On the effect of Fe concentration on Mg dissolution and activation studied using atomic emission spectroelectrochemistry and scanning electrochemical microscopy

Magnesium (Mg) samples prepared with 25 ppm, 220 ppm and 13000 ppm (by weight) of iron (Fe) were subject to specific forms of electrochemical testing with the ability to directly probe the extent of dissolved Mg2+ ion concentration and cathodic reduction during dissolution. To this end, atomic emission spectroelectrochemistry (AESEC) was employed for a direct measurement of Mg2+ dissolved during (and following) anodic polarisation, whilst scanning electrochemical microscopy (SECM) was used as a complimentary tool to observe enhanced catalytic activity for hydrogen evolution during (and following) anodic polarisation. The combination of these methods was able to reveal that prior anodic polarisation was not only responsible for an enhanced catalytic activity, but also for an increase in the rate of Mg2+ dissolution. Additionally, the extent of cathodic activation, and enhanced Mg2+ dissolution, were investigated as a function of the ppmw Fe content, and it is shown that noble elements such as Fe play a role in determining the extent of both anodic and cathodic activation, which is of direct relevance to corrosion of Mg, Mg-anodes and performance of primary Mg-batteries.