A buried steel pipe hydrogen doping testing device under cathodic protection condition

Abstract

The utility model provides a kind of buried steel pipe hydrogen doping testing device under cathodic protection condition, solve the technical problem that existing test environment cannot form double corrosion / hydrogen permeation environment, leading to data and actual working condition disjunction, cannot truly reflect the hydrogen embrittlement risk of hydrogen doping pipeline cathodic protection condition.The utility model discloses a kind of buried steel pipe hydrogen doping testing device under cathodic protection condition, solve the technical problem that existing test environment cannot form double corrosion / hydrogen permeation environment, leading to data and actual working condition disjunction, cannot truly reflect the hydrogen embrittlement risk of hydrogen doping pipeline cathodic protection condition.The utility model provides a kind of buried steel pipe hydrogen doping testing device under cathodic protection condition, solve the technical problem that existing test environment cannot form double corrosion / hydrogen permeation environment, leading to data and actual working condition disjunction, cannot truly reflect the hydrogen embrittlement risk of hydrogen doping pipeline cathodic protection condition.The utility model provides a kind of buried steel pipe hydrogen doping testing device under cathodic protection condition, solve the technical problem that existing test environment cannot form double corrosion / hydrogen permeation environment, leading to data and actual working condition disjunction, cannot truly reflect the hydrogen embrittlement risk of hydrogen doping pipeline cathodic protection condition.The utility model provides a kind of buried steel pipe hydrogen doping testing device under cathodic protection condition, solve the technical problem that existing test environment cannot form double corrosion / hydrogenic

Description

Technical Field

[0001] This utility model relates to the field of gas transmission technology, specifically to a hydrogen doping test device for buried steel pipes under cathodic protection conditions. Background Technology

[0002] With the global energy structure transitioning towards a low-carbon model, the hydrogen energy industry is entering a phase of explosive growth. Natural gas blending with hydrogen, as a key transitional solution for hydrogen storage and transportation, holds significant strategic importance for achieving the "dual-carbon" goal through its large-scale application. However, the unique physicochemical properties of hydrogen (e.g., a molecular diameter of 0.289 nm, which is 75% that of methane) increase its diffusion coefficient in metal lattices by 3 to 6 orders of magnitude compared to conventional natural gas. This high permeability significantly exacerbates the hydrogen embrittlement sensitivity of pipeline steels such as X60 and X80. Studies have shown that when the partial pressure of hydrogen in the pipeline exceeds 0.1 MPa, the adsorption coverage of hydrogen atoms on the metal surface increases exponentially, leading to a 30%-50% decrease in the material's fracture toughness. Furthermore, hydrogen blending also alters the effectiveness of traditional cathodic protection systems for buried steel pipelines. The introduction of hydrogen has a dual effect on traditional cathodic protection systems: on the one hand, hydrogen atoms generated by cathodic polarization diffuse into the metal interior at an accelerated rate under the drive of an electric field, forming an "electrochemical hydrogen charging" effect; on the other hand, hydrogen, as a strong reducing gas, may alter the film structure on the pipe surface, affecting the peel strength of the anti-corrosion coating and the cathodic protection current distribution. This multi-factor coupling effect challenges the applicability of the protection potential window (-0.85V to -1.20V CSE) in existing design specifications (such as NACE SP0169).

[0003] The interaction mechanism between hydrogen and metals, anti-corrosion coatings, and cathodic protection potential after hydrogen blending in natural gas needs to be tested and verified. However, current laboratory testing faces two major technical bottlenecks. First, existing standards only provide a single test environment (internal gas or external soil) for testing corrosion rates. For example, gravimetric and volumetric methods can only simulate the internal gas environment or external soil environment in a single setting. While this simplifies test conditions and makes it easier to control and measure corrosion rates, it cannot simultaneously simulate the dual corrosion / hydrogen permeation environment of the pipeline's inner wall (hydrogen-blended natural gas) and outer wall (soil). This fails to accurately reflect the hydrogen embrittlement risk of hydrogen-blended pipelines under cathodic protection conditions and cannot reflect the synergistic effect mechanism of "internal hydrogen permeation-external hydrogen adsorption" affecting buried pipelines, leading to data that is out of sync with actual operating conditions and has poor reference value in practical engineering applications. Second, hydrogen embrittlement assessment remains at the offline detection stage, making it difficult to quantify the relationship between hydrogen embrittlement risk and corrosion rate, and unable to establish a dynamic correlation model of "corrosion-hydrogen permeation-mechanical damage".

[0004] Therefore, developing dual-environment coupling testing technology that can realistically simulate the full operating environment of pipelines and establishing a quantitative evaluation system for hydrogen embrittlement sensitivity have become core technological bottlenecks that urgently need to be overcome in the field of hydrogen energy storage and transportation. Utility Model Content

[0005] In view of the above problems, this utility model provides a hydrogen doping test device for buried steel pipes under cathodic protection conditions, which solves the technical problem that the existing test environment cannot form a dual corrosion / hydrogen permeation environment, resulting in data that is out of sync with actual working conditions and cannot truly reflect the hydrogen embrittlement risk of hydrogen-doped pipelines under cathodic protection conditions.

