Effects of grain size on the corrosion resistance of wrought magnesium alloys containing neodymium

A range of grain size from 70 μm to 0.7 μm was studied for corrosion resistance of Mg–Y–RE magnesium alloy using electrochemical and constant immersion testing in 3.5 wt.% NaCl solution. The linear polarization resistance (Rp) showed a clear trend of increasing Rp value with grain refinement. The ultrafine grained sample showed the most positive pitting potential as compared to coarse grained samples. One order of magnitude decrease in corrosion rate was observed between coarsest and ultrafine grained microstructure.

► Ultrafine grain Mg–Y–RE showed one order lower magnitude of corrosion rate as compared to coarse grain.
► Higher linear polarization resistance was observed for ultrafine grain Mg–Y–RE.
► Cyclic polarization study showed repassivation behavior for ultrafine grained Mg–Y–RE.
► A power–law relationship between grain size and corrosion rate is proposed.