Buried Metal-to-Soil Potential Estimation Method Based on Finite Difference of Earth Surface Potential

To address the issues of low measurement accuracy, limited applicability, and laboriousness of traditional methods for detecting buried metal-to-soil potential (BMSP), we proposed an estimation method for BMSP based on the finite difference of earth surface potential (ESP). This method was based on the ESP distribution directly above the measurement point of buried metal, and the second-order partial derivative equation of the ESP in the horizontal direction was derived by the finite difference method. Next, we obtained, from the Laplace equation, the soil potential distribution in the vertical direction by inversion. Considering the non-uniformity of the soil medium during the inversion process, we utilized the boundary conditions of the electric field distribution on both sides of the soil interface to construct a soil potential functional equation between the upper and lower layers of soil. This facilitates the calculation of soil potential under layered soil. Finally, we modified the measurements of the BMSP according to the relationship between soil potential and IR drop, thereby achieving an accurate estimation. The accuracy and superiority of the proposed method were verified through a comparison with the CDEGS simulation results. Furthermore, we analyzed the accuracy and adaptability of the method from the configuration parameters and environmental parameters. The results show that the method achieves high detection accuracy under different conditions. The findings of this paper can provide support for the selection of corrosion detection and suppression strategies for buried metal.