Prevention and control of biocorrosion

Microbial colonization of metals and alloys of industrial usage takes place through the formation of biofilms made of bacteria, extracellular polymeric substances (EPS) and mainly water. These biological deposits can drastically modify the corrosion behavior of structural metals and alloys enhancing localized alterations in the type and concentrations of ions, pH, and oxygen levels. However, biofilms also facilitate the formation of diffusional barriers to the exchange of chemical species from and towards the metal/solution interface. Problems due to biocorrosion and biofouling of industrial systems range from heavy microbiological contamination with consequent energy and efficiency losses to structural failures owing to corrosion.The use of appropriate monitoring strategies complemented with field and laboratory microbiological techniques is necessary to reach a proper understanding of the effects derived from microbiological activity and the role of biofilms in the corrosion reaction to later implement effective control and preventive countermeasures. It must be emphasized that this assessment should be made for each industrial system, considering its previous history, present operational conditions, physicochemical composition of the intake water and the number and identity of microbial contaminants.Cleaning procedures, most relevant biocides and other methods for prevention and control of biocorrosion like coatings, and cathodic protection are successively described. Updated information about monitoring strategies is also included in the final part of the paper.     

Phylogenetic characterization of a corrosive consortium isolated from a sour gas pipeline

Biocorrosion is a common problem in oil and gas industry facilities. Characterization of the microbial populations responsible for biocorrosion and the interactions between different microorganisms with metallic surfaces is required in order to implement efficient monitoring and control strategies. Denaturing gradient gel electrophoresis (DGGE) analysis was used to separate PCR products and sequence analysis revealed the bacterial composition of a consortium obtained from a sour gas pipeline in the Gulf of Mexico. Only one species of sulfate-reducing bacteria (SRB) was detected in this consortium. The rest of the population consisted of enteric bacteria with different characteristics and metabolic capabilities potentially related to biocorrosion. Therefore, several types of bacteria may be involved in biocorrosion arising from natural biofilms that develop in industrial facilities. The low abundance of the detected SRB was evidenced by environmental scanning electron microscopy (ESEM). In addition, the localized corrosion of pipeline steel in the presence of the consortium was clearly observed by ESEM after removing the adhered bacteria.     

Effect of W–TiO2 composite to control microbiologically influenced corrosion on galvanized steel

Microorganisms tend to colonize on solid metal/alloy surface in natural environment leading to loss of utility. Microbiologically influenced corrosion or biocorrosion usually increases the corrosion rate of steel articles due to the presence of bacteria that accelerates the anodic and/or cathodic corrosion reaction rate without any significant change in the corrosion mechanism. An attempt was made in the present study to protect hot-dip galvanized steel from such attack of biocorrosion by means of chemically modifying the zinc coating. W–TiO₂ composite was synthesized and incorporated into the zinc bath during the hot-dipping process. The surface morphology and elemental composition of the hot-dip galvanized coupons were analyzed by scanning electron microscopy and energy dispersive X-ray spectroscopy. The antifouling characteristics of the coatings were analyzed in three different solutions including distilled water, seawater, and seawater containing biofilm scrapings under immersed conditions. Apart from electrochemical studies, the biocidal effect of the composite was evaluated by analyzing the extent of bacterial growth due to the presence and absence of the composite based on the analysis of total extracellular polymeric substance and total biomass using microtiter plate assay. The biofilm-forming bacteria formed on the surface of the coatings was cultured on Zobell Marine Agar plates and studied. The composite was found to be effective in controlling the growth of bacteria and formation of biofilm thereafter.     

Surface analysis and materials characterization for the study of biodeterioration and weathering effects on cultural property

Several methods for material characterization and surface analysis such as scanning electron microscopy (SEM), energy dispersion X-ray analysis (EDX), environmental scanning electron microscopy (ESEM), petrographic analyses, Mössbauer spectroscopy (MS), conventional X-ray diffraction (XRD), grazing incidence diffraction (GID), Raman spectroscopy (RS), other spectroscopic techniques like X-ray photoelectron spectroscopy (XPS), reflection electron energy-loss spectroscopy (REELS) and advanced combined applications of synchrotron based μ-X-ray diffraction/μ-X-ray fluorescence (SR-μXRD/μXRF) can be used for assessing weathering and biodeterioration effects on materials (such as stone buildings, metallic artefacts, pigments, mixtures, and processes) of cultural property. Molecular biology techniques to identify the microbial components of biofilms are also described. Different examples of the use of these methods in the field of cultural property preservation are presented.     

