Effect of small concentrations of gallium and lead on anodic activation of aluminium in chloride solution

The presents objective is to investigate the combined effect of alloyed Pb and Ga on surface segregation by heat treatment and ensuing anodic activation of aluminium in chloride solution. Model alloys containing Pb and Ga, which were heat treated in the range 300-600 degrees C, were characterized electrochemically in 5% NaCl solution. Annealing at 600 degrees C resulted in significant segregation of Pb causing limited activation, while Ga remained in solid solution. The presence 50 ppm Ga had only a small contribution to activation, while 1000 ppm Ga contributed significantly by becoming enriched at areas around Pb segregations and spreading radially by dealloying.