Abstract:The differences between the general corrosion and microbiologically influenced corrosion (MIC) of steels were investigated in terms of its electrochemical behavior and surface phenomena. The corrosion potential of steels in the absence of SRB (sulfate-reducing bacteria) shifted to a negative value with the immersion time. However, the potential of the presence of SRB shifted to a positive value after 30 days' incubation, indicating the growth of SRB biofilms on the test metal specimens and the formation of cor… Show more
“…The steel samples in the sterile groundwater exhibited nobler potentials ( E OCP ) than those in the SRB inoculated medium (Figure 2). The E OCP of steel is associated with samples’ surface states, which include: adsorbed ions, corrosion products and biofilms [25,26]. Meanwhile, the E OCP of the insulated sample in the sterile medium was in the pseudo-passive region during the early stages indicating less corrosion reactions on the steel surface (Figure 2).…”
Section: Resultsmentioning
confidence: 99%
“…The insulated sample in the sterile medium exhibited the lowest corrosion rate during the test due to the limited diffusion of corrosive species across the insulation, evidenced by the Warburg coefficient (Table 1). In comparison, the samples in the sterile medium presented lower corrosion rates than those in the SRB inoculated medium, which indicates that the corrosion products film protected the steel surface to some extent in the absence of SRB [25,26]. Figure 6 Evolution of linear polarisation resistance ( R LPR ) with immersion period for the insulated and uninsulated steel samples tested in the sterile and SRB inoculated media.…”
Corrosion under insulation is a major economic concern in the safe operations of water, oil and gas steel pipes. Herein, the external corrosion of X80 pipeline steel was examined beneath a disbonded insulation in groundwater containing sulphate-reducing bacteria (SRB). The results show that the steel under the insulation exhibited different electrochemical behaviour from the uninsulated sample in the bulk solution. A galvanic effect was detected between the steel under insulation and the uninsulated sample. Spectroscopic analysis reveals the rust layer of the insulated steel immersed in the SRB-inoculated groundwater was enriched by FeS from microbial metabolism. The steel under insulation recorded severe localised perforation, while corrosion severity was reduced on the uninsulated sample. Diffusion of ions, film development and insulation degradation played important roles in steel corrosion.
“…The steel samples in the sterile groundwater exhibited nobler potentials ( E OCP ) than those in the SRB inoculated medium (Figure 2). The E OCP of steel is associated with samples’ surface states, which include: adsorbed ions, corrosion products and biofilms [25,26]. Meanwhile, the E OCP of the insulated sample in the sterile medium was in the pseudo-passive region during the early stages indicating less corrosion reactions on the steel surface (Figure 2).…”
Section: Resultsmentioning
confidence: 99%
“…The insulated sample in the sterile medium exhibited the lowest corrosion rate during the test due to the limited diffusion of corrosive species across the insulation, evidenced by the Warburg coefficient (Table 1). In comparison, the samples in the sterile medium presented lower corrosion rates than those in the SRB inoculated medium, which indicates that the corrosion products film protected the steel surface to some extent in the absence of SRB [25,26]. Figure 6 Evolution of linear polarisation resistance ( R LPR ) with immersion period for the insulated and uninsulated steel samples tested in the sterile and SRB inoculated media.…”
Corrosion under insulation is a major economic concern in the safe operations of water, oil and gas steel pipes. Herein, the external corrosion of X80 pipeline steel was examined beneath a disbonded insulation in groundwater containing sulphate-reducing bacteria (SRB). The results show that the steel under the insulation exhibited different electrochemical behaviour from the uninsulated sample in the bulk solution. A galvanic effect was detected between the steel under insulation and the uninsulated sample. Spectroscopic analysis reveals the rust layer of the insulated steel immersed in the SRB-inoculated groundwater was enriched by FeS from microbial metabolism. The steel under insulation recorded severe localised perforation, while corrosion severity was reduced on the uninsulated sample. Diffusion of ions, film development and insulation degradation played important roles in steel corrosion.
“…[ 6 ] SRB were defined as the notorious corrosion‐enhancing anaerobic microorganisms that are ubiquitous in the natural environment. [ 7,8 ] MIC induced by SRB has been extensively investigated in the literature. Zhu et al [ 9 ] found that the corrosion rate of X56 steel in the sea mud containing SRB was 10‐fold higher than that in the sea mud without SRB.…”
Sulfate-reducing bacteria (SRB) are one of the main reasons for the accelerated corrosion of steel. Cathodic polarization has been reported as an effective and economic method against marine corrosion, including microbiologically induced corrosion. However, the interaction between cathodic polarization and microbial activity has not been well defined. In this study, a fluorine-doped tin oxide electrode is used to study the effect of cathodic current on SRB cells. Fluorescence microscopy results clearly show that the attachment degree of SRB is dependent on the electric quantity and current intensity. The large electric quantity and high cathodic current (400 mA/m 2 × 30 h) can effectively inhibit bacterial attachment and subsequent biofilm formation. Furthermore, the effect of cathodic potential on the corrosion behavior of X65 steel in the presence of SRB is systematically investigated. Results show that the impressed charges, the increase of pH, and the formation of calcareous deposits on the electrode surface at the cathodic potential of −1,050 mV/SCE inhibit the attachment of SRB. In turn, the presence of SRB also interferes with the electrochemical reactions that occur during the polarization process, thus increasing the cathodic current. The interaction between SRB-induced corrosion and the process of preventing corrosion by various cathodic potentials is discussed.
Desulfotomaculum kuznetsovii (D. kuznetsovii), a thermophilic sulfate-reducing bacterium (SRB), was identified in a cooling tower of a petroleum refinery by 16S rRNA gene sequencing and its functional gene encoding dissimilatory sulfite reductase (dsrAB). The thermophilic sulfate-reducing bacterial species have been reported for the first time in the cooling towers of an Indian petroleum refinery. The protein coded by dsrAB gene was cloned, expressed, and identified using recombinant DNA technology. Weight loss method, electrochemical and surface analysis showed the corrosion behavior of the isolate. In the presence of D. kuznetsovii, the corrosion rate was higher when compared to control at 55 8C. It suppresses the anodic reaction and enhances the cathodic reaction by the production of organic complex and iron sulfide, respectively. Numerous pitting were noticed on mild steel which is due to the presence of D. kuznetsovii and its role in the corrosion process has been discussed.
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