Electrochemical behavior of microbiologically influenced corrosion on Fe_3Al in marine environment

In this article, microbiologically influenced corrosion behavior of Fe3Al intermetallie compound in microorganism culture medium has been investigated by using weight loss methods, electrochemical techniques, and electron microscopy. Polarization curves showed that a sharp electrical current peak caused by surface pitting could be observed after Fe3Al electrodes were immersed in culture medium for 15 days when the polarization potential was about -790 mV vs SCE. Based on the electrochemical impedance spectroscopy （EIS） and the equivalent circuit parameters of the associated system, the corrosion products were found to exhibit a two-layer structured feature and the microorganisms could induce pitting and erosion corrosion of the inner layer. In addition, the passivating film of the inner layer was absolutely destroyed by microbial metabolic products.

THE ELECTROCHEMICAL BEHAVIOR OF OCEANIC MICROBIOLOGICAL INFLUENCED CORROSION ON CARBON STEEL

The corrosion behavior of carbon steel in the medium of marine microorganisms was investigated by electrochemical impedance spectra, polarization curves, and so on. Experimental results showed that the corrosion potential of carbon steel moved in a negative direction in the unpurified marine microorganism solution, and the polarization style of the cathodic process did not change. The electrochemical impedance spectra showed that the impedance value of the electrode decreased in the medium with bacteria, which indicated that the existence of microorganism could accelerate the corrosion progress of carbon steel.

Microbiologically influenced corrosion of cable bolts in underground coal mines:The effect of Acidithiobacillus ferrooxidans

Reports on corrosion failure of cable bolts,used in mining and civil industries,have been increasing in the past two decades.The previous studies found that pitting corrosion on the surface of a cable bolt can initiate premature failure of the bolt.In this study,the role of Acidithiobacillus ferrooxidans(A.ferrooxidans)bacterium in the occurrence of pitting corrosion in cable bolts was studied.Stressed coupons,made from the wires of cable bolts,were immersed in testing bottles containing groundwater collected from an underground coal mine and a mixture of A.ferrooxidans and geomaterials.It was observed that A.ferrooxidans caused pitting corrosion on the surface of cable bolts in the near-neutral environment.The presence of geomaterials slightly affected the p H of the environment;however,it did not have any significant influence on the corrosion activity of A.ferrooxidans.This study suggests that the common bacterium A.ferrooxidans found in many underground environments can be a threat to cable bolts'integrity by creating initiation points for other catastrophic failures such as stress corrosion cracking.

Characteristics of Authigenic Pyrite and its Sulfur Isotopes Influenced by Methane Seep--Taking the Core A at Site 79 of the Middle Okinawa Trough as an Example

Objective Authigenic pyrite often develops extensively in marine sediments,which is an important product of sulfate reduction in an anoxic environment.It has a specific appearance and complicated sulfur isotopic properties,and acts as important evidence of methane seep in marine sediments.Strong AOM（anaerobic oxidation of methane）activity has developed in the Okinawa Trough.

Chinese Students’ Adaptation of Social Intercourse Influenced by Different Cultural Contexts of China and America in American Universities

1 Statement of the Purpose (1) Statement of the purpose The purpose of the research isto study Chinese studends' adaptation of social intercourse influenced by different cultural contexts of China and America in American universities.And the study will also try to find out the exact problems and obstacles during Chinese students' adapting period in American universities.

Simulation of scenario earthquake influenced field by using GIS

The method for estimating the site effect on groundmotion specified by Borcherdt (1994a, 1994b) is briefly introducedin the paper. This method and the detail geological data and site classification data in San Francisco bay area ofCalifornia, the United States. are applied to simulate the influenced field of scenario earthquake by GIS technology,and the software for simulating has been drawn up. The paper is a partial result of cooperative research project betweenChina Seismological Bureau and US Geological Survey.

Characteristics and factors that influenced damage to dams in the M_s 8.0 Wenchuan earthquake

Based on raw data from dams damaged in the Wenchuan earthquake, including many that were severely damaged, characteristics and factors that influenced the damage are discussed in this paper. Findings from this study include： severely damaged dams were densely distributed along the seismologic fault; small dams, especially small earth-rock dams, had the most serious damage that was caused by a variety of factors; the most serious damage was caused by seismic waves; damage was aggregated by aftershocks; and the extent of the damage patterns increased with the seismic intensity. Damage patterns varied in different intensity zones and cracking was the most common type of damage. Most of the dams had a good base with relatively high bearing capacity, and the walls of the earth-rock dams were mostly of clay soil. This type of base and body material mitigated some of the damage to dams. Reservoir maintenance and other factors also have a significant impact on the seismic safety of the dam. Finally, some recommendations to reduce seismic damage to dams are proposed.

