Studies of the anodic dissolution of aluminium alloys containing tin and gallium using imaging with a high-speed camera

Imaging with a high-speed camera at a resolution of 10–20 μm has been used for the direct observation of the anodic dissolution of aluminium alloys containing Sn and Ga. The imaging allows confirmation that hydrogen bubble evolution occurs from the Sn inclusions within rounded pits during both open circuit corrosion and anodic dissolution. Using microelectrodes with only a few Sn inclusions in their surface, it is shown that the evolution of H2 is not continuous and may be correlated with a potential oscillations between −1.50 V (where H2 evolution occurs) and significantly less negative potentials (where no H2 is evolved). It is proposed that this potential shift is associated with pH changes resulting from H2 evolution itself.