Cathodic polarization characteristics and activation of aluminium in chloride solutions containing indium and zinc ions

Abstract

This work deals with the study of the cathodic and active behaviour of aluminium in acid chloride solutions containing indium and zinc ions. The cathodic behaviour was studied using potentiostatic and potentiodynamic techniques, complemented by SEM and EDX. During cathodization, preferential adsorption of zinc ions occurs, compared to that of H+ and In3+ ions. Once a critical amount of zinc is deposited, preferred indium deposition begins. The synergistic interaction between zinc and indium ions and aluminium leads to its activation in chloride media. This can be explained by displacement reactions that produce an indium accumulation and preferential zinc dissolution. This situation produces a new interface, quasi-free of Zn but rich in In, which favours Cl− ion adsorption at more negative potentials than aluminium, leading to its activation.