MICROBIOLOGICALLY INFLUENCED CORROSION ON WELD OF STAINLESS STEEL 304L

The influence of welding defects on MIC (microbiologically influenced corrosion) was studied.The open circuit potential (OCP) was measured during MIC test. It was found that OCP shifted to a higher level when the system was inoculated with bacteria and it decreased dramatically when MIC started. Among a series of welding defects golden heat tint was found the most susceptible to MIC. The tubercles over pitting were observed with SEM. Some elements inside of the tubercles were analysed with EDXA. Microbiological analysis of a corroded and a non-corroded sample revealed no significant difference between them with the exception of the number of the manganeseoxidising bacteria.

Analysis of Water Temperature Influenced by Arduino-Controlled on Solar Desalinator of Low Cost

The solar desalinator is a low cost installation and operation equipment that can contribute to tackling the problem of water shortages in the world.Because of the importance of this equipment,the present work has the objective to quantify the relation of the temperature of the water with the production of the equipment.For this,a compact desalinator with glass cover in square pyramidal form and a heating system controlled by a logic programmer was built.As a result,it was verified the efficiency of the logic controller as an auxiliary tool for experimental work and the relationship between temperature ranges and desalination production.

Microbiologically Influenced Corrosion Behavior of Fe_(40)(CoCrMnNi)_(60) and Fe_(60)(CoCrMnNi)_(40) Medium Entropy Alloys in the Presence of Pseudomonas Aeruginosa

In this work,the microbiologically influenced corrosion(MIC)of Fe_(40)(CoCrMnNi)_(60) and Fe_(60)(CoCrMnNi)_(40) medium entropy alloys(MEAs)induced by Pseudomonas aeruginosa(P.aeruginosa)was investigated.Corrosion behaviors during 14 days of immersion in sterile and P.aeruginosa-inoculated culture media are presented.Under sterile conditions,both MEAs exhibited good corrosion resistance against the culture medium solution.In the presence of P.aeruginosa,the pitting corrosion of MEAs was promoted.The results of inductively coupled plasma‒mass spectrometry(ICP‒MS)and potentiodynamic polarization tests showed that the presence of P.aeruginosa promoted the selective dissolution of passive film and accelerated the corrosion of MEAs.The results of X-ray photoelectron spectroscopy(XPS)and Mott-Schottky measurements further demonstrated the degradation effect of P.aeruginosa on the passive film.Compared with Fe_(60)(CoCrMnNi)_(40),Fe_(40)(CoCrMnNi)_(60) manifested better resistance to the MIC caused by P.aeruginosa,which may be attributed to more Cr oxides and fewer Fe oxides of the passive film.

Toward a better understanding of microbiologically influenced corrosion caused by sulfate reducing bacteria

Sulfate reducing bacteria(SRB) are often the culprits of microbiologically influenced corrosion(MIC) in anoxic environments because sulfate is a ubiquitous oxidant. MIC of carbon steel caused by SRB is the most intensively investigated topic in MIC because of its practical importance. It is also because biogenic sulfides complicate mechanistic SRB MIC studies, making SRB MIC of carbon steel is a long-lasting topic that has generated considerable confusions. It is expedient to think that biogenic H_2S secreted by SRB acidifies the broth because it is an acid gas. However, this is not true because endogenous H_2S gets its H^+ from organic carbon oxidation and the fluid itself in the first place rather than an external source. Many people believe that biogenic H_2S is responsible for SRB MIC of carbon steel. However, in recent years,well designed mechanistic studies provided evidence that contradicts this misconception. Experimental data have shown that cathodic electron harvest by an SRB biofilm from elemental iron via extracellular electron transfer(EET) for energy production by SRB is the primary cause. It has been demonstrated that when a mature SRB biofilm is subjected to carbon source starvation, it switches to elemental iron as an electron source and becomes more corrosive. It is anticipated that manipulations of EET related genes will provide genetic-level evidence to support the biocathode theory in the future. This kind of new advances will likely lead to new gene probes or transcriptomics tools for detecting corrosive SRB strains that possess high EET capabilities.

