New possibilities of metal corrosion inhibition by organic heterocyclic compounds

It is shown that many heterocyclic organic compounds, e.g., various azoles, are capable of adsorption on metals with formation of strong bonds with the surface. The approach based on the linear free energy relationship (LFER) principle offers a description of the efficiency of corrosion inhibition by these compounds and provides an understanding of the nature of chemical bonds formed by an organic inhibitor with a metal that needs to be protected. Knowledge of the specifics of interaction between azoles and metal surfaces can be helpful in choosing a promising corrosion inhibitor for drastic conditions, for example, in chemical mechanical planarization slurries where simultaneous mechanical polishing and electrochemical dissolution of the surface usually occur. Corrosion inhibition of steel at high temperatures (≥ 150°C) in mineral acid solutions is yet another example of a new successful use of azoles. It is demonstrated that new possibilities for improving the anticorrosive protection of metals are provided not only by using mixtures of some azoles with carboxylate-type organic corrosion inhibitors but also by constructing bilayer nanocoatings from aqueous solutions. For example, strong adsorption of small amounts of rather an exotic compound, dimegin (disodium salt of deuteroporphyrin), not only promotes the passivation of iron in neutral aqueous solutions but also impedes the local depassivation of the metal. Furthermore, it offers wide possibilities for further improvement of adsorption of other heterocyclic chemical compounds due to preliminary modification of the metal surface even by a small dimegin concentration.