Effect of inhibitors on the desorption potentials in the anodic dissolution of iron in acid solutions - A review

The desorption potentials of various types of inhibitors in the anodic dissolution of iron in acidic solutions are considered. Literature data on the effect of inhibitor concentration, role of anions, and the presence of heteroatoms on the desorption potentials are summarized. It is shown that the desorption potentials ennoble with an increase in the concentration of inhibitors. For cationic inhibitors, desorption potentials are observed in the presence of halide ions. Desorption potentials are observed in the presence of nitrogen-containing, sulfur-containing and "green" corrosion inhibitors. The specific features of their protective action mechanism are discussed. The main conclusion from the results obtained by various authors is that the range of desorption potentials does not depend on the chemical nature of inhibitors. Therefore, it is determined by the properties of the anodically polarized metal. The interpretation of the results presented in this review is associated with an analysis of the mechanism of anodic dissolution of iron. The analysis of the data obtained in the review was carried out from the standpoint of the cooperative nature of the metal electronic subsystem. Partial depolarization of the anode was assumed to occur during the adsorption and transition of electrons from oxygen atoms of water molecules, halide ions, and other electron-donating inhibitors. It is assumed that at high anodic overvoltages, a two-dimensional quasi-liquid phase is formed on the metal surface, which leads to the desorption of any inhibitors, regardless of their chemical nature.