Electrochemical behaviors of pyrite and chalcopyrite were studied by measuring polarization curves and electrochemical impedance spectroscopy (EIS) in a NaCl solution at room temperature and under differential stress. The results from differential stress experiments show that there is a negative linear relation between potential difference and elastic stress. The corrosion current density distinctly increased, and the corrosion potential became more negative with an increase in differential stress. The charge transfer electrical resistance increased, the double layer capacitance decreased, and other characteristic parameters are observed with increasing differential stress. The experimental results are significant for sulfide mineral engineering. By using different equivalent electrical circuits, the point defect model, and corrosion theory, we explain the experimental results theoretically. (C) 2010 Elsevier Ltd. All rights reserved.