Galvanic coupling between different alpha and theta phase-containing model Al-Cu alloys, deposited by magnetron sputtering, has revealed that the anodic alpha phase did not suffer corrosion and remained in the passive state in sulphate solution. Conversely, sulphate ions induced pitting of the cathodic theta phase. Pitting susceptibility of the cathode increased when the difference between the copper content of the anode and cathode increased. Similar observations were made for all the galvanic couples; further, the higher the copper content of a phase, then the greater its susceptibility to pitting. (c) 2007 Elsevier Ltd. All rights reserved.