Effects of Hg and Ga on microstructures and electrochemical corrosion behaviors of Mg anode alloys

The effects of Hg and Ga on the electrochemical corrosion behaviors of the Mg-2%Hg, Mg-2%Ga and Mg-2%Hg-2%Ga (mass fraction) alloys were investigated by measurements of polarization curves, galvanostatic tests and measurements of electrochemical impedance spectroscopy. Scanning electron microscopy, X-ray diffractometry and energy dispersive spectrometry were employed to characterize the microstructures and the corroded surface of the above alloys. The results demonstrate that the microstructure of the Mg-2%Ga alloy is solid solution and the Mg-2%Hg and Mg-2%Hg-2%Ga alloys have white second-phases at the grain boundaries. The Mg-2%Ga alloy has the worst electrochemical activity and the best corrosion resistance, showing a mean potential of -1.48 V and a corrosion current density of 0.15 mA/cm(2). The Mg-2%Hg-2%Ga alloy has the best electrochemical activity and the worst corrosion resistance, showing a mean potential of -1.848 V and a corrosion current density of 2.136 mA/cm(2). The activation mechanism of the Mg-Hg-Ga alloy is dissolution-deposition of the Hg and Ga atoms.