Corrosion of pure Mg as a function of grain size and processing route

A cast ingot of pure magnesium was used as the initial material to show the corrosion as a function of grain size. A range of grain size was produced by processing the as-cast specimens using Surface Mechanical Attrition Treatment (SMAT) and the Equal Channel Angular Pressing (ECAP). Open circuit and potentiodyamic polarization (PDP) tests were conducted in 0.1 NaCl solution and using a standard 3-electrode flat-cell and a VMP-3Z potentiostat. The SMAT specimens demonstrated significant corrosion in the as-SMAT condition, both electrochemically and visually. The ECAP specimens exhibit better corrosion resistance compared with that of SMAT and cast specimens. The least noble specimens displayed the most superior corrosion resistance in terms of the Ecorr, which was interpreted in terms of the reaction kinetics as determined by the polarization testing.