Oil field microorganisms cause highly localized corrosion on chemically inhibited carbon steel

Carbon steel pipelines, a means for crude oil transportation, occasionally experience highly localized perforation caused by microorganisms. While microorganisms grown in laboratory culture tend to corrode steel specimens unevenly, they rarely inflict a corrosion morphology consistent with that of pipelines, where centimetre-sized corrosion features are randomly distributed within vast stretches of otherwise pristine metal surface. In this study, we observed that corrosion inhibitors (CIs), widely used for the control of acid gas (H₂S, CO₂) corrosion in oil fields, also affect microbial growth and activity. Inhibited carbon steel resisted biofilm formation and underwent negligible corrosion (< 0.002 mm Fe⁰ year⁻¹), despite 15 months of exposure to oil field waters harbouring a diverse microbiome. In contrast, physical scavenging of CI in these waters led to severe and highly localized corrosion (up to 0.93 mm Fe⁰ year⁻¹) underneath biofilms dominated by methanogenic archaea and sulfate-reducing bacteria. A sharp decline in CI concentration, as well as its active components, quaternary ammonium compounds (QACs), correlated with microbial sulfidogenesis. CIs are ubiquitously present in oil field waters and play an underappreciated role in microbial corrosion mitigation. Physical and biological scavenging of CIs may create local differences in steel inhibition effectiveness and thus result in highly localized corrosion.     

Biodegradation and corrosion behaviour of <Emphasis Type="Italic">Serratia marcescens</Emphasis> ACE2 isolated from an Indian diesel-transporting pipeline

A facultative anaerobic species Serratia marcescens ACE2 isolated from the corrosion products of a diesel-transporting pipeline in North West India was identified by 16S rDNA sequence analysis. The role of Serratia marcesens ACE2 on biodegradation of commercial corrosion inhibitor (CCI) and its influence on the corrosion of API 5LX steel has been enlightened. The degrading strain ACE2 is involved in the process of corrosion of steel API 5LX and also utilizes the inhibitor as organic source. The quantitative biodegradation efficiency of corrosion inhibitor was 58%, which was calculated by gas chromatography mass spectrum analysis. The effect of CCI on the growth of bacteria and its corrosion inhibition efficiency were investigated. Additionally, the role of this bacterium in corrosion of steel has been investigated by powder X-ray diffractometer (XRD) and scanning electron microscope studies. The presence of high-intensity ferric oxides and manganese oxides noticed from the XRD indicates that ACE2 enhances the corrosion process in presence of inhibitor as a carbon source. This basic study will be useful for the development of new approaches for the detection, monitoring and control of microbial corrosion in petroleum product pipelines.     

Bacterial Degradation and Corrosion of Naphtha in Transporting Pipeline

Five naphtha hydrocarbon-degrading bacteria including representative strains of the two classified species (Serratia marcescensAR1, Bacillus pumilusAR2, Bacillus carboniphilus AR3, Bacillus megaterium AR4, and Bacillus cereus AR5) were identified by 16S rDNA gene sequence in a naphtha-transporting pipeline. The naphtha-degrading strains were able to be involved in the corrosion process of API 5LX steel and also utilized the naphtha as the sole carbon source. The biodegradation of naphtha by the bacterial isolates was characterized by gas chromatography-mass spectrometry. Weight-loss measurement on the corrosion of API 5LX steel in the presence/absence of consortia grown in naphtha-water aqueous media was performed. The scanning electron microscope observation showed that the consortia were able to attack the steel API 5LX surface, creating localized corrosion (pit). The biodegradation of naphtha by the strains AR1, AR2, AR3, AR4, and AR5 showed biodegradation efficiency of about 76.21, 67.20, 68.78, 68.78, and 68.15, respectively. The role of degradation on corrosion has been discussed. This basic study will be useful for the development of new approaches for the detection, monitoring, and control of microbial corrosion in a petroleum product pipeline.     

Microbial fouling and corrosion of carbon steel in deep anoxic alkaline groundwater

Understanding the corrosion of carbon steel materials of low and intermediate level radioactive waste under repository conditions is crucial to ensure the safe storage of radioactive contaminated materials. The waste will be in contact with the concrete of repository silos and storage containers, and eventually with groundwater. In this study, the corrosion of carbon steel under repository conditions as well as the microbial community forming biofilm on the carbon steel samples, consisting of bacteria, archaea, and fungi, was studied over a period of three years in a groundwater environment with and without inserted concrete. The number of biofilm forming bacteria and archaea was 1,000-fold lower, with corrosion rates 620-times lower in the presence of concrete compared to the natural groundwater environment. However, localized corrosion was detected in the concrete–groundwater environment indicating the presence of local microenvironments where the conditions for pitting corrosion were favorable.     

