Search Results (25)

The present research features an experimental comparative design and the objective of this work was to determine the susceptibility to microbiological contamination in fatty acid methyl esters (FAMEs) and the FAME–water interface of residual and refined lard, large volume simulating storage conditions as fuel supply chain, and to identify the microorganisms developed. The plates were seeded according to ASTM E-1259 and the instructions provided by the manufacturer of the Bushnell Haas agar. Microbiological growth was observed at the FAME–water interface of FAME obtained from residual lard. Using the MALDI-TOF mass spectrometry technique, Pseudomonas aeruginosa and Streptomyces violaceoruber bacteria were identified in the residual lard FAMEs, with the latter being previously reported in FAMEs. The implications of microorganism development on the physicochemical quality of FAMEs are significant, as it leads to an increase in the acid index, which may negatively impact metals by inducing corrosion. The refined lard FAMEs did not show any development of microorganisms. The present research concluded that residual lard tends to be more prone to microbiological attack if the conditions of water and temperature affect microbial growth. The findings will contribute to the knowledge base for a safer introduction of FAMEs into the biofuel matrix. Full article

Microorganisms take an active part in the processes of microbiologically influenced corrosion, which is protected against by using bactericides—often toxic compounds—with inhibitory properties. There are many studies of eco-friendly “green” biocides/inhibitors, in particular those based on microbial metabolites. Indicators for the processes of microbial corrosion of steel 3 induced by the sulfate-reducing bacteria Desulfovibrio oryzae NUChC SRB2 under the influence of the strains Bacillus velezensis NUChC C2b and Streptomyces gardneri ChNPU F3 have not been investigated, which was the aim of this study. The agar well diffusion method (to determine the antibacterial properties of the supernatants) was used, along with the crystal violet (to determine the biomass of the biofilm on the steel) and gravimetric methods (to determine the corrosion rate). A moderate adhesiveness to steel 3 was established for D. oryzae due to its biofilm-forming ability. The presence of a supernatant on cultures of S. gardneri, B. velezensis and their mixture (2:1) did not reduce the biofilm-forming properties of D. oryzae. Compared to the control, a decrease in the corrosion rate was recorded for the variant of the mixture of the studied bacterial culture supernatants. This indicates the potential of this mixture for use in corrosion protection in environments with sulfate-reducing bacteria, which requires further research. Full article

Background/Objectives: Biocorrosion, driven by microbial colonization and biofilm formation, poses a significant threat to the integrity of metal artifacts, particularly those composed of copper and its alloys. Pseudomonas aeruginosa, a bacterial species that reduces nitrates, plays a key role in this process. This study explores the potential of two metabolite-rich plant extracts, Aloe vera and Opuntia ficus-indica, as sustainable biobased inhibitors of microbial-induced corrosion (MICOR). Methods: The antibacterial and antibiofilm activities of the extracts were evaluated using minimal inhibitory concentration (MIC) assays, time-kill kinetics, and biofilm prevention and removal tests on copper, bronze, and brass samples. Spectrophotometric and microbiological methods were used to quantify bacterial growth and biofilm density. Results: Both extracts exhibited significant antibacterial activity, with MIC values of 8.3% (v/v). A. vera demonstrated superior bactericidal effects, achieving reductions of ≥3 log₁₀ in bacterial counts at lower concentrations. In antibiofilm assays, both extracts effectively prevented biofilm formation and reduced established biofilms, with A. vera exhibiting greater efficacy against them. The active metabolites—anthraquinones, phenolics, flavonoids, and tannins—likely contribute to these effects. Conclusions: These findings highlight the dual role of A. vera and O. ficus-indica extracts as both corrosion and biocorrosion inhibitors. The secondary metabolite profiles of these plants support their application as eco-friendly alternatives in the conservation of metal cultural heritage objects. Full article

