Quantum-Chemical Characteristics as a Criterion of Efficiency of Quaternary Salts with Antibacterial Properties for the
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QUANTUM-CHEMICAL CHARACTERISTICS AS A CRITERION OF EFFICIENCY OF QUATERNARY SALTS WITH ANTIBACTERIAL PROPERTIES FOR THE INHIBITION OF BIOCORROSION OF STEEL I. M. Kurmakova,1, 2 O. S. Bondar,1 and N. R. Demchenko1
UDC 620.193.8+620.197.3
We study the properties of the quaternary salts of pyridinium, imidazopyridinium and imidazoazepinіum as inhibitors of the corrosion of St3ps steel caused by sulfate-reducing bacteria of the Desulfovibrio genus. These bacteria can be regarded as the main component of the corrosive natural communities of soil. It is shown that the role of criterion of the efficiency of quaternary salts in the case of biocorrosion of low-carbon steels can be played by their reaction ability characterized by the electric charges on adsorption-reactive centers, dipole moment, and energy gap. A good correlation dependence of the degree of protection on the energy gap is discovered. Keywords: quaternary salts, corrosion inhibitor, biocidic action.
The contemporary investigations of new inhibitors of the corrosion of steels proposed for various corrosive media are based on the determination of the relationship between their anticorrosive action and the quantumchemical characteristics of molecules [1]. This approach developed by Skrypnik [2], Doroshenko [3], Awada [4], and other researchers makes it possible to predict the efficiency of substances depending on the structure of molecules in the case of corrosion protection, in particular, in acid media. The biocorrosion of steels responsible for about 80% of all corrosion-induced failures [5] is characterized by the predominance of the microbiological factor [6]. Therefore, as an important property of efficient inhibitors of biocorrosion. one can mention their antibacterial action depending on the structure of molecule, concentrations of substances, physiological specific features of bacteria, etc. [7]. In the course of interaction with microorganisms, biocidic substances either penetrate into cells and affect their metabolism, or integrate into the bilipid layer of the membrane and block its activity [6]. In the course of inhibition of the bacterial corrosion of metals by compounds with biocidic action, we observe the following competing processes: the adsorption of particles of the inhibitor on the metal surface leading to the formation of protective films and changes in the structure of the double electric layer and in the kinetics of electrochemical reactions; the adsorption of particles of the inhibitor on the surfaces of bacterial cells, which is the first stage of interaction of the inhibitor (biocide) with microorganisms; the chemotaxis of bacteria; and the formation of biofilms on the metal surface in which the microorganisms become more resistant to the action of the biocide [8, 9]. The antibacterial properties and protective action of the organic substances in the course of bacterial corrosion of steels are not always correlated [10, 11]. The dependences of the inhibiting action of these substances on their characteristics (quite important for th
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