Microbiologically influenced corrosion is a problem commonly encountered in facilities in the oil and gas industries. The present study describes bacterial enumeration and identification in diesel and naphtha pipelines located in the northwest and southwest region in India, using traditional cultivation technique and 16S rDNA gene sequencing. Phylogenetic analysis of 16S rRNA sequences of the isolates was carried out, and the samples obtained from the diesel and naphtha-transporting pipelines showed the occurrence of 11 bacterial species namely Serratia marcescens ACE2, Bacillus subtilis AR12, Bacillus cereus ACE4, Pseudomonas aeruginosa AI1, Klebsiella oxytoca ACP, Pseudomonas stutzeri AP2, Bacillus litoralis AN1, Bacillus sp., Bacillus pumilus AR2, Bacillus carboniphilus AR3, and Bacillus megaterium AR4. Sulfate-reducing bacteria were not detected in samples from both pipelines. The dominant bacterial species identified in the petroleum pipeline samples were B. cereus and S. marcescens in the diesel and naphtha pipelines, respectively. Therefore, several types of bacteria may be involved in biocorrosion arising from natural biofilms that develop in industrial facilities. In addition, localized (pitting) corrosion of the pipeline steel in the presence of the consortia was observed by scanning electron microscopy analysis. The potential role of each species in biofilm formation and steel corrosion is discussed.
Petroleum product pipelines in India contain large numbers of various types of microorganisms that either directly or indirectly enhance corrosion. Field studies have been carried out by CSIR-CECRI to investigate the corrosion problem in petroleum product transporting pipelines in South India. Although Unicor J inhibitor was added in the pipeline to control corrosion, corrosion products were detected in the pipeline. The present study reveals that the degradation of the inhibitor enhances the proliferation of bacteria, which enhances the corrosion. The selection of an inhibitor to control corrosion has also been done.
In this study, Desulfobulbus propionicus (D. propionicus), a sulfate reducing bacterium (SRB) was isolated and identified in cooling towers by molecular biologic techniques. This bacterial species has been reported for the first time in the cooling towers of an Indian petroleum refinery. Corrosion behaviors were analyzed by electrochemical and weight loss methods. The high corrosion rate and the enhancement of anodic current in increased chloride environment was noticed in the presence of D. propionicus indicating that this SRB species enhances the pitting corrosion of mild steel. Propionate metabolism in H2S production is discussed as a new pathway of corrosion enhancement.
Sulfate-reducing bacteria (SRB), an anaerobic bacterial group, are found in many environments like freshwater, marine sediments, agricultural soil, and oil wells where sulfate is present. SRB derives energy from electron donors such as sulfate, elemental sulfur or metals, and fermenting nitrate. It is the major bacterial group involved in the microbiologically influenced corrosion (MIC), souring, and biofouling problems in oil-gas-producing facilities as well as transporting and storage facilities. SRB utilizes sulfate ions as an electron acceptor and produce H2S, which is an agent of corrosion, causing severe economic damages. Various theories have been proposed on the direct involvement of H2S and iron sulfides in corrosion; H2S directly attacks and causes corrosion of metals and alloys. Many reviews have been presented on the aforementioned aspects. This review specifically focused on SRB corrosion and the role of molecular biology tools in SRB corrosion studies viz. cathodic and anodic depolarization theories, corrosion characteristics of thermophilic SRB and influence of hydrogenase, temperature, and pressure in thermophilic SRB corrosion, SRB taxonomy, molecular approaches adopted in SRB taxonomical studies, sulfate and citrate metabolism analyses in completed SRB genomes, and comparative studies on SRB’s dissimilatory sulfite reductase structures.
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