The effect of pyrite (FeS2) on the electrochemical dissolution of fresh and passivated chalcopyrite (CuFeS2) electrodes has been studied. Current density values for the dissolution of CuFeS2 were calculated from EIS measurements. FeS2 increased the dissolution rate of fresh and passivated CuFeS2 electrodes indicating that the galvanic effect continued even after the electrode was chemically passivated. The dissolution rate of CuFeS2 decreased by a factor of 3 after the passivation treatment. Due to the low diffusion rates of ions within the CuFeS2 passive film and due to an increase in the resistance to the transfer of electrons at the electrode/film interface, the activity of FeS2 for the reduction of Fe3+ ions was also reduced by a factor of 2.3 even though FeS2 was not exposed to any chemical treatment. The results in this work indicate that the dissolution rate of the fresh CuFeS2 electrode was controlled by the reduction of Fe3+ ions whereas for the passivated CuFeS2 electrode the dissolution rate was controlled by diffusion within the passive film. (C) 2014 Elsevier Ltd. All rights reserved.