Effect of gallium ions on the electrochemical behaviour of Al, Al-Sn, Al-Zn and Al-Zn-Sn alloys in chloride solutions

The effect of gallium ions on the electrochemical behaviour of two grades of aluminium, Al-1 (99.99%) and Al-11 (99.61%), as well as three of its alloys (Al-Sn, Al-Zn and Al-Zn-Sn) has been investigated in 0.6 M NaCl solutions. The study was performed by means of polarization. potentiostatic current-time and open circuit potential measurements complemented by scanning electron microscope-energy dispersive X-ra); analyzer investigations. It has been found that addition of Ga3+ ions to the electrolyte causes activation of the Al-1 electrode. A pronounced activating influence has been achieved after cathodic polarization of the All electrode in Ga3+ containing electrolyte at -2 V. This is attributed to the deposition of gallium on the electrode surface which gives rise to increased adsorption of Cl- ions at a more electronegative potential. On the other hand, Ga3+ ions have no activating influence on the dissolution of Al-11, Al-Sn, Al-Zn and Al-Zn-Sn electrodes in 0.6 M NaCl solutions. However, the activating effect appears only during polarization measurements in Ga3+ containing solutions. (C) 2001 Elsevier Science Ltd. All rights reserved.