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MIC (microbiologically influenced corrosion) is problematic in many industries, especially in the oil and gas industry. In this work, N80 carbon steel for pipelines was tested with 26Cr3Mo chromium pipeline steel for comparison in SRB (sulfate-reducing bacterium) MIC mitigation using a THPS (tetrakis hydroxymethyl phosphonium sulfate)-based commercial biocide (Biotreat 5475 with 75–80% THPS by mass). Peptide A, a nature-mimicking synthetic cyclic peptide (cys-ser-val-pro-tyr-asp-tyr-asn-trp-tyr-ser-asn-trp-cys) with biofilm dispersal ability was used as a biocide enhancer. Metal coupons covered with 3-d old Desulfovibrio ferrophilus IS5 biofilms were immersed in different biocide solutions. After 1-h treatment, 200 ppm Biotreat 5475, 200 ppm Biotreat 5475 + 200 nM (360 ppb) Peptide A, and 400 ppm Biotreat 5475 achieved 0.5-log, 1.7-log and 1.9-log reductions in sessile cell count on N80, and 0.7-log, 1.7-log, and 1.8-log on 26Cr3Mo, respectively. The addition of 200 nM Peptide A cut the THPS biocide dosage by nearly half. Biocide injection tests in electrochemical glass cells after 1 h exhibited 15%, 70%, and 72% corrosion inhibition efficiency (based on corrosion current density) on N80, and 27%, 79%, 75% on 26Cr3Mo, respectively. Linear polarization resistance and electrochemical impedance spectrometry results also indicated antimicrobial efficacies. [ABSTRACT FROM AUTHOR]

Biocorrosion, also called microbiologically influenced corrosion (MIC), is a common operational threat to many industrial processes. It threatens carbon steel, stainless steel and many other metals. In the bioprocessing industry, reactor vessels in biomass processing and bioleaching are prone to MIC. MIC is caused by biofilms. The formation and morphology of biofilms can be impacted by fluid flow. Fluid velocity affects biocide distribution and MIC. Thus, assessing the efficacy of a biocide for the mitigation of MIC under flow condition is desired before a field trial. In this work, a benchtop closed flow loop bioreactor design was used to investigate the biocide mitigation of MIC of C1018 carbon steel at 25 °C for 7 days using enriched artificial seawater. An oilfield biofilm consortium was analyzed using metagenomics. The biofilm consortium was grown anaerobically in the flow loop which had a holding vessel for the culture medium and a chamber to hold C1018 carbon steel coupons. Peptide A (codename) was a chemically synthesized cyclic 14-mer (cys-ser-val-pro-tyr-asp-tyr-asn-trp-tyr-ser-asn-trp-cys) with its core 12-mer sequence originated from a biofilm dispersing protein secreted by a sea anemone which possesses a biofilm-free exterior. It was used as a biocide enhancer. The combination of 50 ppm (w/w) THPS (tetrakis hydroxymethyl phosphonium sulfate) biocide + 100 nM (180 ppb by mass) Peptide A resulted in extra 1-log reduction in the sulfate reducing bacteria (SRB) sessile cell count and the acid producing bacteria (APB) sessile cell count compared to 50 ppm THPS alone treatment. Furthermore, with the enhancement of 100 nM Peptide A, extra 44% reduction in weight loss and 36% abatement in corrosion pit depth were achieved compared to 50 ppm THPS alone treatment. [ABSTRACT FROM AUTHOR]

