An experimental survey of the cathodic activation of metals including Mg, Sc, Gd, La, Al, Sn, Pb, and Ge in dilute chloride solutions of varying pH

The kinetics of the hydrogen evolution reaction have been reported to increase upon pure magnesium (Mg) surfaces, following prior anodic polarization or corrosion. This phenomenon is termed anodically-induced "cathodic activation," which is not necessarily an elementary concept. The tendencies of other metals to exhibit cathodic activation have not been systematically explored in the past. In this study, an experimental survey of cathodic activation was conducted for different metals on the basis of understanding the origin of the cathodic activation phenomenon on Mg, including the metals Sc, Gd, La, Al, Sn, Pb, and Ge, in 0.1 M NaCl with pH ranging from 3 to 11. Sc, Gd, La, and Mg showed cathodic activation in solutions of various pH, whereas Al showed cathodic activation only in an acidic solution. Sn, Pb, and Ge did not show significant cathodic activation across the pH range tested. It is proposed on the basis of the results herein, metals that tend to directly react with water to form hydroxides in aqueous electrolytes have a higher tendency to demonstrate cathodic activation.