Frumkin correction of corrosion electric field generated by 921A-B10 galvanic couple

Abstract

In order to study the Frumkin correction effect of corrosion electric field generated by 921A-B10 galvanic couple in different concentrations of NaCl solution, the electric double layer (EDL) capacitance of 921A steel and B10 copper alloy at the galvanic potential was acquired by electrochemical impedance spectroscopy (EIS), which was calculated for the experimental value of diffuse layer potential. The theoretical value of diffuse layer potential was got by the theoretical relationship between the diffuse layer potential and the total potential difference of EDL and concentration of supporting electrolyte. According to the Frumkin correction theory, the modified Tafel equation related to diffuse layer potential was obtained. Furthermore, the uncorrected and corrected Tafel equation was used as the boundary condition of the boundary element model (BEM) of corrosion electric field for 921A-B10 galvanic couple, thus the corrosion electric field distribution before and after Frumkin correction was obtained and compared with the experimental results. The results show that the correction effect is 35.6% and 8.8% when the concentration of NaCl is 0.012 M and 0.6 M, respectively. Therefore, it is necessary to correct the Tafel boundary condition during simulation, especially under low electrolyte concentration. The Frumkin correction can greatly reduce the error between results of simulation and experiment.