Simulation calculation method for underground water corrosion characteristics of metal grounding body

Abstract

The present application belongs to the technical field of simulation calculation, and particularly relates to a simulation calculation method for underground water corrosion characteristics of metal grounding body, steps of which comprise: preparing a metal grounding body sample and configuring an electrolyte; performing polarization curve and electrochemical impedance spectrum test, and performing data fitting and corrosion kinetics parameter extraction on the test results; based on the polarization fitting curve obtained through data fitting and the extracted corrosion kinetics parameters, a three-dimensional finite element model of the metal grounding body under actual environmental conditions is established; grid division is performed, simulation calculation is performed on the corrosion rate of the metal grounding body under different environmental conditions, and the corrosion rate distribution is further calculated, so as to realize corrosion rate prediction of the metal grounding body under actual environmental conditions. The present application combines electrochemical experimental test and finite element simulation modeling, and is suitable for quantitative prediction and material comparison and evaluation on the corrosion rate of the metal grounding body in the underground water environment with different pH values and various coexisting corrosive anions.

Description

Technical Field

[0001] The present invention belongs to the technical field of simulation calculation, and in particular relates to a simulation calculation method for underground water corrosion characteristics of a metal grounding body. Background Art

[0002] Power systems widely use metal grounding electrodes as a key component of grounding systems. As they age, grounding electrodes, often buried in water-bearing soil or groundwater, are subject to ionic corrosion. Severe corrosion can lead to increased grounding resistance, fractured connections, and even grounding failure, posing a serious threat to equipment safety and personal protection.

[0003] The metal corrosion process is a complex electrochemical reaction system, and its rate is controlled by a combination of factors, such as pH, ion types and concentrations in the solution, and metal material properties. Among the existing technologies, one method is to use an electrochemical workstation to test the polarization curve of the grounded metal in a simulated solution, and obtain the corrosion current density and corrosion potential through fitting, which are used to roughly estimate the corrosion rate. The advantage of this method is its ease of operation, but it has the following problems: most experiments use a single pH value and a single ion type, which cannot reflect the combined effects of multiple ions in a complex groundwater environment; the polarization parameters are difficult to directly correspond to the actual soil corrosion environment, and the experimental results have poor extrapolation; the evaluation method is limited to data and cannot present the spatial distribution characteristics of the corrosion rate.

[0004] Another approach uses finite element software to model the corrosion process. This approach often simplifies the model, ignoring the ions involved and the acidity and alkalinity of the electrolytes involved in the reaction, and only considers the metal's oxidation reaction and the reduction reaction of oxygen and hydrogen. This approach can describe the localized corrosion morphology, but the simulation accuracy relies on boundary parameter settings, lacks real-world material data, and has low model credibility.

[0005] Therefore, developing a corrosion calculation method that couples experimental data with simulation models and can cover a variety of metal materials and groundwater chemical environments is a key requirement for improving the long-term safety of grounding systems. Summary of the Invention

[0006] In view of the above deficiencies in the prior art, the purpose of the present invention is to provide a simulation calculation method for the groundwater corrosion characteristics of metal grounding bodies, which integrates electrochemical experimental testing and finite element simulation modeling, and is suitable for quantitative prediction of the corrosion rate of metal grounding bodies and material comparative evaluation in groundwater environments with different pH values ​​and coexistence of multiple corrosive anions.

[0007] To achieve the above objectives, the present invention provides a method for simulating and calculating the groundwater corrosion characteristics of a metal grounding body, comprising the following steps:

[0008] S1. Prepare a metal grounding sample and prepare an electrolyte;

[0009] S2. Build an electrochemical testing system to perform polarization curve and electrochemical impedance spectroscopy tests based on a metal grounding body and configured electrolyte. Perform data fitting and extract corrosion kinetic parameters based on the test results. Corrosion kinetic parameters include Tafel slope and exchange current density.

[0010] S3. Using finite element simulation software, based on the polarization fitting curve obtained by data fitting and the extracted corrosion kinetic parameters, a three-dimensional finite element model of the metal grounding body under actual environmental conditions is established, the simulation reaction domain and boundary conditions are set, and the electrode reaction equation and reaction parameters are set;

[0011] S4. Perform mesh division and simulate the corrosion rate of metal grounding bodies under different environmental conditions based on the three-dimensional finite element model, and further calculate the corrosion rate distribution to realize the corrosion rate prediction of metal grounding bodies under actual environmental conditions.

