Electrochemical behaviour of aluminium alloys containing indium and tin in NaCl solution

The electrochemical behaviour of Al, Al-In, Al-Sn and Al-Sn-In alloys in 2 M NaCl solution has been studied using an open circuit potential, potentiodynamic polarization and ac impedance measurements as well as by optical microscopy examination. The addition of alloying components to aluminium produced in all cases a considerable activation of aluminium. The activation is manifested by shifting the open corrosion potential and the pitting potential in the negative direction (for about 0.6V) and significant reducing of the passive potential region. The degree of activation depended on alloying element and it was found that there is an increase in the order: Al < Al-In < Al-Sn The anodic dissolution of the Al-Sn and Al-Sn-In alloys started at open circuit potential which is only 0.45 V more positive than the thermodynamic Al(3+)/Al potential. The ac impedance measurements performed at different potentials in wide potential range (corresponding to passive and active state of each examined samples) confirmed the great activity of Al-Sn and Al-Sn-In alloys compared to aluminium. (C) 2010 Elsevier B.V. All rights reserved.