Microscopies,spectroscopies and spectrometries applied to marine corrosion of copper

Used in combination, surface analytical techniques can resolve spatial relationships between bacteria and localized corrosion, determine specific corrosion mechanisms and differentiate between abiotic and biotic processes. Confocal laser scanning microscopy and scanning vibrating electrode microscopy were used to demonstrate that marine bacteria and anodic sites are co‐located. Environmental scanning electron microscopy coupled with energy dispersive X‐ray spectros‐copy was used to demonstrate dealloying of nickel from copper: nickel alloys. X‐ray absorption spectroscopy, and transmission electron microscopy equipped with electron energy loss spectrometry were used to determine the speciation of copper associated with corrosion products.     

An impedance study on admiralty brass dezincification originated by microbiologically influenced corrosion

In this article we describe a field study of biofouling and microbiologically influenced corrosion (MIC) of admiralty brass heat exchanger tubes in contact with running fresh water on the river Tagus close to Almaraz nuclear power plant in Spain. Dezincification originated by biofouling and MIC was studied using impedance, polarization resistance, gravimetric, scanning electron microscopy (SEM), and X-ray diffraction (XRD) measurements. Close correlation was observed between the biofilms formed and the corrosion process (dezincification) using the different experimental techniques. Impedance data showed a capacitive behavior including two time constants. Kramers-Kronig (KK) transforms were used to validate impedance data. The admiralty tubes' impedance data satisfied the KK relations.     

Microbe-surface interactions in biofouling and biocorrosion processes.

The presence of microorganisms on material surfaces can have a profound effect on materials performance. Surface-associated microbial growth, i.e. a biofilm, is known to instigate biofouling. The presence of biofilms may promote interfacial physico-chemical reactions that are not favored under abiotic conditions. In the case of metallic materials, undesirable changes in material properties due to a biofilm (or a biofouling layer) are referred to as biocorrosion or microbially influenced corrosion (MIC). Biofouling and biocorrosion occur in aquatic and terrestrial habitats varying in nutrient content, temperature, pressure and pH. Interfacial chemistry in such systems reflects a wide variety of physiological activities carried out by diverse microbial populations thriving within biofilms. Biocorrosion can be viewed as a consequence of coupled biological and abiotic electron-transfer reactions, i.e. redox reactions of metals, enabled by microbial ecology. Microbially produced extracellular polymeric substances (EPS), which comprise different macromolecules, mediate initial cell adhesion to the material surface and constitute a biofilm matrix. Despite their unquestionable importance in biofilm development, the extent to which EPS contribute to biocorrosion is not well-understood. This review offers a current perspective on material/microbe interactions pertinent to biocorrosion and biofouling, with EPS as a focal point, while emphasizing the role atomic force spectroscopy and mass spectrometry techniques can play in elucidating such interactions.     

Mitigation of the corrosion-causing Desulfovibrio desulfuricans biofilm using an organic silicon quaternary ammonium salt in alkaline media simulated concrete pore solutions

Abstract

Organic silicon quaternary ammonium salt (OSA), an environmentally friendly naturally occurring chemical, was used as a bacteriostatic agent against sulphate-reducing bacteria (SRB) on a 20SiMn steel surface in simulated concrete pore solutions (SCP). Four different media were used: No SRB (NSRB), No SRB and OSA (NSRB?+?OSA), With SRB (WSRB), With SRB and OSA (WSRB?+?OSA). After biofilm growth for 28 days, optimized sessile SRB cells survived at the high pH of 11.35 and as a result these cells caused the breakdown of the passive film due to the metabolic activities of the SRB. Corrosion prevention results showed that the OSA was effective in mitigating the growth of the sessile SRB cells and reduced corrosion in the SCP. These results were further confirmed by scanning electron microscope images, energy dispersive X-ray analysis, confocal-laser scanning microscopy, X-ray photoelectron spectroscopy and corrosion testing using electrochemical analysis.     