[0012] As a preferred embodiment of the present invention, in S1, the preparation process of the metal grounding body sample is as follows: selecting one of galvanized steel, copper-clad steel, low-carbon steel, red copper, copper alloy, industrial pure aluminum, aluminum alloy or stainless steel as the sample material, and cutting the sample according to the size of the electrolytic cell so that the cut sample size can match the aperture of the electrolytic cell cover plate;

[0013] Use sandpaper to polish the sample surface step by step until the surface shows a uniform metallic luster, then wash the polished sample with deionized water, and then dehydrate the washed sample with anhydrous ethanol;

[0014] The dehydrated sample is placed in a constant temperature drying oven, the temperature is set to 50℃~60℃, and the drying time is set to 30-60 minutes to complete the preparation of the metal grounding sample.

[0015] As a preferred embodiment of the present invention, in said S1, the process of preparing the electrolyte is as follows: pour deionized water into three beakers, select Cl - 、SO4 2- 、HCO3 - As the corrosive anion, and weighing NaCl, Na2SO4, NaHCO3 as the solute of the corresponding corrosive anion, prepare three single ion electrolytes, and accurately configure their concentration ranges so that the three electrolytes meet the following requirements:

[0016] Cl - : 10-100mg / L;

[0017] SO4 2- : 50-200mg / L;

[0018] HCO3 - : 50-500mg / L;

[0019] The pH value that is consistent with the groundwater environment is set as the target value, and the pH value of each electrolyte is adjusted using HCl or H2SO4. During the adjustment, a pH meter is used for real-time monitoring to ensure that the pH value is stable within the range of ±0.05 of the target value.

[0020] As a preferred embodiment of the present invention, in S2, the method for building an electrochemical testing system is to configure a standard three-electrode system, wherein the working electrode is a metal grounding sample, the reference electrode is a silver mercury chloride column, and the auxiliary electrode is a platinum wire. Any single ion electrolyte is selected and added to the electrolytic cell, and the three-electrode electrolytic cell is connected to an electrochemical workstation, and the electrochemical workstation is connected to a computer via a data cable;

[0021] The working electrode, reference electrode, and auxiliary electrode are connected to the working electrode interface, reference electrode interface, and auxiliary electrode interface of the electrochemical workstation respectively. The working electrode is fixed at the working electrode position of the electrolytic cell, the auxiliary electrode is placed at the auxiliary electrode position of the electrolytic cell, and the reference electrode is inserted into the reference electrode position of the electrolytic cell.

[0022] As a preferred embodiment of the present invention, in the S2, the process of performing polarization curve and electrochemical impedance spectroscopy tests is to open the chi660e fitting software installed on the computer, use the electrochemical workstation to perform open circuit potential OCP measurement, obtain the self-corrosion potential of the sample under each set of experimental conditions, and use it as a benchmark for polarization curve test, wherein each set of experimental conditions is for different material metal grounding samples, different electrolytes and different pH values, each combination is a set of experimental conditions;

[0023] Polarization curve test is a destructive test. First, the electrochemical impedance spectroscopy test is performed. The frequency range of the electrochemical impedance spectroscopy scan is 10 -1 Hz~10 5 Hz to obtain parameters including double layer capacitance and interface resistance; then, a polarization curve test was performed based on the open circuit potential. The potential scanning range was set to OCP±0.5V and the scanning rate was 0.01V / min to obtain corrosion kinetic parameters including Tafel slope and exchange current density.

[0024] As a preferred embodiment of the present invention, in the S2, the method for data fitting and corrosion kinetic parameter extraction of the test results is to fit the polarization curve data obtained by the test and extract the corrosion kinetic parameters including Tafel slope and exchange current density for subsequent finite element simulation modeling; according to the measured open circuit potential, the potential scanning range in the polarization curve test is set in the chi660e fitting software, the scanning start potential and the end potential are open circuit potentials of ±0.5V, the scanning rate is selected as 0.01V / min, and the sensitivity of the chi660e fitting software is selected as 1×10 -2 , obtain stable and fitable polarization curve data;

[0025] The polarization curve data under each set of experimental conditions were fitted separately to obtain the polarization fitting curves of different metal grounding bodies under different conditions.

