Scanning electrochemical microscopy (SECM) in the sample generation-tip collection
mode was employed to gain new insights on the effect of aluminum on the anomalous
hydrogen evolution from anodically-polarized magnesium exposed to an aqueous saline
solution. Various experiments were designed to investigate the processes occurring on a
model Mg-Al galvanic pair in regards to the hydrogen evolution reaction occurring separately
at the anodic and cathodic sites. The data obtained in this work do not support the so-called
noble impurity theory for HER on anodically-polarized magnesium, whereas evidences were
obtained that the dark oxy-hydroxide layer formed on this metal may exert a combined
catalytic efficiency toward HER whereas imperfectly passivating the metal surface.
