| Sulfate-reducing bacteria (SRB) as a heterogeneous group of anaerobicheterotrophic bacteria were the main bacteria responsible for the numerous biocorrosioncases. The water type of the oily wastewater which was exploited with oil extractionunder anaerobic conditions, there is a lot of SRB in the water as well as in pipe innerwall.The wastewater easily causes erosion of the equipment and pipe line and at the sametime bring huge economic losses. With the developing of platform for petroleum, highlyattention has been paid on the corrosion phenomenon caused by SRB.In this paper, acomparative study about the microbiologically influenced corrosion behavior of316L SSimmerse in sulphate-reducing bacteria, was performed by using electrochemicalimpedance spectroscopy (EIS), scanning electron microscopy (SEM),energy dispersivespectroscopy(EDS) and fluorescence microscope technique, and influence of salinity,Fe2+concentration,pH value and temperature on corrosion behavior is investigated.Respectively discusses growth characteristics of SRB biofilm on the surface of316L SSimmersed in different water conditions, and then research on electrode surfaceelectrochemical properties was future studied. The potential application value of controlenvironment variables in the inhibition of SRB corrosion were analyzed.The influence of environmental factors on the growth of SRB metabolism is firstlystudied. The results showed that when Cl-concentration is30g/L SRB activities withinthe electrode surface biofilm is the most exuberant， while with the increase ofconcentration of Cl-, the breeding of microorganism is restrained，it could not grow whenCl-concentration over100g/L, thereby inhibiting microbial corrosion occurs.Theexistence of a small amount of Fe2+concentration was better for SRB growing, when theFe2+concentration is10g/L, the number of bacteria can quickly reach the maximumwithin two days after inoculation, and the number is higher than it without the Fe2+.SRBto pH value adaptability is very strong, in the pH value of5.5~7.5environment can grow a lot, but when pH is6.5, SRB growth and metabolic activity is the most exuberant.SRB is very sensitive to temperature, under the condition of40degrees Celsius has themost vigorous growth and metabolic activity, higher or lower temperature can inhibit thegrowth of SRB.Surface analysis showed that, SRB can form biofilms in316L SS surface bygrowth metabolism,and its metabolic products and corrosion products can promote thedissolution and destruction of the passivation film on the stainless steel surface. Theformation of loose biofilm which is rich in corrosion product, extracellular polymers andmetabolites on the surface of coupon and the occurring of badly local corrosion damageof coupon surface beneath the biofilm. Energy spectrum test and analysis show that, theatom content of C, O, S is higher on the corrosion surface caused by microbial corrosion,the corrosion products are mainly composed of iron sulfide, Induce local corrosion of thestainless steel.The electrochemical changes of electrode surface SRB biofilm was finally studiedby means of EIS. The charge transfer resistance with biofilm is decreasing, biofilmpromote charge transfer process of metal surface and accelerate local corrosion of316SS.Equivalent circuit models of double deck film from EIS results bear out the presence ofbiofilm and passivating film on the metal Surface, Equivalent circuit models caneffectively explain the extremely corrosion behavior and corrosion mechanism of316LSS MIC in diffrrernt medium. |
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