Abstract
Corrosion of carbon steel by microorganisms recovered from corroded seal rings at an offshore floating production facility was investigated. Microbial diversity profiling revealed that communities in all sampled seal rings were dominated by Pseudomonas genus. Nine bacterial species, Pseudomonas aeruginosa CCC-IOB1, Pseudomonas balearica CCC-IOB3, Pseudomonas stutzeri CCC-IOB10, Citrobacter youngae CCC-IOB9, Petrotoga mobilis CCC-SPP15, Enterobacter roggenkampii CCC-SPP14, Enterobacter cloacae CCC-APB1, Cronobacter sakazakii CCC-APB3, and Shewanella chilikensis CCC-APB5 were isolated from corrosion products and identified based on 16S rRNA gene sequence. Corrosion rates induced by the individual isolates were evaluated in artificial seawater using short term immersion experiments at 40 °C under anaerobic conditions. P. balearica, E. roggenkampii, and S. chilikensis, which have not been associated with microbiologically influenced corrosion before, were further investigated at longer exposure times to better understand their effects on corrosion of carbon steel, using a combination of microbiological and surface analysis techniques. The results demonstrated that all bacterial isolates triggered general and localised corrosion of carbon steel. Differences observed in the surface deterioration pattern by the different bacterial isolates indicated variations in the corrosion reactions and mechanisms promoted by each isolate.
Highlights
Miseq sequencing generated a total of 789,041 raw-reads, after the bioinformatics processing only 275,501 high-quality sequences were used for the taxonomic classification of the microorganisms present in the three collected samples
An investigation of corroded seal rings showed that the rings were inhabited by a microbial community dominated by members of the following genera Pseudomonas, Martelella, Marinomonas, Shewanella, Alcanivorax, and Halomonas, which have been associated with hydrocarbon degradation
In all sampled seal rings, Pseudomonas was the most abundant genus, which supported the hypothesis that microorganisms participated in the corrosion of the seal rings
Summary
Since microorganisms are characterised by high genetic diversity and genotypic variation occurs as a result of environmental adaptation[41,42], the isolation and study of microorganisms from corroded equipment provide a unique opportunity to expand our knowledge of MIC through the investigation of novel species implicated in corrosion, their metabolic capabilities and their potential role in corrosion. During hydrostatic testing carried out on a floating production storage and offloading (FPSO) facility located on the Australian North West Shelf, several leaks were detected at piping system seal rings. These rings were exposed to production fluids during regular operation (~ 80 °C) for over five years. The ability of the isolates to instigate MIC of carbon steel is examined and discussed
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