The electrochemical behaviour of pure aluminium and three of its alloys were investigated in 0.6 M NaCl in the presence and absence of In3+ ions. The study comprised polarization and potentiostatic current-time measurements complemented by SEM-EDAX investigation. In 0.6m NaCl the corrosion resistance of the alloys decreases in the following order: Al < Al-Sn < Al-Zn similar or equal to Al-Zn-Sn. The addition of In3+ ions to the test electrolyte revealed activation of pure Al which increases with increase of In3+ concentration. Similar results were obtained for the binary Al-Zn and the ternary Al-Zn-Sn alloys, while Al-Zn alloy displayed a higher activation effect with In3+. It is also concluded that the existence of Zn either as an alloying element or present as a cation in the electrolyte leads to an enhanced activity of aluminium in presence of In3+ ions. Deactivation is observed in the case of Al-Sn alloy on addition of In3+ because tin retards the diffusion pathway of In to the bulk alloy, in addition to the presence of iron as an impurity in the alloy.