, the service environment of actual structures often includes the coupling effects of many influencing factors. The testing device of the present invention can be used to test the metal hydrogen diffusion rate while considering the effect of stray current corrosion.

[0029] 2. The testing device of the present invention can take into account the combined effects of stray current and impurity gas when testing the metal hydrogen diffusion rate, and the hydrogen diffusion coefficient obtained by the test is closer to the actual situation of the buried metal. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0031] Figure 1 is a schematic diagram of the device of the present invention;

[0032] Figure 2 Schematic diagram of the connection between the metal sample and the heating component.

[0033] 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

[0034] 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.

[0035] 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.

[0036] 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.

[0037] The metal hydrogen permeation test device of the present invention has the following structure: Figure 1 shown.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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).

[0042] 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.

[0043] 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.

[0044] Specific application examples:

[0045] The following describes in detail the specific method of using the device of the present invention with reference to a specific test example:

[0046] (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.

[0047] (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 / cm 2 , nickel plating time is 40s.

[0048] (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.

[0049] (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.

[0050] 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.

[0051] (5) Open the pressure reducing valve and purge the autoclave group with 1MPa nitrogen for 3 times to exhaust the air in the autoclave. To ensure the stability of the internal environment of the autoclave group, the autoclave group needs to be tested for air tightness before the test. Introduce 15MPa nitrogen into the autoclave group and ensure that the pressure drops within 0.02MPa within 24 hours before conducting the metal hydrogen permeation test;

[0052] 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.

[0053] (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;

[0054] (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;

[0055] (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.

[0056] (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;

[0057] (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.

[0058] 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 metal hydrogen permeation test device taking into account the effect of stray current corrosion, characterized in that: The device comprises an autoclave, a soil box, and an electrolytic cell box, each of which has a mounting hole communicating with its own inner cavity; the three mounting holes are close to each other, and different parts of the metal sample are simultaneously embedded in the three mounting holes, and the surfaces of the embedded parts are in contact with the pressurized hydrogen-containing gas in the autoclave, the soil in the soil box, and the hydrogen evolution solution in the electrolytic cell box, respectively; A platinum electrode inserted into the soil is provided in the soil box, and the platinum electrode is connected to an ammeter, a waveform generator and a metal sample through a wire to form a closed loop; an auxiliary electrode and a reference electrode immersed in the hydrogen evolution solution are provided in the electrolytic cell box, and both are connected to an electrochemical workstation through wires, and the electrochemical workstation is connected to the metal sample through wires; a resistance wire is wound around the surface of the metal sample, and the resistance wire is connected to a heating controller through a wire, and the heating controller is connected to an external power supply.

2. The device according to claim 1, characterized in that The autoclave comprises a first autoclave and a second autoclave, wherein the first autoclave is sequentially connected to a pressure reducing valve and the second autoclave through a pipeline; an air inlet is provided on the first autoclave, and an air outlet and a mounting hole are provided on the second autoclave.

3. The device according to claim 2, characterized in that The gas inlet is connected to a plurality of gas cylinders through pipelines, and the gas cylinders include hydrogen cylinders, oxygen cylinders, carbon dioxide cylinders, inert gas cylinders and natural gas cylinders.

4. The device according to claim 2, characterized in that Pressure gauges are respectively provided on the end covers of the first autoclave and the second autoclave.

5. The device according to claim 1, characterized in that The metal sample is cylindrical, the resistance wire is wound on the side wall surface of the metal sample, and the winding area is greater than 2 / 3 of the side surface of the sample.

6. The device according to claim 1, characterized in that The metal sample is sealed against the mounting holes of the autoclave and the electrolytic cell box, and the metal sample is tightly fitted against the soil in the soil box.

7. The device according to claim 1, characterized in that A through-going reduced-diameter countersunk hole is provided on the side wall of the autoclave, and the countersunk hole is used as a mounting hole.

8. The device according to claim 1, characterized in that The soil box comprises a box-shaped main body and a cover plate. The side edge of the cover plate and the adjacent side wall of the box body are provided with notches, which together form installation holes.

9. The device according to claim 1, characterized in that The electrolytic cell box is made of organic glass plates, and the lower part of the side wall is provided with a notch to form a mounting hole.

10. The device according to claim 1, characterized in that The electrolytic cell box is placed on the soil box. The lower part of the side wall of the electrolytic cell box and the upper part of the side wall of the soil box are respectively provided with notches. The two notches together form a mounting hole adapted to the shape of the end of the metal sample.

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