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Microbiologically influenced corrosion (MIC) is a complex process involving interactions between microorganisms, materials and surrounding environment. Yeast extract (YE) is a routinely added nutritional ingredient in many kinds of microbial culture media. However, the effect of YE on MIC was not clear. In this work, the corrosion behaviors of X70 pipeline steel in the sulfate reducing bacterial (SRB) Desulfovibrio bizertensis SY-1 inoculated media with or without YE were studied. The results showed that the weight loss of coupons in sterile media increased twofold after removing YE from culture media (P = 0.04). While in the SRB culture medium, removing YE decreased the planktonic bacteria number, but significantly promoted the attachment of bacteria on steel surfaces. Besides, the corrosion rate of steel in SRB media without YE was four times higher than with YE (P = 0.003). MIC was not determined by the planktonic SRB cells but the attached biofilm. The results identified effect of YE on D. bizertensis SY-1 growth and confirmed the inhibition role of YE in MIC induced by SRB.

In this work, the photoelectrochemical (PEC) properties of TiO2 nanotube arrays (NTAs) were enhanced by forming heterostructures with non-substituted covalent organic frameworks (H-COFs) and fluoro...

Biofilm plays an important role on microbial corrosion and biofouling in marine environments. Inhibiting biofilm formation on construction surfaces is of great importance. Photocatalytic material with visible-light response, especially BiVO4, is regarded as a promising material for biofilm inhibition due to its green biocidal effect and high antibacterial efficiency. Approaches which can immobilize the photocatalytic particles onto metal surfaces with high mechanical strength are requisite. In this study, zinc matrixes were served as carriers for BiVO4 particles. The BiVO4-inserted zinc matrixes were successfully obtained by ultrasound assisted electrodeposition. The insertion content of BiVO4 showed positive correlation with ultrasound power. Highly enhanced biofilm inhibition properties were obtained by BiVO4 inserted zinc matrixes with an over 95 % decreased bacterial coverage. It was proved that O2− (chief) and OH (subordinate) radicals were responsible for the high biocidal performance. Possible antibacterial mechanism was proposed, indicating that the photoinduced holes would both attack zinc crystals to generate active electrons to form O2− radicals, and react with H2O to generate OH, finally. Furthermore, corrosion resistance of the matrixes was proved to be stable due to the insertion of BiVO4. This study provides a potential application for photocatalyst in marine antifouling and anti-biocorrosion aspects.

Although it is well acknowledged that microbes played a significant role in the marine corrosion, few studies have systematically studied on the relationship between microorganisms and corrosion products under long-term immersion. In this work, the corrosion characteristics of the rust layer formed on carbon steel immersed in the South China sea after 5.5 years were investigated by various surface analysis and microbial community techniques. Magnetite (Fe3O4), iron sulfide and green rust were identified in the inner rust layer. The middle rust layer was dominated by maghemite (γ-Fe2O3), while some Fe3O4 and mackinamite were also detected. The outer rust layer contained several Fe(Ⅲ)-oxyhydroxides, along with a large number of fouling organisms attached. In all rust layers, anaerobic SRB was the dominant bacteria, and might play a key role during the formation of corrosion products. One SRB strain (Desulfovibrio bizertensis SY-1) with highly corrosivity (13.561 mg/cm2) was isolated from these rust layers, and the physiological and metabolic characteristics were also studied. These results helped expand the membership of corrosive SRB and establish better understanding of marine MIC.

Exploring new and high efficiency mimic enzymes is a vital and novel strategy for antibacterial application. Haloperoxidase-like enzymes have attracted wide attention thanks to their amazing catalytic property for hypohalous acid generation from hydrogen peroxide and halides. However, few materials have displayed halogenating catalytic performance until now. Herein, we synthesized N-doped C/CeO2 (N-C/CeO2) composite materials by a combination of the liquid and solid-state method. N-C/CeO2 can possess haloperoxidase-like catalytic activity by catalyzing the bromination of organic signaling compounds (phenol red) with H2O2 at a wide range of temperatures (20 °C to 55 °C), with a solution color changing from yellow to blue. Meanwhile, it exhibits high catalytic stability/recyclability in the catalytic reaction. The synthesized N-C/CeO2 composite can effectively catalyze the oxidation of Br− with H2O2 to produce HBrO without the presence of phenol red. The produced HBrO can resist typical marine bacteria like Pseudomonas aeruginosa. This study provides an efficient biomimetic haloperoxidase and a novel sustainable method for antibacterial application.

