The inhibition effects of sodium dodecylbenzenesulphonate (SDBS) and 2-mercaptobenzoimidazole (2-MBI) on the corrosion of copper in sulphuric acid solution have been studied using electrochemical impedance spectroscopy (EIS) and Tafel polarisation measurements. For 2-MBI, a monotonic increase in inhibition efficiency is observed as a function of concentration. Upon mixing 2-MBI and SDBS, concentration regions showing synergistic inhibition behaviour are identified and it is concluded that electrostatic interactions between adsorbate ions are likely responsible for both phenomena. Different adsorption isotherms were tested for relevance in describing the adsorption behaviour of both 2-MBI and SDBS. 2-MBI obeys the Langmuir isotherm and SDBS adsorption is described successfully by the Temkin isotherm.