[0006] The hydrogen doping test device for buried steel pipes under cathodic protection conditions according to this utility model embodiment is characterized by comprising:

[0007] Experimental test piping is used to connect in series with the gas supply piping of the experimental platform via an insulating connector;

[0008] Connecting wires are used to be soldered onto experimental test pipelines, and are set in groups and arranged at intervals according to a distribution rule;

[0009] The corrosion test piece is used to form a standard part to be tested based on the physical and chemical properties of the experimental test pipeline.

[0010] Branch pipes are used to form gas branch lines on the side wall of experimental test pipelines. They are set in groups and arranged at intervals according to distribution rules.

[0011] A shut-off valve is used to control the opening and closing of a gas branch line by installing it on a branch line pipe.

[0012] A potentiostat is used to monitor and adjust the potential of cathodic protection by connecting it to the experimental test pipeline and the anode ground bed, respectively.

[0013] An anodic ground bed is used as a current output terminal in a cathodic protection circuit to suppress electrochemical corrosion of experimental test pipelines, branch pipelines, and test specimens.

[0014] The internal and external hydrogen environment module is used to connect the branch pipe to form the gas branch terminal, fix the corrosion test piece to be tested at the terminal, and form a dual test environment on both sides of the corrosion test piece.

[0015] In one embodiment of this utility model, the internal and external hydrogen environment constituting module includes:

[0016] The main pipe section is used to connect and fix with the branch pipes to form the terminal cavity of the gas path.

[0017] A fixed flange is used to fix the flange to the opening of the end cavity to form a bearing end face, and a through hole is formed on the bearing end face.

[0018] The adapter flange is used to connect and fix with the fixed flange to form a mating load-bearing end face, and a through hole is formed on the load-bearing end face.

[0019] Flange gaskets are used to adapt to the shape of the bearing end face, forming a buffer and sealing structure between the bearing end face of the fixed flange and the bearing end face of the adapting flange.

[0020] In one embodiment of this utility model, the main pipe section is a horizontally placed straight circular pipe, with the middle sidewall of the straight circular pipe connected and fixed to the branch pipe, and both ends of the straight circular pipe forming open openings; the fixed flange is a circular plate coaxial with the main pipe section, with a through hole coaxial with the main pipe section, the bottom of the circular plate is welded and fixed to the open opening, and the top of the circular plate serves as the bearing end face; the adapter flange is a circular plate coaxial with the fixed flange, with a through hole coaxial with the main pipe section, and the side adjacent to the fixed flange serves as the bearing end face; the flange gasket is formed by metal spiral wound gasket; at one end of the main pipe section, the assembly sequence of fixed flange - flange gasket - corrosion test piece - flange gasket - adapter flange is formed, and the fixed flange and the adapter flange are fixed by axial bolt connection; the same assembly structure is also formed at the other end of the main pipe section.

[0021] In one embodiment of this utility model, the fixed flange and the adapter flange are selected as DN50 standard raised face flanges, and there is a test hole with a diameter of 59mm in the middle of the flange.

[0022] In one embodiment of this utility model, the corrosion test piece to be tested is sealed to the flange by a metal spiral wound flange gasket.

[0023] In one embodiment of this utility model, the surface of the corrosion test piece includes annular sealing watermark lines that match the specifications of the flange gasket.

[0024] In one embodiment of this utility model, the main pipe section includes at least one end cavity.

[0025] In one embodiment of this utility model, the corrosion test piece to be tested is electrically connected to the main pipe section through an electrical conductor.

[0026] The hydrogen doping test device for buried steel pipes under cathodic protection conditions of this utility model, while ensuring the basic stability of existing cathodic protection conditions, forms a dual test environment that can be used for real-time comparison in conjunction with the existing test environment. It effectively registers the corrosion process in the separate internal gas environment, external soil environment, and synchronous internal hydrogen permeation-external hydrogen adsorption environment. This enables the testing process of hydrogen embrittlement risk and corrosion rate to establish a real-time correlation, providing a good test environment guarantee for establishing a dynamic correlation between "corrosion-hydrogen permeation-mechanical damage" through repeated testing. Attached Figure Description

[0027] Figure 1 The figure shown is a schematic diagram of the overall structure of a hydrogen doping test device for buried steel pipes under cathodic protection conditions according to an embodiment of this utility model.

[0028] Figure 2The diagram shown is a schematic representation of the internal and external hydrogen environment testing units of a hydrogen doping test device for buried steel pipes under cathodic protection conditions according to an embodiment of this utility model.

[0029] Figure 3 The diagram shown is a specific assembly schematic of the internal and external hydrogen environment testing units of a hydrogen doping test device for buried steel pipes under cathodic protection conditions according to an embodiment of this utility model.

[0030] Figure 4 The diagram shown is a flowchart illustrating a method for testing hydrogen doping in buried steel pipes under cathodic protection conditions according to an embodiment of this utility model.

[0031] Figure 5 The diagram shown is a schematic of a test process for hydrogen doping testing of buried steel pipes under cathodic protection conditions according to an embodiment of this utility model.

