Microbiologically Influenced Corrosion Research Articles

Responses of soil microbiome to steel corrosion

The process of microbiologically influenced corrosion (MIC) in soils has received widespread attention. Herein, long-term outdoor soil burial experiments were conducted to elucidate the community composition and functional interaction of soil microorganisms associated with metal corrosion. The results indicated that iron-oxidizing (e.g., Gallionella), nitrifying (e.g., Nitrospira), and denitrifying (e.g., Hydrogenophaga) microorganisms were significantly enriched in response to metal corrosion and were positively correlated with the metal mass loss. Corrosion process may promote the preferential growth of the abundant microbes. The functional annotation revealed that the metabolic processes of nitrogen cycling and electron transfer pathways were strengthened, and also that the corrosion of metals in soil was closely associated with the biogeochemical cycling of iron and nitrogen elements and extracellular electron transfer. Niche disturbance of microbial communities induced by the buried metals facilitated the synergetic effect of the major MIC participants. The co-occurrence network analysis suggested possible niche correlations among corrosion related bioindicators.

Leak failure at the TP316L welds of a water pipe caused by microbiologically influenced corrosion

Water leaking through a pinhole from an ASTM A312-TP316L stainless steel pipe was investigated. The pipes had been used for transferring a large amount of potable water. Multiple leaks were found at the circumferential welds of the pipe after a short term of service. An analysis using an optical microscope, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) was conducted to explore the root cause of the failure.The results demonstrated that the perforation of the pipe was due to localized corrosion initiated from the inside at the many small pits penetrating to the outside of the pipe. Corrosion pits were located near the heat-affected zone (HAZ), which is the area most susceptible to a corrosion attack. The microbiologically influenced corrosion (MIC) was identified as the primary cause of perforation failure. Corrosion attacks occurred predominantly at the microstructure of ferrite stringers. Spheroidal corpuscles were observed with a high concentration of sulfur, which indicated that sulfate-reducing bacteria (SRB) were creating a biofilm, accelerating the MIC corrosion process. Slightly concave surfaces near the weld of the pipe exhibited evidence of bacterial attack or residue of microorganisms, where the leak occurred.

A comparative study on the corrosion of gathering pipelines in two sections of a shale gas field

Sixty-eight pipeline failures occurred at the gas-gathering stations located in the southwestern section of a shale gas field, whereas no failures were reported for the corresponding pipelines in the northeastern section of the same field. This paper reports a comprehensive comparative analysis of the pipeline failures in the two sections of the field. Failure case statistical analyses, environmental media inspection, matrix materials examination, macro- and microscopic morphologies observation, corrosion products detection, and CFD analysis were carried out to understand the significant difference between two sections in terms of pipeline failures. Our analyses demonstrate that an abundance of bacteria were present in the water produced in both sections of the shale gas field. Most of the pipeline failures occurred after approximately 1 year. The number of failures tended to increase significantly over 3 years of service. Pitting corrosion at the bottom of pipelines, erosion-corrosion and weld corrosion at elbows were identified as the key contributing causes of the pipeline failures. Microbiologically influenced corrosion (MIC) and under-deposit corrosion was the root cause of sixty-six percent of pitting corrosion failures at the bottom of the pipelines. Erosion-corrosion and weld corrosion at elbows totally accounted for 34% of failures. Flow characteristics in the pipelines were finally determined to be one of the underlying causes of the notable difference in the corrosion behavior of the pipelines in the two sections. Pertinent countermeasures have been proposed in this paper. It is hoped that this work will help corrosion engineers involved with designing, monitoring, and managing pipelines to improve their designs and subsequent monitoring and treatment of pipelines to prevent premature failure of gathering pipelines in shale gas fields.

