Inhibitory protection of steels in acid solutions under high-temperature corrosion conditions. A review. Part 3

• Ya.G. Avdeev and Yu.I. Kuznetsov

A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Leninsky pr. 31, 119071 Moscow, Russian Federation

Abstract: Literature data concerning the protection of steels in acid solutions at elevated temperatures (t≤200°C) by organic nitrogen-containing heterocyclic compounds (NHCs) and formulations based on them are generalized. It is noted that individual NHCs are rarely efficient in steel protection in acid solutions at t>100°C. However, composite inhibitors based on some of these compounds allows their protective effect to be expanded to t=200°C in certain cases. Data on the protection of various steels by composite inhibitors of this kind is discussed. The most outstanding results in the protection of low-carbon and chromium–nickel steels in high-temperature acid solutions are provided by formulations based on triazole derivatives, which effectively inhibit corrosion in mineral (HCl, H₂SO₄, H₃PO₄) and organic (acetic, formic, citric) acids. Problems related to the mechanism of the inhibitory effect of triazoles are discussed. It is shown that the possibility of providing steel protection at these high temperatures is due to the unique mechanism of the inhibitory action of triazoles that are chemisorbed on the metal surface and form a monomolecular layer strongly bound to the surface. Additional physical or chemical polymolecular adsorption of inhibitor molecules occurs on top of that layer, which significantly improves its protective properties. Generalization of data on the inhibitory protection of steels in high-temperature acid solutions with unsaturated organic compounds and NHCs, as well as an analysis of the mechanism of their action made it possible to formulate modern approaches to the creation of high-temperature inhibitors for acid solutions. The bibliography includes 137 sources.

Keywords: high-temperature acid corrosion, steel, corrosion inhibitors, acidizing, hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid, formic acid, citric acid, nitrogen-containing heterocyclic compounds, triazole, diazole, tetrazole

Int. J. Corros. Scale Inhib., 2020, 9, no. 4, 1194-1236 PDF (845 K)
doi: 10.17675/2305-6894-2020-9-4-3

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