[0032] Figure 6 This is a schematic diagram of the structure of the hydrogen doping test device for buried steel pipes under cathodic protection conditions according to an embodiment of this utility model. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this utility model clearer and more understandable, the present utility model will be further described below in conjunction with the accompanying drawings and specific embodiments. Obviously, the described embodiments are only a part of the embodiments of this utility model, and not all of them. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0034] One embodiment of this utility model is a hydrogen doping test device for buried steel pipes under cathodic protection conditions, as follows: Figure 1 As shown. In Figure 1 In this embodiment, the following are included:

[0035] The experimental test pipeline 103 is used to connect in series with the gas supply pipeline 101 of the experimental platform via the insulating connector 102.

[0036] Those skilled in the art will understand that the experimental test pipeline uses the same pipe material as the actual gas transmission pipeline. The gas source pipeline of the experimental platform is connected to the gas source system, which can transport and release (or recover) the experimental natural gas. The gas source system can generate hydrogen-blended natural gas with different hydrogen blending ratios (0%, 5%, 10%, 15%, etc.) according to experimental needs. During the operation of the experimental test pipeline connected in series with the gas source pipeline, the insulating joints at both ends ensure electrical insulation while maintaining communication with the gas source pipeline, allowing the experimental test pipeline to be configured with cathodic protection independently and obtain an independent electrochemical reaction experimental environment.

[0037] Connecting wires 104 are used for soldering onto experimental test pipelines, and are set in groups and arranged at intervals according to a distribution rule.

[0038] The connecting wires are electrically connected to the corrosion test specimen. The distribution rules define the arrangement direction of the welded ends of the connecting wires to the experimental test pipeline, for example, by equal spacing along the axial direction of the experimental test pipeline.

[0039] The corrosion test piece 105 is used to form a standard piece for testing based on the physicochemical properties of the experimentally tested pipeline. In one embodiment of this utility model, the corrosion test piece is in the shape of a disc.

[0040] The corrosion test specimen and the experimental test pipeline have the same physical and chemical properties, but are relatively small and independent in size. Changes in its physical and chemical properties can reflect synchronous changes in the experimental test pipeline under the same testing environment.

[0041] Branch pipe 106 is used to form gas branch lines on the side wall of the experimental test pipeline. They are set in groups and arranged at intervals according to the distribution rules.

[0042] Branch pipes are made of small-diameter pipes with the same physical properties as the experimental test pipes and are connected to the sidewalls of the experimental test pipes. The distribution rules define the arrangement direction of the fixed connection ends of the branch pipes and the experimental test pipes, for example, equidistant spacing along the axial direction of the experimental test pipes, and the branch pipes and connecting wires are located on opposite sides of the axis of the experimental test pipes.

[0043] The shut-off valve 107 is used to be installed on the branch pipe to control the opening and closing of the gas branch.

[0044] By controlling the on / off state of the gas path branches through shut-off valves, a control strategy for the gas path branches is formed, thereby controlling the test scale and test progress.

[0045] The potentiostat 108 is used to electrically connect to the experimental test pipeline and the anode ground bed respectively to monitor and adjust the potential for cathodic protection.

[0046] The anodic ground bed 109 is used as a current output terminal in the cathodic protection circuit to suppress electrochemical corrosion of the experimental test pipeline, branch pipeline and the test specimen.

[0047] Those skilled in the art will understand that the potentiostat, anolyte bed, environmental soil, and experimental test pipeline form a cathodic protection circuit. The potentiostat monitors the real-time potential of the experimental test pipeline through a reference electrode and adjusts the output current to regulate the potential, causing the current to flow through the soil (electrolyte) to the experimental test pipeline, making the pipeline surface a cathode and inhibiting corrosion reactions. The cathodic protection circuit also provides synchronous protection for the electrically connected test specimens, inhibiting electrochemical corrosion reactions.

[0048] The internal and external hydrogen environment module 110 is used to connect the branch pipe to form a gas branch terminal, fix the corrosion test piece to be tested at the terminal, and form a dual test environment on both sides of the corrosion test piece to be tested.

[0049] The dual testing environment is formed at the end of the gas path branch by modules consisting of internal and external hydrogen environments. The distance between the end of the branch and the experimental test pipeline is adjusted by the branch pipe. The dual testing environment is formed on both sides of the corrosion specimen under test. One side is in contact with the hydrogen-doped mixed gas in the gas path branch, and the other side is in contact with the soil (electrolyte) in the test environment.

[0050] The hydrogen doping test device for buried steel pipes under cathodic protection conditions of this utility model, while ensuring the basic stability of existing cathodic protection conditions, forms a dual test environment that can be used for real-time comparison in conjunction with the existing test environment. It effectively registers the corrosion process in the separate internal gas environment, external soil environment, and synchronous internal hydrogen permeation-external hydrogen adsorption environment. This enables the testing process of hydrogen embrittlement risk and corrosion rate to establish a real-time correlation, providing a good test environment guarantee for establishing a dynamic correlation between "corrosion-hydrogen permeation-mechanical damage" through repeated testing.

[0051] An embodiment of this utility model describes an internal and external hydrogen environment testing unit for a hydrogen doping test device for buried steel pipes under cathodic protection conditions, as shown in the example below. Figure 2 As shown. In Figure 2 The internal and external hydrogen environment components include:

[0052] The main pipe section 111 is used to connect and fix with the branch pipe to form the terminal cavity of the gas passage. The terminal cavity may include one or more.