Microbiologically influenced corrosion (MIC) is one of the major corrosion threats in the oil and gas industry. It is caused by environmental biofilms. Glutaraldehyde is a popular green biocide for mitigating biofilms and MIC. This work investigated the efficacy of glutaraldehyde enhancement by food-grade green chemical d-limonene in the biofilm prevention and MIC mitigation using a mixed-culture oilfield biofilm consortium. After 7 days of incubation at 37 °C in enriched artificial seawater in 125 mL anaerobic vials, the 100 ppm (w/w) glutaraldehyde + 200 ppm d-limonene combination treatment reduced the sessile cell counts on C1018 carbon steel coupons by 2.1−log, 1.7−log, and 2.3−log for sulfate reducing bacteria, acid producing bacteria, and general heterotrophic bacteria, respectively in comparison with the untreated control. The treatment achieved 68% weight loss reduction and 78% pit depth reduction. The 100 ppm glutaraldehyde + 200 ppm d-limonene combination treatment was found more effective in biofilm prevention and MIC mitigation than glutaraldehyde and d-limonene used individually. Electrochemical tests corroborated weight loss and pit depth data trends. [ABSTRACT FROM AUTHOR]

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]

The corrosion mechanism of carbon steel under deposit in the presence of sulfate reducing bacterium (SRB) Desulfotomaculum nigrificans was studied using surface analysis, weight loss and electrochemical measurements. Results showed that both the general corrosion and localized corrosion were considerably promoted by SRB under deposit. The corrosion rate of steel in the presence of SRB was approximately 6 times of that for the control according to the weight loss measurements. The maximum corrosion pit depth in the presence of SRB was approximately 7.7 times of that of the control. Both the anodic and cathodic reactions were significantly accelerated by SRB. A galvanic effect in the presence of SRB due to the heterogeneous biofilm led to serious localized corrosion. [ABSTRACT FROM AUTHOR]

Corrosion of X80 pipeline steel under sulfate-reducing bacterium (SRB) biofilms, which formed in a culture medium at different times, in a simulated CO 2 -saturated oilfield produced water was investigated. Both planktonic and sessile SRB cells survived after 21 days of immersion in the water under carbon source starvation. The biofilms pre-cultured with a longer time increased the corrosion rate of the steel. At 37 °C, it took about 4 days for SRB to grow and then participate in the steel corrosion. The SRB also facilitated localized corrosion. The SRB biofilm, once deactivated, would no longer affect the steel corrosion. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Stress corrosion cracking (SCC) is a serious problem threatening structural integrity and safety. Metal corrosion pits can develop into more harmful cracks under mechanical stress. It is known in abiotic corrosion that fast corrosion does not necessarily cause more severe SCC. This is because fast corrosion can prevent or dissolve crack tips and convert them into less harmful pits if the uniform corrosion rate is fast enough. This work experimentally proved the hypothesis that the same phenomenon occurs in biotic corrosion. It was found that a highly corrosive SRB (sulfate reducing bacterium) strain, namely Desulfovibrio ferrophilus (strain IS5), caused fast uniform corrosion and dull pits, but no SCC cracks against X80 carbon steel U-bend coupons (stressed). In comparison, Desulfovibrio vulgaris , a far less corrosive SRB strain caused less corrosion, but generated sharp pits and SCC cracks in a 3-month lab test. This work also revealed that the X80 U-bend had a 44% higher sessile cell count and 34% higher weight loss after a 14-d D. ferrophilus incubation in deoxygenated enriched artificial seawater culture medium at 28 °C when compared with the (flat) square coupons (no stress). This weight loss trend was corroborated by transient electrochemical measurements. [Display omitted] [ABSTRACT FROM AUTHOR]

Biocorrosion is also known as microbiologically influenced corrosion (MIC). Most anaerobic MIC cases can be classified into two major types. Type I MIC involves non-oxygen oxidants such as sulfate and nitrate that require biocatalysis for their reduction in the cytoplasm of microbes such as sulfate reducing bacteria (SRB) and nitrate reducing bacteria (NRB). This means that the extracellular electrons from the oxidation of metal such as iron must be transported across cell walls into the cytoplasm. Type II MIC involves oxidants such as protons that are secreted by microbes such as acid producing bacteria (APB). The biofilms in this case supply the locally high concentrations of oxidants that are corrosive without biocatalysis. This work describes a mechanistic model that is based on the biocatalytic cathodic sulfate reduction (BCSR) theory. The model utilizes charge transfer and mass transfer concepts to describe the SRB biocorrosion process. The model also includes a mechanism to describe APB attack based on the local acidic pH at a pit bottom. A pitting prediction software package has been created based on the mechanisms. It predicts long-term pitting rates and worst-case scenarios after calibration using SRB short-term pit depth data. Various parameters can be investigated through computer simulation. [ABSTRACT FROM AUTHOR]

