Study Of Corrosion Behaviour Induced By Sulfur Bacteria On The Carbon Steel And Stainless Steel

The emphasis of this study lies in the effect on the carbon steel and stainlesssteel of corrosion behaviour induced by pure sulfur bacteria (pure Sulphate-reducingbacteria (SRB) or pure Thiobacillus thioparus (T.P.)) and mixed culture includingSRB and T.P.. We can indicate that the corrosion mechanism induced by sulfurbacteria on the carbon steel and stainless steel in the closed environment byelectrochemical measurements, scanning electron microscopy and surface analysis.The results show that:(1) The aerobic environment can reduce the corrosion process by promoting itspassivation and inhibiting the metabolic activity of SRB, compared with anaerobicenvironment. The bio-film is loose and heterogeneous under aerobic conditions. Itpresents glomerate morphology in the oxygen saturated environment. It’s indicatedthat SRB are prone to build localized anaerobic environment for its survival.(2) Thiobacillus thioparus are short rodshaped. The length is about2-4micrometer. It grows dispersedly and the colony is pale yellow with a round dot. Itsgrowth displays a typical four-stage growth cycle, with a lag phase, an growth phase,a stationary phase, and a death phase. The first three days is lag phase. The4thto7thdays is growth phase. The8thto11thdays is stationary phase. The death phase beginsat12thdays.(3) Effect on the corrosion behavior of different metal induced by Thiobacillusthioparus is different. T.P. can accelerate the corrosion process of carbon steel due to the decrease of pH. But Thiobacillus thioparus can inhibit the corrosion process ofstainless steel. It’s mainly because of the protection of passive film and biolfilm.(4) The addition of T.P. change the corrosion process of carbon steel andstainless steel, slow down the corrosion of carbon steel, compared with SRB workingalone. It is due to the mixed culture forms more compact and protective biofilm on thesurface of metal.