[0053] The fixed flange 112 is used to fix the end cavity to the opening to form a bearing end face, and a through hole is formed on the bearing end face.

[0054] The adapter flange 113 is used to connect and fix with the fixed flange to form a mating load-bearing end face, and a through hole is formed on the load-bearing end face.

[0055] Flange gasket 114 is designed to fit the shape of the bearing end face, forming a buffer and sealing structure between the bearing end faces of the fixed flange and the fitting flange.

[0056] like Figure 2As shown, in one embodiment of this utility model, the main pipe section 111 is a horizontally placed straight circular pipe (e.g., using DN50 pipe). The middle sidewall of the straight circular pipe is connected and fixed to the branch pipe 106, and both ends of the straight circular pipe form open openings. The fixed flange is a circular plate coaxial with the main pipe section 111, with a through hole coaxial with the main pipe section 111. The bottom of the circular plate is welded and fixed to the open opening, and the top of the circular plate serves as the bearing end face. The adapter flange 113 is a circular plate coaxial with the fixed flange, with a through hole coaxial with the main pipe section 111, and the side adjacent to the fixed flange serves as the bearing end face. The flange gasket 114 is formed by a metal spiral wound gasket. At one end of the main pipe section 111, an assembly structure sequence of fixed flange - flange gasket - corrosion test piece - flange gasket - adapter flange is formed. The fixed flange and the adapter flange are connected by axial bolts to ensure the stability of the assembly structure and the sealing of both sides of the corrosion test piece. The same assembly structure sequence is formed at the other end of the main pipe section 111.

[0057] like Figure 2 As shown, in one embodiment of this utility model, the corrosion test piece and the main pipe section are electrically connected by an electrical conductor 115 to ensure that the cathodic protection potential of the test piece is consistent with that of the main pipe body.

[0058] The hydrogen doping test device for buried steel pipes under cathodic protection conditions, as described in this embodiment, provides a flexible structure for forming a dual testing environment. It allows for the deployment of multiple corrosion test specimens in a grouped dual testing environment at the same location while maintaining environmental consistency. This ensures diversity of comparison samples during the testing process, avoiding data acquisition bias caused by sparse sample sizes.

[0059] The assembly structure of the internal and external hydrogen environment testing units of the buried steel pipe hydrogen doping testing device under cathodic protection conditions according to one embodiment of this utility model is as follows: Figure 3 As shown. In Figure 3 In this assembly, both the fixed flange and the adapter flange are DN50 standard raised face flanges, with a 59mm diameter test hole in the center. The corrosion test specimen is sealed to the flange using a spiral wound gasket. The specimen surface is machined with an annular sealing watermark (outer diameter 85.9mm, inner diameter 69.9mm) matching the gasket specifications. The specimen thickness is controlled within the range of 3–6mm. Assembly follows the sequence of flange-gasket-test specimen-gasket-flange, and M16 bolts are used for secure sealing of the assembly structure.

[0060] The hydrogen doping test device for buried steel pipes under cathodic protection conditions according to this utility model provides a stable and effective optimized assembly structure to enhance sealing, further ensuring the sealing and electrical stability of the internal and external hydrogen environment components.

[0061] Using the hydrogen doping test device for buried steel pipes under cathodic protection conditions as described in the above embodiment, hydrogen doping tests on buried steel pipes can be conducted, forming an "internal-external hydrogen isolation." This allows the two sides of the test piece to be exposed to the hydrogen-doped natural gas (internal hydrogen) and the soil environment (external hydrogen) inside the pipe, respectively, simultaneously simulating the coupling effect of the two environments. This design is closer to the actual operating conditions of pipelines and can more realistically reflect the differences in the diffusion paths of hydrogen atoms in the metal lattice and the influence of the superposition of the two environments on the corrosion rate.

[0062] By comparing the corrosion rates of test pieces in internal and external hydrogen environments and evaluating the risk of hydrogen embrittlement by testing the mechanical properties of the test pieces, factors such as corrosion rates in internal and external hydrogen environments, the risk of hydrogen embrittlement in hydrogen-environment pipes, and cathodic protection potential can be correlated to achieve a comprehensive evaluation of the complex corrosion behavior of hydrogen-doped pipelines under actual working conditions.

[0063] This utility model provides an embodiment of a hydrogen doping test method for buried steel pipes under cathodic protection conditions. The method is based on the data acquisition of the hydrogen doping test device for buried steel pipes under cathodic protection conditions described in the above embodiment. The test method is as follows: Figure 4 As shown. In Figure 4 In this embodiment, the following are included:

[0064] Step 100: Establish a dual testing environment under cathodic protection conditions to form a control group and an experimental group for the corrosion test specimens. Deploy the control group in a single soil environment and deploy the experimental group in internal and external hydrogen environments.

[0065] In one embodiment of this utility model, the hydrogen doping test device described in the above embodiment is used to construct a dual test environment for the deployment of a control group and an experimental group, including:

[0066] Prepare circular corrosion test specimens with a diameter of 100 mm and a thickness of 3-6 mm, and machine concentric sealing water ripple lines (outer diameter 85.9 mm / inner diameter 69.9 mm) on their surface;

[0067] The outer edge of the test piece is sealed with epoxy resin, leaving a circular exposed area in the center (e.g., 50 mm in diameter). The surface is then polished to a specific roughness (e.g., Ra ≤ 0.8 μm), and the test pieces are weighed and discarded based on their weight.

