Simulation of Anodic Current and Optimization of the Fitting Equation and the Fitting Algorithm during Constant Voltage Anodization

To investigate the formation mechanism of anodization and to clarify the relationship between the reaction process and the actual structure, we fitted the current density–time curve based on MATLAB. A time-varying function C(t) is introduced to optimize the total current fitting equation used to describe the constant voltage anodization process, which makes the equation more in line with the real reaction process based on the kinetic model of ionic and electronic current. Besides, a new fitting algorithm is developed based on the trust region method, which can effectively improve the fitting effect through iteration. In our work, the initial values of the parameters in the equation were calculated, and finally, the fitting degree of the constant voltage anodization under 40, 50, and 60 V was improved to 0.9842, 0.9693, and 0.9305, respectively. According to the new equation, the fitting degree of the total amount of charge transferred by ions during the reaction and the volume of oxides according to a proportional function can reach 0.9972.