Zinc-Based Additives for Biofouling and MIC Protection: Fabrication Method for Long-Term Efficacy

Microbiologically influenced corrosion (MIC) and biofouling both begin with an initial layer of bacteria accumulating on a hard surface exposed to the natural environment. These bacteria quickly form a biofilm which becomes the feeding source for marine life fouling and the root of both of these highly damaging, expensive types of corrosion. Preventative methods for biofilm development is an ongoing field of study due to critical necessity in many industries including healthcare, aerospace, and oil and gas. Today, biofilm inhibitors for the oil and gas industry may include regular cleaning or scraping of the affected surface, electrochemical processes, or biocide injections which have a negative impact on the environment and provide only temporary relief from MIC. This constant need for MIC and fouling remediation creates a great demand and thus market potential for long-term, more environmentally conscious methods to mitigate and control biofilm development. This study investigates the incorporation of well-known biocidal materials as well as one commercial additive into the fabrication process of underwater structures and surfaces. High Density Polyethylene (HDPE) and Fiber Reinforced Plastic (FRP) with antimicrobial additive were processed. Experiments were conducted per ASTM E2149-13a and F895 to evaluate antibacterial efficacy in the laboratory. Field tests were constructed per ASTM D3623 - 78a for material evaluation in offshore fouling conditions. The manufactured materials were tested against gram-positive and gram-negative bacteria and fouling microorganisms to analyze the effectiveness of biofilm prevention. Results showed positive efficacy of biocidal additives incorporated through the fabrication process in all cases including copper, multiple forms of zinc, and titanium dioxide. The commercially available additive produced the largest zone of inhibition and highest reduction of colony forming units in dynamic flow conditions. Fouling tests show that the incorporation of the additive into HDPE and FRP provides a surface protection and thus serves as an agent for material preservation. Results from this study demonstrate innovative and effective methods for surface protection from MIC and biofouling by incorporating antimicrobial additives into the structural matrix during the manufacturing process.

Corrosion Behavior and Action on Microbes of Copper in a Freshwater Microbiologically Influenced Corrosion Risk Environment

Corrosion Behavior and Action on Microbes of Copper in a Freshwater Microbiologically Influenced Corrosion Risk Environment

Biocorrosion caused by microbial biofilms is ubiquitous around us.

Biocorrosion first surfaced in the scientific literature when Richard H. Gaines associated corrosion with bacterial activities in 1910. It is also known as microbiologically influenced corrosion (MIC). In general, it covers two scenarios. One is that microbes cause corrosion directly, which usually means microbes secrete corrosive metabolites or microbes harvest electrons from a metal for respiration to produce energy. In the second scenario, microbes are behind the initiation or acceleration of corrosion caused by a pre-existing corrosive agent such as water and CO2 , by compromising the passive film (often a metal oxide film on a metal). MIC is caused by microbial biofilms. It is everywhere around us. This work dissects some notable examples with perspectives.

Sulfate reducing bacterium Desulfovibrio vulgaris caused severe microbiologically influenced corrosion of zinc and galvanized steel

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, H2 evolution in the headspace was 5.5 times higher than without Zn coupons, which suggested that proton attack and/or H2S attack also occurred in the corrosion process.

Electron transfer mediator PCN secreted by aerobic marine Pseudomonas aeruginosa accelerates microbiologically influenced corrosion of TC4 titanium alloy

Titanium alloys possess excellent corrosion resistance in marine environments, thus the possibility of their corrosion caused by marine microorganisms is neglected. In this work, microbiologically influenced corrosion (MIC) of TC4 titanium alloy caused by marine Pseudomonas aeruginosa was investigated through electrochemical and surface characterizations during a 14-day immersion test. Results revealed that the unstable surface caused by P. aeruginosa resulted in exposure of Ti2O3 and severe pitting corrosion with maximum pit depth of 5.7 μm after 14 days of incubation. Phenazine-1-carboxylate (PCN), secreted by P. aeruginosa, promoted extracellular electron transfer (EET) and accelerated corrosion. Deletion of the phzH gene, which codes for the enzyme that catalyzes PCN production, from the P. aeruginosa genome, resulted in significantly decreased rates of corrosion. These results demonstrate that TC4 titanium alloy is not immune to marine MIC, and EET contributes to the corrosion of TC4 titanium alloy caused by P. aeruginosa.