Role of <Emphasis Type="Italic">Serratia marcescens</Emphasis> ACE2 on diesel degradation and its influence on corrosion

A facultative anaerobic species Serratia marcescens ACE2 isolated from the corrosion products of diesel transporting pipeline in North West, India was identified by 16S rDNA sequence analysis. The role of Serratia marcesens ACE2 on biodegradation of diesel and its influence on the corrosion of API 5LX steel has been elucidated. The degrading strain ACE2 is involved in the process of corrosion of steel API 5LX and also utilizes the diesel as an organic source. The quantitative biodegradation efficiency (BE) of diesel was 58%, calculated by gas-chromatography–mass spectrum analysis. On the basis of gas-chromatography–mass spectrum (GC–MS), Fourier Transform infrared spectroscopy (FTIR) and X-ray diffractometer (XRD), the involvement of Serratia marcescens on degradation and corrosion has been investigated. This basic study will be useful for the development of new approaches for detection, monitoring and control of microbial corrosion.     

An assessment of alternative diesel fuels: microbiological contamination and corrosion under storage conditions

Experiments were designed to evaluate the nature and extent of microbial contamination and the potential for microbiologically influenced corrosion of alloys exposed in a conventional high sulfur diesel (L100) and alternative fuels, including 100% biodiesel (B100), ultra-low sulfur diesel (ULSD) and blends of ULSD and B100 (B5 and B20). In experiments with additions of distilled water, all fuels supported biofilm formation. Changes in the water pH did not correlate with observations related to corrosion. In all exposures, aluminum 5052 was susceptible to pitting while stainless steel 304L exhibited passive behavior. Carbon steel exhibited uniform corrosion in ULSD and L100, and passive behavior in B5, B20, and B100.     

The role of bacteria in pit propagation of carbon steel

Pit propagation in carbon steel exposed to a phosphate-containing electrolyte required either stagnant conditions or microbial colonization of anodic regions. A scanning vibrating electrode (SVE) was used to resolve formation and inactivation of anodic and cathodic sites on carbon steel. In sterile, continuously aerated medium, pits initiated and repassivated, while in the absence of aeration, pits initiated and propagated. Pit propagation was also observed in continuously aerated medium inoculated with a heterotrophic bacterium, originally isolated from a corrosion tubercle formed on a steel pipe in a fresh water environment. Autoradiography of bacteria following uptake of (14)C-acetate into cellular material in combination with SVE analysis demonstrated that sites of anodic activity coincided with sites of bacterial activity. Prelabeled bacteria also preferentially attached to corrosion products over the anodic sites. Confocal laser scanning microscopy demonstrated that attraction to anodic sites did not depend on bacterial viability and was not specific for iron as a substratum. The results suggest that bacteria may preferentially attach to the corrosion products formed over corrosion pits. The biofilms over these anodic sites may create stagnant conditions within corrosion pits that result in pit propagation.     

Microbial Iron Respiration Can Protect Steel from Corrosion

Microbiologically influenced corrosion (MC) of steel has been attributed to the activity of biofilms that include anaerobic microorganisms such as iron-respiring bacteria, yet the mechanisms by which these organisms influence corrosion have been unclear. To study this process, we generated mutants of the iron-respiring bacterium Shewanella oneidensis strain MR-1 that were defective in biofilm formation and/or iron reduction. Electrochemical impedance spectroscopy was used to determine changes in the corrosion rate and corrosion potential as a function of time for these mutants in comparison to the wild type. Counter to prevailing theories of MC, our results indicate that biofilms comprising iron-respiring bacteria may reduce rather than accelerate the corrosion rate of steel. Corrosion inhibition appears to be due to reduction of ferric ions to ferrous ions and increased consumption of oxygen, both of which are direct consequences of microbial respiration.     

Experimental investigation of microbiologically influenced corrosion of selected steels in sugarcane juice environment

In the current study, ferritic stainless grades AISI 439 and AISI 444 were investigated as possible construction materials for machinery and equipment in the cane-sugar industry. Their performance in corrosive cane-sugar juice environment was compared with the presently used low carbon steel AISI 1010 and austenitic stainless steel AISI 304. The Tafel plot electrochemical technique was used to evaluate general corrosion performance. Microbiologically influenced corrosion (MIC) behaviour in sugarcane juice environment was studied. Four microbial colonies were isolated from the biofilms on the metal coupon surfaces on the basis of their different morphology. These were characterized as Brevibacillus parabrevis, Bacillus azotoformans, Paenibacillus lautus and Micrococcus sp. The results of SEM micrographs showed that AISI 439 and AISI 304 grades had suffered maximum localized corrosion. MIC investigations revealed that AISI 444 steel had the best corrosion resistance among the tested materials. However from the Tafel plots it was evident that AISI 1010 had the least corrosion resistance and AISI 439 the best corrosion resistance.     

