Evaluation method for corrosion behavior of small hole of anticorrosive coating under action of current

Abstract

The invention provides a method for evaluating the corrosion behavior of a small hole of an anticorrosive coating under the action of current. The method comprises the following steps: (1) acquiring corrosion kinetic parameters of a metal material; (2) constructing a parameterized multi-physical field model; (3) simulating a corrosion evolution process; (4) verifying the reliability of the model through experiments; and (5) constructing a comprehensive evaluation index. Obtaining corrosion kinetic parameters (corrosion potential, corrosion current density, Tafel slope and exchange current density) of the metal material through a potentiodynamic polarization curve test; the method comprises the following steps: preparing an anticorrosive coating metal sample with artificial pores, constructing a parameterized multi-physical field model by combining finite element software, and simulating local current density distribution and corrosion evolution under different pore diameters (greater than or equal to 2 mm), spacing (greater than or equal to 0 mm) and current density (greater than or equal to 0 A / m < 2 >); the reliability (corrosion potential error lt, 20%) of the model is verified through experiments, a comprehensive evaluation index is constructed based on multi-parameter sensitivity analysis, and rapid evaluation of the corrosion risk of the small hole of the anticorrosive coating and protection scheme optimization are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical fields such as corrosion evaluation of metal materials, and particularly relates to a method for evaluating the pitting corrosion behavior of an anti-corrosion layer under the action of an electric current. Background Art

[0002] In traditional studies on the corrosion of metal materials, most focus on the influence of a single factor on corrosion, making it difficult to comprehensively and accurately reflect the corrosion process under actual working conditions. However, the actual situation is that metal corrosion is a complex process involving the interaction of multiple physical fields.

[0003] In the actual application scenarios of metal materials, the anti-corrosion layer plays a key role in delaying metal corrosion. However, the anti-corrosion layers of most metal materials have varying degrees of damage, and pitting corrosion caused by local failure of the anti-corrosion layer has become one of the main forms of material failure. Once small holes appear in the anti-corrosion layer, the corrosion process of the metal matrix under the action of an electric current presents localized characteristics. And pitting corrosion has autocatalytic properties, and the local corrosion rate increases exponentially under the action of an electric current. The traditional weight loss method cannot capture the local dynamic change process, and the existing methods are difficult to quantify the coupling relationship of current density distribution, the distance between the anti-corrosion layer and the metal, and the pore diameter of the small holes, resulting in a lack of theoretical basis for the protection design.

[0004] Most current patents are directed at the evaluation method for the current corrosion of the entire metal matrix. For example, Patent CN119198527A discloses a method and system for evaluating the direct current stray current corrosion of oil and gas pipelines; Patent CN112251756A discloses a system and method for judging the dynamic direct current corrosion risk of buried metal pipelines. However, none of these patents involve the evaluation method for the pitting corrosion behavior after the anti-corrosion layer of the metal matrix is damaged, presenting an obvious technical gap. Summary of the Invention

[0005] In view of the defects and deficiencies existing in the prior art, the present invention provides a method for evaluating the pitting corrosion behavior of an anti-corrosion layer under the action of an electric current, aiming to solve the technical problem that the traditional evaluation method is difficult to quantify the coupling relationship of current density distribution, the distance between the anti-corrosion layer and the metal, and the pore diameter of the small holes. The method includes: obtaining the corrosion kinetic parameters (corrosion potential, corrosion current density, Tafel slope, and exchange current density) of the metal material through potentiodynamic polarization curve testing; preparing an anti-corrosion layer metal specimen with artificial small holes, and constructing a parameterized multi-physical field model in combination with finite element software to simulate the local current density distribution and corrosion evolution under different pore diameters (≥2 mm), distances (≥0 mm), and current densities (≥0 A / m 2 ) ; verifying the reliability of the model through experiments (corrosion potential error < 20%), and constructing a comprehensive evaluation index based on multi-parameter sensitivity analysis to achieve rapid assessment of the pitting corrosion risk of the anti-corrosion layer and optimization of the protection scheme.

