Initial micro-galvanic corrosion behavior between Mg2Ca and α-Mg via quasi-in situ SEM approach and first-principles calculation

Abstract The initial micro-galvanic corrosion behavior of Mg‒30wt%Ca alloy only containing Mg2Ca and α-Mg was studied by immersion testing in a 0.9% NaCl solution at 37oC. The quasi-in situ SEM and TEM results show that Mg2Ca corroded easier than α-Mg, indicating that Mg2Ca acted as an anode. The work function (Φ) for Mg2Ca calculated by first-principles is significantly lower compared to that for α-Mg. The Volta potential measured by a scanning Kelvin probe force microscope reveals that the Mg2Ca had a relatively low Volta potential (ψ) value. The lower Φ and ψ values for Mg2Ca indicate a lower electrochemical nobility, which is consistent with the experimental phenomenon.