In vitro corrosion of Mg-6Zn-1Mn-4Sn-1.5Nd/0.5Y alloys

The microstructure evaluation, surface morphology, chemical compositions and phase analysis of the biomedical Mg-6Zn-1Mn-4Sn-1.5Nd/0.5Y (ZMT614-1.5Nd/0.5Y) alloys were investigated by means of optical microscopy, EPMA, X-ray EDS, XRD and FTIR. The corrosion behavior was evaluated using weight-loss measurement, hydrogen evolution, electrochemical and pH measurements. The results demonstrate that the microstructure for both ZMT614-1.5Nd alloy and ZMT614-0.5Y alloy is characterized by alpha-Mg and intermetallic compounds, most of which are distributed along the grain boundaries. These second phases contain Mg2Zn, Mg2Zn11, Mg2Sn and single metal Mn, together with Mg12Nd phase for the ZMT614-1.5Nd alloy, and with Mg24Y5 phase for the ZMT614-0.5Y alloy. Honeycomb-like corrosion product layers form. The corrosion resistance of the ZMT614-0.5Y alloy is higher than that of the ZMT614-1.5Nd alloy, which is ascribed to the addition of the element Y into the alloy delaying the corrosion initiation in comparison to that of Nd element in the alloy.