Risk assessment of biocorrosion corrosion in underground steel structures

The aim of the work is to develop a methodology for assessing the bio-corrosive aggressiveness of soils in the areas where oil pipelines are laid, which does not require long-term corrosion tests. The assessment of soil bio-corrosion risk is based on its integrated corrosion and microbiological tests. To conduct field and laboratory corrosion tests, the most typical for Russia soils were selected, which are universal in terms of options for the development of bio-corrosion damage: high humus and high clay content loams, low humus and high sand content loams, and muddy swamp soil. In the testing process, samples of the steel 20 were used, the corrosion resistance of which is comparable to the corrosion resistance of pipe steels. The results of laboratory and field research of the soil are presented in this article. The main external factor affecting the level of soil bio-corrosive activity is microbial consortium composition (qualitative and quantitative). The formation of microbiocenoses is influenced by the composition and structure of the soil, its moisture content and the content of organic and inorganic substances in free form, the temperature factor affecting the accumulation of organic substances in the upper soil horizons in the summer, pH conditioned by the presence of mineral substances in soluble form. For the assessment of biocorrosive activity, from among the electrochemical indicators, the specific soil electrical resistance is informative, which characterizes the soil moisture and mineralization, affecting the development of microbiocenosis.