[0026] As a preferred embodiment of the present invention, in the S3, the method for establishing the three-dimensional finite element model is to use COMSOL software, select the tertiary current distribution physical field for simulation modeling, use the COMSOL geometry construction function to construct a metal grounding body model, divide the calculation domain into metal grounding bodies, soil, groundwater and air, and set corresponding material parameters according to the physical properties of each calculation domain, wherein the physical properties include conductivity and diffusion coefficient.

[0027] As a preferred embodiment of the present invention, in said S3, setting the simulation reaction domain and boundary conditions is specifically as follows: in the tertiary current distribution physical field, electrolytes are added to represent different reaction domains participating in the reaction, the surface of the metal grounding body is set to represent the boundaries of different regions participating in the reaction, and the metal grounding body reaction is set to simulate the electrochemical reaction of each position participating in different reaction domains;

[0028] Specifically, the electrode reaction equation and reaction parameters are set to set different electrochemical reaction types of metal grounding bodies in the air, soil and groundwater areas, considering hydrogen evolution reaction, oxygen reduction reaction and metal dissolution reaction caused by corrosive ions. At the electrolyte contact surface, the electrode reaction boundary conditions are set based on the polarization curve data. For metal grounding bodies located in the groundwater area, the reaction between corrosive ions and metal grounding bodies is additionally considered. Cl - 、SO4 2 、HCO3 - The influence on the electrochemical reaction rate and the construction of multi-ion synergistic corrosion mechanism.

[0029] As a preferred embodiment of the present invention, the electrode reaction equation is as follows:

[0030] ;

[0031] ;

[0032] Where, Represents the total current density, which is the sum of the local current densities. The current density of the mth local reaction is ; is the electric double layer current density; n represents the unit normal vector; represents the overall reaction rate; represents the reaction rate of the mth local reaction; represents the electrical double layer reaction rate.

[0033] As a preferred embodiment of the present invention, in the aforementioned S4, the metal grounding body, soil, air, and groundwater are meshed, the metal grounding body mesh is a free tetrahedron mesh, the area in contact with the metal grounding body is divided into an extremely fine mesh, and the remaining areas are divided into a regular mesh;

[0034] An ion reaction was set on the surface of the metal grounding body. The Tafel slope and exchange current density were set in the reaction parameters. The transient study module of COMSOL was used for calculation. The simulation time step was set to annual or quarterly. The PARDISO solver was selected and the relative tolerance was set to 0.001. The corrosion rate of the metal grounding body under different environmental conditions was obtained. Based on the simulation results, the electrolyte current density distribution diagram of different calculation domains was output, and the corrosion rate distribution was further calculated to identify local high corrosion risk areas.

[0035] The algorithm and simulation involved in the present invention can be executed by an electronic device, which includes a memory, a processor, and a computer program stored in the memory and capable of running on the processor. The above-mentioned algorithm calculation and simulation are realized by executing the software through the processor.

[0036] The beneficial effects of the present invention are:

[0037] The present invention uses Tafel curves and impedance spectra to obtain the true electrode kinetic parameters (Tafel slope and exchange current density) of each material under different corrosion media and pH conditions. Compared with the traditional input of empirical data or literature values, the model boundary conditions have stronger physical correspondence and environmental adaptability. Therefore, the established finite element corrosion simulation model is more accurate in the calculation of corrosion current density and can truly reflect the reaction behavior of the material in the actual groundwater environment. It can improve the consistency between the corrosion rate prediction results and the actual performance, providing a scientific basis for the estimation of the service life of the grounding body.

[0038] The present invention constructs a process for extracting and simulating electrochemical parameters. The simulation no longer relies on assumptions or empirical values, but is directly controlled by experimental behavior data of the material-environment relationship. Therefore, the corrosion calculation results have iterative optimization characteristics and can dynamically adjust the model input as the test conditions change. Ultimately, the entire corrosion assessment system has strong applicability, greatly improving the robustness and adaptability of corrosion prediction.

