In-situ layered double hydroxides on Mg−Ca alloy: Role of calcium in magnesium alloy

Abstract Mg−Al layered double hydroxides (LDHs), produced on cast Mg−xCa (x=0.5, 0.8, 2.0, wt.%) alloys by an in-situ growth method, showed good corrosion resistance compared to the bare magnesium substrate. The influence mechanism of the second phase (Mg2Ca) on LDHs production was investigated. Increasing Ca content increased the amount of Mg2Ca, decreasing the grain size and the corrosion rate of the alloys. The increased amount of the second phase particles and the grain refinement promoted the growth of LDHs, and thus led to the decreasing of corrosion rate of the Mg−xCa alloys with LDHs. A higher Mg2Ca amount resulted in forming fluffy LDHs. Due to the dual effects of the second phase (Mg2Ca) for LDHs growth and microgalvanic corrosion, LDHs/Mg−0.8Ca showed the lowest corrosion rate.