The corrosion behavior of carbon steel was investigated in the presence of SRB and IOB separately in their respective culture media and in the mixed culture of SRB and IOB in artificially produced water with 4.2 mg/L dissolved oxygen. The results showed that IOB inhibited the growth of planktonic SRB, but promoted the growth of sessile SRB when SRB was cultured together with IOB. The mixture of SRB and IOB had a synergistic effect enhancing the pitting corrosion of the coupons. The limited amount of dissolved oxygen played a key role in the formation of corrosion products. [ABSTRACT FROM AUTHOR]

Desulfovibrio ferrophilus (IS5) corrosion of X65 carbon steel was impacted by gravity. Six o'clock position (6P) had the highest sessile count due to gravity assisting planktonic cell settling in early biofilm formation, leading to most severe static corrosion followed by 9P and 12P. The 7-d weight loss at 6P was 49.6 ± 4.4 mg/cm2 (3.3 mm/a in uniform corrosion rate) followed by 9P with 35.7 ± 2.6 mg/cm2 (2.4 mm/a) and 12P with 20.5 ± 5.5 mg/cm2 (1.4 mm/a). The trend was supported by electrochemical measurements. The weight loss differences reduced considerably when there was agitation, supporting the gravity hypothesis. • Early SRB biofilm growth is impacted by gravity, favoring 6 o'clock position (6P). • The biofilm sessile cell count sequence is 6P > 9P (side way) >12P (face down). • Weight loss and pit depth sequences after 7-day SRB incubation are 6P > 9P > 12P. • 6P has a uniform corrosion rate of 3.3 mm/a vs. 1.4 mm/a for 12P for 7-d incubation. • Agitation lowered weight loss differences, supporting gravity impact hypothesis. [ABSTRACT FROM AUTHOR]

• Rough surface finish on a coupon facilitates early biofilm development. • Highly-corrosive D. ferrophilus IS5 provides large weight losses. • 36 grit has higher sessile cell count and higher weight loss than 600 grit at 7 d. • These differences wane over time as suggested by 30 d data. • Electrochemical data support weight loss data with additional transient information. Carbon steel microbiologically influenced corrosion (MIC) by sulfate reducing bacteria (SRB) is known to occur via extracellular electron transfer (EET). A higher biofilm sessile cell count leads to more electrons being harvested for sulfate reduction by SRB in energy production. Metal surface roughness can impact the severity of MIC by SRB because of varied biofilm attachment. C1018 carbon steel coupons (1.2 cm2 top working surface) polished to 36 grit (4.06 μm roughness which is relatively rough) and 600 grit (0.13 μm) were incubated in enriched artificial seawater inoculated with highly corrosive Desulfovibrio ferrophilus IS5 at 28 ℃ for 7 d and 30 d. It was found that after 7 d of SRB incubation, 36 grit coupons had a 11% higher sessile cell count at (2.0 ± 0.17) × 108 cells/cm2, 52% higher weight loss at 22.4 ± 5.9 mg/cm2 (1.48 ± 0.39 mm/a uniform corrosion rate), and 18% higher maximum pit depth at 53 μm compared with 600 grit coupons. However, after 30 d, the differences diminished. Electrochemical tests with transient information supported the weight loss data trends. This work suggests that a rougher surface facilitates initial biofilm establishment but provides no long-term advantage for increased biofilm growth. [ABSTRACT FROM AUTHOR]