Microbiologically influenced corrosion caused by sulfate-reducing bacteria (SRB) poses a serious threat to marine engineering facilities. This study focused on the interaction between the corrosion behavior of two aluminum alloys and SRB metabolic activity. SRB growth curve and sulfate variation with and with aluminum were performed to find the effect of two aluminum alloys on SRB metabolic activity. Corrosion of 5052 aluminum alloy and Al-Zn-In-Cd aluminum alloy with and without SRB were performed. The results showed that both the presence of 5052 and Al-Zn-In-Cd aluminum alloy promoted SRB metabolic activity, with the Al-Zn-In-Cd aluminum alloy having a smaller promotion effect compared with 5052 aluminum alloy. The electrochemical results suggested that the corrosion of the Al-Zn-In-Cd aluminum alloy was accelerated substantially by SRB. Moreover, SRB led to the transformation of Al-Zn-In-Cd aluminum alloy corrosion product from Al(OH)3 to Al2S3 and NaAlO2.

Biocides are often used to mitigate the microbially influenced corrosion (MIC) of construction materials in many fields. To study the effect of inadequate dosing of non-oxidizing biocide tetrakis (hydroxymethyl) phosphonium sulfate (THPS) on corrosion of pipeline steel caused by microorganisms, a novel marine isolate Desulfovibrio hontreensis SY-21 was selected as a test microorganism. Weight loss rate determination, morphological analyses, and corrosion product analyses combined with electrochemical measurements were performed to investigate the influence of THPS on the MIC of X70 pipeline steel. The responses of sessile and planktonic cells of D. hontreensis to THPS were also studied. Results showed that D. hontreensis cells could significantly promote steel corrosion and induce local corrosion pits. With a THPS addition within the tolerance range of D. hontreensis for the biocide, MIC of the steel was further promoted by 65%. The growth of planktonic cells was inhibited by the biocide, but the number of biofilm cells was significantly increased. This study revealed that THPS concentrations within a specific range increased the corrosive effect of the presence of D. hontreensis by promoting the growth of sessile cells and biofilm formation. Therefore, the use of the biocide in practical applications needs to be properly considered and managed.

Graphitic carbon nitride (g-C3N4), as a novel carbon material, has gained widespread attention during the last years. Although the g-C3N4 can be synthesized by utilizing various N-rich precursors, the photocatalytic performance of the derived g-C3N4 significantly alters depending on the type of used precursor. In our study, we choose economical urea, dicyandiamide, and melamine as precursors to prepare g-C3N4 under the wrap with tin foil, which are labeled as g-C3N4-U, g-C3N4-D, and g-C3N4-M, respectively. The sizes of g-C3N4-U, g-C3N4-D, and g-C3N4-M are about 2 μm, 4 μm, and 3 μm, and the thickness of them is around 8 nm, 15 nm, and 15 nm, respectively. We find that the g-C3N4-U exhibits the best photocatalytic degradation effect towards Rhodamine B (RhB) among the synthesized g-C3N4 samples. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), atomic force microscopy (AFM), X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible diffuse reflectance spectra (UV-visible DRS), photoluminescence (PL) spectra, electrochemical measurements, N2 adsorption-desorption isotherms, and electron spin resonance (ESR) are used to study the characteristics of the prepared g-C3N4 samples. It is found that the thinner mesoporous nanostructure of g-C3N4-U results in enhanced separation efficiency of the photo-induced carriers as well as effective utilization of the superoxide radical ( $$ \cdotp {\mathrm{O}}_2^{-} $$ ), which improved the catalytic performance of g-C3N4-U.

In microbiologically influenced corrosion (MIC) induced by sulfate-reducing bacteria (SRB), the electrons released from iron were transferred via extracellular electron transfer (EET) to the inner cells. Electron mediators and carbon starvation have also been found to promote steel corrosion. This study aimed to investigate the synergistic effects of electron mediators and carbon starvation on MIC and their effect on biofilm catalytic activity. The results demonstrated that the weight losses of X70 steel were 0.68 and 1.03 mg/cm2 in 100% and 10% carbon source (CS) SRB solution, respectively. The addition of riboflavin and cytochrome c increased the corrosion rate by 1.76 and 1.87 times, respectively, in the 100% CS SRB medium compared to the medium without exogenous redox mediators. For the 10% CS SRB medium, the corrosion rate increased by 1.40 and 1.89 times, respectively, when riboflavin and cytochrome c were added. The addition of riboflavin and cytochrome c also enhanced the biocatalytic activity of the SRB biofilm in both the 100% and 10% CS SRB media.

