In vitro corrosion of micro-arc oxidation coating on Mg-1Li-1Ca alloy — The influence of intermetallic compound Mg2Ca

The presence of second phase Mg2Ca has remarkable impacts on the formation and degradation of MAO coating. Microstructure, formation and degradation behaviors of substrate and MAO coating were performed. Results revealed that pitting and filiform corrosion occurred on bare Mg-1Li-1Ca alloy. MAO coating significantly improved the corrosion resistance of alloy. The roles of Mg2Ca on the formation and degradation mechanisms of MAO coating were discussed. Micro-arc oxidation for the Mg-Li-Ca alloy initiated at α-Mg phase with depleted Ca content. The growth rate of coating on α-Mg phase is faster than that of GBs/Mg2Ca. The MAO coating began to degrade from intermetallic compound Mg2Ca, then it underwent the attack from the solution and stress concentration caused by corrosion products.