[0068] The test pieces were divided into two groups: the control group test pieces were buried underground after being electrically connected to the experimental test pipeline by connecting wires, so that a circular soil exposure area with a diameter of 50 mm (area 2πD, D=50 mm) was formed on both sides of the test piece; the experimental group test pieces formed a double-sided coupled exposure (area) condition of hydrogen-doped natural gas environment (50 mm exposure area) and soil environment (50 mm exposure area) through the internal and external hydrogen environment construction module.

[0069] In one embodiment of this utility model, it further includes:

[0070] The power failure potential protection window (-0.85V to -1.20V CSE) should be set according to engineering specifications, and the cathodic protection current density should be 10-50mA / m. 2 Range adjustment. The total protection current I is calculated using the defect number correction formula:

[0071] I = x·A defect ·i req

[0072] A defect For the area of ​​a single defect, i req Let x be the required current density, x be the number of defects, and I be the total current.

[0073] Adjust the cathodic protection potential and select the anode ground bed according to the total protection current I.

[0074] The hydrogen doping test method for buried steel pipes under cathodic protection in this embodiment of the invention utilizes an effective improvement to the existing test environment to create a dual test environment, ensuring the consistency of the test basis for factors such as gas source, soil, pressure, temperature, and humidity in the control and experimental groups under the two exposure environments. This avoids asynchronous factors in the test environment.

[0075] Step 200: Continuously monitor the on-state and off-state potentials during the dual test process.

[0076] The dual testing process is always carried out under cathodic protection conditions. The potential at the pipeline-soil interface is continuously monitored by a potentiostat, and the cathodic protection potential is corrected based on the potential change threshold.

[0077] In one embodiment of this utility model, the data acquisition process for continuously monitoring the pipeline-soil interface potential using a potentiostat includes:

[0078] Monitoring of energized potential signal: Connect the output terminal of the potentiostat to the terminal block of the pipe / test piece, and place the reference electrode vertically close to the surface to be measured to form a measurement circuit;

[0079] Set the target protection potential (-0.85V to -1.20V CSE) and current density range (10-50mA / m). 2 ), activate the automatic polarization function to perform potential correction;

[0080] The potentiostat has a built-in data acquisition module that continuously records the potential of the pipe-soil interface under energized conditions, with a sampling frequency of not less than 1Hz.

[0081] Monitoring of power outage potential signals: Set the interruption period of the potentiostat's control current (e.g., an interruption period of 12 seconds on / 3 seconds off). The instrument automatically switches its working state according to the preset sequence, forming intermittent measurements.

[0082] Maintain the set protection potential during the power-on phase;

[0083] The high-speed acquisition channel (e.g., sampling rate ≥ 1 kHz) is triggered at the moment of power failure to synchronously record the potential decay curve;

[0084] The first stable plateau value within a specific time window (e.g., 0.1-0.3s) after a power outage is extracted using the data playback function as the true polarization potential (e.g., typical value -0.85V vs CSE).

[0085] This invention's method for testing hydrogen doping in buried steel pipes under cathodic protection conditions utilizes different signal acquisition densities for both on-state and off-state potential signal detection. This ensures real-time monitoring of whether the current output remains stable within the set protection potential range, while also eliminating IR drop interference from soil, coating leaks, etc., and enabling real-time monitoring of changing trends to obtain the true protection potential (i.e., polarization potential) of the pipe surface. This achieves timely detection of over-protection, under-protection, or cathodic protection system faults, and ensures the timing accuracy of basic potential data.

[0086] Step 300: Based on the dual testing cycle, a quantitative comparison of key parameters is formed between the control group and the experimental group. Key parameters include corrosion rate, hydrogen doping influence coefficient, mechanical performance indicators, and fracture behavior parameters.

[0087] After the dual testing period is completed, the test pieces of the control group and the experimental group are preprocessed and the key parameters are quantified separately to achieve the normalization of the key parameter quantification data.

[0088] In one embodiment of this utility model, the data quantification of corrosion rate testing includes:

[0089] via t i After (i = 1, 2, 3...) hours of environmental exposure, mechanical grinding combined with chemical cleaning was used to remove corrosion products from the surface of the test piece. After ultrasonic cleaning with anhydrous ethanol, the sample was vacuum dried.

[0090] The mass loss ΔW was determined using an analytical balance (accuracy 0.1 mg). i (i = 1, 2, 3...), calculate the corrosion rate of each group of test pieces according to the formula:

[0091]

[0092] Where: V i,corr Let ΔW be the corrosion rate (mm / a). i The mass loss is (g), and ρ is the material density (7.85 g / cm³ for steel). 3 ), ΔA is the exposed area of ​​the test piece (cm²) 2 ), t i Exposure time (hours).

[0093] In one embodiment of this utility model, the data quantification of the hydrogen doping influence coefficient test includes:

[0094] Based on the difference in corrosion rates between the two sets of test pieces, the impact of hydrogen-doped natural gas pipelines on the corrosion of cathodic protection pipes was determined.