[0006] The technical solution specifically adopted by the present invention to solve its technical problems is as follows:

[0007] A method for evaluating the pitting corrosion behavior of an anti-corrosion coating under the action of current, comprising the following steps:

[0008] (1) Obtain the corrosion kinetic parameters of the metal material: Analyze the corrosion potential, corrosion current density, anodic / cathodic Tafel slope, and anodic / cathodic exchange current density through potentiodynamic polarization curve testing;

[0009] (2) Construct a parametric multi-physics field model: Define the geometric parameters of the anti-corrosion coating pores, the spacing of metal defects, and the current density as dynamically adjustable variables, construct an electrochemical corrosion model through finite element software, and define the anodic / cathodic reaction kinetic parameters at the metal-electrolyte interface, including the corrosion potential, corrosion current density, and Tafel slope;

[0010] (3) Simulate the corrosion evolution process: Generate the local current density distribution and corrosion thickness change data under different working conditions based on parametric scanning, analyze the autocatalytic characteristics of pitting corrosion through steady-state solution of the initial current distribution and transient solution of the dynamic corrosion evolution;

[0011] (4) Experimentally verify the reliability of the model: Apply current to the anti-corrosion coating specimen with artificial pores, compare the corrosion potential error and the macroscopic morphology consistency, and verify the reliability of the simulation results;

[0012] (5) Construct a comprehensive evaluation index: Allocate weights based on multi-parameter sensitivity analysis, generate a dimensionless index for quantifying the corrosion risk through weighted summation after linearly normalizing the parameters, and divide the risk levels according to the preset thresholds.

[0013] Further, the potentiodynamic polarization curve test is carried out in a simulated soil electrolyte, and the electrolyte is Yingtan soil simulation solution. The test current density covers 0 - 60 A / m 2 , and the corrosion potential, corrosion current density, anodic / cathodic Tafel slope, and anodic / cathodic exchange current density are analyzed by the Tafel extrapolation method.

[0014] Further, the geometric parameters of the anti-corrosion coating pores include a pore diameter of 2 - 10 mm, the interface spacing between the metal defect and the anti-corrosion coating is 0 - 5 mm, and the current density range is 0 - 60 A / m 2 , and the parameter range generates multi-condition corrosion data through parametric scanning.

[0015] Further, the anti-corrosion coating material is epoxy resin or polyurethane, with a thickness of 3 mm, and artificial pores are prepared by laser processing.

[0016] Further, the parametric scan includes a steady-state solution for the initial current distribution and a transient solution for corrosion evolution. The time step is set to 5 days, and the total duration is 31 days.

[0017] Further, the experimental verification includes connecting three groups of specimens in series and applying a current density of 10 A / m 2 , with the relative error of the corrosion potential less than 20%, and the corrosion morphology is matched through macroscopic observation and thickness measurement.

[0018] Further, through the multi-parameter sensitivity analysis, it is determined that the contribution weight of the current density to the corrosion risk is the highest, the weight of the small hole aperture of the anti-corrosion layer is the lowest, and the weight of the interface spacing is in the middle.

[0019] Further, in the finite element software, the conductivity of the electrolyte domain is defined as 0.02242 S / m, and the conductivity of the anti-corrosion layer is defined as 6.67×10 -5 S / m, which is used to construct the electrochemical corrosion model.

[0020] Further, the comprehensive evaluation index processes the parameters through linear normalization, and the threshold division includes low risk, medium risk, and high risk.

[0021] Further, the method is used for the risk assessment of the anti-corrosion layer breakage of oil and gas pipelines or buried metal structures, and the exponential growth effect of the local current density is quantified through the corrosion thickness cloud map.

[0022] Compared with the prior art, the present invention and its preferred embodiments at least include the following beneficial effects:

[0023] Experimental and numerical simulation closed-loop verification system:

[0024] Corrosion kinetic parameters (corrosion current density, Tafel slope, etc.) are obtained through potentiodynamic polarization experiments, combined with the finite element model to simulate the current density distribution. The experimental verification shows that the error of the corrosion potential and the macroscopic morphology consistency are high, solving the defect that the traditional weight loss method cannot capture local dynamic changes.

