The inhibition effects of sodium dodecylbenzenesulphonate (SDBS) and 2-mercaptobenzoxazole (2-MBO) on corrosion of copper in sulphuric acid solution have been studied using electrochemical impedance spectroscopy (EIS) and Tafel polarization measurements. For 2-MBO, a monotonous increase in inhibition efficiency was observed as a function of concentration. For SDBS, however, an optimum in the inhibition efficiency was observed for a certain concentration, which is ascribed to the formation of hemi-micellar aggregates that provoke inhibitor desorption from the metal/solution interface at higher concentrations. Upon mixing 2-MBO and SDBS inhibitors, concentrations range showing synergistic inhibition behaviour were identified, and it is concluded that electrostatic interactions between the adsorbed ions. Different adsorption isotherms were tested for describing the adsorption behaviour of both 2-MBO and SDBS. (C) 2007 Elsevier B.V. All rights reserved.