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Shewanella oneidensis MR-1 is an attractive model microbe for elucidating the biofilm-metal interactions that contribute to the billions of dollars in corrosion damage to industrial applications each year. Multiple mechanisms for S. oneidensis-enhanced corrosion have been proposed, but none of these mechanisms have previously been rigorously investigated with methods that rule out alternative routes for electron transfer. We found that S. oneidensis grown under aerobic conditions formed thick biofilms (∼50 µm) on stainless steel coupons, accelerating corrosion over sterile controls. H 2 and flavins were ruled out as intermediary electron carriers because stainless steel did not reduce riboflavin and previous studies have demonstrated stainless does not generate H 2 . Strain ∆mtrCBA, in which the genes for the most abundant porin-cytochrome conduit in S. oneidensis were deleted, corroded stainless steel substantially less than wild-type in aerobic cultures. Wild-type biofilms readily reduced nitrate with stainless steel as the sole electron donor under anaerobic conditions, but strain ∆mtrCBA did not. These results demonstrate that S. oneidensis can directly consume electrons from iron-containing metals and illustrate how direct metal-to-microbe electron transfer can be an important route for corrosion, even in aerobic environments., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

In this work, microbiologically influenced corrosion (MIC) of 304 stainless steel (SS) caused by Bacillus cereus was investigated by electrochemical measurements and surface analyses in simulated Beijing soil solution under aerobic condition. The nitrate-reducing bacterium (NRB), B. cereus, was isolated from Beijing soil and identified using 16S rDNA. Confocal laser scanning microscopy (CLSM) images showed that the largest pit depths on 304 SS with and without B. cereus after 14 days of incubation were 7.17 and 4.59 μm, respectively, indicating that pitting corrosion was accelerated by B. cereus. X-ray photoelectron spectroscopy (XPS) and energy dispersive spectrometry (EDS) results revealed that B. cereus and its metabolic products were detrimental to the integrity of the passive film on 304 SS. The electrochemical results showed that B. cereus significantly reduced the corrosion resistance of 304 SS and accelerated the anodic dissolution reaction, thereby speeding up the corrosion process., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

The mitigation of microbiologically influenced corrosion (MIC) of 304L stainless steel (SS) against Pseudomonas aeruginosa by a Salvia officinalis extract was investigated using electrochemical and surface analysis techniques. The extract was characterized by HPLC-Q-TOF-MS and its antibiofilm property was evaluated. The data revealed the presence of well-known antimicrobial and anticorrosion compounds in the extract. The S. officinalis extract was found effective in preventing biofilm formation and inhibiting mature biofilm. Electrochemical results indicated that P. aeruginosa accelerated the MIC of 304L SS, while the extract was found to prevent the MIC with an inhibition efficiency of 97.5 ± 1.5%. This was attributed to the formation of a protective film by the adsorption of some compounds from the extract on the 304L SS surface., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Microbiologically influenced corrosion (MIC) of S32654 (654SMO) super austenitic stainless steel (SASS) by acid producing bacterium (APB), Acidithiobacillus caldus SM-1, a strain of sulfur-oxidizing bacteria (SOB) used in biohydrometallurgy field, was investigated using electrochemical measurements and surface characterizations during a 14-day immersion test. The results indicated that S32654 SASS was susceptible to MIC by APB, and A. caldus SM-1 was capable of producing an aggressive acidic environment underneath the biofilm, resulting in the dissolution of the passive film and severe pitting attacks against S32654 SASS, which is commonly regarded as a corrosion resistant material., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The present study investigated the antibacterial performance, corrosion resistance and surface properties of antibacterial austenitic 317L-Cu stainless steel (317L-Cu SS). After 4.5wt% copper was added to 317L stainless steel (317L SS), the new alloy underwent solid solution and aging heat treatment. Fluorescent staining using 4',6-diamidino-2-phenylindole (DAPI) revealed that the 317L-Cu SS showed strong antibacterial efficacy, achieving a 99% inhibition rate of sessile Staphylococcus aureus cells after 5days. The corrosion data obtained by potentiodynamic polarization curves indicated that in comparison with 317L SS, the pitting potential and corrosion current density of 317L-Cu slightly decreased due to the addition of Cu. The 317L-Cu SS exhibited no cytotoxicity against zebrafish (Danio rerio) embryos. The experimental results in this study demonstrated that the new alloy has potential applications in medical and daily uses., (Copyright © 2016 Elsevier B.V. All rights reserved.)

