This work investigates microbiologically influenced corrosion (MIC) of API(1) 5L X52 linepipe steel by a sulfate-reducing bacteria (SRB) consortium. The SRB consortium used in this study was cultivated from a sour oil well in Louisiana, USA. 16S rRNA gene sequence analysis indicated that the mixed bacterial consortium contained three phylotypes: members of the Proteobacteria (Desulfomicrobium sp.), Firmicutes (Clostridium sp.) and Bacteroidetes (Anaerophaga sp.). The biofilm and pit morphology that developed with time were characterized with field emission scanning electron microscopy (FESEM). In addition, electrochemical impedance spectroscopy (EIS), polarization resistance (Rp) and open circuit potential (OCP) were used to analyze the corrosion behavior. Through circuit modeling, EIS results were used to interpret the physicoelectric interactions between the electrode, biofilm and solution interfaces. The results confirmed that extensive localized corrosion activity of SRB is due to a formed biofilm in conjunction with a porous iron sulfide layer on the metal surface. Energy dispersive spectroscopy (EDS) revealed the presence of different sulfides and oxide constituents in the corrosion products for the system exposed to the SRB consortium.

Subject
Hydrogen sulfide, Steel surfaces, Bacterial growth, Corrosion rate, Iron sulfides, Steel coupons, Open circuits, Biofilms, Corrosion products, Surface analysis, Bacteria, Microorganisms, Microbiologically influenced corrosion
Keywords:
Carbon steel API 5L X52, microbiologically influenced corrosion (MIC), sulfate reducing bacteria (SRB), biofilm and pipeline
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2013
Association for Materials Protection and Performance (AMPP)
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