Instrumental analysis of microbiologically influenced corrosion

Appropriate application of techniques for detection andmonitoring of microbiologically influenced corrosion isessential for understanding the mechanistic nature of theinteractions and for obtaining control methods. This paperreviews techniques and methods applied tomicrobiologically influenced corrosion in recent years.The techniques presented in this paper includeelectrochemical noise measurement, concentric electrodes,scanning vibrating electrode mapping, electrochemicalimpedance spectroscopy, atomic force microscopy,confocal laser microscopy, Fourier transform infraredspectroscopy, x-ray photoelectron spectroscopy, Augerelectron spectroscopy, extended x-ray absorption finestructure and utilization of piezoelectric materials. Thesetechniques are reviewed regarding the heterogeneouscharacteristics of microbial consortia and their possibleinfluences on metal substrata. We hope this review willmotivate application and combination of new techniquesfor practical detection and on-line monitoring of theimpact of biofilms on engineering alloys.     

Electrochemical behavior of the 316L steel type in a marine culture of microalgae (<Emphasis Type="Italic">Porphyridium purpureum</Emphasis>) under the 12/12 h photoperiod and effect of different working electrode exposure conditions on the biofilm–metal interface

The industrial crops of microalgae use processes calling upon the presence of parts of metal nature such as steel 316L type. The goal of this study is to test the electrochemical behavior of this material in a marine culture of microalgae. Porphyridium purpureum was used under a photoperiod of alternation darkness/light 12/12 h, in order to apprehend the problems of biocorrosion involved in the biofouling. The evolution of the free potential of corrosion, according to the position of the samples and for different surface roughness, observations of the surface quality under the electron microscope with sweeping were carried out. The results showed that, overall, the strain P. purpureum does not have a corrosive effect on the 316L. The free potential of corrosion lies between −0.307 and −0.005 V(SCE). The adhesion of the cells seems stronger on the interface air/solid of the half-plunged sample with surface grit polished 1,000, confirmed by the presence of biofilm on the air part. The photoperiod acts on the evolution of the generated free potential of corrosion of the one 24-h period oscillation. Furthermore, the samples plunged horizontally lead to a stabilizing effect on the potential of free corrosion.     

Improvement of biofouling resistance on bacterial cellulose membranes

Bacterial cellulose possesses excellent biocompatibility and mechanical strength that show great potentials for biomaterial applications. In this study, the surface modifications of bacterial cellulose (BC) membranes were facilitated using either simple coating or chemical grafting methods. The surface coating method is to simply immobilize BC membranes with poly(ethylene glycol) (PEG) solutions of concentration from 1 to 10%, followed by post-treatment with argon (Ar) plasma. The chemical method involved grafting mPEG (monofunctional methyl ether PEG) on BCs. The outcomes of surface modifications were characterized by surface chemical compositions (electron spectroscopy for chemical analysis (ESCA), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), thermogravimetry analysis (TGA), and surface morphology (atomic force microscopy (AFM) and scanning electron microscopy (SEM)). The effects of resistance to biofouling were verified by quantifying the adsorption of proteins and mammalian cells. The results showed that the PEG coating on BCs improved the resistance to cell adhesion by more than 30%. On the other hand, the specific chemical grafting resulted in a particularly high resistance to biofouling that the density of adherent cells reduced by more than 70% when compared to that on pristine BC. We have demonstrated that the two proposed methods were effective for the preparation of bioinert BC membranes with great potentials for applications in biomaterials and tissue engineering.     

