Simulation of electrical parameters of a galvanic cell in the process of microarc oxidation

Microarc oxidation is a promising technology for producing wear-resistant anticorrosive coatings for goods made of valve metals and alloys and is used in many industries. One of the main problems of this technology is low controllability caused by the complexity and interconnectedness of physical and chemical phenomena occurring during the coating process. To solve such problems, digital twins are currently actively used. The paper covers the development of mathematical models that are advisable to use as structural elements of the digital twin of the microarc oxidation process. An equivalent electrical circuit of a galvanic cell of microarc oxidation is given, which takes into account the electrolyte resistance, the part coating resistance in the form of a parallel connection of nonlinear active resistance and capacitive reactance. The authors propose a mathematical model describing the behavior of the equivalent electrical circuit of a galvanic cell of microarc oxidation. A technique for determining the parameters of this model was developed, including the construction of a waveform of changes in the resistance of the cell and its approximation, estimation of the values of resistances and capacitance of the galvanic cell equivalent circuit. The authors proposed a calculation method and developed a Simulink model of the microarc oxidation process, which allows simulating the current and voltage waveforms of a galvanic cell. The analysis of the model showed that the model is stable, controllable and observable, but poorly conditioned, which leads to modelling errors, the maximum value of which is 7 % for voltage and 10 % for current. By the parametric identification method using experimental current and voltage waveforms, the dependences of the parameters of the galvanic cell equivalent circuit on the oxidation time are obtained. It is found that the change in the period average of the galvanic cell active resistance correlates with the coating thickness.