Corrosion Mechanism And Process Of Carbon Steel Influenced By Marine Anaerobic Microorganism

The corrosion of metallic construction is a complex electrochemistry process which refers to many factors such as chemistry, physics, biology and so on. The anaerobic bacteria sulfate-reducing bacteria (SRB) has been studied widely, and found that it is the bacteria that related to the corrosion of metal. There is significance in research for SRB influenced corrosion, it can offer scientific basis for putting forward available method for anti-biocorrosion.In this study, the SRB was enriched using the liquid Postgate's C culture medium, and at the same time, iron-reducing bacteria was also found exist in the medium according to the molecular biology study. And then the enriched SRB was purified by solid plate culture medium. The enriched bacteria and the purified bacteria were used to study their effect on the corrosion of carbon steel.Four parts are involved in this study. Firstly, the effect of the enriched bacteria on the corrosion of carbon steel was studied by electrochemistry method and surface analytic technique. The result showed that the corrosion process was inhibited firstly and then accelerated in the environment containing enriched bacteria. In the first three days, the reason of corrosion inhibition was due to the occurred iron phosphate influenced by the iron-reducing bacteria, and then H2S coming from metabolism of SRB became the main factor which induced to accelerate corrosion rate.The corrosion behavior of carbon steel in the purified SRB and the metabolized products that leached the SRB was respectively studied by EIS. The result showed that the metabolized products can accelerate the process of corrosion of carbon steel, but the effectiveness is not so distinguish compared with the purified SRB. It can be conclude from the result that SRB play an important role in the corrosion of the carbon steel.The possible main factor of the accelerated corrosion was studied by simulating the quantum of bio-sulfide: Na2S, H2S, cysteine was separately used as the simulated factor. The results showed that the hydrogen sulfide in the bacteria metabolic products is the main reason in the corrosion process of the steel with the system of containing activated SRB. And the effect of cysteine is less than SRB and its metabolic products. The process of microbiologically influenced mineralization and its effect on the corrosion of metal was studied by electrochemistry impedance spectroscopy (EIS) and surface observation and analysis techniques. The results showed that the substance which has sheet configuration regarded as green rust was observed on the inner rust layer under the influence of enriched anaerobic bacteria, and the bacteria cell was found on the surface of green rust. And the corrosion rate of steel with iron oxide layer inoculated SRB was accelerated in initial stage and then decreased. In addition, iron-reducing bacteria may be related to the inhibition of corrosion.