This paper presents experimental and theoretical results concerning the corrosion inhibitor effect of imidazole and five of its derivatives on iron surface. Gravimetric methods and polarization curves were the experimental techniques used in this study. The polarization curves showed that the inhibitors have an anodic role on the electrochemical process. Weight-loss measurements indicated that the adsorption process obeys Langmuir's isotherm. The theoretical study was done using ab initio calculations for the organic molecules and complexes formed between imidazoles and a Fe atom, a Fe2+ ion, and a Fe3+ ion. Correlations between structural properties of the compounds and their experimental inhibitor efficiencies were analyzed. A satisfactory correlation between quantum-mechanical parameters and inhibition efficiency was found. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.048204jes] All rights reserved.