Bifunctional antibacterial and anticorrosive broad-spectrum rosin thiourea iminazole quaternary ammonium salt (RTIQAS) was investigated to inhibit microbiologically influenced corrosion (MIC) caused by anaerobic gram-negative sulfate reducing bacterium (SRB) Desulfovibrio vulgaris against X80 carbon steel and aerobic gram-positive bacterium Bacillus licheniformis against 316L stainless steel. It also indicated that RTIQAS was more effective than common commercial biocides THPS (tetrakis hydroxymethyl phosphonium sulfate) and glutaraldehyde at the same concentration against X80 carbon steel corrosion by D. vulgaris. In the molecular simulation, the interaction energy confirmed the favorable adsorption of RTIQAS on the metal surfaces, indicating its potential as an effective corrosion inhibitor. • A bifunctional antibacterial and anticorrosive inhibitor RTIQAS was synthesized. • RTIQAS had antibacterial performances against anaerobic Desulfovibrio vulgaris on X80 carbon steel. • RTIQAS presented antibacterial abilities against aerobic Bacillus licheniformis on 316 L stainless steel. • RTIQAS showed better inhibition effect than two common commercial biocides against D. vulgaris. • RTIQAS molecules were adsorbed on iron surface based on molecular [ABSTRACT FROM AUTHOR]

Abstract: Generally speaking, a much higher concentration of biocide is needed to treat biofilms compared to the dosage used to for planktonic bacteria. With increasing restrictions of environmental regulations and safety concerns on large-scale biocide uses such as oil field applications, it is highly desirable to make more effective use of biocides. In this paper a green biocide enhancer ethylenediaminedisuccinate (EDDS) that is a biodegradable chelator, was found to enhance the efficacy of glutaraldehyde in its treatment of sulfate-reducing bacteria (SRB) biofilms. Experiments were carried out in 100 ml anaerobic vials with carbon steel coupons. The ATCC 14563 strain of Desulfovibrio desulfuricans was used. Biofilms on coupon surfaces were visualized using scanning electron microscopy (SEM). Experimental results showed that EDDS reduced the glutaraldehyde dosages considerably in the inhibition of SRB biofilm establishment and the treatment of established biofilms on carbon steel coupon surfaces. [Copyright &y& Elsevier]

Sulfate-reducing bacterium Desulfovibrio vulgaris promoted the microbiologically influenced corrosion (MIC) of CoCrFeMnNi high entropy alloy (HEA) and led to pitting corrosion. D. vulgaris caused the formation of metal sulfides and thinning of passive film. The corrosion resistance decreased, and pit depths increased when the carbon source reduced to 40%. The relative expression of hydrogenase genes hydA and hydB in the biofilms under 40% carbon source significantly increased, indicating that the indirect electron transfer mediated by 2H+/H 2 might play an important role in promoting the HEA MIC by D. vulgaris under starvation. • Desulfovibrio vulgaris promotes CoCrFeMnNi HEA MIC and causes pitting corrosion. • The presence of D. vulgaris causes the thinning of HEA passive film. • In the starved 40% carbon source level, D. vulgaris leads to more aggressive HEA MIC. • Two hydrogenase genes (hydA and hydB) upregulate in the starvation condition. • The indirect electron transfer mediated by 2H+/H 2 may play an important role in starvation. [ABSTRACT FROM AUTHOR]

• More Fe2+ leads to better planktonic and sessile Desulfovibrio vulgaris growth. • More Fe2+ increases dissolved H 2 S concentration despite increased FeS precipitation. • More Fe2+ in the culture medium increases carbon steel weight loss and pit depth. • With more Fe2+, increased corrosion is primarily attributed to more sessile cells. • Electrochemical measurements corroborate weight loss and pit depth data. Ferrous ion (Fe2+) in a sulfate reducing bacteria (SRB) culture medium is known to enhance microbiologically influenced corrosion (MIC) of carbon steel, but the underlining mechanism is controversial. This work showed that it was due to better sessile cell growth that was likely attributed to Fe2+ detoxification of H 2 S. Two hundred ppm (w/w) initial Fe2+ in the ATCC 1249 medium achieved a 4.7 times higher Desulfovibrio vulgaris sessile cell count and 5.0 times higher C1018 carbon steel weight loss, compared to 20 ppm. Linear polarization resistance, electrochemical impedance spectroscopy and potentiodynamic polarization measurements corroborated weight loss and pitting data trends. [ABSTRACT FROM AUTHOR]

