Effect of low concentration electrolytes on the formation and corrosion resistance of PEO coatings on AM50 magnesium alloy

•The formation process and corrosion properties of PEO coatings formed in phosphate, aluminate, and mix of phosphate and aluminate electrolytes have been systematically investigated.•Coatings prepared from single phosphate electrolytes and phosphate-aluminate low concentration electrolytes have greater potential than aluminate coatings based on microstructure and corrosion performance of layers.•In the case of low concentration solution, the thickness of aluminate-based coating cannot be significantly increased by increasing concentration of electrolyte.