Microorganisms cause microbiologically influenced corrosion, for the prevention of which bactericide inhibitors are used. The aim of the work was to study in vitro the sensitivity of SRB Desulfovibrio oryzae NUChC SRB1 to different concentrations of dimethyl sulfoxide (DMSO), and evaluate the indicators of the microbial corrosion of steel induced by this bacterium in the presence of the pharmaceutical drugs DMSO and paracetamol. The sensitivity of SRB D. oryzae to 1–100% DMSO (v/v) was studied via the dilution method in Postgate’s “C” liquid medium. The corrosion activity of D. oryzae against steel 3 was investigated under DMSO and paracetamol treatment at a final concentration of 45% (v/v) and 0.2% (w/v), respectively, according to the ability of bacteria to form a biofilm on the surface of the steel samples (via the crystal violet method) and the effect on the corrosion rate (via the gravimetric method). It was revealed that DMSO affected D. oryzae NUChC SRB1 and exhibited bactericidal properties (at a concentration range of 10–100%, v/v) and antibiofilm properties (at a concentration of 45%, v/v). Despite its antibiofilm properties confirmed by the reduction in bacterial biofilm mass, anticorrosion features were not observed in the model 35-day conditions of the microbial corrosion of steel in an anaerobic environment with bacterial sulfate reduction. Paracetamol (0.2%, w/v) did not affect biofilm formation by SRB under these conditions, and significantly contributed to an increase in the rate of the microbial corrosion of steel. The prospect of further research is to assess the effect of DMSO and paracetamol on the indicators of microbial corrosion induced by SRB under the influence of the concentrations of these compounds found in wastewater, to clarify the possible additional causes of damage to the equipment of treatment plants. Further research should also be directed at investigating the antimicrobial properties of complexes of compounds with DMSO, which should be considered as an ecological solution to the problem of microbiologically influenced corrosion prevention. Full article

The effects of the symbiosis of sulfate-reducing bacteria (SRB) and total general bacteria (TGB) on the microbiologically influenced corrosion (MIC) of carbon steel were investigated in this research. The SRB was the main corrosive bacterium, and TGB induced slightly general MIC. The symbiosis of SRB and TGB induced more severe MIC and pitting corrosion than SRB. The main corrosion products were FeS, Fe₂O₃, and FeOOH. The presence of TGB facilitates MIC and pitting corrosion by providing a locally anaerobic shelter for SRB. An MIC mechanism of the symbiosis of SRB and TGB was proposed. Full article

The disposal of high-level radioactive waste (HLW) and spent nuclear fuel (SF) presents a unique challenge for the prediction of the long-term performance of corrodible structures since HLW/SF containers are expected, in some cases, to have lifetimes of one million years or longer. Various empirical and deterministic models have been developed over the past 45 years for making predictions of long-term corrosion behaviour, including models for uniform and localised corrosion, environmentally assisted cracking, microbiologically influenced corrosion, and radiation-induced corrosion. More recently, fracture-mechanics-based approaches have been developed to account for joint mechanical–corrosion degradation modes. Regardless of whether empirical or deterministic models are used, it is essential to be able to demonstrate a thorough mechanistic understanding of the corrosion processes involved. In addition to process models focused on specific corrosion mechanisms, there is also a need for performance-assessment models as part of the overall demonstration of the safety of a deep geological repository. Performance-assessment models are discussed in Part 2 of this review. Full article