Highlights • D. vulgaris is pre-grown on C1018 carbon steel coupons before the starvation test. • Carbon source starvation weakens the SRB biofilm but still increases weight loss. • Weight loss is 6.6 mg/cm2 for 20% carbon source vs. 3.3 mg/cm2 for 100% after 10 d. • Pit depth and electrochemical measurement data corroborate weight loss trend. • Iron corrosion by SRB belongs to extracellular electron transfer MIC (EET-MIC). Abstract Microbiologically influenced corrosion (MIC) of carbon steel by sulfate reducing bacterium (SRB) Desulfovibrio vulgaris under organic carbon starvation was investigated using electrochemical methods to support weight loss and pitting data. 20% carbon source led to the highest weight loss (6.6 mg/cm2), while 100% had the lowest (3.3 mg/cm2) after 10 days. Linear polarization resistance and electrochemical impedance spectrometry data confirmed the weight loss and pitting data trends. The data in this work support the theory that carbon steel corrosion by SRB is due to electron harvest from extracellular iron oxidation by SRB, which belongs to extracellular electron transfer MIC (EET-MIC). [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Molecular simulation confirms that sodium pyrithione (SPT) inhibits iron corrosion. • SPT is found to inhibit planktonic and sessile sulfate reducing bacteria (SRB). • SRB corrosion rate in simulated oilfield produced water is reduced by SPT. • SRB corrosion weight loss data are corroborated by electrochemical measurements. Abstract Anti–bacterial and anti–corrosion properties of sodium pyrithione (SPT) were studied using experimental methods and quantum chemical calculations. SPT at 80 mg/L reduced planktonic and sessile sulfate reducing bacteria (SRB) on X80 carbon steel to undetectable levels. The corrosion inhibition efficiency of SPT against microbiologically influenced corrosion exceeded 80% based on weight loss, which was corroborated by electrochemical data. Molecular modeling showed that SPT molecule provided electrons to the unoccupied orbitals of the Fe surface with a large binding energy of SPT on the Fe (1 1 0) plane, which favored SPT adsorption on the carbon steel. [ABSTRACT FROM AUTHOR]

Abstract A biocide enhancer is a chemical that can enhance the efficacy of a biocide or reduce its dosage. In this work, a novel peptide was tested as a biocide enhancer. A chemically synthesized 14-mer peptide (Peptide A), which was found non-biocidal, has an amino acid sequence derived from sea anemone Actinia equina that possesses a biofilm-free exterior. Peptide A at 180 ppb (w/w) or 100 nM enhanced 100 ppm tetrakis hydroxymethyl phosphonium sulfate (THPS) against an oilfield biofilm consortium grown on C1018 carbon steel in an enriched artificial seawater medium. The combination of 100 nM Peptide A + 100 ppm THPS led to additional 2-log reduction, 1-log reduction, 1-log reduction in sessile sulfate reducing bacteria (SRB) cell count, sessile acid producing bacteria (APB) cell count, and sessile general heterotrophic bacteria (GHB) cell count, in comparison with the treatment using 100 ppm THPS alone in a 14-day laboratory biofilm prevention test. The data in this work suggest that non-biocidal Peptide A is a promising biocide enhancer that should be further explored. Graphical abstract Image 1 Highlights • Cyclic Peptide A is engineered based on a 12-mer sequence in Equinatoxin II protein. • Peptide A reduces tetrakis (hydroxymethyl) phosphonium sulfate (THPS) dosage. • Peptide A at ppb levels enhances the biocide against an oilfield biofilm consortium. • The biocide cocktail reduces carbon steel weight loss and maximum pit depth. • Linear polarization resistance results corroborate weight loss and pitting data. [ABSTRACT FROM AUTHOR]