Microbially influenced corrosion of galvanized steel pipes in aerobic water systems

Aims: To investigate the role of heterotrophic bacteria in the corrosion of galvanized steel in the presence of water. Methods and Results: Samples were taken from corroding galvanized steel pipes conveying water for specialist applications, and heterotrophic bacteria were isolated and cultured. The majority of bacteria were Gram‐negative aerobes and included Pseudomonas sp., Bacillus pumilus, Afipia spp. and Blastobacter denitrificans/Bradyrhizobium japonicum. Zinc tolerance was assessed through growth and zinc disc diffusion experiments. In general, zinc negatively influenced growth rates. An unidentified yeast also isolated from the system demonstrated a high tolerance to zinc at concentrations up to 4 g l^?1. Coupon experiments were performed to assess corrosion by the bacteria on galvanized steel and steel coupons. The majority of isolates as pure culture biofilms (69%) accelerated corrosion of galvanized coupons, assessed as zinc release, relative to sterile control coupons (P < 0·05). Pure culture biofilms did not increase the corrosion of steel, with four isolates demonstrating protective effects. Conclusions: Pure culture biofilms of heterotrophic bacteria isolated from a corroding galvanized pipe system were found to accelerate the corrosion of galvanized steel coupons. Significance and Impact of the Study: Microbially influenced corrosion is a potential contributor to sporadically occurring failures in galvanized steel systems containing water. Management strategies should consider microbial control as a means for corrosion prevention in these systems.     

Biofilms and corrosion interactions on stainless steel in seawater

Biofouling and biocorrosion lead to an important modification of the metal/ solution interface inducing changes in the type and concentration of ions, pH values, oxygen levels, flow velocity, etc. Metal dissolution in seawater is mainly conditioned by two different processes: (a) biofouling settlement and (b) corrosion products formation.Corrosion-resistant alloys such as stainless steel present an ideal substratum for microbial colonization, rather similar to inert non-metallic surfaces, due to the lack of corrosion products. Stainless steels are sensitive to pitting and other types of localized corrosion in chloride-containing media such as seawater. Biofilms and bacterial metabolism may accelerate the initiation of crevice attack by depletion of oxygen in the crevice solution due to microbial respiration. Bacterial colonization occurs within a period of 24–72 h on stainless steel samples exposed to natural seawater and, depending on environmental conditions, a copious and patchy biofilm is generally formed.Different interpretations of biofilms' effects on corrosion are critically discussed. A practical case, involving polluted harbour seawater, is reported to illustrate biofilm and corrosion interactions on stainless steel samples.     

The effect of corrosion inhibitors on microbial communities associated with corrosion in a model flow cell system

A model flow cell system was designed to investigate pitting corrosion in pipelines associated with microbial communities. A microbial inoculum producing copious amounts of H₂S was enriched from an oil pipeline biofilm sample. Reservoirs containing a nutrient solution and the microbial inoculum were pumped continuously through six flow cells containing mild steel corrosion coupons. Two cells received corrosion inhibitor “A”, two received corrosion inhibitor “B”, and two (“untreated”) received no additional chemicals. Coupons were removed after 1 month and analyzed for corrosion profiles and biofilm microbial communities. Coupons from replicate cells showed a high degree of similarity in pitting parameters and in microbial community profiles, as determined by 16S rRNA gene sequence libraries but differed with treatment regimen, suggesting that the corrosion inhibitors differentially affected microbial species. Viable microbial biomass values were more than 10-fold higher for coupons from flow cells treated with corrosion inhibitors than for coupons from untreated flow cells. The total number of pits >10 mils diameter and maximum pitting rate were significantly correlated with each other and the total number of pits with the estimated abundance of sequences classified as Desulfomicrobium. The maximum pitting rate was significantly correlated with the sum of the estimated abundance of Desulfomicrobium plus Clostridiales, and with the sum of the estimated abundance of Desulfomicrobium plus Betaproteobacteria. The lack of significant correlation with the estimated abundance of Deltaproteobacteria suggests not all Deltaproteobacteria species contribute equally to microbiologically influenced corrosion (MIC) and that it is not sufficient to target one bacterial group when monitoring for MIC.     