Background: The use of nitinol (NiTi) archwires in orthodontic treatment has increased significantly due to unique mechanical properties. The greatest obstacle for safe orthodontic treatment is chemically or microbiologically induced corrosion, resulting in nickel (Ni) release. The aim of this investigation was to enhance corrosion resistance and introduce antibacterial properties to NiTi archwires by coating them with copper (Cu) doper titanium nitride (TiN-Cu). Methods: NiTi archwires were coated with TiN-Cu using cathodic arc evaporation (CAE) and direct current magnetron sputtering (DC-MS). The morphology of the sample was analyzed via field emission scanning electron microscopy (FESEM) and chemical composition was assessed using energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and Fourier transformed infrared spectroscopy (FTIR). Inductively coupled plasma optical emission spectrometry (ICP-OES) was used to estimate the ion release. The biocompatibility of samples was investigated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Antibacterial activity was tested against Streptococcus mutans and Streptococcus mitis. Results: Physicochemical characterization revealed well-designed coatings with the presence of TiN phase with incorporated Cu. TiN-Cu-nanocoated archwires showed a statistically lower Ni release (p < 0.05). Relative cell viability was the highest in 28-day eluates of TiN-Cu-nanocoated archwires (p < 0.05). The most remarkable decrease in Streptococcus mitis concentrations was observed in the case of TiN-Cu-coated archwires (p < 0.05). Conclusion: Taking into account biocompatibility and antibacterial tests, TiN-Cu-nanocoated archwires may be considered as a good candidate for further clinical investigations. Full article

The microbiologically influenced corrosion of 201 stainless steel by Shewanella algae was investigated via modulating the concentration of fumarate (electron acceptor) in the medium and constructing mutant strains induced by ΔOmcA. The ICP-MS and electrochemical tests showed that the presence of S. algae enhanced the degradation of the passive film; the lack of an electron acceptor further aggravated the effect and mainly affected the early stage of MIC. The electrochemical tests and atomic force microscopy characterization revealed that the ability of ΔOmcA to transfer electrons to the passive film was significantly reduced in the absence of the c-type cytochrome OmcA related to EET progress, leading to the lower corrosion rate of the steel. Full article

The present paper describes a study case of the failure investigation of duplex stainless steel (UNS S31803) on the tube and tube sheet sections of BEM TEMA-type shell and tube heat exchanger with seawater as the cooling medium. The heat exchanger’s shell design pressure was 22.6 MPa at 422 K, and the tube design pressure was 1 MPa at 339 K. Although UNS S31803 offers high strength, high resistance to chloride-induced SCC, and high resistance to pitting attack in chloride environments, the heat exchanger in this study experienced some material degradation after 28 months of use; 102 out of 270 tubes failed, 26 tubes leaked and were plugged on both sides, and scale plugged 76 tubes. The examination in this study case revealed the formation of white-colored biofilm inside the tubes; XRD examination revealed that the film contained CaCO₃. Using microstructural examination on the inner surface of the tube, the austenite grains were shown to have been preferentially attacked; this phenomenon is typical in duplex stainless steel which fails due to crevice corrosion. According to the examination result, the failure in this case was caused by crevice corrosion between the substrate and surface deposits that was enhanced by microbiological-induced corrosion (MIC). Recommendations to avoid similar failures are also suggested in this paper. Full article

This paper clarifies the causes of a corrosion process observed in austenitic stainless-steel pipes, grade 316L, used for conducting freshwater in a port area. During the pressure test of the installation, before it was put into service, about five months after its construction, a loss of pressure was detected due to leaks of the fluid contained and the presence of corrosion damage on the wall of the tubes, in some cases even passing through the thickness of the tube. An analysis of the chemical composition of the pipe material was carried out, as well as semi-quantitative analysis of the chemical composition of the deposits in the defects, and a culture of sulfate-reducing bacteria (SRB) in Kliguer medium of the stagnant waters within the facility. All this makes it possible to conclude that the observed process fits within the so-called microbiologically induced corrosion (MIC), and, in all probability, it can be affirmed that this process is promoted by the presence and proliferation of sulfate-reducing bacteria (SRB). Full article

The behavior and mechanisms of the stress-assisted microbiologically influenced corrosion (MIC) of X80 pipeline steel induced by sulfate-reducing bacteria (SRB) were investigated using focused ion beam-scanning electron microscopy (FIB). Electrochemical results show that SRB and stress have a synergistic effect on the corrosion of X80 steel. SRB accelerated the transformation of Fe₃O₄ into iron-sulfur compounds and may have caused the film breakage of X80 steel products. The obtained FIB results provide direct evidence that SRB promotes the corrosion of X80 steel. Full article

