Corrosion of low carbon steel by microorganisms from the ‘pigging’ operation debris in water injection pipelines (original) (raw)
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MICROBIOLOGICALLY INFLUENCED CORROSION OF MILD STEEL IN
In this study, the roles of microorganisms on the corrosion of mild steel in various simulated crude oil environments have been investigated experimentally under three (3) operating conditions namely: pH, salinity and nitrate. Since the presence of water supports microbial life, physicochemical properties and Total Microbial Count (TMC)) of the formation water was determined before adding it to crude oil. Corrosion analyses were performed by weight loss technique, microstructure examination and Fourier Transform Infrared Spectroscopy (FTIR). Microbiological analyses by isolation and identification using appearance factors were conducted on the biofilms formed. The result of physicochemical and biological characterization show that the levels of measured parameters favour the promotion of microbiologically influenced corrosion (MIC). The corrosion rates showed that high acidity (pH < 6) and high alkalinity (pH > 8) favours the growth and activities of microorganisms while increase in salinity and nitrate concentration of crude oil media hinders the growth and activities of microorganisms in the corrosion of mild steel. Microstructure examination depicted more severe pitting corrosion of mild steel in crude oil environment dominant in acidity than salinity and nitrate concentration. FTIR mainly revealed absorption band of –OH, COOH and NH2 indicating the presence of extracellular polymeric substances (EPS). Seven isolates of bacteria, predominantly negative gram strain (Gram-negative), were observed. In all, this study provides valuable insight into the MIC of mild steel by bacteria in crude oil environments.
Journal of Industrial Microbiology & Biotechnology, 1992
The corrosion of AISI C1020 carbon steel in an anoxic, marine, sulphide-containing environment was examined as a function of bacterial physiology and consortial complexity. The carbon steel was exposed to three organism;Eubacterium limosum, Desulfovibrio sp. andDesulfobacter sp. which were provided with H2/CO2, butanol, glucose, and acetate as carbon and electron sources. A consortium of these bacteria utilizing hydrogen gave rise to relatively high corrosion rates (5.7×10−4 mhos cm−2) with respect to corrosion resulting from bacteria supplied with organic electron sources (0.6–1.6×10−4 mhos cm−2). Disproportionation of electrons between sulphate reduction and fermentation had a significant effect on the corrosion rate in the case ofDesulfovibrio. Surface examination using scanning electron microscopy coupled with electrochemical impedance spectroscopy supported the hypothesis that the corrosion rate was controlled by the relative intactness of a ferrous sulphide film in which the bacteria were embedded.
Role of Indigenous Bacteria in Corrosion of Two Types of Carbon Steel
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This study aimed to investigate the presence of both aerobic and anaerobic bacteria in a water sample collected from a nuclear power plant and establish if the indigenous bacteria or the products of their metabolic activities could initiate the corrosion of two different types of carbon steel (i.e., A570, 1045). The aerobic (heterotrophic, iron-oxidizing) and anaerobic (sulfate-reducing) bacteria were detected in low numbers in the water sample. Three bacterial strains were isolated by the enrichment procedure from this sample. Based on phenotypic and genotypic characteristics, the isolated bacteria were identified as Stenotrophomonas maltophilia IBBCn1 (MT893712), Stenotrophomonas maltophilia IBBCn2 (MT893713), and Bacillus thuringiensis IBBCn3 (MT893714). The bacteria existing in the water sample were able to initiate the corrosion of carbon steel A570 and 1045. The sulfate-reducing bacteria were detected in higher numbers than the heterotrophic bacteria and iron-oxidizing bacteri...