Constructing nanostructured functional film on EH40 steel surface for anti-adhesion of Pseudomonas aeruginosa

Biofilm formation is an important cause of microbiologically influenced corrosion (MIC), and inhibition of microbial adhesion is one of the most effective ways to control biofilm formation. In this work, nanostructured functional film of EH40 steel is prepared by one-step anodization in NaOH solution to inhibit adhesion of Pseudomonas aeruginosa (P. aeruginosa) without and with light. Results show that the functional films fabricated on EH40 steel surface in a series of NaOH solutions inhibit the adhesion of P. aeruginosa, and its anti-adhesion performance first increases and then decreases with varying concentrations of NaOH solution. The optimal anti-adhesion performance under dark condition, i.e., anti-adhesion rate of 92.7% compared with bare steel, is obtained for the nanostructured oxide film fabricated in 12 M NaOH solution under anodization potential of 1.0 V for 2 h. Under visible light irradiation, the best anti-adhesion rate increases to 99.9% due to hydroxyl radicals (OH) produced by the nanostructured oxide film with photocatalytic activity.

Myrtus communis extract: a bio-controller for microbial corrosion induced by sulphate reducing bacteria

ABSTRACT This study aimed to study the inhibitory effect of the Myrtus communis extract on the microbiologically influenced corrosion (MIC) induced by sulphate reducing bacterial (SRB) consortium in the cooling tower water. The SRB consortium was grown on the surface of the st37 steel and its effects on the surface corrosion were evaluated. The results of electrochemical measurements and microscopic observations revealed that the extract could significantly reduce the corrosion by inhibiting the SRB biofilm formation. The addition of the 0.781 mg ml−1 of the extract into the SRB medium led to a considerable reduction (about seven times) in the corrosion process of the st37 steel and kept it at an almost constant value. Based on Gas chromatography-mass spectrometry analysis, 2-Furancarboxaldehyde, 5-(hydroxymethyl) (42.396%) was the most abundant compound identified in the plant extract. The molecular identification has proved that most population of SRB consortium was related to Desulfovibrio vulgaris species.

Application of EIS to Assess Microbiologically Influenced Steel Corrosion in Marine Fouling Crevice Conditions

