Crystal orientation and electrochemical corrosion of polycrystalline Mg

In this study, scanning Kelvin probe, in situ scanning vibrating electrode technique and micro-electrochemical electrolyte cell are employed to investigate the corrosion of polycrystalline pure Mg. It is found that differently oriented Mg grains have different electrochemical activities and corrosion behavior. The grain with a basal orientation is more stable and corrosion resistant, exhibiting a more positive corrosion potential, lower anodic polarization current density, larger impedance, and thinner surface film than the grain with a non-basal orientation. A corrosion model is proposed to explain the differences in electrochemical corrosion performance between these grains.

► Micro-electrochemical probes reveal corrosion performance of individual Mg grains.
► Mg basal crystal plane is more corrosion resistant than other crystal planes.
► Differences in surface film influence the corrosion of differently oriented grains.