[0095] The influence coefficient K of hydrogen doping was quantified by comparing the corrosion rates of pure soil samples (control group) and hydrogen-doped soil samples (experimental group). H :

[0096]

[0097] V Hcorr / V 0corr Corrosion rates were measured in coupled environments and pure soil environments, respectively.

[0098] In one embodiment of this utility model, the data quantification of mechanical performance index testing includes:

[0099] Slow strain rate tensile test (SSRT) specimens were cut from the test pieces of the control group and the experimental group according to the standard.

[0100] SSRT tests were conducted using an electronic universal testing machine to collect mechanical performance indicators in order to quantify macroscopic deformation and load-bearing capacity.

[0101] The degree of hydrogen embrittlement (plastic loss rate Δδ / δ0) is evaluated by the elongation at break (δ) of the test specimen material.

[0102] In one embodiment of this utility model, the data quantification of fracture behavior parameter testing includes:

[0103] Fracture behavior parameters were simultaneously acquired during SSRT testing to quantify the crack propagation law and critical fracture conditions during the fracture process, and the fracture surface microstructure was analyzed and quantified by field emission scanning electron microscopy (FE-SEM).

[0104] This invention's method for testing hydrogen-doped buried steel pipes under cathodic protection simulates different corrosion processes of hydrogen-doped pipelines under actual service conditions using test pieces formed from control and experimental groups. The test pieces are exposed to both sides of the hydrogen-doped natural gas (internal hydrogen) and the soil environment (external hydrogen), respectively. This synchronously simulates the coupling effect of the two environments during actual pipeline operation, more realistically reflecting the differences in hydrogen atom diffusion paths within the metal lattice and the impact of the dual-environment superposition on the corrosion rate. Furthermore, it obtains key parameters from different testing dimensions, greatly enriching the measurable factors of the corrosion process.

[0105] Step 400: Construct a multivariate regression model based on key parameters and potential correction data to quantify the relationship between corrosion rate and hydrogen embrittlement sensitivity.

[0106] The hydrogen embrittlement sensitivity of the sample under different testing environments can be quantified by using key parameters. For example:

[0107] FE-SEM was used to observe the fracture morphology. If intergranular fracture or cleavage fracture characteristics were observed, it was determined that there was a tendency for hydrogen embrittlement.

[0108] A Pearson correlation matrix was established between the plasticity loss rate (Δδ / δ0) and the corrosion rate (Vcorr) measured at the same time. When the correlation coefficient r>0.85, a significant coupling effect was determined.

[0109] Furthermore, a multiple regression model was constructed by combining key parameters with potential correction data from a potentiostat:

[0110] Δδ / δ0=a·K H ·V corr +b·E cathodic +c

[0111] In the formula, a, b, and c are model coefficients, Δδ / δ0 is the plasticity loss rate, and V corr E represents the corrosion rate. cathodic The cathodic protection potential deviation (cathodic protection potential deviation = (actual protection potential - ideal protection potential) / ideal protection potential), K H The effect coefficient of hydrogen doping.

[0112] The effects of external and internal hydrogen on the hydrogen embrittlement performance of the specimen can be directly compared under cathodic protection conditions.

[0113] The hydrogen-doped test method for buried steel pipes under cathodic protection conditions of this utility model compares the corrosion rate differences between test pieces in internal and external hydrogen environments and evaluates the risk of hydrogen embrittlement by combining the mechanical property tests of the test pieces. It can link factors such as the corrosion rate in internal and external hydrogen environments, the risk of hydrogen embrittlement in the pipe material in the hydrogen environment, and the cathodic protection potential, and comprehensively evaluate the complex corrosion behavior of hydrogen-doped pipelines under actual working conditions.

[0114] A test procedure based on the hydrogen doping test method for buried steel pipes under cathodic protection conditions according to an embodiment of this utility model is as follows: Figure 5 As shown. In Figure 5 The process includes the construction of a dual testing environment, the processing of cathodic protection potential acquisition, the acquisition of key parameters of the experimental group, the evaluation of the coupling effect using key parameters in combination with corrosion rate, and the basic process of evaluating the relationship between corrosion rate and hydrogen embrittlement sensitivity by constructing a multivariate regression model.

[0115] This utility model provides an embodiment of a hydrogen doping test method for buried steel pipes under cathodic protection conditions. This method utilizes the hydrogen doping test device developed in the above embodiment to continuously monitor and collect signals and data, including:

[0116] Step 200: Continuously monitor the on-state potential and off-state potential during the dual test process.

[0117] The dual testing process is always carried out under cathodic protection conditions. The potential at the pipeline-soil interface is continuously monitored by a potentiostat, and the cathodic protection potential is corrected based on the potential change threshold.

[0118] In one embodiment of this utility model, the data acquisition process for continuously monitoring the pipeline-soil interface potential using a potentiostat includes:

[0119] Monitoring of energized potential signal: Connect the output terminal of the potentiostat to the terminal block of the pipe / test piece, and place the reference electrode vertically close to the surface to be measured to form a measurement circuit;

[0120] Set the target protection potential (-0.85V to -1.20V CSE) and current density range (10-50mA / m). 2 ), activate the automatic polarization function;

[0121] The potentiostat has a built-in data acquisition module that continuously records the potential of the pipe-soil interface under energized conditions, with a sampling frequency of not less than 1Hz.

