Criteria of additivity in the protective effect of components of mixed corrosion inhibitors in chamber protection of zinc and steel

• O.A. Betretdinova, A.Yu. Luchkin, O.A. Goncharova, Yu.I. Kuznetsov, N.N. Andreev and S.S. Vesely

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

Abstract: The use of mixed formulations whose components complement and synergistically enhance the protective effect of each other is a promising method for increasing the efficiency of the inhibitory protection of metals. This article analyzes the criteria of additivity in the protective effect of components of mixed corrosion inhibitors. It is shown that they depend on the parameter used for estimating the protection efficiency. An equation is given that allows one to separate the effects of synergism and antagonism of inhibitors based on data on the times of complete metal protection by each of the mixture components, the mixture itself, and the corrosion resistance of the metal in the absence of inhibitors. A coefficient reflecting the mutual effect of the components of mixed inhibitors is introduced. The approach the we developed was used to estimate the mutual effect of components in mixtures of carboxylic acids (tridecanoic, stearic, oleic, linolenic) with urotropine in the chamber protection of zinc and steel. It has been shown that in the case of zinc, only oleic acid and urotropine synergistically enhance the protective effects of each other. The other mixtures are characterized by an antagonism in the protective effect. In contrast, in the case of steel, all the mixtures studied were characterized by well-pronounced synergism. Moreover, for the mixture based on stearic acid, the coefficient of mutual enhancement of the protective effect of components reaches 250. It has been found that the synergy in the protective effect is a direct indication that the mixed inhibitor should be used rather than any of its components. However, an antagonism is not a complete contraindication preventing the use of mixtures. For example, the antagonistic mixture of tridecanoic acid with urotropine protects zinc much more efficiently than its components taken separately. Taking the complexity of the chamber protection process into account, no unambiguous conclusion about the nature of antagonistic and synergistic interactions of components in mixed inhibitors are made. However, it is assumed that the interactions of compounds during their adsorption on metals are in question.

Keywords: corrosion inhibitors, mixed corrosion inhibitors, chamber metal protection, synergism of inhibitor action, criteria for the mutual effects of inhibitors

Int. J. Corros. Scale Inhib., 2020, 9, no. 2, 771-779 PDF (186 K)
doi: 10.17675/2305-6894-2020-9-2-24

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