The efficiency of various variants of the component composition of alkaline electrolytes of plasma electrolytic oxidation (PEO) was studied. Technical liquid glass, NaOH, Na2B4O7, Na3PO4, and NaAlO2 were used as components of aqueous solutions. All of the studied components of electrolytes are the most common for use in PEO processes of aluminum alloys. The influence of the component composition of electrolytes on their stability during 30 days of exposure was evaluated, and the most stable compositions were selected. The structure and properties of coatings formed on samples of aluminum alloy AK6 during PEO are studied. The dependences of the hardness of coatings and their growth rate on the composition of the electrolyte are established. Possible variants of coating growth in the PEO process with different component composition of electrolytes are proposed.