[0025] Multi-parameter coupled dynamic modeling:

[0026] The small hole aperture of the anti-corrosion layer (≥2 mm), the metal defect spacing (≥0 mm), and the current density (≥0 A / m 2 ) are set as dynamically adjustable variables. Multi-condition data are generated through parametric scanning to quantify the coupling relationship among the three, providing a theoretical basis for the protection design.

[0027] Comprehensive evaluation index quantifies risk:

[0028] Based on sensitivity analysis, it is determined that the contribution weight of current density to corrosion risk is the highest, and the weight of the small hole aperture of the anti-corrosion layer is the lowest. A dimensionless index is constructed through linear normalization, and low-risk (<0.3), medium-risk (0.3 - 0.6), and high-risk (>0.6) levels are divided, filling the gap in the existing evaluation system.

[0029] Special analysis of local corrosion after the anti-corrosion layer is damaged:

[0030] Focus on the autocatalytic characteristics of small holes in the anti-corrosion layer (exponential growth of local current density). By combining artificial small hole specimens with models, the mechanism of local corrosion acceleration is revealed.

[0031] High-precision engineering practicality:

[0032] The model is highly matched with the experimental data (corrosion thickness error <20%), and can be directly used to optimize the anti-corrosion schemes of oil and gas pipelines and buried metal structures, reducing maintenance costs. Description of the drawings

[0033] The present invention will be further described in detail below in conjunction with the drawings and specific embodiments:

[0034] Figure 1 It is the technical roadmap of the embodiment of the present invention;

[0035] Figure 2 It is the schematic diagram of the experimental device for metal electrochemical corrosion under the action of current in the embodiment of the present invention;

[0036] Figure 3 It is the polarization curve of X80 pipeline steel without current in the embodiment of the present invention;

[0037] Figure 4 It is the schematic diagram of the structure of the small hole corrosion experimental specimen in the embodiment of the present invention;

[0038] Figure 5 It is the schematic diagram of the experimental device for corrosion after the anti-corrosion layer is damaged in the embodiment of the present invention;

[0039] Figure 6 It is the three-dimensional schematic diagram of the metal corrosion model with small holes in the anti-corrosion layer in the embodiment of the present invention;

[0040] Figure 7 It is the two-dimensional cross-sectional view of the metal corrosion model with small holes in the anti-corrosion layer in the embodiment of the present invention;

[0041] Figure 8 It is the comparison diagram of the experimental and simulation results of the macroscopic morphology of small hole corrosion in the embodiment of the present invention;

[0042] Figure 9 It is the cloud diagram of the change in the thickness of the metal with small hole corrosion in the embodiment of the present invention. Specific embodiments

[0043] To make the features and advantages of this patent more obvious and understandable, specific embodiments are given below for detailed description as follows:

[0044] It should be noted that the following detailed description is illustrative and aims to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used in this specification have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs.

[0045] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to this application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0046] As Figure 1 shown, an evaluation method for pitting corrosion behavior of an anti-corrosion coating under the action of current according to an embodiment of the present invention includes the following steps:

[0047] Step S1: Obtaining corrosion kinetic parameters. By using a metal specimen without an anti-corrosion coating, a potentiodynamic polarization curve test is carried out in a simulated electrolyte to determine the electrochemical corrosion kinetic parameters of the metal.

[0048] Step S2: Constructing pitting corrosion characteristics. By preparing a metal specimen with an anti-corrosion coating with artificial holes, a current corrosion experiment is carried out in a simulated electrolyte to determine the corrosion behavior of the metal specimen and the corrosion changes on the metal surface.

[0049] Step S3: Constructing a parametric model. A metal with parametric geometric characteristics of the anti-corrosion coating holes is constructed, and the basic properties and electrochemical parameters of the anti-corrosion coating and the metal are defined.

