Anomalous Hydrogen Evolution on Magnesium

When Mg undergoes anodic polarization in a corrosive environment, the rate of hydrogen evolution (HE) increases with increasing applied anodic potential or current, which is opposite of the expected behavior based on standard electrochemical kinetics. This anomalous HE has been the recent focus of researchers worldwide. In this work, the behavior of sputtered Mg thin films and scratched Mg electrodes is presented. HE vanished when the potential of a pit in Mg thin films was increased into the region where a salt film formed. The peak anodic current on scratched samples was not anomalous, as it decreased slightly with increased potential. These observations indicate that the HE rate on Mg depends on the nature of the surface and that anomalous HE results from the surface being more catalytic to the HE reaction with increasing dissolution rate.