Four kinds of Ag3PO4 materials were prepared by controlling the experimental conditions, which were developed as oxidase mimics. Experimental results showed that different synthesis methods led to distinct crystal structures, morphologies, and surface properties, which contributed to diverse oxidase-like activities of Ag3PO4 materials. Among them, Ag3PO4 microcubes (APMCs) can efficiently catalyze the oxidation of colorless 3,3′,5,5′-tetramethylbenzidine in the presence of dissolved oxygen to form a blue-colored oxide, presenting the best intrinsic oxidase mimetic ability. The higher-energy [110] facets with more oxygen vacancies exposed and more active sites coupled with more negative charge and larger specific surface area of APMCs contributed to its enhanced oxidase mimetic performance. Besides, mercury ions were proved to remarkably and selectively stimulate the oxidase-like ability of APMCs owing to the formation of Ag–Hg amalgam on its surface. Based on the stimulating effect of Hg2+ towards APMCs, a simple and rapid method for colorimetric determination of Hg2+ was thus established via the significant signal amplification and megascopic color variation. Under the optimal conditions, the sensing system showed a good linear relationship ranging from 0.1 to 7.0 μM and a detection limit of 20 nM for Hg2+, exhibiting high selectivity and good colour stability. Moreover, the colorimetric method was successfully applied to determine Hg2+ in real water samples. Considering these advantages, the developed colorimetric sensing system is expected to hold bright prospects for trace determination of Hg2+ in biological, environmental, and food samples.

Pseudomonas aeruginosa PAO1 is widely distributed in fresh water, soil, and marine environments and can act as electrochemically active bacteria for bioconversion in bioelectrochemical systems. Phenazine, an active redox compound produced by PAO1, could be beneficial for its producers as an alternative respiratory pigment. Here, we demonstrated that phenazine promoted electron transfer of PAO1 to poised-potential electrodes, thus facilitating the anaerobic growth of P. aeruginosa PAO1. The growth and extracellular electron transfer of P. aeruginosa PAO1 were studied under four anaerobic conditions: with poised potential but without phenazine, with phenazine but without poised potential, with both phenazine and poised potential, and without phenazine and without poised potential in a phosphate-buffered saline medium bioreactor. The results showed that anaerobic conditions, without polarized electrode or without phenazine, did not support the colony formation of P. aeruginoa PAO1 on filters. Phenazine enhanced the electron transport between P. aeruginosa PAO1 and poised-potential electrode. These findings provided an insight into understanding the anaerobic respiration of P. aeruginosa PAO1 with poised-potential electrodes.

Four kinds of Ag

In this paper, nanoparticles decorated Ce

Zn coatings are widely applied due to their low cost and negative potential in steel construction and reinforcing steel bars in concretes. However, Zn coatings have been found to perform unsatisfactorily in moist and alkaline environments. In the aqueous alkali environments that inevitably form when concretes fail, galvanized reinforcing steel bars have extremely low corrosion resistance and, consequently, are subject to corrosion. Facing these problems, various additives, including organic and inorganic compounds, have been introduced into Zn coatings to obtain enhanced corrosion resistance, with fewer experiments focusing on organometallic compound composited coatings. As a typical organometallic compound, ferrocene possesses high resistance to corrosive media, such as acids and alkalis. This makes ferrocene an extremely appropriate additive for composite Zn coatings. In this study, Zn-Ferrocene composite coatings were synthesized via electrodeposition with ultrasound assistance. Ferrocene was successfully incorporated using electrochemical control, with a maximum ferrocene content determined to be 19.4% of the C present in the composite coating. The surface morphologies and crystalline structures of the resultant coatings were significantly altered to thin, flake-like hexagonal crystals, a characteristic that was associated with the electrodepositing atomic matrix. The addition of ferrocene greatly improved the wear resistance of the composite coatings, with a 25% mass loss of pure zinc within the coating. The best properties were obtained at an ultrasound assistance level of 15 W. In addition, the corrosion mechanism of the composite coatings was studied at the molecular level. It was found that the corrosion resistance of the composite coatings in alkaline solutions was noticeably enhanced, with an Rct value doubled showing the charge transfer process was inhibited. These results indicate that ultrasound-assisted Zn-Ferrocene composite coatings hold much promise for their potential use in reinforced steel bars in concretes and other abrasive environments.

