The electrochemical behaviour of chalcopyrite (CuFeS2) was studied by polarisation curve and electrochemical impedance spectroscopy (EIS) in FeCl3 solution at room temperature under differential stress. Experimental results showed the relation between chalcopyrite potential difference and elastic stress is Delta phi(CuFeS2)(H) = -VdP/ZF. The corrosion current density and charge transfer electrical resistance increased distinctly, whereas double-layer capacitance decreased and the corrosion potential became more negative with increasing differential stress. The EIS data have been analyzed and discussed in the simple equivalent circuit model, the Randles equivalent electrical circuit model and the point defect model, respectively. The experimental results are significant for mineral processing and hydrometallurgy. (C) 2010 Elsevier B.V. All rights reserved.