Microbiologically influenced corrosion (MIC) can cause severe degradation of civil infrastructure. Recently, severe localized corrosion of steel H-piles submerged in a brackish natural water in a Florida bridge was associated with MIC and fouling (Permeh et al., 2017). The localized corrosion cells/pits were of up to 3" in diameter and penetrated through the steel thickness. Microbiological and chemical analysis of the water samples showed a high population of sulfate reducing bacteria (SRB) and a high concentration of sulfate ions amongst other nutrients. The steel piles had noticeable heavy marine growth which were thought to have an effect on the corrosion process by supporting biofilm development, creating localized corrosion and differential aeration cells (Little et al, 2007). In the work described here electrochemical impedance spectroscopy (EIS) was conducted to characterize the development of biofilm in association with fouling crevice environments.Electrochemical impedance spectroscopy (EIS) has been widely used to assess the electrochemical properties of corrosion systems and has been applied to assess physical biofilm conditions for microbiologically influenced corrosion (MIC) (Mansfeld , 2005). EIS measurements over a wide range of frequencies can be used to identify the electrical characteristics associated with the biofilm and the steel substrate. Both laboratory and field exposure tests were conducted. Field exposure tests included long term exposure (~300 days) of steel coupons at a Florida bridge site that sustained macro- and microfouling organisms. Laboratory tests were conducted in nutrient-rich test solutions inoculated with sulfate reducing bacteria (SRB) in either de-aerated or naturally aerated conditions as well as with idealized crevice geometries. EIS testing was made at the OCP condition with 10 mV AC perturbation voltage from frequencies 100 kHz > f >100 mHz.EIS of the specimens inoculated with SRB and with crevices resulted in impedance responses with multiple loops in the Nyquist diagram. Fitting of the impedance response to equivalent circuit analogs were made to identify biofilm, surface layers, and the steel interfacial characteristics during the experimental exposure (Permeh et al.,2019). For non-crevice specimens without SRB inoculations, the impedance response related to the solution resistance, steel interfacial capacitance and charge transfer resistance, characterized by the Randles circuit. However, for the inoculated specimens, impedance dispersion at high frequencies (sometimes showing a loop in the Nyquist diagram) on first approximation was related to the capacitive and resistive characteristics of the biofilm. In crevice environments, a more complicated behavior arose due to uneven current distribution and heterogeneous impedance within the crevice. The impedance behavior for the porous and laminate crevices can be characterized by multiple time constants associated with the crevice outer material, steel interface, and the current distribution effects in the crevice that can be considered by treatments such as a transmission line. In the inoculated non-crevice specimens, the high frequency impedance dispersion was more readily apparent in the Bode phase angle plot. In that representation, the impedance initially showed a uniform valley with a distinct trough between 10 and 100 mHz. With time, two unique troughs developed at frequencies below 1 Hz (Figure 1) for the inoculated specimens. An increase in capacitance was attributed to biofilm growth.In part to provide a quantitative comparison of the overall impedance of the systems (despite the complicating factors for the crevice specimens), on first approach, the total impedance at 100 mHz (|Z100mHz¬|) was compared. The differences in the total impedance for the various test conditions would reflect the resistive and capacitive electrical behavior of the electrolyte, biofilm, and the steel interface that in turn are directly or indirectly related to SRB activity. EIS identified the development of surface films including by an increase in its capacitive behavior that resulted in lower relative total impedance at a given low frequency (i.e. 100 mHz). Test results confirmed that SRB proliferation and corrosion can occur as the fouling macroorganism can accommodate different environmental condition.

New Highly Microbial-Induced Corrosion-Resistant Ni-P-Based Coating with Superior Mechanical Properties.

Microbiologically Influenced Corrosion (MIC) has been recognized as a widespread problem in the oil and gas industries because it causes substantial economic losses. Sulfate reducing bacteria (SRB) is one of the essential microorganisms families that have always been linked to MIC mechanisms causing localized corrosion problems. Since the bacterial adhesion on the metal surfaces is a prerequisite condition for the biofilm formation, controlling, and prevention of the colonization/proliferation of the microbial biofilms is of the critical impact regarding the MIC prevention and ensuring the public safety. Titanium-nickel shape memory alloy (TiNi SMA) nanoparticles have several marvelous features, ranging from the physical and chemical properties to the biological performance. Our electroless-plated NiP-TiNi nanocomposite coating (NiP-TiNi NCC) is used to determine the suitability of using it as an inhibition system for SRB on carbon steel (CS). The influence of anaerobic bacteria SRB on the corrosion behavior of API X80 CS, NiP, and NiP-TiNi coatings in simulated seawater was studied by electrochemical impedance spectroscopy (EIS) after different periods of incubation time (7, 10, 14, 21, 28 days). The corrosion products and biofilm formation of the incubated specimens’ surfaces after 7, 10, and 28 days of incubation are checked using the scanning electron microscope (SEM) and X-ray photoelectron spectroscopy. EIS results revealed that the antimicrobial performance of the NiP-TiNi NCC is more efficient compared to the TiNi-free coating that has an inhibition efficiency of 87.5 % after 28 days of incubation time with SRB. Furthermore, SEM, EDS and XPS results confirm that negligible corrosion occurrs for the coated surfaces. Also, The mechanical properties of this coating was proved be superior compared to the Carabon steel and the NiP-based coatings.