Based on the establishment of a moisture transport model, a prediction model for chloride transport in unsaturated concrete was developed. The moisture transport model considers both the diffusion of water vapor and seepage of liquid water in concrete under drying-wetting conditions. The moisture transport model was verified by wetting and drying tests. In the transport model of chloride ions, both diffusion and convection were considered. Tests of specimens under drying-wetting cycles with four types of cycles were carried out to verify the chloride transport model. Furthermore, a new device was developed to mimic tidal and splash zones of a marine environment to achieve different time ratios of drying-wetting. The measured results of chloride content corresponded with the simulated results. The results showed that the chloride content in concrete displayed no relationship with the ratio of drying and wetting times. The chloride content of concrete in mimicked tidal and splash zones significantly varied with height, especially in the surface layer of concrete, and the chloride content of concrete at the junction of the splash and tidal zones was the highest.

Sulfate-reducing bacteria (SRB) are one of the chief inducers of microbiologically influenced corrosion in marine environment. In our previous work, a novel chitosan‑zinc film was electrodeposited and found to be effectively antibacterial, so research on the corrosion behavior of chitosan‑zinc films in SRB medium is highly significant for estimating the films to be applied in real-sea environment. In this paper, detection of SRB metabolism, electrochemical methods and surface analyses were performed to clarify the corrosion behavior. During 6 d exposure in SRB, obvious inhibition on SRB growth and metabolism were found by monitoring the environment corrosive factors. By calculating the corrosion rate and analyzing surface morphologies, chitosan‑zinc films showed relatively high corrosion resistance. After exposure, biofilm together with corrosion products formed on zinc film, while corrosion product layer with little bacteria attached on chitosan‑zinc composite film. Further electrochemical results showed that the addition of chitosan did not change the anodic and cathodic behavior of the films, but enhanced the corrosion resistance by reducing the corrosive ability SRB medium, inhibiting bacteria attachment and raising the films' electric conductibility to a certain extent.

Sulfate-reducing bacteria (SRB) are a major bacterial group involved in microbiologically influenced corrosion. The interaction between SRB and metals had been the focus of numerous investigations. In this paper, the interaction between SRB and 5052 aluminum alloy was studied using biological and electrochemical methods. Electrochemical analysis suggested that the corrosion rate of the aluminum alloy was accelerated substantially by SRB. This effect was based on the consumption of hydrogen, which in return promoted SRB metabolic activity. Deeper and larger micropits were found on alloy surfaces immersed in SRB. Energy dispersive spectroscopy analyses demonstrated that the concentration of Al on the surface of samples immersed with SRB was lower, while the concentrations of C, O, and S were higher than those without SRB. The results give an insight into clarifying the interaction between SRB and Al.

In this work, a pure Bacillus sp. and a consortium of microbes were isolated from inner rust layer of carbon steel from marine environment. Corrosion behavior of Q235 carbon steel was investigated in the presence and in the absence of Bacillus sp. and with consortium of microbes separately. Weight loss, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and energy dispersive spectrum (EDS) tests were conducted to observe the influence on corrosion behavior of carbon steel in the presence and in the absence of bacteria. The results showed that corrosion potential (E-corr) decreased and the corrosion current density increased in the presence of bacteria, in contrast with the sterile medium with the same exposure time interval. The weight loss was observed and micrometer-scale pitting further confirmed by SEM on the carbon steel surface in the presence of bacteria especially with the Bacillus sp. Most importantly in the present work Bacillus sp. behaved like sulfate reducing bacteria (SRB). Further, it was confirmed that in natural environment Bacillus sp. could also act like sulfate-reducing bacteria and deteriorating carbon steel, especially in the form of localized pitting/corrosion.

Correction for ‘Effect of graphene oxide on anticorrosion performance of polyelectrolyte multilayer for 2A12 aluminum alloy substrates’ by Xia Zhao et al., RSC Adv., 2017, 7, 33764–33774.