Microbial iron respiration can protect steel from corrosion

Microbiologically influenced corrosion (MC) of steel has been attributed to the activity of biofilms that include anaerobic microorganisms such as iron-respiring bacteria, yet the mechanisms by which these organisms influence corrosion have been unclear. To study this process, we generated mutants of the iron-respiring bacterium Shewanella oneidensis strain MR-1 that were defective in biofilm formation and/or iron reduction. Electrochemical impedance spectroscopy was used to determine changes in the corrosion rate and corrosion potential as a function of time for these mutants in comparison to the wild type. Counter to prevailing theories of MC, our results indicate that biofilms comprising iron-respiring bacteria may reduce rather than accelerate the corrosion rate of steel. Corrosion inhibition appears to be due to reduction of ferric ions to ferrous ions and increased consumption of oxygen, both of which are direct consequences of microbial respiration.     

Molecular characterization of putative biocorroding microbiota with a novel niche detection of Epsilon- and Zetaproteobacteria in Pacific Ocean coastal seawaters

Submerged metal surfaces in marine waters undergo rapid microbial colonization and biocorrosion, causing huge damage to marine engineering facilities and significant financial losses. In coastal areas, an accelerated and particularly severe form of biocorrosion termed accelerated low water corrosion (ALWC) is widespread globally. While identification of biocorroding microorganisms and the dynamics of their community structures is the key for understanding the processes and mechanisms leading to ALWC, neither one is presently understood. In this study, analysis of constructed clone libraries and qPCR assays targeting group-specific 16S rRNA or functional marker genes were used to determine the identity and abundance of putative early carbon steel surface-colonizing and biocorroding microbes in coastal seawater. Diverse microbial groups including 10 bacterial phyla, archaea and algae were found to putatively participate in the surface-colonizing process. Analysis of the community structure of carbon steel surface microbiota revealed a temporal succession leading to ALWC. By extending the current state of knowledge, our work demonstrates the global importance of Alphaproteobacteria (mainly Rhodobacterales), Gammaproteobacteria (mainly Alteromonadales and Oceanospirillales), Bacteroidetes (mainly Flavobacteriales) and microalgae as the pioneer and sustaining surface colonizers that contribute to initial formation and development of surface biofilms. We also discovered Epsilonproteobacteria and the recently described Zetaproteobacteria as putative corrosion-causing microorganisms during early steps of the ALWC process. Hence, our study reports that Zetaproteobacteria may be ubiquitous also in non-hydrothermal coastal seawaters and that ALWC of submerged carbon steel surfaces in coastal waters may involve a highly diverse, complex and dynamic microbial consortium. Our finding that Epsilon- and Zetaproteobacteria may play pivotal roles in ALWC provides a new starting point for future investigation of the ALWC process and mechanism in marine environments. Further studies of Epsilon- and Zetaproteobacteria in particular may thus help with the design of effective corrosion prevention and control strategies.     

Utilization of cathodic hydrogen by hydrogen-oxidizing bacteria

Summary Hydrogen is consumed by methanogenic, sulphate-reducing, and homoacetogenic bacteria and members of these bacterial groups are able to grow chemolithotrophically with hydrogen as sole energy source. Cathodic hydrogen consumption by sulphate-reducing bacteria has been proposed as one of the factors in the anaerobic corrosion of metals. Desulfovibrio spp. were able to utilize cathodic hydrogen from mild steel as the only source of energy for growth with sulphate or nitrate as terminal electron acceptor. Other hydrogen-oxidizing bacteria such as Methanospirillum hungatei, Acetobacterium woodii and Wolinella succinogenes were also able to utilize cathodic hydrogen from mild steel for energy generation and growth. Weight loss studies of mild steel coupons under different growth conditions of Desulfovibrio spp. indicated that hydrogen removal alone is not the cause of corrosion and the depolarization phenomenon probably plays a role only in the initiation of the anaerobic microbial corrosion process.     

Identification of key factors in Accelerated Low Water Corrosion through experimental simulation of tidal conditions: influence of stimulated indigenous microbiota

Biotic and abiotic factors favoring Accelerated Low Water Corrosion (ALWC) on harbor steel structures remain unclear warranting their study under controlled experimental tidal conditions. Initial stimulation of marine microbial consortia by a pulse of organic matter resulted in localized corrosion and the highest corrosion rates (up to 12-times higher than non-stimulated conditions) in the low water zone, persisting after nine months exposure to natural seawater. Correlations between corrosion severity and the abundance and composition of metabolically active sulfate-reducing bacteria (SRB) indicated the importance and persistence of specific bacterial populations in accelerated corrosion. One phylotype related to the electrogenic SRB Desulfopila corrodens appeared as the major causative agent of the accelerated corrosion. The similarity of bacterial populations related to sulfur and iron cycles, mineral and tuberculation with those identified in ALWC support the relevance of experimental simulation of tidal conditions in the management of steel corrosion exposed to harbor environments.     