[0039] There are complex chemical mechanisms such as synergistic corrosion or passivation film destruction between common ions in groundwater. The present invention combines the above ions under different pH conditions, and the model can truly reflect the corrosion dynamics coupling effect under the coexistence of multiple ions; ultimately, it can achieve corrosion simulation that is closer to the natural environment, providing comprehensive and reliable data support for material performance evaluation in complex groundwater scenarios. All materials are compared under a unified test method, the same modeling structure and equivalent boundary conditions; therefore, the output corrosion rate is horizontally comparable and can be used for performance ranking and grade evaluation between different materials; thus, it solves the problem of inconsistent evaluation methods for different materials and incomparable data in existing research; ultimately, a standardized material corrosion resistance evaluation system can be constructed to provide a quantitative technical path for the optimization of grounding grid materials.

[0040] The test process and modeling involved in this invention both adopt a universal platform and standard equipment, have good engineering portability, and are suitable for promotion and use under different laboratory or field conditions; and can be further expanded to consider multi-factor coupled corrosion mechanisms such as temperature, soil resistivity, and microbial participation in reactions, and have the potential to become the basic model for regional grounding anti-corrosion planning, life prediction systems, and intelligent material selection systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a schematic diagram of the process of the present invention;

[0042] Figure 2 is a schematic diagram of a metal grounding body portion cut out from a three-dimensional finite element model in an embodiment of the present invention;

[0043] Figure 3 is an overall schematic diagram of a three-dimensional finite element model in an embodiment of the present invention;

[0044] Figure 4 Schematic diagram of mesh division of a three-dimensional finite element model in an embodiment of the present invention;

[0045] Figure 5 1 is a diagram of the electrolyte current density distribution of the metal grounding body in an embodiment of the present invention. DETAILED DESCRIPTION

[0046] The embodiments of the present invention are further described below with reference to the accompanying drawings:

[0047] like Figure 1As shown, a simulation calculation method for groundwater corrosion characteristics of metal grounding bodies includes the following steps:

[0048] S1. Prepare a metal grounding sample and prepare an electrolyte;

[0049] S2. Build an electrochemical testing system to perform polarization curve and electrochemical impedance spectroscopy tests based on a metal grounding body and configured electrolyte. Perform data fitting and extract corrosion kinetic parameters based on the test results. Corrosion kinetic parameters include Tafel slope and exchange current density.

[0050] S3. Using finite element simulation software, based on the polarization fitting curve obtained by data fitting and the extracted corrosion kinetic parameters, a three-dimensional finite element model of the metal grounding body under actual environmental conditions is established, the simulation reaction domain and boundary conditions are set, and the electrode reaction equation and reaction parameters are set;

[0051] S4. Perform mesh division and simulate the corrosion rate of metal grounding bodies under different environmental conditions based on the three-dimensional finite element model, and further calculate the corrosion rate distribution to realize the corrosion rate prediction of metal grounding bodies under actual environmental conditions.

[0052] The Tafel slope represents the slope of the relationship between potential and logarithmic current density in the electrode polarization curve and is a key parameter for characterizing the corrosion reaction rate. The exchange current density is the current density at which the oxidation and reduction reaction rates are equal when the electrode reaches electrochemical equilibrium, reflecting the corrosion activity of the metal surface. Electrochemical impedance spectroscopy measures the impedance of a system at different frequencies using a small perturbation voltage. It is used to analyze charge transfer and electrode interface behavior during the corrosion process. Polarization curves represent the curves of the metal electrode potential versus current density in a specific electrolyte environment and are used to analyze corrosion behavior and mechanisms.

[0053] In S1, the preparation process of the metal grounding body sample is as follows: select one of galvanized steel, copper-clad steel, low-carbon steel, copper, copper alloy, industrial pure aluminum, aluminum alloy or stainless steel as the sample material, cut the sample according to the size of the electrolytic cell, ensure that the sample can be stably fixed in the electrolytic cell to avoid the drift of the sample position during the test, and make the cut sample size match the aperture of the electrolytic cell cover;

[0054] Use sandpaper to polish the sample surface step by step to remove the oxide layer, rust and other impurities until the surface shows a uniform metallic luster to ensure the consistency of subsequent tests. Then, wash the polished sample with deionized water and then dehydrate it with anhydrous ethanol to avoid recurrence of oxidation reaction.