The present research seeks to address biologically influenced corrosion by electrodepositing a novel 4,5dichloro-2-n-octyl-4-isothiazolin-3-one(DCOIT)-zinc composite films for enhanced corrosion resistant properties. Investigated by electrochemical methods, energy dispersive spectroscopy distribution mapping, and infrared absorption spectroscopy, a deposition mechanism was proposed wherein the DCOIT molecule chelated the zinc ion to participate in electrodeposition. The DCOIT-zinc chelate produced obvious alterations in the surface morphology and crystal orientations. Thermogravimetric analysis determined the DCOIT mass fraction in the composite film was 5%. The DCOIT-zinc composite film demonstrated uniform corrosion in natural seawater and the enhanced anticorrosion property was achieved by successfully embedding DCOIT. (C)2016 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.

In this study, novel Z-scheme MoS2/Bi2WO6 (MB) heterostructured hierarchical flower-like microspheres were successfully prepared via an in-situ growth method on exfoliated MoS2 nanosheets. Experimental results indicated that the content of MoS2 played a key role in controlling the morphology and photocatalytic activity of MB heterostructures. MB-9 exhibited a highly enhanced photocatalytic activity under visible light irradiation compared to pure MoS2, Bi2WO6 and other MB composites, which can be ascribed to the stable Z-scheme heterostructure, leading to the efficient transfer and the separation of photoinduced electrons and holes. The photocatalytic degradation efficiency of rhodamine B (RhB) can reach 100% within 90 min and almost all of Pseudomonas aeruginosa (P. aeruginosa) can be killed after 60 min by MB-9. In addition, MB-9 displayed a nice stability during the photocatalytic process, which favored a long-term use. Moreover, a possible photocatalytic mechanism was proposed based on the active species trapping experiments and electron spin resonance (ESR) tests, verifying that the photogenerated holes (h+) and ⋅O2− radicals were the dominating active species, which followed the Z-scheme reaction mechanism. It is hoped that this work can provide valuable information on developing novel Z-scheme heterostructures with enhanced photocatalytic activities for potential environmental purification and energy conversion.

In the paper, a novel BiOI/MoS2 (BMS) heterojunction was prepared by a facile hydrothermal method. BiOI nanoplates grew in-situ on the surface of exfoliated MoS2 nanosheets, followed by anisotropic growth and self-assembly, forming a hierarchical flower-like heterostructure finally. Experimental results illustrated that MoS2 as well as the BiOI amounts play a vital role in influencing the morphology and photocatalytic activity of BMS heterojunctions. Among the obtained photocatalysts, BMS-8 displayed the strongest photocatalytic performance under visible light irradiation towards the degradation of rhodamine B (RhB) and disinfection of Pseudomonas aeruginosa (P. aeruginosa). The highly enhanced photocatalytic activity can be attributed to the synergistic effect and formation of a type II heterostructure between BiOI and MoS2, boosting the catalytic active sites, enhancing visible light harvesting, and promoting the efficient separation of photoinduced charge carriers. Moreover, BMS-8 composite showed a good stability in photocatalytic reaction, which favored a long-term use. The active species trapping experiments validated the dominating role of photogenerated holes (h+) and ⋅O2− radicals in the photocatalytic process for BMS-8 heterojunction. It is anticipated that this work can promote further interest in constructing novel heterostructures with controllable morphology and highly efficient photocatalytic activity for potential environmental purification and energy conversion.

Developing environmental and cost-effective antifouling technologies is essential to solve serious biofouling problems. Recently, enzyme mimics and halogenating enzymes have caught progressively attention as valuable tools to combat biofilm formation. In this work, the core-shell structure of CeO2@C, as one effective haloperoxidase-like enzyme mimics, was successfully synthesized using the carbon sphere as template through a simple coprecipitation method. Through the UV–vis absorption spectra and kinetic measurements, the CeO2@C displays intrinsic haloperoxidase-like activity via catalyzing the bromination of organic signaling compounds. Meanwhile, the prepared CeO2@C catalyst process high catalytic stability and recyclability, corresponding to a well catalytic performance repeatability after refresh of raw substrates (at least 10 times). The antibactrial property of CeO2@C as haloperoxidase mimicry is evaluated by immersing titanium plate/CeO2@C modified titanium plates into bacterial suspensions with different conditions for 4 h at 37 °C. It can catalyze the oxidation of Br− with H2O2 to the corresponding hypobromous acid (HBrO), which exhibits strong antibacterial activity against Gram-negative (Escherichia coli), Gram-positive (Staphylococcus aureus) bacteria and typical marine (Pseudomonas aeruginosa) bacteria. This study introduces a stable, non-poisonous and inexpensive biomimetic material for antibacterial, antifouling and disinfection applications based on novel sustainable and conservation methods.