Abstract <p>The effect of silicon contained in aluminum alloys on the structure, phase composition, and thermophysical properties of coatings formed by microarc oxidation has been demonstrated. The studies have been performed using samples made of AK12pch eutectic alloy with a silicon content of ~12% of Si and foreign-produced M244 hypereutectic alloy with a silicon content of ~26% of Si. Microarc oxidation coatings have been formed on all samples in a capacitive setup in a silicate-alkaline electrolyte using the same process conditions for all samples. The structure of the alloys and the resulting coatings has been analyzed. The coating thickness, porosity, microhardness, phase composition, and heat capacity have been determined. It has been found that silicon in the aluminum alloy contributes to an increase in the coating thickness, porosity, and heat capacity. Silicon in the alloy also contributes to an increase in the fraction of the amorphous phase in the coating and the amount of silicon oxide.</p>