A novel scanning electrochemical microscopy strategy for the investigation of anomalous hydrogen evolution from AZ63 magnesium alloy

The evolution of hydrogen gas from corroding magnesium arises not exclusively from the cathodic half-cell reaction due to the consumption of the electrons released by the dissolving metal, but anodized magnesium generates significant amounts of H-2 gas as well. In addition, the increase of the anodic overpotential enhances the rate of hydrogen gas generation. Therefore, spatially-resolved detection of the actual sites for hydrogen evolution related to anodically-activated sites is attempted using scanning electrochemical microscopy (SECM). This work describes a new experimental procedure for SECM based on a three-step (off-on-off) anodization operation sequence that was designed to obtain new insights into the behavior of magnesium and magnesium alloys when they are subjected to anodic polarization. Results obtained with scanning electrochemical microscopy (SECM) and scanning vibrating electrode technique (SVET) experiments presented here demonstrate the catalytic properties of the magnesium-oxide film for the hydrogen-evolution reaction.