PEO of AZ31 Mg alloy in a silicate-based hybrid electrolyte system – Effect of glycerol and WO₃ particles

Plasma electrolytic oxidation of AZ31 Mg alloy was conducted in silicate-glycerol hybrid electrolytes with added WO₃ particles. The individual and combined effects of glycerol and WO₃ particles on the morphology, composition, mechanical properties, and scratch and corrosion resistance of the developed PEO layer were evaluated. The results revealed that although the addition of WO₃ particles to the aqueous silicate electrolyte does not enhance corrosion resistance, the PEO layer developed in the optimized hybrid electrolyte with added WO₃ particles significantly improves electrochemical corrosion resistance. The addition of 0.5 g/L WO₃ and 30 mL/L glycerol has reduced the corrosion rate of PEO-coated Mg alloy by ∼ 45 times. The optimized addition of glycerol, with or without particles, effectively enhances surface hardness and coating adhesion. The results indicate that incorporating glycerol into the aqueous electrolyte improves the in-situ incorporation of particles, facilitates the fabrication of a smoother PEO layer, and enhances mechanical properties, coating adhesion, and corrosion resistance.