Dissimilar metal galvanic couple compatibility evaluation method and system based on linear analysis technology

Abstract

The invention discloses a dissimilar metal galvanic couple compatibility evaluation method based on a linear analysis technology, and the method comprises the following steps: 1, drawing a polarization curve graph of which the horizontal axis is logarithmic current density X and the longitudinal axis is potential Y according to the original polarization curve data for the polarization curve data of a dissimilar metal A material; and 2, obtaining an intersection point of the cathode polarization curve and the anode polarization curve, and making a self-corrosion potential line Y = Y0 through the intersection point. The method is suitable for the technical field of corrosion protection, and relates to a galvanic corrosion compatibility evaluation method for a dissimilar metal connection structure in an automobile, a plan curve analysis technology is integrated into dissimilar metal galvanic compatibility evaluation, and the method is suitable for evaluating the compatibility of the dissimilar metal connection structure. The experimental period can be remarkably shortened, and the compatibility of the dissimilar metal galvanic couple in the automobile can be quickly evaluated.

Description

Technical Field

[0001] This invention belongs to the field of corrosion protection technology and is a method and system for evaluating the compatibility of dissimilar metal galvanometers based on linear analytical techniques. Background Technology

[0002] With advancements in automotive manufacturing technology and the trend towards lightweighting, the application of dissimilar metal materials in vehicles is becoming increasingly widespread. However, when these materials come into contact with corrosive environments such as humid or salty conditions, they are prone to forming galvanic cells, accelerating the corrosion process. This phenomenon not only affects the structural integrity of components but also shortens their service life, thereby posing a threat to the reliability and safety of the entire vehicle. Therefore, the scientific assessment of dissimilar metal galvanic corrosion in automobiles and the optimized selection of materials with good compatibility have become key areas of focus in the industry.

[0003] Traditional methods for analyzing galvanic corrosion, such as long-cycle accelerated experiments and electrochemical impedance spectroscopy, often face challenges such as long experimental cycles and difficulty in separating superimposed reaction information, making it difficult to quickly and accurately elucidate the key mechanisms in the corrosion process. To address these challenges, this invention employs an evaluation method based on linear analytical inversion techniques. By analyzing the metal polarization curves, it can effectively extract the independent characteristics of the cathodic and anodic reactions, thus avoiding interference caused by information superposition in traditional methods. Linear analytical inversion techniques offer advantages such as short experimental cycles and high computational accuracy, enabling rapid separation of key material reaction characteristics and precise calculation of the corrosion current density versus potential intersection point, achieving efficient evaluation of the galvanic compatibility level of materials. Summary of the Invention

[0004] The purpose of this invention is to provide a linear analytical technique for evaluating the compatibility of dissimilar metal galvanic couplings. This method eliminates the need for lengthy experimental verification, significantly improving the analytical efficiency of dissimilar metal galvanic coupling corrosion. It also provides effective data support for the scientific selection of materials and corrosion protection strategies in automobiles, helping to enhance the rationality of vehicle material matching and its protective capabilities.

[0005] To achieve the compatibility assessment of dissimilar metal galvanometers in automobiles, this invention provides a method for assessing the compatibility of dissimilar metal galvanometers based on linear analytical techniques, including: Step 1: For the polarization curve data of dissimilar metal materials, plot coordinates based on the original polarization curve data, with the horizontal axis X representing the logarithmic current density and the vertical axis Y representing the potential polarization curve. Step 2: Obtain the intersection of the cathode and anodic polarization curves. Draw a straight line perpendicular to the vertical axis through the intersection. This straight line is the self-corrosion potential line Y=Y0. Draw a tangent line L1 from the cathode polarization interval. The slope of the tangent line is defined as the cathode Tafel slope η1 of the metal A material. Step 3: The intersection of the tangent in the cathodic polarization region and the self-corrosion potential line is (X0, Y0). Define X0 as the self-corrosion current and Y0 as the self-corrosion potential.