[0050] Step S4: Solving the numerical simulation of pitting corrosion under the action of current. Using finite element numerical simulation software, the model of the metal with anti-corrosion coating holes under the action of current is solved, and parametric scanning is carried out on the model of the metal with anti-corrosion coating holes under the action of current. The parameters include the hole diameter of the anti-corrosion coating holes (2 - 10 mm), the distance between the bottom of the metal defect and the interface of the anti-corrosion coating (0 - 5 mm), and the current density (0 - 30 A / m 2 ), and the corrosion data of the defect under different conditions are obtained.

[0051] Step S5: Experiment and simulation verification. According to the solution results of the numerical simulation of pitting corrosion under the action of current, verification is carried out with the experiment in Step S2.

[0052] Step S6: Construction of a comprehensive evaluation system. Establish a method for evaluating the pitting corrosion behavior of the anti-corrosion coating under the action of current. According to the coupling effects of multiple factors such as the geometric characteristics of the pits, the properties of the metal substrate, and the current intensity, construct a comprehensive evaluation system for the pitting corrosion behavior of the anti-corrosion coating.

[0053] As a preferred solution of this embodiment, the construction method of the pitting corrosion characteristics in step S2 is as follows:

[0054] Prepare anti-corrosion coating pits with different pore diameters by laser processing, set anti-corrosion coatings with different heights, assemble them, apply current in the simulated electrolyte for corrosion experiments, and characterize the corrosion morphology and depth of the metal surface after disassembly:

[0055] Preparation of anti-corrosion coating pits. Select appropriate anti-corrosion materials and use laser processing to prepare anti-corrosion coating pits with different pore diameters and anti-corrosion coatings with different heights respectively.

[0056] Assembly of specimens. Select the metal materials stored dry in step S1 and assemble them with the anti-corrosion coatings prepared in step S11.

[0057] Conduct current pitting corrosion experiments. Place the anti-corrosion coating metal specimens with prepared artificial pits in the simulated electrolyte prepared in step S1, apply current to the specimens, and conduct current corrosion experiments.

[0058] Characterization of the corrosion morphology of the metal specimens. Disassemble the anti-corrosion coating metal specimens with artificial pits, characterize the corrosion morphology and corrosion depth of the metal surface, and analyze their corrosion behavior.

[0059] As a preferred solution of this embodiment, the following method is used to construct the parametric model in step S3:

[0060] Construction of the model. Establish a suitable cuboid metal model and construct an anti-corrosion coating model on its surface.

[0061] Setting of the positions of the pits and defects. Open pits on the anti-corrosion coating model and set initial defects of the metal material at the positions directly below the pits.

[0062] Definition of properties. Define the basic properties of the anti-corrosion coating and electrochemically define the metal material using the corrosion kinetic parameters obtained in step S1.

[0063] Construction of the electrolyte model. Construct an electrolyte model outside the anti-corrosion coating and set its conductivity.

[0064] Setting of geometric parameters. Set geometric parameters such as the pore diameter of the pits in the anti-corrosion coating, the thickness of the anti-corrosion coating, the spacing between the metal and the anti-corrosion coating, and the magnitude of the current density as adjustable variables.

[0065] Apply current to set up a current leakage area on the upper surface of the electrolyte, and apply different values of current uniformly in this area, with the direction perpendicular to the anticorrosion layer.

[0066] As a preferred solution of this embodiment, the numerical simulation software in step S4 includes COMSOL, ANSYS or ABAQUS, which supports multi-physics field coupling analysis.

[0067] As a preferred solution of this embodiment, in step S5, the experiment and simulation verification are carried out according to the following method:

[0068] Verify the reliability of the model by verifying the corrosion potential of the metal material in the state without the anticorrosion layer, and compare and analyze the simulation results with the measured values in step S1.

[0069] Characterize the macroscopic morphology. For the surface changes of the metal material with pitting corrosion, compare and analyze the simulation results with the morphology of the experimental specimens obtained in step S2 at the macroscopic level.

