Activation of Mg–Hg anodes by Ga in NaCl solution

The electrochemical and corrosion behaviors of Mg–5Hg–XGa alloys (X = 0, 1, 5 and 22 at.%) in 3.5 wt.% NaCl solution were studied by direct current (dc) and alternate current (ac) measurements under different polarization conditions. Scanning electron microscopy (SEM), energy spectrum analysis (ESA) and X-ray diffraction (XRD) were employed to characterize the microstructure and phase composition of the above alloys. Intermetallic compounds Mg3Hg, Mg21Ga5Hg3 and Mg5Ga2 were formed with the additions of 1, 5 and 22 at.% Ga into Mg–5Hg alloy. Attention was paid to the influence of Ga on electrochemical properties and microstructure. The best electrochemical activity occurs in Mg–5Hg–1Ga alloy, with an open circle potential of −2.124 V and a mean potential of −1.992 V. The best corrosion resistance of the Mg alloys occurs in Mg–5Hg–5Ga alloy, with a corrosion current density of 0.42 mA cm−2. Activation mechanism of Mg–Hg–Ga alloy is dissolution–deposition of Hg and Ga atoms.