Role of dealloying on the electrochemical behaviour of aluminium alloyed with trace amounts of gallium

Homogenised AlGa model binary alloys, prepared from pure components and containing 50-1000 ppm by weight Ga, were heat-treated further in the temperature range 300-600 °C. Electrochemical polarisation tests in 5 wt% NaCl solution did not indicate anodic activation, since Ga remained stable in the solid solution alloy as long as passivity breakdown did not occur by applying potentials above the critical pitting potential. Alkaline etching caused significant enrichment of Ga by dealloying of the Al component, and anodic activation occurred by subsequent exposure to chloride solution. Segregated Ga dissolved back into aluminium by annealing for 1 h at 600 °C after etching, eliminating anodic activation.