[0070] Match the corrosion thickness, and verify the change in the pitting corrosion thickness of the simulation results with the change in the thickness of the experimental specimens in step S2.

[0071] As a preferred solution of this embodiment, in step S6, the comprehensive evaluation system is constructed according to the following method:

[0072] Visualization analysis. Analyze the potential contour map of the metal material, the magnitude of the local current density, and the contour map of the change in the corrosion thickness of the metal material for the results of the model solution in step S3.

[0073] Determine the weights through multi-parameter sensitivity analysis. Conduct sensitivity analysis from multiple parameters, including but not limited to the geometric characteristics of the small holes in the anticorrosion layer, the change in the distance between the anticorrosion layer and the bottom interface of the metal defect, and parameters such as the magnitude of the applied current.

[0074] Construct a comprehensive evaluation index: After standardizing the parameters, perform weighted summation to obtain a dimensionless evaluation index. Based on the results of the above visualization analysis and multi-parameter sensitivity analysis, construct a comprehensive evaluation index to evaluate the pitting corrosion behavior of the anticorrosion layer under the action of current.

[0075] The following further demonstrates and introduces the detailed implementation process of each step of this embodiment:

[0076] Step S1: Obtain corrosion kinetic parameters

[0077] Prepare an X80 steel specimen with a working area of 1 cm 2 and use Yingtan soil simulation liquid as the electrolyte. The schematic diagram of the experimental device for metal electrochemical corrosion under the action of current is as Figure 2 shown.

[0078] By open-circuit potential measurement and potentiodynamic polarization curve measurement, the polarization curve of X80 steel in the electrolyte without current was obtained, as Figure 3 shown.

[0079] The corrosion potential E corr , corrosion current i corr , anodic Tafel slope β a , cathodic Tafel slope β c , anodic exchange current density i 0,a , cathodic exchange current density i 0,c and other corrosion kinetic parameters were obtained and summarized in Table 1.

[0080] Table 1 Corrosion kinetic parameters of X80 steel

[0081]

[0082] During the experiment, electrochemical experiments under current were carried out, and two current densities of 10 A / m 2 and 20 A / m 2 were set, and the corrosion data are shown in Table 2.

[0083] Table 2 Electrochemical parameters of X80 steel under current

[0084]

[0085] Step S2: Construction of pitting corrosion characteristics

[0086] First, the metal material needs to be prepared, and the preparation process refers to the process of Example Step S1. The working area of the prepared metal specimen is a circle with a diameter of 20 mm. The schematic diagram of the pitting corrosion experiment specimen structure is as Figure 4 shown. Figure 4 Among them, Component 1 is the prepared metal specimen, which is the area where corrosion occurs; Component 2 is a circular ring made of acrylic material, which is used to control the distance between the anti-corrosion layer and the metal specimen; Component 3 is the anti-corrosion layer, whose main function is to isolate the electrolyte from the electrode, and small holes are pre-drilled in the anti-corrosion layer to simulate pitting corrosion.

[0087] In the pitting corrosion experiment, a current source is used, and a resistance box and an ammeter are used to regulate and monitor the current size in real time to ensure that the current is always stably maintained at the set value of 10 A / m 2 . To effectively reduce experimental errors, three groups of pitting corrosion experiments are set in series. By systematically regulating the pore size of the anti-corrosion layer (2 mm, 5 mm, and 10 mm respectively) and the distance between the anti-corrosion layer and the working electrode specimen (the distance values are set to 0 mm, 2 mm, 5 mm), the relevant characteristics of pitting corrosion are deeply explored. The schematic diagram of the pitting corrosion experimental device is asFigure 5 as shown

