Gumenyuk O. Effect of N-, O-, S-containing heterocyclic compounds on steel surface state in aggressive media.

The dissertation is devoted to study of physicochemical bases of media influence on anticorrosion efficiency of N-, O-, S-containing heterocyclic compounds, mechanism of their action on metal surface, correlation of the protective properties with the thermodynamic, electronic characteristics of applied compounds. On the basis of the analysis of dependence of the inhibiting and adsorption properties of the studied compounds on their structure, thermochemical parameters, the conclusion was made about the basic criteria of inhibitors selection for corrosive media with different рН values, namely solubility, availability of reactive sites (nitrogen atoms in structure of amino and imido groups; condensed rings with pi-bonding system; phenyl radicals), charge density on them; thermodynamic characteristics of molecules (formation enthalpy, complete energy), molecule polarity. Based on adsorption, UV- and Auger-spectroscopies data the mechanism of action of N-, O-, S-containing heterocyclic compounds was proposed: in acidic medium protective action of 2-Thioxo-2,3-dihydro-1H-quinazolin-4-one; Phenyl-thiazol-2-yl-amine; 1-H-Benzoimidazole-2-thiol derivatives is due to complex compounds on the metallic surface; in neutral 3% NaCl medium - by replacement anions-activators from the metallic surface providing formation uniform oxide film; in alkaline media the protective action is explained by chemisоrption with metal complexes formation, and shielding of metallic surface as a result of physical adsorption. For the first time an opportunity was shown of use of the overdue pharmaceutical preparations in anticorrosion protection. Effective inhibitor on the basis of the epsylon-Caprolactam production waste with the additive by 1-H-Benzoimidazole-2-thiol derivative was developed for the aggressive media with different рН values. The basic developments of this dissertation work were tested at some Ukrainian plants.