[0006] Step 4: Draw a tangent line from the intersection point (X0, Y0) to the polarization region of the anode. The slope of the tangent line is defined as the anode Tafel slope η2 of the metal A material.

[0007] Step 5: Repeat the above steps for dissimilar metal B, for example, repeat steps one to four, and store the linearly analyzed polarization curve results of metal A / B into the database to achieve the following functions: ① Determine the anode and cathode of metal A / B, with the one with the lower self-corrosion potential being the anode and the one with the higher self-corrosion potential being the cathode; ② Obtain the intersection of the polarization curves of the two metals.

[0008] Step 6: Combining the intersection data of metal A / B polarization curves, acceleration factor and compatibility level evaluation criteria, calculate the galvanic corrosion rate Vcorr of dissimilar metal connection structures in automobiles using Faraday's formula (Formula 1), and determine compatibility based on the pre-set corrosion rate threshold.

[0009] Vcorr=(K•Icorr•M) / (n•ρ•F) (1) Where K is the acceleration factor, which is greater than 1 by default; Icorr is the corrosion current density, obtained from the intersection of polarization curves; M is the molar mass of the material; n is the number of electrons transferred in the material; ρ is the material density; and F is the Faraday constant, which is 96485 C / mol.

[0010] Preferably, the polarization curve includes data on the relationship between electrode potential and current density obtained through electrochemical experiments.

[0011] Preferably, step one includes: for the polarization curve data of dissimilar metal materials, taking the logarithm of the current density data in the original polarization curve, and plotting a polarization curve with the logarithmic current density *r* as the horizontal axis and the potential *r* as the vertical axis. In step one, for the polarization curve data of dissimilar metal A, taking the logarithm of the current density data in the original polarization curve, and plotting a polarization curve with the logarithmic current density *r* as the horizontal axis and the potential *r* as the vertical axis. This method, by applying logarithmic coordinates, intuitively displays the current density changes over a wide range, which helps to accurately analyze the polarization characteristics and linear range features of the material, and provides effective support for the subsequent extraction of self-corrosion parameters and the linear analysis of the polarization range.

[0012] Preferably, in step two, the intersection of the cathode and anodic polarization curves is obtained by analyzing the polarization curves of the dissimilar metal A, and the potential value of the intersection is used as the self-corrosion potential to plot the corresponding self-corrosion potential line. This method clarifies the physical meaning of the self-corrosion potential and self-corrosion current by locating the intersection point, and uses the self-corrosion potential line as a reference benchmark to provide basic support for the subsequent linear fitting of the cathode and anodic polarization intervals and the accurate calculation of the Tafel slope, thereby achieving efficient analysis and result verification of the key features of the polarization curve.

[0013] Preferably, in step three, by linearly fitting the curve within the cathodic polarization range, the intersection point of the fitted straight line and the self-corrosion potential line can be quickly determined, and the abscissa of this intersection point is defined as the self-corrosion current, and the ordinate is defined as the self-corrosion potential. This method, through precise fitting of the cathodic polarization range, can effectively eliminate the interference of curve noise and nonlinear factors, thereby accurately extracting the self-corrosion parameters and laying a precise foundation for subsequent analysis of the anodic polarization range and further calculation of the Tafel slope.

[0014] Preferably, in step four, from the intersection of the self-corrosion potential lines... By drawing a tangent line to the anodic polarization region and calculating the slope of the tangent line, the current-potential relationship of metal A during the anodic reaction process can be described more quickly. This helps to analyze the polarization characteristics of the metal in the anodic region and provides parameters for evaluating the galvanic corrosion behavior between metals and optimizing material selection.

[0015] Preferably, in step five, analytical data obtained rapidly using linear analysis is utilized, and the intersection data of the cathode and anode are automatically extracted, reducing human error. Simultaneously, the electrochemical parameters and curve intersections of multiple metals are stored in a database, providing data support for galvanic corrosion compatibility analysis.