[0088] Step S3: Modeling of Metal with Small Holes in the Anticorrosion Layer

[0089] Perform numerical simulation using COMSOL finite element numerical simulation software. During model construction, establish a cuboid electrolyte domain model with the electrolyte domain size set to 1m×1m×1m (length×width×depth). Set a rectangular current source leakage surface at the geometric center of the upper surface of the electrolyte domain, with the rectangular size being 100mm×100mm. Among them, the current density of the current source leakage is set to 0 - 60A / m 2 . Place a metal plate model on the lower surface of the electrolysis domain. The metal plate model size is set to 1000mm×1000mm×1mm (length×width×depth). Construct an anticorrosion layer model on the outer surface of the metal plate, with the anticorrosion layer thickness being 3mm. Open small holes at the geometric center of the anticorrosion layer surface, and set initial defects on the metal plate at the position directly below the small holes. Set the small hole diameter of the anticorrosion layer, the depth of the initial defect, and the current value size as adjustable variables. The small hole diameter of the anticorrosion layer is set to 2mm, 5mm, and 10mm; the initial defect of the metal plate is characterized by a rectangular defect, with the defect size being 100mm×100mm (length×width), and the height is set to 0mm, 2mm, and 5mm. The schematic diagram of the modeling of the metal with small holes in the anticorrosion layer is as Figure 6 shown, and its two-dimensional cross-sectional schematic diagram is as Figure 7 shown, Figure 7 among them; 10 is the electrolyte domain, 20 is the anticorrosion layer, 30 is the initial metal defect, and 40 is the metal material.

[0090] Define the basic properties of the constructed model. The conductivity of the electrolyte domain is 0.02242S / m, and the conductivity of the anticorrosion layer is 6.67×10 -5 S / m. In the COMSOL finite element software, the kinetic expressions of the anodic and cathodic reactions related to metal material corrosion can be represented by the Tafel equation:

[0091] Anodic reaction kinetic expression:

[0092]

[0093] In the formula, i a is the anodic local current density, i 0,a is the exchange current density of the anodic reaction, E is the electrode potential, E eq,a is the equilibrium potential of the anodic reaction of the electrode, and β a is the Tafel slope in the kinetics of the anodic reaction.

[0094] Cathodic reaction kinetic expression:

[0095]

[0096] In the formula, i c is the local current density of the cathode, and i 0,c is the exchange current density of the cathode reaction, and E eq,c is the equilibrium potential of the cathode reaction of the electrode, and β c is the Tafel slope in the kinetics of the cathode reaction.

[0097] The corrosion kinetic parameters of the metal material are the corrosion kinetic parameters measured in step S1 of the usage example.

[0098] Step S4: Numerical simulation solution of pitting corrosion under current

[0099] In the numerical simulation solution of pitting corrosion under current, the COMSOL software's built-in free tetrahedral mesh is used to mesh the electrolyte domain, and local mesh refinement is implemented in the areas around the initial metal defects and the small holes of the anticorrosion layer. An iterative solver is used for the solution, and the solution process is divided into two stages: steady-state solution and transient solution. During the steady-state solution, the initial current distribution state is obtained through relevant calculations; the transient solution time step range is from 1 day to 31 days, the time step is 5 days, and dynamic calculations are carried out to obtain the evolution of the corrosion morphology over time.

[0100] Parametric scans are performed on parameters such as the aperture of the small holes in the anticorrosion layer, the distance between the bottom of the metal defect and the interface of the anticorrosion layer, and the current density to obtain the corrosion data of the metal defects under different conditions.

[0101] Step S5: Verification of the metal corrosion morphology

[0102] The corrosion potential measured by the electrochemical experiment under the current in step S1 of the example is compared and analyzed with the simulation results. As can be seen from Table 3, the relative errors between the two are both less than 20%. This result fully shows that the simulation calculation based on this model has high reliability.

[0103] Table 3 Comparison table of simulation results and experimental results

[0104]

[0105] For the macroscopic morphology characterization of the pitting corrosion of the metal material, a macroscopic comparison and analysis of the simulation results and the morphology of the experimental specimens obtained in step S2 was carried out, as Figure 8 shown. Figure 8 Among them, (a1-c1) are the experimental results, and (a2-c2) are the simulation results. As can be seen from the figure, the corrosion degree is the most significant directly below the small hole area. The experimental results and the simulation results are highly consistent, and the two verify each other, strongly confirming the feasibility of the model.

