The influence of cations such as Cu2+, Al3+ and Li+ on the corrosion behaviour of 8090-T851(Al-Li) alloy in a pH 2.0 HCl solution was investigated by weight loss and polarisation techniques. Weight loss experiments showed that the effect of cation is a strong function of its nature and concentration and the effect became significant only above a critical concentration. Of the cations studied, Cu2+ ions were found to be the most aggressive corrosion activators followed by Al3+ ions while Li+ ions showed little effect. Polarisation experiments inferred that Cu2+ ions influence the corrosion process mainly by accelerating the cathodic reaction. While a decrease in both cathodic and anodic reactions was evident in the presence of Al3+ ions at higher concentration, Li+ ions showed no remarkable affect either on cathodic or anodic reactions. Critical analyses of results of the two experiments indicated that the corrosion activation by Al3+ ions is due to their chemical reactivity with the corroding substrate. Little enhancement in corrosion by Li+ ions is attributed to the increase in solution conductivity in their presence.