Biofilms and corrosion interactions on stainless steel in seawater

Biofouling and biocorrosion lead to an important modification of the metal/ solution interface inducing changes in the type and concentration of ions, pH values, oxygen levels, flow velocity, etc. Metal dissolution in seawater is mainly conditioned by two different processes: (a) biofouling settlement and (b) corrosion products formation.Corrosion-resistant alloys such as stainless steel present an ideal substratum for microbial colonization, rather similar to inert non-metallic surfaces, due to the lack of corrosion products. Stainless steels are sensitive to pitting and other types of localized corrosion in chloride-containing media such as seawater. Biofilms and bacterial metabolism may accelerate the initiation of crevice attack by depletion of oxygen in the crevice solution due to microbial respiration. Bacterial colonization occurs within a period of 24–72 h on stainless steel samples exposed to natural seawater and, depending on environmental conditions, a copious and patchy biofilm is generally formed.Different interpretations of biofilms' effects on corrosion are critically discussed. A practical case, involving polluted harbour seawater, is reported to illustrate biofilm and corrosion interactions on stainless steel samples.     

Corrosion behavior of carbon steel in the presence of two novel iron-oxidizing bacteria isolated from sewage treatment plants

In this work, two novel iron oxidizing bacteria (IOB), namely Gordonia sp. MZ-89 and Enterobacter sp. M01101, were isolated from sewage treatment plants and identified by biochemical and molecular methods. Then, microbially influenced corrosion (MIC) of carbon steel in the presence of these bacteria was investigated. The electrochemical techniques such as potentiodynamic polarization measurements and electrochemical impedance spectroscopy (EIS) were used to measure the corrosion rate and observe the corrosion mechanism. The results showed that the existence of these microorganisms decreased the corrosion potential and enhanced the corrosion rate. Scanning electron microscopy (SEM) images revealed the ground boundary attacks and pitting on carbon steel samples in the presence of these bacteria after polarization. Corrosion scales were identified with X-ray diffraction (XRD). It was demonstrated that these bacteria can greatly affect the crystalline phase of corrosion products that also confirmed by SEM results. It was inferred that these bacteria were responsible for the corrosion of carbon steel, especially in the form of localized corrosion.     

Mycocrystallization of gold ions by the fungus Cylindrocladium floridanum

The size and morphology determines the thermodynamic, physical and electronic properties of metal nanoparticles. The extracellular synthesis of gold nanoparticles by fungus, Cylindrocladium floridanum, which acts as a source of reducing and stabilizing agent has been described. The synthesized nanoparticles were characterized using techniques such as UV–Vis spectroscopy, X-ray diffraction (XRD), scanning electron microscopy, energy dispersive X-ray analysis (EDAX), and high-resolution transmission electron microscopy (HR-TEM). Based on the evidence of HR-TEM, the synthesized particles were found to be spherical with an average size of 19.05 nm. Powder XRD pattern proved the formation of (111)-oriented face-centered cubic crystals of metallic gold. This microbial approach by fungus for the green synthesis of spherical gold nanoparticles has many advantages such as economic viability, scaling up and environment friendliness.     

Effect of Tricalcium Magnesium Silicate Coating on the Electrochemical and Biological Behavior of Ti-6Al-4V Alloys

In the current study, a sol-gel-synthesized tricalcium magnesium silicate powder was coated on Ti-6Al-4V alloys using plasma spray method. Composition of feed powder was evaluated by X-ray diffraction technique before and after the coating process. Scanning electron microscopy and atomic force microscopy were used to study the morphology of coated substrates. The corrosion behaviors of bare and coated Ti-6Al-4V alloys were examined using potentiodynamic polarization test and electrochemical impedance spectroscopy in stimulated body fluids. Moreover, bare and coated Ti-6Al-4V alloys were characterized in vitro by culturing osteoblast and mesenchymal stem cells for several days. Results demonstrated a meaningful improvement in the corrosion resistance of Ti-6Al-4V alloys coated with tricalcium magnesium silicate compared with the bare counterparts, by showing a decrease in corrosion current density from 1.84 μA/cm² to 0.31 μA/cm². Furthermore, the coating substantially improved the bioactivity of Ti-6Al-4Valloys. Our study on corrosion behavior and biological response of Ti-6Al-4V alloy coated by tricalcium magnesium silicate proved that the coating has considerably enhanced safety and applicability of Ti-6Al-4V alloys, suggesting its potential use in permanent implants and artificial joints.     