[0122] Monitoring of power outage potential signals: Set the interruption period of the potentiostat's control current (e.g., an interruption period of 12 seconds on / 3 seconds off). The instrument automatically switches its working state according to the preset sequence, forming intermittent measurements.

[0123] Maintain the set protection potential during the power-on phase;

[0124] The high-speed acquisition channel (e.g., sampling rate ≥ 1 kHz) is triggered at the moment of power failure to synchronously record the potential decay curve;

[0125] The first stable plateau value within a specific time window (e.g., 0.1-0.3s) after a power outage is extracted using the data playback function as the true polarization potential (e.g., typical value -0.85V vs CSE).

[0126] This invention's method for testing hydrogen doping in buried steel pipes under cathodic protection conditions utilizes different signal acquisition densities for both on-state and off-state potential signal detection. This ensures real-time monitoring of whether the current output remains stable within the set protection potential range, while also eliminating IR drop interference from soil, coating leaks, etc., and enabling real-time monitoring of changing trends to obtain the true protection potential (i.e., polarization potential) of the pipe surface. This achieves timely detection of over-protection, under-protection, or cathodic protection system faults, and ensures the timing accuracy of basic potential data.

[0127] Step 300: Based on the dual testing cycle, a quantitative comparison of key parameters is formed between the control group and the experimental group. Key parameters include corrosion rate, hydrogen doping influence coefficient, mechanical performance indicators, and fracture behavior parameters.

[0128] After the dual testing period is completed, the test pieces of the control group and the experimental group are preprocessed and the key parameters are quantified separately to achieve the normalization of the key parameter quantification data.

[0129] In one embodiment of this utility model, the data quantification of corrosion rate testing includes:

[0130] via t i After (i = 1, 2, 3...) hours of environmental exposure, mechanical grinding combined with chemical cleaning was used to remove corrosion products from the surface of the test piece. After ultrasonic cleaning with anhydrous ethanol, the sample was vacuum dried.

[0131] The mass loss ΔW was determined using an analytical balance (accuracy 0.1 mg). i (i = 1, 2, 3...), calculate the corrosion rate of each group of test pieces according to the formula:

[0132]

[0133] Where: V i,corr Let ΔW be the corrosion rate (mm / a). i The mass loss is (g), and ρ is the material density (7.85 g / cm³ for steel). 3 ), ΔA is the exposed area of ​​the test piece (cm²) 2 ), t i Exposure time (hours).

[0134] In one embodiment of this utility model, the data quantification of the hydrogen doping influence coefficient test includes:

[0135] Based on the difference in corrosion rates between the two sets of test pieces, the impact of hydrogen-doped natural gas pipelines on the corrosion of cathodic protection pipes was determined.

[0136] The influence coefficient K of hydrogen doping was quantified by comparing the corrosion rates of pure soil samples (control group) and hydrogen-doped soil samples (experimental group). H :

[0137]

[0138] V Hcorr / V 0corr Corrosion rates were measured in coupled environments and pure soil environments, respectively.

[0139] In one embodiment of this utility model, the data quantification of mechanical performance index testing includes:

[0140] Slow strain rate tensile test (SSRT) specimens were cut from the test pieces of the control group and the experimental group according to the standard.

[0141] SSRT tests were conducted using an electronic universal testing machine to collect mechanical performance indicators in order to quantify macroscopic deformation and load-bearing capacity.

[0142] The degree of hydrogen embrittlement (plastic loss rate Δδ / δ0) is evaluated by the elongation at break (δ) of the test specimen material.

[0143] In one embodiment of this utility model, the data quantification of fracture behavior parameter testing includes:

[0144] Fracture behavior parameters were simultaneously acquired during SSRT testing to quantify the crack propagation law and critical fracture conditions during the fracture process, and the fracture surface microstructure was analyzed and quantified by field emission scanning electron microscopy (FE-SEM).

[0145] Step 400: Construct a multivariate regression model based on key parameters and potential correction data to quantify the relationship between corrosion rate and hydrogen embrittlement sensitivity.

[0146] The hydrogen embrittlement sensitivity of the sample under different testing environments can be quantified by using key parameters. For example:

[0147] If the fracture morphology is observed by SEM, and intergranular fracture or cleavage fracture features are observed, it is determined that there is a tendency for hydrogen embrittlement.

[0148] A Pearson correlation matrix was established between the plasticity loss rate (Δδ / δ0) and the corrosion rate (Vcorr) measured at the same time. When the correlation coefficient r>0.85, a significant coupling effect was determined.

[0149] Furthermore, a multiple regression model was constructed by combining key parameters with potential correction data from a potentiostat:

[0150] Δδ / δ0=a·K H ·V c0rr +b·E cath0dic +c

[0151] In the formula, a, b, and c are model coefficients, Δδ / δ0 is the plasticity loss rate, and V corr E represents the corrosion rate. cathodic The cathodic protection potential deviation (cathodic protection potential deviation = (actual protection potential - ideal protection potential) / ideal protection potential), K H The effect coefficient of hydrogen doping.

[0152] The effects of external and internal hydrogen on the hydrogen embrittlement performance of the specimen can be directly compared under cathodic protection conditions.