[0055] The dehydrated sample is placed in a constant temperature drying oven, the temperature is set to 50℃~60℃, and the drying time is set to 30-60 minutes to complete the preparation of the metal grounding sample.

[0056] The process of preparing the electrolyte is as follows: pour deionized water into three beakers, select Cl - 、SO4 2- 、HCO3 - As the corrosive anion, and weighing NaCl, Na2SO4, NaHCO3 as the solute of the corresponding corrosive anion, prepare three single ion electrolytes, and accurately configure their concentration ranges so that the three electrolytes meet the following requirements:

[0057] Cl - : 10-100mg / L;

[0058] SO4 2- : 50-200mg / L;

[0059] HCO3 - : 50-500mg / L;

[0060] The pH value that is consistent with the groundwater environment is set as the target value, and the pH value of each electrolyte is adjusted using HCl or H2SO4. During adjustment, a high-precision pH meter is used for real-time monitoring to ensure that the pH value is stable within the range of ±0.05 of the target value.

[0061] In S2, the method for setting up the electrochemical test system is to configure a standard three-electrode system, wherein the working electrode is a metal grounded sample, the reference electrode is a silver mercury chloride column, and the auxiliary electrode is a platinum wire (0.5×37 mm). Select any configured single ion electrolyte (100 ml) and add it to the electrolytic cell (total volume 200 ml). The three-electrode electrolytic cell is connected to an electrochemical workstation (known equipment). The electrochemical workstation is connected to a computer via a USB data cable to ensure that the connection is normal and there is no disconnection, to ensure good electrode contact, and stable data acquisition;

[0062] The working electrode, reference electrode, and auxiliary electrode are connected to the working electrode interface, reference electrode interface, and auxiliary electrode interface of the electrochemical workstation respectively. The working electrode is fixed at the working electrode position of the electrolytic cell, the auxiliary electrode is placed at the auxiliary electrode position of the electrolytic cell, and the reference electrode is inserted into the reference electrode position of the electrolytic cell.

[0063] The process of conducting polarization curve and electrochemical impedance spectroscopy tests is to open the chi660e fitting software installed on the computer, ensure that the electrochemical workstation is compatible with the software, repeatedly check the electrode access status, initialize the fitting software parameters for subsequent tests, and use the electrochemical workstation to perform open circuit potential (OCP) measurements (3 to 5 minutes after stabilization of the potential). The self-corrosion potential of the sample under each set of experimental conditions is obtained and used as the benchmark for the polarization curve test. Each set of experimental conditions is a combination of different material metal grounding samples, different electrolytes, and different pH values. Each combination is a set of experimental conditions.

[0064] Polarization curve test is a destructive test. First, the electrochemical impedance spectroscopy test is performed. The frequency range of the electrochemical impedance spectroscopy scan is 10 -1 Hz~10 5 Hz to obtain parameters including double-layer capacitance and interface resistance (these parameters can reflect the corrosion resistance of metal grounding bodies in electrolytes) for subsequent electrochemical kinetic characteristics analysis; then, a polarization curve test was performed based on the open circuit potential. The potential scanning range was set to OCP±0.5V and the scanning rate was 0.01V / min to obtain corrosion kinetic parameters, including Tafel slope and exchange current density.

[0065] The method for data fitting and corrosion kinetic parameter extraction of the test results is to fit the polarization curve data obtained from the test and extract the corrosion kinetic parameters including Tafel slope and exchange current density for subsequent finite element simulation modeling; according to the measured open circuit potential, the potential scanning range in the polarization curve test is set in the chi660e fitting software, and the scanning start potential and end potential are open circuit potentials of ±0.5 V, the scanning rate is selected as 0.01 V / min, and the sensitivity of the chi660e fitting software is selected as 1×10 -2 , obtain stable and fitable polarization curve data;

[0066] Polarization curve data for each set of experimental conditions were fitted separately to obtain polarization fitting curves for different metal grounding bodies under different conditions. Extrapolation fitting is generally performed in the strong polarization region (overpotentials above 0.05-0.1V). The overpotential of the electrode reaction exhibits a linear relationship with the logarithm of the current density, and the fitted straight line region is the desired Tafel slope.