Highlights • Archaeoglobus fulgidus is a very corrosive sulfate reducing archaeon at 80 °C. • Pre-grown A. fulgidus biofilm is more corrosive under carbon source starvation. • Its corrosion type is extracellular electron transfer MIC (EET-MIC). • This archaeon is capable of using elemental iron as an electron donor. • Linear polarization resistance data support MIC weight loss and pit depth data. Abstract Mature sulfate reducing archaeon (Archaeoglobus fulgidus) biofilm at 80 °C was found more corrosive against C1018 carbon steel under organic carbon starvation. After 3-day pre-growth in enriched artificial seawater medium (EASW), C1018 coupons with biofilms were placed in fresh EASW with reduced carbon source levels for an additional 7 days of incubation. Coupon weight losses were 0.9 mg/cm2, 2.0 mg/cm2 and 1.4 mg/cm2 for this subsequent 7-day starvation period, corresponding to 0%, 90% and 100% carbon source reductions, respectively. Electrochemical tests corroborated the weight loss data, providing evidence for the utilization of elemental iron as electron donor through extracellular electron transfer. [ABSTRACT FROM AUTHOR]

Highlights • Cu MIC by sulfate reducing bacteria (SRB) is shown to be metabolite MIC (M-MIC). • Carbon starvation reduces H 2 S secretion and thus decreases M-MIC of Cu. • In comparison, carbon starvation causes more aggressive MIC against carbon steel. • Cu MIC by SRB causes considerable uniform corrosion with occasional pits. • Cu MIC by SRB and carbon steel MIC by SRB belong to two different MIC types. Abstract Cu corrosion by Desulfovibrio vulgaris , an example of sulfate reducing bacteria (SRB), was investigated. D. vulgaris was first pre-grown in full-strength ATCC 1249 medium with coupons for three days. Then, the medium was switched to fresh media with decreased levels of carbon source. Unlike microbiologically influenced corrosion (MIC) of carbon steel by D. vulgaris , carbon starvation reduced Cu corrosion during the additional seven days of incubation. Experimental data and a thermodynamic analysis indicated that Cu MIC by SRB was caused by secreted sulfide rather than by electron harvesting for energy production, unlikely in the carbon steel MIC by SRB. [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]

• Ti is not completely immune to SRB (sulfate reducing bacteria) corrosion. • Carbon source starvation and riboflavin both accelerate Ti MIC by D. vulgaris. • Various electrochemical tests confirm increased Ti MIC under SRB starvation. • SRB MIC of Ti mechanism is extracellular electron transfer-MIC (EET-MIC) • Ti MIC pit depth of up to 6.2 µm is observed after 14 d SRB incubation. Desulfovibrio vulgaris biofilm was pre-grown on Ti coupons for 7 d and then the biofilm covered coupons were incubated again with fresh culture media with 10 % (reduced) and 100 % (normal) carbon source levels, respectively. After the pre-growth, sessile D. vulgaris cell count reached 107 cells/cm2. The sessile cell counts were 2 × 107 and 4.2 × 107 cells/cm2 for 10 % and 100 % carbon sources, respectively after the subsequent 7 d starvation test. The maximum pit depth after the 7 d pre-growth was 4.7 µm. After the additional 7 d of the starvation test, the maximum pit depth increased to 5.1 µm for 100 % carbon source vs 6.2 µm for 10 % carbon source. Corrosion current density (i corr) from potentiodynamic polarization data at the end of the 7 d starvation test for 10 % carbon source was more than 3 times of that for 100 % carbon source, despite a reduced sessile cell count with 10 % carbon source. The polarization resistance (R p) started to decrease within minutes after 20 ppm (w/w) riboflavin (electron mediator) injection. The carbon starvation data and riboflavin corrosion acceleration data both suggested that D. vulgaris utilized elemental Ti as an electron source to replace carbon source as the electron donor during carbon source starvation. [ABSTRACT FROM AUTHOR]