Anaerobic microbiologically influenced corrosion mechanisms interpreted using bioenergetics and bioelectrochemistry： A review

Microbiologically influenced corrosion （MIC） is a major cause of corrosion damages, facility failures, and financial losses, making MIC an important research topic. Due to complex microbiological activities and a lack of deep understanding of the interactions between biofilms and metal surfaces, MIC occurrences and mechanisms are difficult to predict and interpret. Many theories and mechanisms have been pro- posed to explain MIC. In this review, the mechanisms of MIC are discussed using hioenergetics, microbial respiration types, and biofilm extracellular electron transfer （EET）. Two main MIC types, namely EET-MIC and metabolite MIC （M-ME）, are discussed. This brief review provides a state of the art insight into MIC mechanisms and it helps the diagnosis and prediction of occurrences of MIC under anaerobic conditions in the oil and gas industry.

Tribocorrosion behavior in artificial seawater and anti-microbiologically influenced corrosion properties of TiSiN-Cu coating on F690 steel

The TiSiN-Cu nanocomposite coating was deposited on F690 steel substrate by arc ion plating. The structure and composition, tribocorrosion behavior and anti-microbiologically influenced corrosion(MIC)properties of TiSiN-Cu coating were investigated. The results show that the TiSiN-Cu coating has unique nanocomposite structures. The results of tribocorrosion show that the potential and current change of F690 steel and TiSiN-Cu coatings tend to be opposite. The reason is that the F690 steel is non-passivated metal and the TiSiN-Cu coating has passivation phenomenon. The TiSiN-Cu coating possesses excellent tribocorrosion resistance. Cu ion released from TiSiN-Cu coating can effectively inhibit the corrosion caused by SRB.

Microbiologically influenced corrosion of titanium caused by aerobic marine bacterium Pseudomonas aeruginosa

Microbiologically influenced corrosion(MIC) is a big threat to the strength and safety of many metallic materials used in different environments throughout the world. The metabolites and bioactivity of the microorganisms cause severe deterioration on the metals. In this study, MIC of pure titanium(Ti) was studied in the presence of a highly corrosive aerobic marine bacterium Pseudomonas aeruginosa. The results obtained from electrochemical test showed that Ti was corrosion resistant in the abiotic culture medium after 14 d, while the increased corrosion current density(i_(corr)) obtained from polarization curves and the decreased charge transfer resistance(R_(ct)) from electrochemical impedance spectroscopy(EIS)indicated the accelerated corrosion of Ti caused by P. aeruginosa biofilm. For further confirmation of the above results, the surface of Ti was investigated using scanning electron microscopy(SEM), confocal laser scanning microscopy(CLSM) and X-ray photoelectron spectroscopy(XPS). According to the XPS results, TiO_2 was formed in both abiotic and biotic conditions, while unstable oxide Ti_2O_3 was detected in the presence of P. aeruginosa, leading to the defects in the passive film and localized corrosion. Pitting corrosion was investigated with the help of CLSM, and the largest pit depth found on Ti surface immersed in P. aeruginosa was 1.2 μm. Ti was not immune to MIC caused by P. aeruginosa.

Microbiologically influenced corrosion of Cu by nitrate reducing marine bacterium Pseudomonas aeruginosa

The microbiologically influenced corrosion(MIC) mechanisms of copper by Pseudomonas aeruginosa as a typical strain of nitrate reducing bacteria(NRB) was investigated in this lab study.Cu was immersed in deoxygenated LB-NO3 seawater inoculated with P.aeruginosa and incubated for 2 weeks.Results showed that this NRB caused pitting and uniform corrosion.The maximum pit depths after 7 d and 14 d in125 mL anaerobic vials with 50 mL broth were 5.1 μm and 9.1 μm,accompanied by specific weight losses of 1.3 mg/cm2(7 d) and 1.7 mg/cm2(14 d),respectively.Electrochemical measurements corroborated weight loss and pit depth data trends.Experimental results indicated that extracellular electron transfer for nitrate reduction was the main MIC mechanism and ammonia secreted by P.aeruginosa could also play a role in the overall Cu corrosion process.

