The mechanism and efficiency of corrosion inhibition using 1,2,3-benzotriazole (BTAH) as the inhibitor on stainless steel corrosion in sulphuric acid medium were studied. Electrochemical impedance spectroscopy (EIS) as well as the potentiodynamic polarization was used for the quantification of inhibition efficiency and determination of the mechanism of interaction of the metal surface with the inhibitor molecule. Under the present experimental condition 1,2,3-benzotriazole was found to be an efficient inhibitor for the acid corrosion of austenitic stainless steel and the inhibition efficiency of up to 97% was obtained. In presence of inhibitor there is a diffusional contribution on the mechanism of the corrosion process was observed in impedance measurements at low frequency region. Effect of temperature on the mechanism and also on the efficiency of the corrosion inhibition process was studied using the Arrhenius approximation of the rate law. Polarization experiments were performed at different solution temperatures. Thermodynamic parameters for the corrosion process were obtained and interpreted. The adsorption of the inhibitor, BTAH, on the stainless steel surface in the acid medium (0.1 M H2SO4) obeyed the Langmuir adsorption isotherm. Present results were discussed and compared with the similar results reported by some other groups. (C) 2008 Elsevier B.V. All rights reserved.