ELECTROCHEMICAL STUDIES ON SINGLE-CRYSTAL ALUMINUM SURFACES

The electrochemical behaviour of single-crystal aluminium oriented in the (111), (110) and (100) directions in chloride-and indium-containin g solutions was studied. It was found that the susceptibility of the s ingle crystals to the onset of pitting attack in the chloride solution varied in the order (111)>(110)>(100). This was evident from pitting potential and induction time data, where the most noble pitting potent ial values and the longest induction periods were recorded for the (10 0) surface. This was explained in terms of differences in the surface energy of (111), (110) and (100) planes. It was also found that cathod ic reduction reactions (hydrogen evolution and oxygen reduction reacti ons) proceeded at a greater rate on the (100) surface. In addition, th e time delay between the addition of indium ions to solution and the o nset of activation of the immersed electrode by the indium species was shorter for the (100) surface. This was attributed to the more effici ent incorporation of indium into the (100) lattice. (C) 1998 Elsevier Science Ltd. All rights reserved.