Effect of high rates of mass transport on oxygen reduction at copper electrodes: Implications for aluminium corrosion

The reduction of oxygen at copper microelectrodes (25 mu m diameter) in aqueous solution (pH 7) has been studied under conditions of high mass transport, similar to those experienced by similar to mu m, sized copper-containing inclusions in aluminium alloys during corrosion. Contrary to previous studies at copper electrodes operating at lower mass transport rates, oxygen reduction limiting currents show an apparent number of electrons which decrease towards 2 as the mass transport rate increases (mass transfer coefficients up to ca. 0.55 cm s(-1)), rather than a 4-electron process. These new data suggest that the treatment of oxygen reduction as a 4-electron transfer process at micron and smaller-sized copper intermetallics in aluminium alloys may require revision. Crown Copyright (C) 2008 Published by Elsevier B.V. All rights reserved.