The effect of a novel corrosion inhibitor, bis-(1-benzotriazolymethylene)-(2,5-thiadiazoly)-disulfide (BBTD), on the corrosion of copper in 3% NaCl and 0.5 M HCl has been investigated. Results reveal that BBTD is a good inhibitor and behaves better in 3% NaCl than in 0.5 M HCl solution. Potentiodynamic polarisation studies clearly showed that BBTD is mixed-type inhibitor for copper in chloride solutions. It decreases the,anodic reaction rate more strongly than the cathodic reaction rate and it renders the open circuit potential of copper more positive in either HCl or NaCl solutions. The FT-IR spectra indicated that BBTD prevented copper from corrosion by adsorption on the copper surface to form a protective complex with the Cu(I) ion.. (C) 2003 Elsevier B.V. All rights reserved.