The main part of sewer pipelines is commonly made up of precast reinforced concrete pipes (RCPs). However, they often suffer from microbiologically induced concrete corrosion (MICC), which has made them less durable than expected. In this study, three-edge bearing tests (TEBT) are performed on full-scale RCPs with preset wall losses to determine how MICC influences their bearing performance. For this purpose, several bearing indices such as D-load, peak load, ultimate load, ring deflection, ring stiffness, and failure energy are presented or specified to characterize the load-carrying capacity, stiffness, and toughness of these RCPs. It is found that crown concrete corrosion hardly changes the mechanical behavior of the first elastic zone of RCPs, so that D-load is not affected, but it shortens the crack propagation zone significantly, leading to a reduction in ultimate and peak loads. Furthermore, RCPs’ ring stiffness and toughness are negatively correlated to thickness of wall loss, while the transverse deformability of the ring cross-section is positively correlated with it. Additionally, it was found that crown corrosion affects the ultimate load of different sizes of RCP in different ways. The 2000 mm RCP is affected the most, with a 50 percent reduction in ultimate load. The 1000 mm RCP follows, with a 36 percent reduction, and the 1500 mm RCP has a reduction of less than 20 percent. This research contributes to comprehending the degradation of in-service sewage pipes, hence informing decision making on sewer maintenance and rehabilitation. Full article

Microbiologically induced concrete corrosion (in wastewater pipes) occurs mainly because of the diffusion of aggressive solutions and in situ production of sulfuric acid by microorganisms. The prevention of concrete biocorrosion usually requires modification of the mix design or the application of corrosion-resistant coatings, which requires a fundamental understanding of the corrosion process. In this regard, a state-of-the-art review on the subject is presented in this paper, which firstly details the mechanism of microbial deterioration, followed by assessment methods to characterize biocorrosion and its effects on concrete properties. Different types of corrosion-resistant coatings are also reviewed to prevent biocorrosion in concrete sewer and waste-water pipes. At the end, concluding remarks, research gaps, and future needs are discussed, which will help to overcome the challenges and possible environmental risks associated with biocorrosion. Full article

Microbiologically induced corrosion (MIC) leads to the degradation/deterioration of concrete pipes, due to the formation of gypsum. Magnesium hydroxide powders may protect the concrete surface by maintaining alkaline pH values at the surface, or by neutralizing the biogenic produced sulfuric acid. An accelerated sulfuric acid spraying test in a custom-made spraying chamber used to examine the consumption of magnesium hydroxide coating, which was applied on poly (methyl methacrylate) plates, instead of applying it on concrete substrates. In that way, only the magnesium hydroxide coating can interact with the acid and can be examined separately. Surface pH measurements and the mass changes were daily conducted, during the four-day accelerated spraying test. The mineralogical phases of the surface were determined by using X-ray Diffraction (XRD) measurements. Full article

Concrete sewer pipes can be corroded by the biogenic sulfuric acid (H₂SO₄) generated from microbiological activities in a process called biocorrosion or microbiologically induced corrosion (MIC). In this study, inhibitors that can reduce Acidithiobacillus thiooxidans growth and thus may reduce the accumulation of biofilm components responsible for the biodegradation of concrete were used. D-tyrosine, tetrakis hydroxymethyl phosphonium sulfate (THPS) and TiO₂ nanoparticles were investigated as potential inhibitors of sulfur-oxidizing bacteria (SOB) growth. Results showed that most of the chemicals used can inhibit SOB growth at a concentration lower than 100 mg/L. TiO₂ nanoparticles exhibited the highest biocide effect and potential biocorrosion mitigation activity, followed by D-tyrosine and THPS. Full article