Galvanostatic anodic polarisation curves and galvanic corrosion of high purity Mg in 3.5% NaCl saturated with Mg(OH)2

Measured polarisation curves were used in a BEM model of Mg galvanic corrosion. The Mg galvanostatic anodic polarisation curves indicated: (a) the existence of the uni-positive Mg+ ion, (b) some hydrogen dissolved in the Mg metal, and (c) self corrosion was more important than the applied current density in causing weight loss. Galvanic corrosion of the high purity Mg consisted of: (a) corrosion that decreased in depth from the steel–Mg interface, and (b) heterogeneous corrosion that was denser closer to the steel–Mg interface. There was good agreement between the BEM model and the experimental measurements.

► The data were consistent with the existence of the uni-positive Mg+ ion. ► Some hydrogen dissolved in Mg during the Mg anodic polarisation curve. ► Self corrosion caused more weight loss than the applied current during anodic polarisation. ► Galvanic corrosion of HP Mg included heterogeneous corrosion, denser closer to the steel–Mg interface.