Aluminium activation produced by gallium

Abstract

The electrochemical behaviour of pure aluminium in the presence of gallium ions or in direct contact with gallium, in chloride, acetic acid solutions or distilled water is reported. The enhance activity of aluminium is described and discussed. Two active regions were observed, one at approximately -1.5 V and the second at near -1.1 V. Two activation mechanisms are proposed. One where a critical surface concentration of liquid gallium is achieved, a Ga-Al amalgam is responsible for the activation process (-1.5 V) and a uniform attack morphology is observed. This process is favoured by the exothermic Al ion hydrolysis reaction and hindered by Ga losses at the active interface. And a second at higher anodic potentials (near -1.1 V), and in chloride containing media, where the presence of solid Ga (saturated amalgam) at the interface facilitates a chloride adsorption process which depolarised the anodic reaction, and produced localised attack.