The investigation of oil microbocenosis influence on the corrosion process of pipe steel

Abstract

The paper presents the results of model laboratory experiments carried out to assess the influence of oil microbocenosis bacteria on the corrosion process on the internal surfaces of oil pipelines made of steel 17G1S. It is known that the bacteria of this group most often include hydrocarbon-oxidizing bacteria (HOB), sulfate-reducing bacteria (SRB), sulfur-oxidizing, or thionic (TB) and iron-oxidizing bacteria (IOB). In model experiments with 17G1S steel samples alloyed with 1% manganese we used corrosion-hazardous bacteria of the genera Desulfotomaculum, Paracoccus, Pseudomonas and Sphaerotilus, isolated from a damaged section of an oil pipeline at a field in the northern part of the Samara Region. In the initial phase of the experiment, the titer of the analyzed bacteria was quite high (SRB 10⁴10⁵, TB 1010⁴ cells/cm), but by the end of the experiment, only sulfate-reducing bacteria with quantitative characteristics of 110 cells/cm were isolated from the culture liquid, may be due to the high adhesion capacity of mass cultures of the bacteria. On the surface of the steel samples the method of electron microscopy revealed unevenly distributed loose deposits, but the cells of the bacteria themselves were not visible in them. The morphological features of the revealed corrosion deposits indicated their bacterial origin, which was also confirmed by biochemical analysis of corrosion products suspension, in particular, by revealing a high mass concentration of sulfides, protein, and the dehydrogenase. Aerobic and anaerobic microbiological interactions occurring in the oil microbocenosis on the internal surfaces of pipelines have been experimentally confirmed and are in good agreement with the data of other researchers. It has been established that the main role in the corrosion destruction steel samples belongs to SRB, whose participation can be carried out according to two main mechanisms: hydrogen cracking and anodic dissolution of iron. Pits and through holes are formed on the steel surface, and the local corrosion rate can approaches 7,3 mm/year. The experiments proved the active role of oil microbocenoses, the basis of the microbiont of which consists of four bacteria, in the rapid destruction of oil pipelines in the Samara Region.