Determination of the equivalent electric circuit parameters of a galvanic cell in the micro-arc oxidation process

A method for determining the thickness of microarc coatings based on the use of electrochemical impedance spectroscopy during the microarc oxidation process is proposed. To obtain the studied oxide coatings, a silicate-alkaline  electrolyte was used in the following technological modes: sinusoidal electric current in the anode-cathode mode at a current density of 11 A/dm². The frequency range of electrochemical impedance spectroscopy ranges from 20 Hz  to 2 MHz. During the study, the structure was revealed and the elements values of the electrical circuit of the galvanic cell were determined, taking into account electrochemical impedances by parametric optimization. The proposed  equivalent electrical circuit takes into account the processes of ion diffusion through the oxide layer and the imperfection of the electrical capacitance of the coating, which is due to its porous structure. A regression and correlation  analysis of the experimental data obtained was performed, during which the strong inverse correlation of the proportionality factor of the constant phase element of electrical circuit of the galvanic cell with the thickness of the formed  coatings was found. The method of indirect measurement of the thickness of oxide coatings has satisfactory accuracy and can be used for laboratory studies. With an increase in the accuracy and speed of measuring operations, industrial application of this method is also possible. The proposed galvanic cell equivalent electrical circuit can be implemented in the decision support subsystem of an intelligent microarc oxidation system.