The present work is concerned with the study of the activation mechani
sm of Al in alloys produced by indium. The electrochemical behaviour o
f aluminium in NaCl solutions containing In3+ ions and the dissolution
of Al-In and In-Al alloys were studied using potentiostatic, galvanos
tatic and potentiodynamic techniques, complemented by SEM. It was conc
luded that the aluminium activation is obtained only when indium comes
into a true metallic contact with aluminium within an active pit and
in the presence of chloride ions. Polarization curves for dissolution
of Al-In and In-Al alloys were compared. The results suggest that the
initial step in the dissolution mechanism of the Al-In alloy can be in
terpreted through chloride ion adsorption on a surface In-Al alloy. Th
is adsorption occurs at more electronegative potentials than that of p
ure aluminium, thus avoiding repassivation.