Changes of the surface structure of corn stalk in the cooking process with active oxygen and MgO-based solid alkali as a pretreatment of its biomass conversion

This study presents a novel, efficient and environmentally friendly process for the cooking of corn stalk that uses active oxygen (O₂ and H₂O₂) and a recoverable solid alkali (MgO). The structural changes on the surface of corn stalk before and after cooking were characterized by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) techniques. The results showed that lignin and extractives were effectively removed, especially those on the surface of corn stalk. Additionally, the changes included becoming fibrillar, the exposure of cellulose and hemi-cellulose and the pitting corrosion on the surface, etc. The results also showed that the removal reaction is from outside to inside, but the main reaction is possibly on the surface. Furthermore, the results of active oxygen cooking with a solid alkali are compared with those of alkaline cooking in the paper.     

Electrospun core-shell nanofibers from homogeneous solution of poly(vinyl alcohol)/bovine serum albumin

We report on the preparation and characterization of core-shell structure of bovine serum albumin (BSA) blended poly(vinyl alcohol) (PVA) composite nanofibers by using electrospinning process. The core-shell structure nanofibers have been electrospun from the homogeneous solution of BSA (as shell) and PVA (as core). The morphology, chemical compositions, structure and thermal properties of the resultant products were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDX), high-resolution transmission electron microscopy (HR-TEM), Fourier transform infrared (FT-IR) spectroscopy, differential scanning calorimetry, thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS) techniques. The blending ratio of PVA and BSA, molecular weight of BSA and the applied voltage of electrospinning process were observed to be the key influence factors on the formation of core-shell nanofibers structure. Based on the experimental findings, we proposed a possible physical mechanism for the formation of core-shell nanofibers structure of PVA blended BSA composite.     

Interruption of Electrical Conductivity of Titanium Dental Implants Suggests a Path Towards Elimination Of Corrosion

Peri-implantitis is an inflammatory disease that results in the destruction of soft tissue and bone around the implant. Titanium implant corrosion has been attributed to the implant failure and cytotoxic effects to the alveolar bone. We have documented the extent of titanium release into surrounding plaque in patients with and without peri-implantitis. An in vitro model was designed to represent the actual environment of an implant in a patient’s mouth. The model uses actual oral microbiota from a volunteer, allows monitoring electrochemical processes generated by biofilms growing on implants and permits control of biocorrosion electrical current. As determined by next generation DNA sequencing, microbial compositions in experiments with the in vitro model were comparable with the compositions found in patients with implants. It was determined that the electrical conductivity of titanium implants was the key factor responsible for the biocorrosion process. The interruption of the biocorrosion current resulted in a 4–5 fold reduction of corrosion. We propose a new design of dental implant that combines titanium in zero oxidation state for osseointegration and strength, interlaid with a nonconductive ceramic. In addition, we propose electrotherapy for manipulation of microbial biofilms and to induce bone healing in peri-implantitis patients.     

Review--Interactions between diatoms and stainless steel: focus on biofouling and biocorrosion

There is a considerable body of information regarding bacterially enhanced corrosion, however, this review focuses on diatoms (unicellular algae) whose contribution to biocorrosion is less well studied. The reasons why diatoms have been neglected in studies of biocorrosion in natural waters are discussed and the question whether diatoms should be considered as inert with respect of electrochemical processes is considered. A particular focus is given to the case of stainless steels (SS), which are widely used in variety of applications in natural waters. Basic information on the cell biology of diatoms is included in the review, particularly with respect to their ability to 'sense' and adhere to surfaces. Investigations at the nanoscale are reviewed as these studies provide information about the behavior of cells at interfaces. Recent advances include the use of atomic force microscopy (AFM), although only a few studies have been applied to diatoms. Regarding the electrochemical behavior of SS, the mechanisms by which diatoms influence the potential ennoblement process is discussed. Such studies reveal the association of diatoms, in addition to bacteria, with biocorrosion processes.