Microbiologically influenced corrosion of 304 stainless steel by halophilic archaea Natronorubrum tibetense

The corrosion behavior of 304 stainless steel(SS)in the presence of aerobic halophilic archaea Natronorubrum tibetense was investigated.After 14 days of immersion,no obvious pitting pit was observed on the SS surface in the sterile medium.By contrast,the SS exhibited serious pitting corrosion with the largest pit depth of 5.0μm in the inoculated medium after 14 days.The results of electrochemical tests showed that the barrier property of the passive film decreased faster in the inoculated medium.The X-ray photoelectron spectroscopy results indicated that the detrimental Fe2+and Cr6+increased in the passive film under the influence of archaea N.tibetense,which resulted in the accelerated deterioration of passive film and promoted the pitting corrosion.Combined with the energy starvation tests,the microbiologically influenced corrosion mechanism of 304 SS caused by halophilic archaea N.tibetense was discussed finally.

Microbiologically influenced corrosion of 304L stainless steel caused by an alga associated bacterium Halomonas titanicae

Algae are reported to be corrosive,while little is known about the role of the algae associated bacteria in the corrosion process.In the present study,Halomonas titanicae was isolated from a culture of an alga strain,Spirulina platensis,and identified through 16 S rRNA gene analysis.Corrosion behavior of 304L stainless steel(SS)coupons in the presence and absence of H.titanicae was characterized by using electrochemical measurements and surface analysis.The results showed that H.titanicae significantly accelerated the corrosion rate and decreased the pitting potential of 304L SS in the biotic medium.After removal of the corrosion products and biofilms,severe pitting corrosion caused by H.titanicae was observed.The largest pit depth after 14 d reached 6.6μm,which was 5.5 times higher than that of the sterile control(1.2μm).This is the first report revealing that an alga associated bacterium can induce microbiologically influenced corrosion(MIC),and a further concern is raised that whether algae play a role in the MIC process.

Enhanced resistance of 2205 Cu-bearing duplex stainless steel towards microbiologically influenced corrosion by marine aerobic Pseudomonas aeruginosa biofilms

An antibacterial 2205-Cu duplex stainless steel （DSS） was shown to inhibit the formation and growth of corrosive marine biofilms by direct contact with copper-rich phases and the release of Cu^2＋ ions from the 2205-Cu DSS surface. In this work, the microbiologically influenced corrosion （MIC） resistance of 2205- Cu DS5 in the presence of the corrosive marine bacterium Pseudornonos aeruginosa was investigated. The addition of copper improved the mechanical properties such as the yield strength, the tensile strength and the hardness of 2205 DSS. Electrochemical test results from linear polarization resistance （LPR）, electrochemical impedance spectroscopy （EI5） and critical pitting temperature （CPT） measurements showed that 2205-Cu DSS possessed a larger polarization resistance （Rp）, charge transfer resistance （Rct） and CPT values, indicating the excellent MIC resistance of2205-Cu DSS against the corrosive P. aeruginosa biofilm. The live]dead staining results and the SEM images of biofilm confirmed the strong antibacterial ability of 2205-Cu DSS. The largest pit depth of 2205-Cu DSS was considerably smaller than that of 2205 DSS after 14d in the presence ofP. aeruginosa （2.2 μm vs 12.5 μm）. 2205-Cu DSS possessed a superior MIC resistance to regular 2205 DSS in the presence of aerobic P. aeruginosa.

Electrochemical studies of microbiologically influenced corrosion of X80 steel by nitrate-reducing Bacillus licheniformis under anaerobic conditions

In this work, the impact of a wild-type nitrate-reducing Bacillus licheniformis strain on the corrosion behavior of X80 steel under anaerobic conditions was studied by electrochemical tests and biofilm characterization. The bioelectrochemical, electrochemical, and chemical reactions between X80 steel and microorganisms were investigated comprehensively. The results show that B. licheniformis can accelerate the corrosion of X80 steel substrate in early immersing by two ways: biocatalytic cathodic nitrate reduction and acidification induced by bacterially-secreted acids. However, the corrosion rate of X80 steel decreased after immersing for ca. 1 week in B. licheniformis culture due to iron biomineralization. This work provides direct insights into the mechanism of microbiologically influenced corrosion of carbon steel by the nitrate-reducing bacterium.