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 10 ppm (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. [ABSTRACT FROM AUTHOR]

The effects of magnetic fields (MFs)on the corrosion of 304 stainlesssteel (SS304) caused by oil-field sulfate-reducing bacteria (SRB)were investigated. Experimental data showed that the MF lowered thepopulation of planktonic SRB by almost 4 orders of magnitude and delayedthe formation of SRB biofilms on the SS304 coupons. The mass lossesand surface images of the coupons indicated that the application ofan MF considerably reduced the pitting corrosion of SS304. EDX andXPS analyses of the coupon surfaces demonstrated that the main corrosionproducts without an MF and with 2 and 4 mT MFs were FeS, FeO, andFe2O3, respectively. The application of MFscould be an environmentally friendly method for mitigating microbiologicallyinfluenced corrosion (MIC) on SS304. [ABSTRACT FROM AUTHOR]

Abstract: Nitrate injection is used to suppress reservoir souring in oil and gas fields caused by Sulfate Reducing Bacteria (SRB) through promotion of nitrate respiration by Nitrate Reducing Bacteria (NRB). However, it is not well publicized that nitrate reduction by NRB can cause Microbiologically Influenced Corrosion (MIC) because nitrate reduction coupled with iron oxidation is thermodynamically favorable. NRB benefits bioenergetically from this redox reaction under biocatalysis. This work showed that the Bacillus licheniformis biofilm, when grown as an NRB biofilm, caused a 14.5μm maximum pit depth and 0.89mg/cm2 normalized weight loss against C1018 carbon steel in one-week lab tests. [Copyright &y& Elsevier]

• Data confirm extracellular electron transfer MIC (EET-MIC) mechanism. • Riboflavin enhances Desulfovibrio ferrophilus IS5 EET-MIC considerably. • Very high carbon steel pitting corrosion rate for a pure-strain SRB is shown. • H 2 evolution data rule out acid and H 2 S corrosion as significant contributors. • D. ferrophilus biofilm starts to respond to riboflavin injection within minutes. EET (extracellular electron transfer) is behind MIC (microbiologically influenced corrosion) of carbon steel by SRB (sulfate reducing bacteria). This work evaluated 20 ppm (w/w) riboflavin (an electron mediator) acceleration of C1018 carbon steel MIC by Desulfovibrio ferrophilus IS5 in enriched artificial seawater (EASW) after 7-d incubation in anaerobic vials at 28 °C. Twenty ppm riboflavin did not significantly change cell growth or alter the corrosion product varieties, but it led to 52% increase in weight loss and 105% increase in pit depth, compared to the control without 20 ppm riboflavin. With 20 ppm riboflavin supplement in EASW, D. ferrophilus yielded weight loss-based corrosion rate of 1.57 mm/y (61.8 mpy), and pit depth growth rate of 2.88 mm/y (113 mpy), highest reported for short-term pure-strain SRB MIC of carbon steel. Electrochemical tests in 450 mL glass cells indicated that the biofilm responded rather quickly to the riboflavin injection (20 ppm in broth) to the culture medium. Polarization resistance (R p) began to decrease within minutes after injection. Within 2 h, the riboflavin injection led to 31% decrease in R p and 35% decrease in R ct + R f from electrochemical impedance spectroscopy (EIS). The Tafel corrosion current density increased 63% 2 h after the injection. [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]

