Discovery of Al2O3 particles incorporation mechanism in plasma electrolytic oxidation of AM60B magnesium alloy

Al2O3 particles were suspended in the aluminate electrolyte to form a ceramic coating on an AM60B magnesium alloy by plasma electrolytic oxidation (PEO), and a new mechanism for the Al2O3 particle incorporation in the coating was discovered. Energy Dispersive Spectroscopy (EDS) results showed that Al2O3 addition increased the Al content in the coating. The absence of Al2O3 particles combined with the increased MgAl2O4/MgO phase ratio in the coatings with the addition of Al2O3 indicated that the Al2O3 particles participated in chemical reactions during the coating formation, as opposed to a previously reported understanding of simple mechanical incorporation.

► Al2O3 particles were added into the electrolyte for plasma electrolytic oxidation (PEO) of AM60B magnesium alloy.
► A new chemical reaction mechanism for the incorporation of Al2O3 in the PEO coating was proposed based on our studies.
► It provides another possible mechanism during PEO processes depending on the operating conditions, in addition to the conventionally known mechanical trapping mechanism.