[0067] In S3, the method for establishing a three-dimensional finite element model is to use COMSOL software, select the tertiary current distribution physical field for simulation modeling, use COMSOL's geometric construction function to build a metal grounding body model, divide the calculation domain into metal grounding bodies, soil, groundwater and air, and set the corresponding material parameters according to the physical properties of each calculation domain, where the physical properties include conductivity and diffusion coefficient.

[0068] The tertiary current distribution physics field is a multi-physics coupling field in COMSOL that takes into account factors such as solution conductivity, polarization, and electrode reaction kinetics. It is suitable for simulating electrode reaction processes in actual corrosion environments.

[0069] The schematic diagram of the three-dimensional finite element model is as follows Figure 2 and Figure 3 As shown, Figure 2 This is a schematic diagram after optimizing the intercepted part (for ease of display). Figure 2 In the process of conducting current from equipment or structures on the ground to the metal grounding body ( Figure 2 The underground part of the middle down conductor is the metal grounding body). Figure 3 This is the actual modeling diagram in COMSOL. Figure 3 In the figure, the entire three-dimensional finite element model is modeled as a circle, with air above the ground and soil and groundwater below the ground. The columnar structure near the center of the circle is the downconductor, the shallow soil above the groundwater, and the deep soil below the groundwater. In this modeling example, only one layer of groundwater is considered, but multiple layers of groundwater can also be set according to modeling requirements.

[0070] Specifically, the simulation reaction domain and boundary conditions are set as follows: in the tertiary current distribution physical field, electrolytes are added to represent different reaction domains participating in the reaction, the surface of the metal ground body is set to represent the boundaries of different regions participating in the reaction, and the metal ground body reaction is set to simulate the electrochemical reactions at various locations under different reaction domains;

[0071] Specifically, the electrode reaction equation and reaction parameters are set to set different electrochemical reaction types of metal grounding bodies in the air, soil and groundwater areas, considering hydrogen evolution reaction, oxygen reduction reaction and metal dissolution reaction caused by corrosive ions. At the electrolyte contact surface, the electrode reaction boundary conditions are set based on the polarization curve data. For metal grounding bodies located in the groundwater area, the reaction between corrosive ions and metal grounding bodies is additionally considered. Cl - 、SO4 2 、HCO3 - The influence on the electrochemical reaction rate and the construction of multi-ion synergistic corrosion mechanism.

[0072] The equations of the reaction domain (ground body, soil, groundwater and air) can be set as well-known formulas, including general equations describing the relationship between substance concentration changes, current density distribution and reaction rate in electrochemical systems, basic equations describing the relationship between current density and concentration changes, and general equations describing substance fluxes.

[0073] The electrode reaction equation is as follows:

[0074] ;

[0075] ;

[0076] Where, Represents the total current density, which is the sum of the local current densities. The current density of the mth local reaction is ; is the electric double layer current density; n represents the unit normal vector; represents the overall reaction rate; represents the reaction rate of the mth local reaction; represents the electrical double layer reaction rate.

[0077] The above two equations mainly describe the relationship between the current density and reaction rate of different source terms in the electrochemical system. The source term on the right represents the accumulation of current or reaction rate generated by different electrochemical reaction processes. The specific reaction kinetics calculation expression added is the anode and cathode Tafel equation, and the key corrosion parameters under different ions measured in the electrochemical test: the anode and cathode Tafel slope and the exchange current density are substituted into the electrode reaction of the corresponding ions to complete the parameter setting. The equilibrium potential of the reaction in groundwater is related to the pH value and can be corrected according to the Nernst formula. The equilibrium potential of the metal grounding body at different pH values ​​is calculated separately. The equilibrium potential of the grounding body reaction at other locations is set according to the corresponding metal reaction equilibrium potential based on the existing parameters to ensure consistency across the entire domain.

[0078] In S4, Figure 4 As shown in the figure, the metal grounding body, soil, air, and groundwater are meshed. The metal grounding body mesh uses a free tetrahedron mesh. The area in contact with the metal grounding body is divided into an extremely fine mesh, and the rest of the area is divided into a regular mesh.

[0079] An ion reaction is set on the surface of the metal grounding body. The Tafel slope and exchange current density are set in the reaction parameters. The transient study module of COMSOL is used for calculation. The simulation time step is set to annual or quarterly. The solver is selected as PARDISO. The relative tolerance is set to 0.001. The corrosion rate of the metal grounding body under different environmental conditions is obtained. According to the simulation results, the electrolyte current density distribution diagram of different calculation domains is output. During the simulation process, the electrolyte current density distribution diagram of the metal grounding body (from the surface soil to the bottom of the groundwater) output by a certain calculation is as follows: Figure 5 shown.