In order to solve the challenging problem of microbial infections caused by microorganisms on medical implants, it is imperative to develop novel antimicrobial biomaterials. This work demonstrated that 317L-Cu stainless steel (SS), created by adding copper through a solution and aging heat treatment process, exhibited good antibacterial properties against staphylococcus aureus, achieving 2 log reduction of planktonic cells after 5 days of incubation. In this study, the antibacterial test was performed using the plate count method, the fluorescence cell staining method and the quantitative polymerase chain reaction (qPCR) method. It is well known that a high concentration of copper ion can lead to cytotoxicity. This work explored the cytotoxicity of 317L-Cu SS through real-time cell analysis (RTCA). Experimental results demonstrated that the 317L-Cu SS possessed a satisfactory antibacterial ability against S. aureus, and the antibacterial rate based on the reduction of sessile cell count reached 98.3% after 24-hour treatment. The bacterial adhesion and the biofilm thickness were considerably reduced by the 317L-Cu SS. The results of RTCA suggested that 317L-Cu SS did not introduce cytotoxicity to mouse cells, indicating its suitability as a medical implant material.

Microbiologically Influenced Corrosion (MIC) is a serious problem in many industries because it causes huge economic losses. Due to its excellent resistance to chemical corrosion, 2707 hyper duplex stainless steel (2707 HDSS) has been used in the marine environment. However, its resistance to MIC was not experimentally proven. In this study, the MIC behavior of 2707 HDSS caused by the marine aerobe Pseudomonas aeruginosa was investigated. Electrochemical analyses demonstrated a positive shift in the corrosion potential and an increase in the corrosion current density in the presence of the P. aeruginosa biofilm in the 2216E medium. X-ray photoelectron spectroscopy (XPS) analysis results showed a decrease in Cr content on the coupon surface beneath the biofilm. The pit imaging analysis showed that the P. aeruginosa biofilm caused a largest pit depth of 0.69 μm in 14 days of incubation. Although this was quite small, it indicated that 2707 HDSS was not completely immune to MIC by the P. aeruginosa biofilm.

Carbon steels are widely used in the oil and gas industry from downhole tubing to transport trunk lines. Microbes form biofilms, some of which cause the so-called microbiologically influenced corrosion (MIC) of carbon steels. MIC by sulfate reducing bacteria (SRB) is often a leading cause in MIC failures. Electrogenic SRB sessile cells harvest extracellular electrons from elemental iron oxidation for energy production in their metabolism. A previous study suggested that electron mediators riboflavin and flavin adenine dinucleotide (FAD) both accelerated the MIC of 304 stainless steel by the Desulfovibrio vulgaris biofilm that is a corrosive SRB biofilm. Compared with stainless steels, carbon steels are usually far more prone to SRB attacks because SRB biofilms form much denser biofilms on carbon steel surfaces with a sessile cell density that is two orders of magnitude higher. In this work, C1018 carbon steel coupons were used in tests of MIC by D. vulgaris with and without an electron mediator. Experimental weight loss and pit depth data conclusively confirmed that both riboflavin and FAD were able to accelerate D. vulgaris attack against the carbon steel considerably. It has important implications in MIC failure analysis and MIC mitigation in the oil and gas industry.

Cu-bearing antibacterial stainless steels have been gaining popularity in recent years due to their strong antibacterial performances. However, only a few studies were reported for their actual performances against microbiologically influenced corrosion (MIC). In this study, electrochemical methods and surface analytical techniques were applied to study the MIC resistance characteristics of a 304L-Cu stainless steel (SS) against Escherichia coli in comparison with 304L SS as control. Corrosion tests for specimens after a 21-day exposure to a Luria-Bertani (LB) culture medium with E. coli demonstrated that the 304L-Cu SS considerably reduced the maximum MIC pit depth and the specific weight loss compared with 304L SS (8.3μm and 0.2mg/cm(2) vs. 13.4μm and 0.6mg/cm(2)). Potentiodynamic polarization tests showed that the corrosion current density of the 304L-Cu SS was as much as 4 times lower than that of the 304L SS, indicating that the 304L-Cu SS is a better choice for applications in MIC-prone environments., (Copyright © 2014 Elsevier B.V. All rights reserved.)

