Electrochemical Corrosion Characterization of As-Cast Mg-7Li Alloy

The electrochemical corrosion behavior of as-cast Mg-7Li alloy in 3.5wt% NaCl aqueous solution was investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and electrochemical workstation. Results showed that the Ecorr and the Icorr of Mg-7Li alloy were -1.5857V and 2.235×10-4A/cm2, respectively. The cathode process was chiefly the hydrogen evolution reaction, and the corrosion rate of Mg-7Li alloy was mainly controlled by anode dissolution. The corrosion products on the alloy surface consisted of Mg(OH)2, Li2O2 and Al(OH)3. The electrochemical impedance spectroscopy (EIS) of Mg-7Li alloy contained two capacitive loops and one inductive loop. The inductance value increased to 250 ohm•cm-2 with a rise in frequency at low frequency region. The value of capacitive reactance decreased with increasing frequency at medium frequency. The capacitive reactance maintained the value of 50 ohm•cm-2 with increasing frequency at high frequency region.