[0080] After obtaining the electrolyte current density distribution maps of different calculation domains, the corrosion rate distribution is further calculated to identify local high corrosion risk areas, thereby realizing the corrosion rate prediction of metal grounding bodies under actual environmental conditions.

Claims

1. A simulation calculation method for groundwater corrosion characteristics of metal grounding bodies, characterized in that The following steps are involved: S1. Prepare a metal grounding sample and prepare an electrolyte; S2. Build an electrochemical testing system to perform polarization curve and electrochemical impedance spectroscopy tests based on a metal grounding body and configured electrolyte. Perform data fitting and extract corrosion kinetic parameters based on the test results. Corrosion kinetic parameters include Tafel slope and exchange current density. S3. Using finite element simulation software, based on the polarization fitting curve obtained by data fitting and the extracted corrosion kinetic parameters, a three-dimensional finite element model of the metal grounding body under actual environmental conditions is established, the simulation reaction domain and boundary conditions are set, and the electrode reaction equation and reaction parameters are set; The three-dimensional finite element model was established by using COMSOL software, selecting the tertiary current distribution physical field for simulation modeling, and using COMSOL's geometry construction function to construct a metal grounding body model, dividing the calculation domain into the metal grounding body, soil, groundwater, and air. Specifically, the simulation reaction domain and boundary conditions are set as follows: in the tertiary current distribution physical field, electrolytes are added to represent different reaction domains participating in the reaction, the surface of the metal ground body is set to represent the boundaries of different regions participating in the reaction, and the metal ground body reaction is set to simulate the electrochemical reactions at various locations under different reaction domains; Specifically, the electrode reaction equation and reaction parameters are set to set different electrochemical reaction types of metal grounding bodies in the air, soil and groundwater areas, considering hydrogen evolution reaction, oxygen reduction reaction and metal dissolution reaction caused by corrosive ions. At the electrolyte contact surface, the electrode reaction boundary conditions are set based on the polarization curve data. For metal grounding bodies located in the groundwater area, the reaction between corrosive ions and metal grounding bodies is additionally considered. Cl - 、SO4 2 、HCO3 - The impact on electrochemical reaction rate and the construction of multi-ion synergistic corrosion mechanism; The electrode reaction equation is as follows: ； ； Where, Represents the total current density, which is the sum of the local current densities. The current density of the mth local reaction is ; is the electric double layer current density; n represents the unit normal vector; represents the overall reaction rate; represents the reaction rate of the mth local reaction; represents the electrical double layer reaction rate; S4. Perform meshing and simulate the corrosion rate of the metal grounding body under different environmental conditions based on the three-dimensional finite element model, and further calculate the corrosion rate distribution to achieve the corrosion rate prediction of the metal grounding body under actual environmental conditions; The metal grounding body, soil, air, and groundwater are meshed. The free tetrahedron mesh is used for the metal grounding body. The area in contact with the metal grounding body is meshed to an extremely fine degree, and the rest of the area is meshed to a regular degree. An ion reaction was set on the surface of the metal grounding body. The Tafel slope and exchange current density were set in the reaction parameters. The transient study module of COMSOL was used for calculation. The simulation time step was set to annual or quarterly. The PARDISO solver was selected and the relative tolerance was set to 0.

001. The corrosion rate of the metal grounding body under different environmental conditions was obtained. Based on the simulation results, the electrolyte current density distribution diagram of different calculation domains was output, and the corrosion rate distribution was further calculated to identify local high corrosion risk areas.

2. The method for simulating and calculating the groundwater corrosion characteristics of a metal grounding body according to claim 1, characterized in that: In S1, the preparation process of the metal grounding body sample is as follows: selecting one of galvanized steel, copper-clad steel, low-carbon steel, red copper, copper alloy, industrial pure aluminum, aluminum alloy or stainless steel as the sample material, cutting the sample according to the size of the electrolytic cell so that the cut sample size can match the aperture of the electrolytic cell cover; Use sandpaper to polish the sample surface step by step until the surface shows a uniform metallic luster, then wash the polished sample with deionized water, and then dehydrate the washed sample with anhydrous ethanol; The dehydrated sample is placed in a constant temperature drying oven, the temperature is set to 50℃~60℃, and the drying time is set to 30-60 minutes to complete the preparation of the metal grounding sample.

