Effect of Some Substituted Anilines on the Corrosion of Iron in Nitric Acid Solutions

Introduction The corrosion of iron has been extensively studied in various media. In nitric acid solutions, the corrosion of iron is much faster than in other mineral acids at comparable concentrations. This is attributed to an autocatalytic process involving some nitrogen oxides, nitrous acid and/or some iron complexes. At high nitric acid concentrations, passivation of iron takes place. The factors affecting the dissolution and the passivation processes are not fully understood. The effect of various inhibitors on the corrosion of iron in acid media has been studied. Thus Ammar et al. have studied the passivation of iron and the effect of some anions, e.g. Br− and I− on the passive film. The effect of amides as inhibitors for iron in nitric acid has been reported by Fouda and Gouda. These authors have found that the corrosion process is controlled by the reaction of amides with HNO3 and not by the surface reaction. The effect of aniline and some aminobenzoic acids on the rate of corrosion of iron has been reported. The present work is aimed at examining the efficiencies of some aniline substitutes as corrosion inhibitors for the corrosion of iron in concentrated nitric acid solution.