Effect of Sn on Microstructure and Electrochemical Properties of Mg Alloy Anode Materials

Morphologies, microstructure and composition distribution of the magnesium anode materials were studied by metallographic microscopy, X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). The corrosion behavior and electrochemical properties of Mg alloy were also investigated by constant current method, potential polarization, and drainage. The results show that Sn and Pb can restrain β-Mg17Al12 phase precipitation along the grain boundary and Mg-Al-Pb-Sn magnesium alloys have uniform and fine grain size. With the content of tin increasing, the content of particle Mg2Sn phase increases. After uniform heat treatment, most of β-Mg17Al12 phase dissolve, while most of Mg2Sn and Mg2Pb do not dissolve. The tin can improve self-corrosion potential and reduce release hydrogen rate. Magnesium anode has high discharge potential and current efficiency with 2wt% tin. With the current density increasing, the release hydrogen rate improves, owing to negative variance effect of magnesium alloys. The current efficiency is up to 88% at 10 mA/cm2. The main composition of the corrosion products are Mg(OH)2, SnO2 and MgSnO3 that are easier to peel off, which leads to more negative and stable work potential and can accelerate reaction continuously.