3. The method for simulating and calculating the groundwater corrosion characteristics of a metal grounding body according to claim 1, characterized in that: In the above S1, the process of preparing the electrolyte is as follows: pour deionized water into three beakers, select Cl - 、SO4 2- 、HCO3 - As the corrosive anion, and weighing NaCl, Na2SO4, NaHCO3 as the solute of the corresponding corrosive anion, prepare three single ion electrolytes, and accurately configure their concentration ranges so that the three electrolytes meet the following requirements: Cl - :10-100mg / L; SO4 2- :50-200mg / L; HCO3 - :50-500mg / L; The pH value that is consistent with the groundwater environment is set as the target value, and the pH value of each electrolyte is adjusted using HCl or H2SO4. During the adjustment, a pH meter is used for real-time monitoring to ensure that the pH value is stable within the range of ±0.05 of the target value.

4. The method for simulating and calculating the groundwater corrosion characteristics of a metal grounding body according to claim 1, characterized in that: In the aforementioned S2, the method for constructing the electrochemical testing system is to configure a standard three-electrode system, wherein the working electrode is a metal grounded sample, the reference electrode is a silver mercury chloride column, and the auxiliary electrode is a platinum wire. Any single ion electrolyte is selected and added to the electrolytic cell. The three-electrode electrolytic cell is connected to an electrochemical workstation, and the electrochemical workstation is connected to a computer via a data cable. The working electrode, reference electrode, and auxiliary electrode are connected to the working electrode interface, reference electrode interface, and auxiliary electrode interface of the electrochemical workstation respectively. The working electrode is fixed at the working electrode position of the electrolytic cell, the auxiliary electrode is placed at the auxiliary electrode position of the electrolytic cell, and the reference electrode is inserted into the reference electrode position of the electrolytic cell.

5. The method for simulating and calculating the groundwater corrosion characteristics of a metal grounding body according to claim 4, characterized in that: In the aforementioned S2, the process of performing polarization curve and electrochemical impedance spectroscopy tests is to open the chi660e fitting software installed on the computer, use the electrochemical workstation to perform open circuit potential (OCP) measurement, obtain the self-corrosion potential of the sample under each set of experimental conditions, and use it as the benchmark for the polarization curve test, wherein each set of experimental conditions is a combination of different material metal grounding samples, different electrolytes, and different pH values, and each combination is a set of experimental conditions; Polarization curve test is a destructive test. First, electrochemical impedance spectroscopy test is performed. The frequency range of electrochemical impedance spectroscopy scanning is 10 -1 Hz~10 5 Hz to obtain parameters including double layer capacitance and interface resistance; then, a polarization curve test was performed based on the open circuit potential. The potential scanning range was set to OCP±0.5V and the scanning rate was 0.01V / min to obtain corrosion kinetic parameters including Tafel slope and exchange current density.

6. The method for simulating and calculating the groundwater corrosion characteristics of a metal grounding body according to claim 5, characterized in that: In the above S2, the method for data fitting and corrosion kinetic parameter extraction of the test results is to fit the polarization curve data obtained by the test and extract the corrosion kinetic parameters including Tafel slope and exchange current density for subsequent finite element simulation modeling; according to the measured open circuit potential, the potential scanning range in the polarization curve test is set in the chi660e fitting software, the scanning start potential and the end potential are open circuit potentials of ±0.5V, the scanning rate is selected as 0.01V / min, and the sensitivity of the chi660e fitting software is selected as 1×10 -2 , obtain stable and fitable polarization curve data; The polarization curve data under each set of experimental conditions were fitted separately to obtain the polarization fitting curves of different metal grounding bodies under different conditions.

7. The method for simulating and calculating the groundwater corrosion characteristics of a metal grounding body according to claim 1, characterized in that: In the above-mentioned S3, corresponding material parameters are set according to the physical properties of each calculation domain, wherein the physical properties include conductivity and diffusion coefficient.

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