In the microbiologically influenced corrosion (MIC) caused by sulfate reducing bacteria (SRB), iron oxidation happens outside sessile cells while the utilization of the electrons released by the oxidation process for sulfate reduction occurs in the SRB cytoplasm. Thus, cross-cell wall electron transfer is needed. It can only be achieved by electrogenic biofilms. This work hypothesized that the electron transfer is a bottleneck in MIC by SRB. To prove this, MIC tests were carried out using 304 stainless steel coupons covered with the Desulfovibrio vulgaris (ATCC 7757) biofilm in the ATCC 1249 medium. It was found that both riboflavin and flavin adenine dinucleotide (FAD), two common electron mediators that enhance electron transfer, accelerated pitting corrosion and weight loss on the coupons when 10ppm (w/w) of either of them was added to the culture medium in 7-day anaerobic lab tests. This finding has important implications in MIC forensics and biofilm synergy in MIC that causes billions of dollars of damages to the US industry each year., (Copyright © 2014 Elsevier B.V. All rights reserved.)

The microbiologically influenced corrosion (MIC) resistance of a novel Cu-bearing 2205 duplex stainless steel (2205 Cu-DSS) against an aerobic marine Pseudomonas aeruginosa biofilm was investigated. The electrochemical test results showed that Rp increased and icorr decreased sharply after long-term immersion in the inoculation medium, suggesting that 2205 Cu-DSS possessed excellent MIC resistance to the P. aeruginosa biofilm. Fluorescence microscope images showed that 2205 Cu-DSS possessed a strong antibacterial ability, and its antibacterial efficiency after one and seven days was 7.75% and 96.92%, respectively. The pit morphology comparison after 14 days between 2205 DSS and 2205 Cu-DSS demonstrated that the latter showed a considerably reduced maximum MIC pit depth compared with the former (1.44 μm vs 9.50 μm). The experimental results suggest that inhibition of the biofilm was caused by the copper ions released from the 2205 Cu-DSS, leading to its effective mitigation of MIC by P. aeruginosa.

Three types of stainless steel (304 SS, 410 SS, and 2205 SS) were evaluated for their corrosion behaviors in microbiologically influenced corrosion (MIC) by Desulfovibrio ferrophilus strain IS5, a relatively new and very corrosive sulfate-reducing bacteria (SRB) strain. The incubation lasted for 7 days in enriched artificial seawater at 28°C and the results showed that 410 SS had a rather large weight loss (6.2 mg/cm2) and a maximum pit depth (118 µm), but 2205 SS and 304 SS did not suffer from significant weight loss or pitting. Electrochemical tests indicated that 2205 SS was slightly more resistant to SRB MIC than 304 SS, while 410 SS was far less resistant. [ABSTRACT FROM AUTHOR]

Highlights • Electrochemical noise with Hilbert spectral analysis is used to investigate the corrosion mechanism by marine P. aeruginosa biofilm. • Metastable pitting occurred in the region uncovered by P. aeruginosa. • P. aeruginosa likely dissolved the passive film and produced soluble CrO 3 , leading to stable pitting. Abstract The corrosion mechanism of a 2205 duplex stainless steel (DSS) in Pseudomonas aeruginosa inoculated medium was investigated using the information of electrochemical current noise (ECN) transients derived from Hilbert spectra and surface analysis. The pit depths from confocal laser scanning microscopy (CLSM) were analyzed stochastically. Results showed that metastable pitting and stable pitting occurred simultaneously, and they were controlled by different mechanisms in the presence of P. aeruginosa. Metastable pitting occurred in the region uncovered by P. aeruginosa unlike stable pitting. P. aeruginosa likely dissolved the passive film and produced soluble CrO 3, leading to stable pitting. [ABSTRACT FROM AUTHOR]

Extracellular electron transfer (EET) is believed to be a bottleneck in microbiologically influenced corrosion (MIC), also known as biocorrosion, by electro-active microbes. However, there is a lack of any direct evidence at the genetic level to confirm this so far in the literature. In this work, water-soluble electron transfer mediator molecule phenazine‑1‑carboxamide (PCN) produced by Pseudomonas aeruginosa was found to mediate the EET between P. aeruginosa and 2205 DSS (duplex stainless steel), thus regulating the corrosion rate. The phzH gene in P. aeruginosa encodes the enzyme which converts PCA (phenazine‑1‑carboxamide) to PCN. A P. aeruginosa mutant strain with phzH knockout (Δ phzH strain) and a strain with phzH restored ( phzH -complemented mutant, phzH -comp.) were genetically engineered to confirm that phzH regulates EET-MIC of 2205 DSS by P. aeruginosa . Various electrochemical corrosion data in this work demonstrated that the corrosion rate decreased considerably after knocking out phzH and it largely recovered after phzH was restored. For the first time, it was demonstrated that a gene responsible for the production of an electron transfer mediator in P. aeruginosa regulated MIC, thus confirming at the genetic level that EET is a bottleneck in the MIC by P. aeruginosa . [ABSTRACT FROM AUTHOR]

