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

• DOI: 10.1016/j.jma.2021.06.017
• Publication Date: 2021-07-24T11:07:31Z
• Authors: Chen Xu; Jianfeng Wang; Chen Chen; Chao Wang; Yufeng Sun; Shijie Zhu; Shaokang Guan
• Keywords: First-principles calculations; Mining engineering. Metallurgy; TN1-997; Galvanic corrosion; Volta potential; 02 engineering and technology; 0210 nano-technology; Quasi-in situ SEM; Work function; 01 natural sciences; Magnesium alloy; 0104 chemical sciences

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 37 °C. 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.