[0153] An embodiment of this utility model provides a hydrogen doping test device for buried steel pipes under cathodic protection conditions, comprising:

[0154] The memory is used to store the program code in the data processing process of the hydrogen doping test method for buried steel pipes under cathodic protection conditions described in the above embodiments;

[0155] The processor is used to execute program code in the data processing process of the hydrogen doping test method for buried steel pipes under cathodic protection conditions described in the above embodiments.

[0156] The processor can be a DSP (Digital Signal Processor), an FPGA (Field-Programmable Gate Array), an MCU (Microcontroller Unit) system board, a SoC (System on a Chip) system board, or a PLC (Programmable Logic Controller) minimum system including I / O.

[0157] One embodiment of this utility model is a hydrogen doping test device for buried steel pipes under cathodic protection conditions, as follows: Figure 6 As shown. In Figure 6 In this embodiment, the following are included:

[0158] The potential monitoring module 20 is used to continuously monitor the on-state potential and off-state potential during the dual test process.

[0159] The data processing module 30 is used to generate a quantitative comparison of key parameters between the control group and the experimental group based on the dual testing cycle. The key parameters include corrosion rate, hydrogen doping influence coefficient, mechanical performance index and fracture behavior parameters.

[0160] Model building module 40 is used to construct a multivariate regression model based on key parameters and potential correction data to quantify the relationship between corrosion rate and hydrogen embrittlement sensitivity.

[0161] The above description is merely a preferred embodiment of this utility model, but the protection scope of this utility model is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this utility model should be included within the protection scope of this utility model. Therefore, the protection scope of this utility model should be determined by the scope of the claims.

Claims

1. A hydrogen doping test device for buried steel pipes under cathodic protection conditions, characterized in that, include: Experimental test piping is used to connect in series with the gas supply piping of the experimental platform via an insulating connector; Connecting wires are used to be soldered onto experimental test pipelines, and are set in groups and arranged at intervals according to a distribution rule; The corrosion test piece is used to form a standard part to be tested based on the physical and chemical properties of the experimental test pipeline. Branch pipes are used to form gas branch lines on the side wall of experimental test pipelines. They are set in groups and arranged at intervals according to distribution rules. A shut-off valve is used to control the opening and closing of a gas branch line by installing it on a branch line pipe. A potentiostat is used to monitor and adjust the potential of cathodic protection by connecting it to the experimental test pipeline and the anode ground bed, respectively. An anodic ground bed is used as a current output terminal in a cathodic protection circuit to suppress electrochemical corrosion of experimental test pipelines, branch pipelines, and test specimens. The internal and external hydrogen environment module is used to connect the branch pipe to form the gas branch terminal, fix the corrosion test piece to be tested at the terminal, and form a dual test environment on both sides of the corrosion test piece.

2. The hydrogen doping test device for buried steel pipes under cathodic protection conditions as described in claim 1, characterized in that, The internal and external hydrogen environment constitutive module includes: The main pipe section is used to connect and fix with the branch pipes to form the terminal cavity of the gas path; A fixed flange is used to fix the flange to the opening of the end cavity to form a bearing end face, and a through hole is formed on the bearing end face; The adapter flange is used to connect and fix with the fixed flange to form a mating load-bearing end face, and a through hole is formed on the load-bearing end face; Flange gaskets are used to adapt to the shape of the bearing end face, forming a buffer and sealing structure between the bearing end face of the fixed flange and the bearing end face of the adapting flange.

3. The hydrogen doping test device for buried steel pipes under cathodic protection conditions as described in claim 2, characterized in that, The main pipe section is a horizontally placed straight circular pipe. The middle sidewall of the straight circular pipe is connected and fixed to the branch pipe, and the two ends of the straight circular pipe form open openings. The fixed flange is a circular plate coaxial with the main pipe section, with a through hole coaxial with the main pipe section. The bottom of the circular plate is welded and fixed to the open opening, and the top of the circular plate serves as the bearing end face. The adapter flange is a circular plate coaxial with the fixed flange, with a through hole coaxial with the main pipe section, and the side adjacent to the fixed flange serves as the bearing end face. The flange gasket is formed by metal spiral wound gasket. At one end of the main pipe section, the assembly sequence is fixed flange - flange gasket - corrosion test piece - flange gasket - adapter flange. The fixed flange and the adapter flange are fixed by axial bolts. The same assembly structure is formed at the other end of the main pipe section.

4. The hydrogen doping test device for buried steel pipes under cathodic protection conditions as described in claim 2, characterized in that, The fixed flange and the adapter flange are selected as DN50 standard raised face flanges, with a test hole of 59mm in diameter in the middle of the flange.

5. The hydrogen doping test device for buried steel pipes under cathodic protection conditions as described in claim 2, characterized in that, The corrosion test specimen is sealed to the flange using a spiral wound flange gasket.

6. The hydrogen doping test device for buried steel pipes under cathodic protection conditions as described in claim 2, characterized in that, The surface of the corrosion test piece includes annular sealing watermarks that match the flange gasket specifications.

7. The hydrogen doping test device for buried steel pipes under cathodic protection conditions as described in claim 2, characterized in that, The main pipe section includes at least one end cavity.

8. The hydrogen doping test device for buried steel pipes under cathodic protection conditions as described in claim 2, characterized in that, The corrosion test specimen is electrically connected to the main pipe section via a wire.

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