Inhibitor protection of steels in acid and neutral media by the derivatives of 2-mercaptobenzimidazole
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INHIBITOR PROTECTION OF STEELS IN ACID AND NEUTRAL MEDIA BY THE DERIVATIVES OF 2-MERCAPTOBENZIMIDAZOLE O. L. Humenyuk, O. I. Syza, and O. M. Krasovs’kyi
UDC 620.193:620.197.3
We study the anticorrosion properties of newly synthesized derivatives of 2-mercaptobenzimidazole and the efficiency of their action in compositions based on the wastes of production of εcaprolactam at the Chernihiv “Khimvolokno” Open Joint-Stock Company. A conclusion is made that these compounds can be used as corrosion inhibitors for 20 steel placed in acid and neutral media. The efficiency of application of protective compositions based on the wastes of production of ε-caprolactam with admixtures of the derivatives of 2-mercaptobenzimidazole is demonstrated for working media with pH 1–6.5.
Despite the existence of numerous works devoted to the application of the derivatives of benzimidazole as inhibitors of corrosion in metals [1–4], the investigation of the anticorrosion action of newly synthesized substances of this sort is of significant interest. The structure of these compounds enables us to believe that they would have inhibiting properties not only in acid but also in neutral media. This is of especial importance for thermal power engineering where inner surfaces of equipment periodically operate in contact with aqueous media with broad ranges of pH values [5]. It is well known that the corrosion rates in acid and neutral media are limited by different stages of cathodic processes [6–8]. Thus, in acid media, this is the stage of discharge of hydrogen ions. In neutral media, this role is played by the diffusion of oxygen to the surface. Therefore, it is customary to use different classes of corrosion inhibitors for the protection of steels in media with different pH values. However, it is possible that functional groups of different types in the derivatives of 2-mercaptobenzimidazole may equip these compounds with certain universal properties. Hence, the main aim of the tests is to study the influence of the structure of molecules on the anticorrosion efficiency of the corresponding substances and the mechanism of their action in corrosive media with different pH values. Experimental Procedure New heterocyclic compounds were synthesized according to the regularities of the influence of electronic structure on the protective properties of substances established in [3, 9]. The derivatives of 2-mercaptobenzimidazole (Table 1) are synthesized in the processes of interaction of benzimidazolile-2-thione (In-1) with bromderivatives in the process of boiling in isopropanol (In-2 and In-3 compounds obtained with an output of 70– 97% ) and with chloroacetamide derivative of 4-(4-F-phenyl)-2-phenylaminothiazole-3 in the process of boiling in ethanol (In-5 compound obtained with an output of 86–96%) as well as in the process of interaction of ethers of the 2-methyl-benzimidazolile-2-thioacetic acid with cyclohexanilsemicarbazide (In-4 compound) (Fig. 1). Protective compositions were prepared on the basis of K-wastes (cubic wastes of regenerati
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