The microbiologically influenced corrosion (MIC) of zinc and galvanized steel caused by a sulfate reducing bacterium (SRB) was investigated. After 7 days of incubation of Desulfovibrio vulgaris in 125 mL anaerobic vials (100 mL culture medium) at 37 °C, the sessile cell coverage on the galvanized steel was slightly higher than that on pure zinc: (1.9 ± 0.2) × 109 cells/cm2 vs. (9.0 ± 1.8) × 108 cells/cm2. The weight losses for galvanized steel and pure zinc were 31.5 ± 2.5 mg/cm2 and 35.4 ± 4.5 mg/cm2, respectively, which were 101 higher than that for carbon steel. The corrosion current densities of galvanized and pure zinc were 25.5 μA/cm2 and 100 μA/cm2, respectively after the 7-day incubation, confirming that galvanized steel was less prone to SRB MIC despite having a slightly higher sessile cell count. In both cases, the corrosion product was mainly ZnS. Three MIC mechanisms were possible for the severe corrosion against the two metals. Extracellular electron transfer MIC (EET-MIC) was thermodynamically favorable for zinc. Furthermore, in the presence of Zn coupons, H 2 evolution in the headspace was 5.5 times higher than without Zn coupons, which suggested that proton attack and/or H 2 S attack also occurred in the corrosion process. • Desulfovibrio vulgaris forms dense biofilms on zinc and galvanized steel. • Three MIC mechanisms are possible for the severe MIC of the two metals. • Zinc and galvanized steel weight losses are 10X larger than that of C1018 carbon steel. • Electrochemical test results are consistent with weight loss and pitting data trends. • H 2 evolution is used to detect corrosion by proton and H 2 S attacks. [ABSTRACT FROM AUTHOR]

• Carbon steel MIC by SRB belongs to extracellular electron transfer MIC (EET-MIC). • Cu MIC by SRB belongs to metabolite-MIC (M-MIC), unaffected by EET. • EET-MIC is accelerated by an electron mediator, but M-MIC is not. • Electron mediator is a useful tool to distinguish EET-MIC from M-MIC. • H 2 detection is a very sensitive tool to confirm M-MIC with H 2 evolution. Carbon steel MIC (microbiologically influenced corrosion) and copper MIC by Desulfovibrio vulgaris (a sulfate reducing bacterium) were shown to behave very differently. Carbon steel MIC was accelerated with an 84 % weight loss increase by 20 ppm (w/w) riboflavin (an electron mediator) while Cu MIC was not. This was because the former belongs to extracellular electron transfer (EET)-MIC while the latter metabolite (M)-MIC. Cu MIC by biogenic H 2 S yielded a large amount of H 2. This work proved that an electron mediator can distinguish EET-MIC from M-MIC, and H 2 gas detection is very sensitive in identifying M-MIC with H 2 evolution. [ABSTRACT FROM AUTHOR]

• Cu MIC by sulfate reducing bacteria (SRB) is proven to be metabolite-MIC (M-MIC). • A smaller headspace leads to a higher dissolved [H 2 S] and lower sessile cell count. • This higher [H 2 S] with fewer sessile cells leads to more severe Cu weight loss. • High [H 2 S] causes severe uniform corrosion accompanied by pitting corrosion of Cu. • Low [H 2 S] causes uniform corrosion accompanied by intergranular corrosion of Cu. Microbiologically influenced corrosion (MIC) of copper by Desulfovibrio vulgaris , a sulfate reducing bacterium (SRB), was investigated in anaerobic vials with a fixed broth volume of 40 mL but varied headspace volumes (10 mL, 85 mL 160 mL). It was found that the headspace volume variation had a very large effect on the dissolved [H 2 S] in the broth and the cell counts of planktonic and sessile cells, as well as Cu corrosion severity. A 16× smaller headspace led to a 1.6-fold increase in the dissolved [H 2 S], a 13-fold decrease in sessile SRB cell count, a 32-fold decrease in planktonic cell count and a 3.7-fold increase of Cu weight loss. SEM images revealed that different headspace volumes caused different corrosion patterns on the immersed coupons. With a lower headspace volume, pitting corrosion was observed, while with a higher headspace volume, intergranular corrosion was seen. The results confirmed that SRB MIC of Cu belongs to metabolite-MIC (M-MIC) by H 2 S, unlike SRB MIC of carbon steel that belongs to extracellular electron transfer-MIC (EET-MIC) that is directly correlated with sessile cell counts rather than dissolved [H 2 S].. [ABSTRACT FROM AUTHOR]