This work is focused on researching corrosion mechanism modifications of 1018 carbon steel in alkaline sour medium (0.1 M (NH4)(2)S and 10 ppm CN-) using inhibitor formulation (IHF) composed of hydroxyoleic imidazoline (C12H42ON2), HI, and arninoether (C20H28O3N2) AE. The accelerated formation of corrosion products was thereby carried out in the presence of the formulation alone and of each of its components separately; these films were subsequently characterized by electrochemical impedance spectroscopy and scanning electron microscopy. The study in the presence of the IHF components revealed that the films formed have different nature, because their physical and chemical properties such as thickness, porosity and (electronic and ionic) conductivity are determined by the media where they are grown. The film formed in the presence of HI has a homogeneous, non-porous topography that impairs the diffusion process of H-0, in addition, its electronic conductivity is above that observed in the film formed with AE. Then, it was determined that the film formed with IHF presents some distinctive component characteristics which interact in a complementary way improving film passivity. (c) 2005 Elsevier Ltd. All rights reserved.