The electrochemical impedance of copper in benzotriazole (BTAH)-inhibited media is affected by the addition of sulfides. The caused order of magnitude decreases in the polarization resistance and increases in the double layer capacity. The appearance of sulfur peaks in the X-ray photoelectron spectroscopy (XPS) spectra of the sulfide-treated surfaces is accompained by a significant increase in the atom percent of Cu and a significant decrease in the atom percent of N and of C (and hence, of BTAH) in the surface layer. The results are explained on the basis of the ability of the sulfides to break down the protective BTA film and be adsorbed on the copper surface to catalyze its corrosion. The XPS spectra suggest the formation of copper sulfides.