A Contribution to the Understanding of the Mechanism of Corrosion Inhibitors (Part 2)

Synergism of Anions and Amines

Abstract

Concerning the synergistic action of anions and amines for the corrosion inhibition of iron in acid solutions, three different models, depending on the kinds of anions and amines, have been proposed. In perchloric acid solutions, primary fatty amines adsorb over the Br^--covered iron surface as ammonium cations, while tertiary fatty amines adsorb on the iron surface as: NR together with Br^- anions. These two different models are called, respectively, overlap adsorption and coadsorption. Some organic acids and amines also show a synergistic effect for the corrosion inhibition of iron in perchloric acid solutions. Mechanism for this case can be explained in terms of the electrostatic coadsorption of RCOO^-, which is the adsorbed species of organic acid, and (NRH)⁺ cation.