[0016] Preferably, in step six, by combining the intersection data of different metal polarization curves and the acceleration factor, the galvanic corrosion rate of the dissimilar metal connection structure is calculated using the Faraday formula. The acceleration factor value can be adjusted according to different types of dissimilar metal combinations and environmental conditions, thus realizing the comprehensive application of corrosion current and acceleration factor.

[0017] The second aspect of this application also provides a heterogeneous metal galvanometer compatibility evaluation system based on linear analytical techniques, including any of the heterogeneous metal galvanometer compatibility evaluation methods based on linear analytical techniques described above. Attached Figure Description

[0018] Figure 1 This is a diagram illustrating the architecture of a heterogeneous metal galvanometer compatibility assessment method based on linear analytical techniques according to the present invention. Figure 2The results of linear analysis fitting of the polarization curves of bare steel plate and magnesium-aluminum alloy in Embodiment 1 of the present invention are shown. Figure 3 This is the compatibility evaluation result of bare steel plate and magnesium-aluminum alloy in Embodiment 1 of the present invention. Detailed Implementation

[0019] The following embodiments further illustrate specific implementations of the dissimilar metal galvanometer compatibility assessment method based on linear analytical techniques of the present invention. The dissimilar metal galvanometer compatibility assessment method based on linear analytical techniques of the present invention is not limited to the descriptions in the following embodiments.

[0020] Dissimilar metals refer to combinations of metals with different electrochemical properties. Especially when they come into contact in electrolyte environments (such as rainwater, moisture, and salt spray), they are prone to forming a galvanic cell effect, causing the metal with the more negative potential to corrode more quickly. For example, the connection between copper pipes and a steel water tank in a car engine cooling system can be considered a dissimilar metal combination.

[0021] The present invention will be further described below with reference to specific embodiments, so that those skilled in the art can better understand and implement the technical solution of the present invention. A method for evaluating the compatibility of dissimilar metal galvanic plates based on linear analytical techniques is used to evaluate the galvanic compatibility of bare steel sheets and magnesium-aluminum alloys in an acidic environment for automobiles, including the following steps: Step 1: Based on the polarization curve data of the bare steel plate material, plot a polarization curve with the logarithmic current density X on the horizontal axis and the potential Y on the vertical axis. Step 2: Obtain the intersection of the cathodic and anodic polarization curves of the bare steel plate, and draw the self-corrosion potential line Y = -0.32V through the intersection. Using a linear analytical method, draw the tangent line L1 from the cathodic polarization interval, and the cathodic Tafel slope of the bare steel plate is -53mV / dec.

[0022] Step 3: The intersection of the tangent in the cathodic polarization region and the self-corrosion potential line is (0.38 A / m). 2 The self-corrosion current of the bare steel plate is defined as 0.38 A / m², and the self-corrosion potential is defined as -0.32 V. This step yields the self-corrosion current and self-corrosion potential. Corrosion current density refers to the current corresponding to the self-corrosion potential; the current divided by the material reaction area equals the current density.

[0023] Step 4: From the intersection point (0.38A / m) 2 A tangent line is drawn from the polarization region of the anode (-0.32V), and the slope of the tangent line is defined as the anode Tafel slope of the bare steel plate, which is 15mV / dec.

[0024] Step 5: Repeat steps 1 to 5 for the magnesium-aluminum alloy, and store the polarization curve results of the bare steel plate / magnesium-aluminum alloy after linear analysis into the database to achieve the following functions: ① Determine the anode and cathode of the bare steel plate / magnesium-aluminum alloy polarization, with the magnesium-aluminum alloy as the anode and the bare steel plate as the cathode; ② Obtain the intersection point of the polarization curves of the two metals, such as... Figure 2 As shown, the self-corrosion current at its intersection is 2.5 A / m. 2 Meanwhile, the self-corrosion potential at the intersection is -0.52V, which is between the self-corrosion potentials of the two dissimilar metals, indicating that the intersection was obtained reasonably.

