Preferred crystallographic pitting corrosion of pure magnesium in Hanks’ solution

We examined the corrosion behavior of Mg in Hanks’ solution to determine the potential of a biodegradable pure Mg implant. Abrupt corrosion, initiated by Fe impurity, was observed in the latter stage of experimentation in the form of preferred crystallographic pitting (PCP) propagating along the (0 0 0 1) basal plane in the grain. Herein, we report the mechanism behind PCP corrosion of Mg and evaluate potential solutions to suppress PCP corrosion. In particular, the addition of Mn inhibits PCP initiation by converting Fe impurities to Fe-Mn compounds, while refining the grain size by extrusion reduces PCP propagation.

► We investigated the nature of Mg corrosion in Hanks’ solution. ► Unique pitting occurred along a preferred crystallographic plane was first found. ► The solutions to prevent PCP were suggested through understanding of the mechanism. ► Addition of trace Mn and reduction of the grain size prevent the PCP effectively.