(Keynote) Corrosion of 1018 Plain Carbon Steel in Petroleum-Based and Renewable Diesel Fuel/Seawater Mixtures

The substitution of biofuels for conventional fuels can result in unexpected issues and forms of corrosion. A study was conducted on corrosion rates and the identification of corrosion products that formed on plain-carbon 1018 steel (UNS G10180) exposed in seawater/fuel mixtures of petroleum-based F-76; a 50%:50% by volume (50:50 v/v) blend of F-76 and hydro-treated renewable diesel derived from algae (HRD-76); or HRD-76 for various time durations (i.e., 3 days, 10 days, 1 month, 6 months, and 1 year). The 1018 coupons were immersed in bottles with the bottom half of the sample submerged in the seawater layer and the top half in the fuel layer. The 1018 steel has a composition which is within specifications for steels typically used for pipelines and storage vessels and tanks. Energy dispersive X-ray analyses (EDXA), X-ray diffraction (XRD), Raman spectroscopy, and FTIR spectroscopy were used to identify the corrosion products. To differentiate between abiotic electrochemical corrosion and microbiologically influenced corrosion (MIC), various permutations of filtered and unfiltered fuel and seawater combinations were used as the exposure media. A 0.22 micron filter was used to produce sterile seawater and fuel. Both aerobic and anaerobic conditions were examined. Natural, off-shore, surface seawater and synthetic seawater according to ASTM International specifications were used in the study. Hence, the test conditions were aerobic or anaerobic of the following seawater-fuel mixtures: 1) filtered seawater/filtered fuel, 2) filtered seawater/non-filtered fuel, 3) non-filtered seawater/filtered fuel, and 4) non-filtered seawater/non-filtered fuel.Corrosion rates of 1018 plain-carbon steel in the seawater-fuel mixtures were driven primarily by oxygen reduction and were highest in HRD-76, followed by the F-76/HRD-76 blend, and then F-76. This ordering corresponded to that of the dissolved-oxygen diffusion coefficients which were also ordered from highest to lowest as HRD-76, F-76/HRD-76 blend, and F-76.The region of steel in the seawater layer was most severely corroded due to the high corrosivity induced by chlorides. Corrosion was dominated by abiotic mechanisms and overshadowed any effects of MIC. At the fuel/water interface and zones submerged in the seawater layer, rust formation showed an inner black layer identified as magnetite and an outer red/yellow layer identified as lepidocrocite and goethite. The amount of magnetite in the inner layer increased with increasing content of HRD-76 in the fuels. Hence, the highest amount of magnetite was observed for the coupons exposed in HRD-76 followed by those in the HRD-76/F-76 50v:50v blend and least in the F-76. White precipitates identified as Mg(OH)2 (magnesium hydroxide), MgO (magnesium oxide), Na2CO3 (sodium carbonate), Na2CO3•H2O (thermonatrite), Na3H(CO3)2(H2O)2 (trona), CaCO3 (calcite and aragonite) formed in the fuel zone and was shown to be a consistent visual indicator for a high corrosion rate of steel. Precipitation was likely induced by a high amount of oxygen reduction (in the fuel layer) that generated OH-, which precipitated the carbonates and hydroxides. The presence of the white precipitates was most abundant on the coupons exposed to the HRD-76 and to a lesser degree on those exposed to the HRD-76/F-76 50v:50v blend, which is consistent with higher rates of oxygen diffusion and hence corrosion in the HRD-76 fuel. Acknowledgements: This work was supported under the Hawaii Natural Energy Institute’s Asia Pacific Research Initiative for Sustainable Energy Systems (APRISES) program, University of Hawaii at Manoa, Office of Naval Research (Grant Award Number N00014-13-1-0463).