Different electrochemical techniques and surface analysis methods were used to continuously monitor the corrosion of 2205 duplex stainless steel (DSS) in P. aeruginosa inoculated medium. It was found that linear polarization resistance and electrochemical impedance spectroscopy, significantly inhibited the attachment and growth of the biofilm, due to an internal electric field, leading to lower corrosion rates. In comparison, electrochemical noise as a passive electrochemical measurement technique did not adversely impact the biofilm, and the corrosion rate and the largest pit depth distribution from electrochemical noise were the closest to those from weight-loss data, making it a more suitable technique to monitor MIC by fragile biofilms. [ABSTRACT FROM AUTHOR]

• Stainless steel alloying elements impact SRB sessile cell count considerably. • A lower PREN leads to more severe passive film damage and SRB corrosion. • MIC severity after 14-day incubation is 2205 SS < 316L SS < 304 SS < 410 SS. • 410 SS has the lowest PREN, highest sessile cell count, and most severe MIC. • 410 SS has 0.75 ± 0.12 mg/cm2 weight loss and 35 μm pit depth after 14 days. Stainless steels (SS) are not immune to microbiologically influenced corrosion (MIC) especially in the presence of sulfate reducing bacteria (SRB). It is necessary to study the influence of alloying elements on the MIC. SRB MIC behaviors of four stainless steels (2205 SS, 316L SS, 304 SS, and 410 SS), with different alloying element compositions were compared after 14 days of incubation at 37°C in enriched artificial seawater inoculated with Desulfovibrio sp. The sessile cell sequence was 410 SS > 316L SS > 304 SS > 2205 SS, inversely proportional to Cr content. The uniform corrosion rate (based on weight loss) sequence was 410 SS > 304 SS > 316L SS > 2205 SS, which matches the pitting resistance equivalent number (PREN) sequence inversely. 410 SS with the lowest Cr and Mo contents suffered the most severe pitting, with pit depth of 35 μm and weight loss of 0.75 mg/cm2 (0.91 mm/a pitting rate and 25 μm/a uniform corrosion rate). The other three stainless steels with higher Cr and Mo contents suffered only metastable pits. The semiconductor characteristics and the re-passivation abilities of the passive films were found to be affected by Cr and Mo contents. [ABSTRACT FROM AUTHOR]

In this work, the effects of aging time on intergranular and pitting corrosion behavior of Cu-bearing 304L and 304L stainless steels were investigated by using the double loop electrochemical potentiokinetic reactivation (DL-EPR) and the potentiostatic polarization electrochemical methods. The results showed that the Cu-bearing 304L stainless steel possessed a higher intergranular corrosion tendency and a higher pitting corrosion rate for extended aging time. The TEM observation and 3D APT analysis confirmed that above behavior could mainly attribute to the precipitation of the Cu-rich phase in the Cu-bearing 304L stainless steel. [ABSTRACT FROM AUTHOR]

• A mixed-culture oilfield biofilm is grown in enriched artificial seawater. • It attaches to 304 SS (stainless steel) slightly better than on 316 SS. • R p of 316 SS from LPR is two times of that of 304 SS during 14-day incubation. • i corr of 316 SS is ten times lower than that of 304 SS at the end 14-day incubation. • 316 SS is considerably more resistant to MIC by the oilfield biofilm than 304 SS. Stainless steel (SS) has wide applications in oilfields because of their outstanding corrosion resistance. However, SS is susceptible to localized MIC (microbiologically influenced corrosion). In this study, the MIC caused by an oilfield mixed-culture consortium (labelled as Consortium II) in enriched artificial seawater against commonly utilized 304 SS and 316 SS was evaluated. Sessile cell count results showed that Consortium II had better growth on 304 SS surface than on 316 SS with 79% more sulfate reducing bacteria (SRB) and 37% more acid producing bacteria (APB). Pitting corrosion was observed. The corrosion resistance (R p) from linear polarization resistance (LPR) of 316 SS was two times as much as that for 304 SS during the 14-day incubation, while the corrosion current density (i corr) of 304 SS was 101 higher than that for 316 SS (2.19 µA/cm2 vs. 0.19 µA/cm2) at the end of the incubation. These results suggested that 316 SS was considerably more resistant to MIC by the oilfield biofilm than 304 SS. [ABSTRACT FROM AUTHOR]