[0025] Step Six: Based on the intersection data of the polarization curves of bare steel sheets and magnesium-aluminum alloys, the acceleration factor, and the standards for compatibility level assessment, evaluate the galvanic corrosion of bare steel sheets and magnesium-aluminum alloy materials in automobiles, and provide a compatibility judgment. The corrosion rate, calculated as galvanic corrosion current density multiplied by the acceleration factor, is 5.2 mm / year. According to Table 1 of the compatibility judgment table in *GALVANIC COMPATIBILITY OF ELECTRICALLY CONDUCTIVE MATERIALS*, it falls under Level 6 incompatibility.

[0026] Combining the intersection data of metal A / B polarization curves, acceleration factors, and compatibility level evaluation standards, the galvanic corrosion rate Vcorr of dissimilar metal connection structures in automobiles is calculated using Faraday's formula (Formula 1), and compatibility is determined based on a pre-set corrosion rate threshold. Vcorr=(K•Icorr•M) / (n•ρ•F) (1) Where K is the acceleration factor, which defaults to greater than 1; Icorr is the corrosion current density, which can be obtained experimentally from the intersection of polarization curves; M is the molar mass of the material, n is the number of electrons transferred in the material, ρ is the material density; and F is the Faraday constant, taken as 96485 C / mol. All parameters except Icorr can be found online.

[0027] Table 1

[0028] For example: The galvanic corrosion rate was calculated using Faraday's formula: V corr =(K•I corr •M) / (n•ρ•F) in: K = 1.5 (simulated acid rain environment acceleration factor) I corr = 0.35A / m 2 (Taken from the intersection current density) For AA6061 aluminum alloy (anodine material): M = 26.98 g / mol n=3 ρ = 2.70 g / cm³ F = 96485 C / mol The calculation yields: V corr ≈0.18 mm / year In this example, V corr ≈0.18 mm / year, which falls under "Incompatible Level 4", indicating that this combination has a moderate to high risk of galvanic corrosion in simulated acid rain environments, and long-term use without protective measures is not recommended.

[0029] A linear analytical method for assessing the galvanic corrosion compatibility of dissimilar metals in automobiles enables efficient separation and analysis of electrochemical behavior details such as electrode potential and current density, accelerating the resolution of cathodic / anodic polarization curves. This method significantly shortens the experimental cycle, facilitates rapid prediction of galvanic corrosion compatibility between dissimilar metals, and improves the accuracy and efficiency of the assessment, making it suitable for practical applications such as rapid evaluation and design.

[0030] Polarization curve data are obtained through electrochemical experiments, showing the relationship between electrode potential and current density. They are typically plotted with potential on the ordinate and current density on the abscissa. These figures require experimental methods such as potentiodynamic polarization scanning, and are therefore considered "existing" measured data for research purposes. This paper processes the polarization data, taking the logarithm of the current density on the X-axis to more clearly demonstrate the linear polarization pattern. "Polarization" refers to the phenomenon where the electrode potential of an electrode system deviates from its original open-circuit potential when subjected to an applied current or voltage. This deviation reflects the tendency of oxidation or reduction reactions on the material surface and is used to study corrosion mechanisms and assess material corrosion resistance.

[0031] The dissimilar metal galvanic compatibility assessment method of this application can be applied to the testing and assessment of electric vehicle batteries. It can be widely used in any field where dissimilar metal connections exist and corrosion reliability assessment is required, such as aerospace, shipbuilding, and rail transportation.

[0032] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. In particular, it should be noted that any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention for those skilled in the art.