Corrosion behavior of carbon steel in the presence of iron-oxidizing bacterium Pseudomonas sp. DASEWM1

The present study describes the microbiologically influenced corrosion (MIC) of carbon steel due to iron-oxidizing bacteria (IOB), isolated from the rust deposited on carbon steel’s surface exposed to river water. Bacterial isolates, meant for corrosion investigation, were identified as Pseudomonas sp. DASEWM1. In this work, corrosion tests were carried out to estimate the extent of corrosion. Corrosion products deposited on the steel’s surface were identified using X-ray diffraction and Fourier transformed infrared techniques. It is observed that the degree of corrosivity in inoculated nutrient broth (NB) depends upon bacterial concentration and the amount of the constituents of extracellular polymeric substances (EPS). The observance of a lesser amount of vivianite which is protective in nature, as corrosion product formed on corroded carbon steel exposed to inoculated NB, is suggested as an additional factor responsible for increased metal corrosion. Corrosion of steel in inoculated NB appears to be due to (1) oxidation of ferrous ions to ferric ions by iron-oxidizing bacteria (IOB), thereby decreasing the amount of ferrous ions available for vivianite formation, (2) some Fe3+ gets bound to EPS, thus offer electrons for the oxygen reduction reaction. Overall, this process leads to the increased alkalinity of NB. Lastly, a possible mechanism of MIC due to IOB has been proposed by considering the above mentioned reactions.

An integrated dynamic failure assessment model for offshore components under microbiologically influenced corrosion

The microbiologically influenced corrosion (MIC) is a serious issue that should be considered for effective risk-based integrity management of offshore systems under MIC. This paper presents a proper methodology by using a hybrid Bayesian network (BN) and Markov process to predict the MIC rate, failure probability, and critical failure year of an internally corroded subsea pipeline. The BN model is developed to probabilistically obtain the MIC rate, considering the dynamic non-linearity and interdependency among vital input factors. The effects of the nonlinear interactions of various prominent factors are evaluated, and their degree of influence is explored. The Markov process is employed to predict the failure probability, critical failure year, and the time evolution MIC pit depth distribution using the predicted MIC rate as a transition intensity. The developed model is adaptive and captures the evolving impact of MIC. The proposed integrated methodology is tested on a case study, and the most critical parameters that influence the MIC rate and system failure are identified. The proposed approach would provide an early warning guide for a timely intervention to prevent total failure of corroded subsea pipelines and associated consequences.

Failure analysis of a welded stainless-steel piping system with premature pitting

A failure analysis of welded pipes (ASTM A312 Grade TP 316L) in a water treatment plant was done and it is presented in this paper. The premature failure was detected by several water leakages caused by pitting corrosion three months after hydrostatic tests and before transferring the plant to the operator. The leakages were located near the bottom of the circumferential butt welds of the entire piping system. The samples were analyzed using visual inspection, radiographic examination, optical emission spectrometry, ferrite number (FN) measurements, metallographic examination and Scanning Electron Microscopy (SEM) coupled with Energy Dispersive Spectrometry (EDS). The results showed that the corrosion rate was extremely high compared to other studies available in the literature for austenitic stainless steel and the pits were in the weld metal and the Heat Affected Zone (HAZ) of the circumferential welds. The lack or deficiency of a purging gas during the field welding generated heat-tinted zones around the welds. Visual inspection showed that the pits were preferentially located at heat-tinted zones and they have large sub-surface cavities. The SEM inspection confirmed the presence of structures compatible with sulfate-reducing bacteria and iron-oxidizing bacteria and revealed that the failure was caused by microbiologically-influenced corrosion (MIC). The review of standards and codes used to perform hydrostatic testing of austenitic stainless steel piping systems showed that the water used for hydrostatic tests should have been treated before testing or the surfaces should have been deeply drained and dried. The failure was caused by the water used during the hydrostatic testing since it was not fully drained from the piping system and remained stagnant leading to MIC.