[0106] Step S6: Establish an evaluation method for the pitting corrosion behavior of the anticorrosion coating under the action of current

[0107] Parametric scans are carried out for parameters such as the pore diameter of the anticorrosion coating, the distance between the bottom of the metal defect and the interface of the anticorrosion coating, and the current density, and the obtained simulation results are visually analyzed, as Figure 9 shown. In Figure 9 , (a1-c1) are different pore diameters of the anticorrosion coating, and (a1-a3) are different interface distances between the bottom of the metal defect and the anticorrosion coating.

[0108] Sensitivity analysis is carried out from the three parameters: the pore diameter of the anticorrosion coating, the distance between the bottom of the metal defect and the interface of the anticorrosion coating, and the magnitude of the applied current, as shown in Table 4.

[0109] Table 4 Parameter definitions

[0110] Parameter Name Symbol Physical Meaning Value Range Unit Small Hole Aperture d Aperture of Small Hole in Damaged Anticorrosion Coating ≥2 mm Interface Spacing s Vertical Distance from Center of Small Hole to Bottom of Metal Defect ≥0 mm Current Density i Applied DC Current Intensity ≥0 <![CDATA[A / m 2 >

[0111] The degree of influence of each parameter on the pitting corrosion behavior of the anticorrosion coating is determined through the sensitivity analysis results. The higher the degree of influence of a parameter, the higher the weight assigned to it. For example, if the current density has the most significant influence on the corrosion behavior, its weight can be set to a relatively high value. Secondly, each parameter is standardized. Parameters such as the pore diameter of the anticorrosion coating, the distance between the bottom of the metal defect and the interface of the anticorrosion coating, and the current density are transformed into dimensionless standardized values according to their value ranges and the action directions on the corrosion behavior, so as to be comprehensively considered on the same scale. Then, based on the standardized parameter values and their respective weights, a comprehensive evaluation index is constructed by weighted summation.

[0112] This index can quantitatively reflect the pitting corrosion behavior of the anticorrosion coating under the action of current. The higher the value, the more serious the pitting corrosion of the anticorrosion coating under the current parameter combination, and vice versa, the relatively lighter the corrosion situation, providing a comprehensive quantitative index for evaluating and comparing the pitting corrosion behavior of the anticorrosion coating under different working conditions.

[0113] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the present invention should have the ordinary meanings understood by those of ordinary skill in the field to which the present invention pertains. The "first", "second" and similar terms used in the present invention do not denote any order, quantity or importance, but are only used to distinguish different components. Words such as "comprising" or "including" mean that the elements or objects appearing before this word cover the elements or objects listed after this word and their equivalents, without excluding other elements or objects. Words such as "connected" or "coupled" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Upper", "lower", "left", "right", etc. are only used to indicate relative positional relationships, and when the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0114] As described above, the above are only preferred embodiments of the present invention, and are not intended to limit the present invention in any other form. Any person skilled in the art may use the technical content disclosed above to make changes or modifications into equivalent embodiments with equivalent changes. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the technical solution content of the present invention still fall within the protection scope of the technical solution of the present invention.

[0115] This patent is not limited to the above best mode. Anyone inspired by this patent can obtain other various forms of a method for evaluating the pitting corrosion behavior of a coating under the action of a current. All equal changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope covered by this patent.

