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

Abstract

The effect of gallium ions on the electrochemical behaviour of two grades of aluminium, Al I (99.99%) and Al II (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-ray analyzer investigations. It has been found that addition of Ga 3+ ions to the electrolyte causes activation of the Al I electrode. A pronounced activating influence has been achieved after cathodic polarization of the Al I electrode in Ga 3+ 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, Ga 3+ ions have no activating influence on the dissolution of Al II, 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 Ga 3+ containing solutions.