Claims

1. A method for evaluating the compatibility of dissimilar metal galvanic couples based on linear analytical techniques, characterized in that, include: Step 1: Based on the polarization curve data of the dissimilar metal material, plot a coordinate system with the horizontal axis X representing the logarithmic current density and the vertical axis Y representing the potential polarization curve. Step 2: Obtain the intersection of the cathode and anodic polarization curves. Draw a straight line perpendicular to the vertical axis through the intersection. This straight line is the self-corrosion potential line Y=Y0. Draw a tangent line L1 from the cathode polarization interval. The slope of the tangent line is defined as the cathode Tafel slope η1 of the metal A material. Step 3: The intersection of the tangent in the cathodic polarization region and the self-corrosion potential line is (X0, Y0). Define X0 as the self-corrosion current and Y0 as the self-corrosion potential. Step 4: Draw a tangent line from the intersection point (X0, Y0) to the polarization region of the anode. The slope of the tangent line is defined as the anode Tafel slope η2 of the metal A material. Step 5: Repeat the above steps for dissimilar metal B, and store the linearly analyzed polarization curve results of metal A / B into the database; Step Six: Combining the intersection data of the metal A / B polarization curves, the acceleration factor, and the compatibility level evaluation criteria, calculate the galvanic corrosion rate V of the dissimilar metal connection structure using Faraday's formula. corr Compatibility is determined based on a pre-set corrosion rate threshold; In corr =(K•I corr •M) / (n•ρ•F) (1) Where K is the acceleration factor, which defaults to greater than 1; I corr The corrosion current density is obtained from the intersection of the polarization curves; M is the molar mass of the material, n is the number of electrons transferred in the material, ρ is the material density; F is the Faraday constant, which is 96485 C / mol.

2. The method for evaluating the compatibility of dissimilar metal galvanic couples based on linear analytical techniques as claimed in claim 1, characterized in that, The polarization curve includes data on the relationship between electrode potential and current density obtained through electrochemical experiments.

3. The method for evaluating the compatibility of dissimilar metal galvanic couples based on linear analytical techniques as claimed in claim 1, characterized in that, Step one includes: taking the logarithm of the current density data in the original polarization curve of the dissimilar metal material to obtain the logarithmic current density. Horizontal axis, potential Plot the polarization curves on the vertical axis.

4. The method for evaluating the compatibility of dissimilar metal galvanic couples based on linear analytical techniques as claimed in claim 1, characterized in that, Step two includes: analyzing the polarization curves of dissimilar metal materials, obtaining the intersection of the cathode and anodic polarization curves, and using the potential value of the intersection as the self-corrosion potential to draw the corresponding self-corrosion potential line.

5. The method for evaluating the compatibility of dissimilar metal galvanic couples based on linear analytical techniques as claimed in claim 1, characterized in that, Step three includes quickly determining the intersection of the fitted straight line and the self-corrosion potential line by performing linear fitting on the curve within the cathodic polarization range.

6. The method for evaluating the compatibility of dissimilar metal galvanic couples based on linear analytical techniques as claimed in claim 1, characterized in that, Step four includes starting from the intersection of the self-corrosion potential lines. Draw a tangent line to the anodic polarization region and calculate the slope of the tangent line, which is defined as the anodic Tafel slope η2 of metallic material A.

7. The method for evaluating the compatibility of dissimilar metal galvanic couples based on linear analytical techniques as claimed in claim 1, characterized in that, Step five includes using the analytical data obtained quickly through linear analysis, automatically extracting the intersection data of the cathode and anode, and storing the electrochemical parameters and curve intersections of multiple metals into a database.

8. The method for evaluating the compatibility of dissimilar metal galvanic couples based on linear analytical techniques as claimed in claim 1, characterized in that, Step six includes calculating the galvanic corrosion rate of dissimilar metal connection structures in automobiles using Faraday's formula, combining the intersection data of metal A / B polarization curves, acceleration factors, and compatibility level evaluation standards, and determining compatibility based on the compatibility judgment table.

9. A heterogeneous metal galvanic couple compatibility evaluation system based on linear analytical technology, characterized in that, This includes any of the above-mentioned methods for evaluating the compatibility of dissimilar metal galvanic couples based on linear analytical techniques.

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