Claims

1. A method for evaluating the pinhole corrosion behavior of an anti-corrosion layer under the action of electric current, characterized in that: The following steps are involved: (1) Obtaining corrosion kinetic parameters of metal materials: analyzing corrosion potential, corrosion current density, anode / cathode Tafel slope and anode / cathode exchange current density through potentiodynamic polarization curve testing; (2) Constructing a parameterized multi-physics model: defining the anti-corrosion layer pore geometry parameters, metal defect spacing, and current density as dynamically adjustable variables, constructing an electrochemical corrosion model using finite element software, and defining the anode / cathode reaction kinetic parameters at the metal-electrolyte interface, including corrosion potential, corrosion current density, and Tafel slope; (3) Simulating the corrosion evolution process: Based on parametric scanning, the local current density distribution and corrosion thickness change data under different working conditions are generated. The initial current distribution is solved in a steady state and the dynamic corrosion evolution is solved in a transient state to analyze the autocatalytic characteristics of pinhole corrosion. (4) Experimental verification of model reliability: Apply current to the anti-corrosion layer sample with artificial small holes, compare the corrosion potential error and macroscopic morphology consistency, and verify the reliability of the simulation results; (5) Construct a comprehensive evaluation index: weights are assigned based on multi-parameter sensitivity analysis, and a dimensionless index for quantifying corrosion risk is generated by weighted summation after linear normalization of parameters. The risk level is then divided according to preset thresholds.

2. The method for evaluating the pinhole corrosion behavior of an anti-corrosion layer under the action of electric current according to claim 1 is characterized in that: The potentiodynamic polarization curve test was carried out in a simulated soil electrolyte, the electrolyte was Yingtan soil simulation liquid, the test current density covered 0-20 A / m², and the corrosion potential, corrosion current density, anode / cathode Tafel slope and anode / cathode exchange current density were analyzed by Tafel extrapolation method.

3. The method for evaluating the pinhole corrosion behavior of an anti-corrosion layer under the action of electric current according to claim 1 is characterized in that: The small hole geometric parameters of the anti-corrosion layer include a dynamically adjustable pore size of ≥2 mm, a distance between the metal defect and the anti-corrosion layer interface of ≥0 mm, and a current density of ≥0 A / m. The parameter range generates multi-condition corrosion data through parametric scanning.

4. The method for evaluating the pinhole corrosion behavior of an anti-corrosion layer under the action of electric current according to claim 1 is characterized in that: The anti-corrosion layer material is epoxy resin or polyurethane, has a thickness of 3 mm, and artificial small holes are prepared by laser processing.

5. The method for evaluating the pinhole corrosion behavior of an anti-corrosion layer under the action of electric current according to claim 1 is characterized in that: The parametric scan includes a steady-state solution for initial current distribution and a transient solution for corrosion evolution, with a time step set to 5 days and a total duration of 31 days.

6. The method for evaluating the pinhole corrosion behavior of an anti-corrosion layer under the action of electric current according to claim 1, characterized in that: The experimental verification includes three groups of samples connected in series, the applied current density is 10 A / m², the relative error of corrosion potential is less than 20%, and the corrosion morphology is matched by macroscopic observation and thickness measurement.

7. The method for evaluating the pinhole corrosion behavior of an anti-corrosion layer under the action of electric current according to claim 1, characterized in that: Through the multi-parameter sensitivity analysis, it is determined that the contribution weight of current density to corrosion risk is the highest, the weight of pore diameter of the anti-corrosion layer is the lowest, and the weight of interface spacing is in the middle.

8. The method for evaluating the pinhole corrosion behavior of an anti-corrosion layer under the action of electric current according to claim 1 is characterized in that: In the finite element software, the conductivity of the electrolyte domain is defined as 0.02242 S / m, and the conductivity of the anti-corrosion layer is defined as 6.67×10 -5 S / m, used to construct electrochemical corrosion models.

9. The method for evaluating the pinhole corrosion behavior of an anti-corrosion layer under the action of electric current according to claim 1, characterized in that: The comprehensive evaluation index processes parameters through linear normalization, and the threshold division includes low risk, medium risk and high risk.

10. The method for evaluating the pinhole corrosion behavior of an anti-corrosion layer under the action of electric current according to claim 1, characterized in that: The method is used for risk assessment of damage to the anti-corrosion layer of oil and gas pipelines or buried metal structures, and quantifies the exponential growth effect of local current density through corrosion thickness cloud maps.

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