Pilyashenko-Novokhathy A. Ecological aspects of formation and functioning of corrosion aggressive communities of soil micro organisms.

The thesis covers the materials on research of the mechanisms of formation and functioning of corrosion active arrangements of soil microorganisms, and looking for ways of evaluation criteria of potential corrosion danger of soil in real conditions of exploitation of underground constructions. The effect of technogenic burden on quantitative and qualitative compositions of microbial soil community, located close to underground metal constructions has been researched. A possible allocation of functions between groups of microorganisms, composing corrosion active communities in the overall corrosion process has been suggested for the first time. Trophic mechanisms, which make it possible to sustain a steady composition of microorganism communities and a high grows rate of biocorrosion process have been determined. It has been proved, that the degree of corrosion destruction of underground constructions can be evaluated without digging out the construction for carrying out surface examination, on the basis of defining the composition of microbial metabolites in adjacent subsoil. Synergic effect of joint activity of corrosion active bacteria of several systematic groups has been revealed (sulfatereducing bacteria, thionic bacteria, and bacteria group of Pseudomonas). It was stated, that level of activity of hydrogenase sulfatereducing bacteria determines intensity of processes of microbial corrosion. It has been demonstrated for the first time, that out of three known sulfatereducing bacteria of hydrogenase type, the existence of hydrogenise of [Fe-Ni]- type does determine the speed rate of biocorrosion processes. It has been theoretically substantiated for the first time and proven experimentally, that the selection of potential value of cathode protection depends on the composition of soil anions, in which the construction is used. The formula of defining of effective criteria of cathode protection with relative concentration of soil anions, taken into account, has been suggested. Requirements for inhibitor features, which can be made use of, for the protection of underground metal communication lines against microbial corrosion, have been defined.