Biocorrosion and Localization of Degradation Processes on the Steel Surface of a Gas Main
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BIOCORROSION AND LOCALIZATION OF DEGRADATION PROCESSES ON THE STEEL SURFACE OF A GAS MAIN E. І. Кryzhanivskyi,1 M. S. Polutrenko,1 P. О. Маrushchak,2,3 and I. М. Zakiyev4 We establish basic regularities of influence of sulfate-reducing bacteria on the biocorrosion of 17G1S-U steel. The mechanisms of degradation of steel surfaces are generalized by the methods of topographic analysis, microindentation, and fractographic diagnostics. We also propose inhibitors of biocorrosion and substantiate the efficiency of their application. Keywords: biocorrosion, fracture mechanisms, surface protection, efficiency of the inhibitor.
Introduction The investigations of biocorrosion of steels of oil and gas mains can be regarded as a part of multidisciplinary stage in the prediction of the integrity of structures with high operating risks [1]. Special attention should be given in this case to the engineering diagnostics of corrosion of oil and gas pipelines in the underground media with regard for the influence of the chemical nature of soils, their humidity, specific resistance, redox potential, and sulfate-reducing bacteria (SRB), which are predominant in the microbial association of soil microorganisms [2, 3]. It is known that the long-term operation of gas mains leads to the damage of their insulation and causes local and pitting corrosion. We observe the formation of favorable conditions for the initiation and development of the manifestations of corrosion processes and, in particular, of biocorrosion [4]. Numerous defects were detected in the regions of soil with excess moisture content in which the water and temperature conditions change as a result of the construction of gas pipelines and, hence, the evolution of SRB is activated [5]. The processes of microbial corrosion of the metals run in the biofilms formed on the surface of the pipe, which serves as a site of accumulation of the SRB cells and the products of their metabolism ( H 2S , NH 3, CO 2 , and carbon acids) [2, 6] responsible for the localized (pitting) corrosion leading to the through perforation of the pipes. Microorganisms not only produce corrosion-active metabolites but also directly participate in the electrochemical reactions on the surfaces of gas pipelines. The relationship between the distribution of the zones of active corrosion and the microstructure of steel was studied in [7, 8]. It was discovered that biocorrosion leads to the selective dissolution of structural phases, which induces the formation of developed topography. This facilitates the adhesion of SRB to pipe walls and localizes corrosion defects [7, 8]. Therefore, it is important to study the influence of SRB on the kinetics of corrosion of the metal in gas mains and the influence of inhibitors on the minimization of biocorrosion rate. 1 2 3 4
Іvano-Frankivsk National Technical University of Oil and Gas, Іvano-Frankivsk, Ukraine. Pulyui Ternopil National Technical University, Ternopil, Ukraine. Corresponding author; e-mail: [email protected]. National Aviation University, Kyiv, Uk
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