Ufa University of Science and Technology, Ufa, Russia

N. Yu. Dudareva, Professor at the Department of Internal Combustion Engines, Principal Researcher, Doctor of Technical Sciences, Associate Professor, e-mail: dudareva.nyu@ugatu.su

Central Scientific Research Automobile and Automotive Engines Institute NAMI, Moscow, Russia
A. V. Kolomeichenko, Head of the Innovative Technology Department, Centre for Agricultural Engineering, Doctor of Technical Sciences, Professor, e-mail: a.kolomiychenko@nami.ru

Wuhan Textile University, Wuhan, China¹ ; Vladimir State University named after Alexander and Nikolay Stoletovs, Vladimir, Russia² ; National University of Science and Technology MISIS, Moscow, Russia³
V. B. Deev, Professor at the Faculty of Mechanical Engineering and Automation¹, Principal Researcher², Professor at the Department of Metal Forming³, Doctor of Technical Sciences, Professor, (Corresponding Author), e-mail: deev.vb@mail.ru

This paper describes a study that looked at the effect of the structure of coatings produced by microarc oxidation (MAO) on wrought aluminium alloy AK4-1 on the corrosion resistance of specimens. Different processing modes were applied that were determined by three factors: the capacity of the unit and the concentration of caustic potash and sodium metasilicate in the electrolyte. The coating thickness, coating porosity and corrosion rate of the specimens were used as output parameters. A complete factorial experiment of type 23 was designed and conducted. Images of microsections obtained with a scanning electron microscope were used for studying the coating structure, determined by its porosity and thickness. The porosity was analyzed based on images of the specimens with the help of ImageJ programme. For the corrosion resistance study, the specimens were immersed in a corrosive solution and their corrosion rate was determined. Regression and correlation analyses of the obtained data were carried out in the MS Excel programme. The correlation analysis showed that the corrosion rate strongly depends on the coating thickness. An increase in the coating thickness leads to an increase in the corrosion rate. It is assumed that the coating material does not corrode, and corrosion is the result of the aggressive solution penetrating through cracks to the substrate material, which is what basically corrodes. An increased thickness of the coating is associated with a greater number of cracks in it, which leads to an increased corrosion rate. It was also found that a greater capacity of the unit contributes to the coating thickness on the AK4-1 alloy. Regression equations were also obtained that relate the corrosion rate to the porosity and thickness of the coating, as well as the corrosion rate, porosity and thickness of the coating to the microarc oxidation modes.
Support for this research was provided by the Ministry of Science and Higher Education of the Russian Federation under Governmental Assignment No. FEUE-2023-0007 (UUST).

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