Early detection of oxidized surfaces using Shewanella oneidensis MR-1 as a tool

Corrosion is a natural global problem of immense importance. Oxidation of iron and steel not only compromises the structural stability of a widely used and versatile material but it also creates an abrasive compound (iron oxide) that can score the surfaces of metals, rendering them useless for the purpose for which they were designed. Clearly, the identification of corrosion in its nascent stages is a high priority for reasons that range from aesthetics to economics. Many bacteria in the facultatively aerobic genus Shewanella have the capacity to respire some metal oxides, such as iron oxide, by way of a variety of oxide-binding proteins lodged in their outer membrane. In this study, a rapid, cost-effective system for the specific early detection of a variety of oxidized steel surfaces is described, taking advantage of bacteria with natural affinities for iron oxides, to identify the sites of nascent corrosion.     

The dual role of microbes in corrosion

Corrosion is the result of a series of chemical, physical and (micro) biological processes leading to the deterioration of materials such as steel and stone. It is a world-wide problem with great societal and economic consequences. Current corrosion control strategies based on chemically produced products are under increasing pressure of stringent environmental regulations. Furthermore, they are rather inefficient. Therefore, there is an urgent need for environmentally friendly and sustainable corrosion control strategies. The mechanisms of microbially influenced corrosion and microbially influenced corrosion inhibition are not completely understood, because they cannot be linked to a single biochemical reaction or specific microbial species or groups. Corrosion is influenced by the complex processes of different microorganisms performing different electrochemical reactions and secreting proteins and metabolites that can have secondary effects. Information on the identity and role of microbial communities that are related to corrosion and corrosion inhibition in different materials and in different environments is scarce. As some microorganisms are able to both cause and inhibit corrosion, we pay particular interest to their potential role as corrosion-controlling agents. We show interesting interfaces in which scientists from different disciplines such as microbiology, engineering and art conservation can collaborate to find solutions to the problems caused by corrosion.     

Microorganisms in Heat Supply Systems and Internal Corrosion of Steel Pipelines

In laboratory experiments with batch cultures of thermophilic microorganisms isolated from urban heat supply systems, the growth of sulfate-reducing, iron-oxidizing, and iron-reducing bacteria was found to accelerate the corrosion rate of the steel-3 plates used in pipelines. In the absence of bacteria and dissolved oxygen, minimal corrosion was determined. The aforementioned microorganisms, as well as sulfur-oxidizing bacteria, were found to be widespread in water and corrosion deposits in low-alloy steel pipelines (both delivery and return) of the Moscow heat networks, as well as in the corrosion deposits on the steel-3 plates in a testing unit supplied with the network water. The microorganisms were found in samples with a water pH ranging from 8.1 to 9.6 and a temperature lower than 90°C. Magnetite, lepidocrocite, goethite, and X-ray amorphous ferric oxide were the corrosion products identified on the steel-3 plates, as well as siderite, aragonite, and S⁰. The accumulation of corrosion deposits and variation in the total and local corrosion of the steel plates in a testing unit were considered in terms of the influence of microbial processes.     

Surface Potential Measurement of Bacteria Using Kelvin Probe Force Microscopy

Surface potential is a commonly overlooked physical characteristic that plays a dominant role in the adhesion of microorganisms to substrate surfaces. Kelvin probe force microscopy (KPFM) is a module of atomic force microscopy (AFM) that measures the contact potential difference between surfaces at the nano-scale. The combination of KPFM with AFM allows for the simultaneous generation of surface potential and topographical maps of biological samples such as bacterial cells. Here, we employ KPFM to examine the effects of surface potential on microbial adhesion to medically relevant surfaces such as stainless steel and gold. Surface potential maps revealed differences in surface potential for microbial membranes on different material substrates. A step-height graph was generated to show the difference in surface potential at a boundary area between the substrate surface and microorganisms. Changes in cellular membrane surface potential have been linked with changes in cellular metabolism and motility. Therefore, KPFM represents a powerful tool that can be utilized to examine the changes of microbial membrane surface potential upon adhesion to various substrate surfaces. In this study, we demonstrate the procedure to characterize the surface potential of individual methicillin-resistant Staphylococcus aureus USA100 cells on stainless steel and gold using KPFM.