Accelerating effect of catalase on microbiologically influenced corrosion of 304 stainless steel by the halophilic archaeon Natronorubrum tibetense

The role of metabolic catalase in microbiologically influenced corrosion (MIC) of 304 stainless steel by Natronorubrum tibetense was investigated. Under sterile condition, the catalase concentration in the culture medium had no effect on the corrosion of stainless steel. In contrast, the addition of catalase in the inoculated culture medium resulted in more severe pitting corrosion of stainless steel. The potentiodynamic polarization results demonstrated that catalase mainly promoted the cathodic process of MIC of the stainless steel. Scanning electrochemical microscopy (SECM) further confirmed the accelerating effect of catalase on the cathodic oxygen reduction reaction of MIC.

N-substituted carbazoles as corrosion inhibitors in microbiologically influenced and acidic corrosion of mild steel: Gravimetric, electrochemical, surface and computational studies

Corrosion inhibition potentials of 3,6-dibromo-9-phenylcarbazole (DBPCZ) and 3(9H-carbazol-9-yl)-1,2-propanediol (CZPD) were investigated for 1 M HCl solution and microbiologically influenced corrosion (MIC) of mild steel using electrochemical and gravimetric methods, respectively. Potentiodynamic polarization results showed that DBPCZ and CZPD are mixed-type inhibitors (with predominant cathodic influence) of mild steel corrosion in 1 M HCl. DBPCZ and CZPD exhibited 81% and 87% inhibition efficiencies respectively as revealed by polarization measurements. Adsorption of DBPCZ and CZPD molecules on the steel surface in 1 M HCl was best defined by Frumkin adsorption isotherm. Uninhibited corrosion of steel by sulphate-reducing bacteria (SRB), which proceeded at the rate of 0.02 g cm−2 day−1 was subdued by 98% in the presence of 300 ppm of DBPCZ. Quantum chemical calculations suggested that the major molecular fragment in DBPCZ and CZPD molecules involved in donor-acceptor exchanges with Fe atom in mild steel is the carbazole ring. Monte Carlo simulations showed that the carbazole ring of the inhibitor molecules approaches Fe(110) in a near-flat orientation with predicted adsorption energies (Eads) of -114.24 kcal/mol and -119.85 kcal/mol for DBPCZ/Fe(110) and CZPD/Fe(110) respectively.

Distinguishing two different microbiologically influenced corrosion (MIC) mechanisms using an electron mediator and hydrogen evolution detection

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 H2S yielded a large amount of H2. This work proved that an electron mediator can distinguish EET-MIC from M-MIC, and H2 gas detection is very sensitive in identifying M-MIC with H2 evolution.

Survey and Evaluation of Spacecraft-Associated Aluminum-Degrading Microbes and Their Rapid Identification Methods.

Aluminum corrosion has become a major obstacle in spacecraft construction given that aluminum is used extensively throughout the construction process. Despite its many attributes in strength and durability, aluminum is susceptible to corrosion, in particular, corrosion due to microbial contamination. Scientists have encountered a number of problems with microbial aluminum corrosion within spacecraft components. Here, we summarize recent findings with regard to the phenomenon of microbiologically influenced corrosion (MIC) on space stations in the context of microbial strains isolated from the Mir space station (Mir) and the International Space Station (ISS). Given that strains found on spacecraft are of terrestrial origin, an understanding of the contribution of Al-corrosive microbes to corrosion and related risks to space travel and astronaut health is essential for implementation of prevention strategies. Accordingly, an efficient rapid identification method of microbes with the capability to degrade aluminum is proposed. In particular, onboard implementation of a matrix-assisted laser desorption/ionization-time of flight mass spectrometer (MALDI-TOF MS) is addressed. The use of a MALDI-TOF MS on board spacecraft will be crucial to future successes in space travel given that traditional methods of identifying corrosive species are far more time-consuming. Identification of microbes by way of a MALDI-TOF MS may also aid in the study of microbial corrosion and be a valuable asset for MIC prevention.