Microbiologically influenced corrosion of ferritic steel–zirconium-based metal waste form alloy under simulated geological repository environment

The present work focused on investigating the microbiologically influenced corrosion (MIC) susceptibility of ferritic steel–Zr-based metal waste form (MWF) alloy in simulated ground water media, cultured with a common biofilm former Bacillus sp. Total viable count studies showed a good bacterial attachment on the surface of MWF alloy. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) examination of the biofilm MWF surface revealed preferential adhesion of microbes on Fe–Zr-rich intermetallic phases. Anodic polarisation and electrochemical impedance spectroscopic (EIS) studies showed active corrosion potential (E_corr), higher passive current density (I_pass) and decreased polarisation resistance (R_p) values, confirming the corrosion susceptibility of MWF alloy under Bacillus sp. biofilm.     

Cover Picture: Materials and Corrosion. 06/2021

Cover: The effect of the presence of redox active molecules during a mild anodic polarization of AISI 304 stainless steels was studied with a focus on corrosion and microbially influenced corrosion (MIC) processes. The two-part publication demonstrates that the presence of minute amounts of flavins in the preconditioning medium is capable of altering the pit nucleation processes (Part I) and promotes subsequent biofilm formation (Part II). Unexpectedly, biofilms formed on surfaces preconditioned in the presence of flavins led to corrosion inhibition. More detailed information can be found in: Nina Wurzler, Oded Sobol, Korinna Altmann, Jörg Radnik, Ozlem Ozcan, Preconditioning of AISI 304 stainless steel surfaces in the presence of flavins – Part I: Effect on surface chemistry and corrosion behavior, Materials and Corrosion 2021 , 72, 974. and Nina Wurzler, Jan D. Schutter, Ralph Wagner, Matthias Dimper, Vasile-Dan Hodoroaba, Dirk Lützenkirchen-Hecht, Ozlem Ozcan, Preconditioning of AISI 304 stainless steel surfaces in the presence of flavins – Part II: Effect on biofilm formation and microbially influenced corrosion processes, Materials and Corrosion 2021 , 72, 983.     

致密气油水共存条件下L360N管线钢的微生物腐蚀行为研究

目的 通过实验模拟L360N管线钢在致密气油水共存条件下的微生物腐蚀(MIC)行为,探究凝析油对MIC行为的影响。方法 模拟6组凝析油体积占比不同的腐蚀环境,结合失重测试和电化学实验分析了凝析油对腐蚀速率的影响规律。通过最大可能计数法(MPN法)计数试片表面的细菌固着量。采用激光显微镜、扫描电镜(SEM)、能谱仪(EDS)、光电子能谱仪(XPS)表征分析腐蚀形态和产物形貌、成分。结果 凝析油溶于水中会直接影响微生物腐蚀行为。水中存在的凝析油可显著降低L360N管线钢的均匀腐蚀速率,但不同条件下浸泡的试片表面均有明显的点蚀。所有试片表面的细菌固着量都不低于10⁴ cells/cm²,且都有生物膜形成,主要化学成分是Fe2O3和FeS。另外,在高凝析油体积占比条件下,膜内的硫化物更倾向于局部沉积,使得生物膜结构更加不均匀。电化学测试表明,随着时间的延长,各条件下的电荷转移电阻(Rct)和腐蚀电流密度(Jcorr)都变化至相近水平,凝析油含量升高不能长期抑制膜下固着菌的代谢活性。结论 L360N管线钢在不同凝析油体积占比的油水介质中均有MIC发生。其原因在于凝析油含量升高不能完全抑制生物膜的形成,还促使生物膜结构更加不均匀,为固着菌代谢提供了适宜的环境,有利于点蚀的发生。     

The influence of sulphate-reducing bacteria biofilm on the corrosion of stainless steel AISI 316

This work investigates microbially-influenced corrosion (MIC) of stainless steel AISI 316 by two sulphate-reducing bacteria, Desulfovibrio desulfuricans and a local marine isolate. The biofilm and pit morphology that developed with time were analyzed using atomic force microscopy (AFM). Electrochemical impedance spectroscopy (EIS) results were interpreted with an equivalent circuit to model the physicoelectric characteristics of the electrode/biofilm/solution interface. D. desulfuricans formed one biofilm layer on the metal surface, while the marine isolate formed two layers: a biofilm layer and a ferrous sulfide deposit layer. AFM images corroborated results from the EIS modeling which showed biofilm attachment and subsequent detachment over time.     

Microbial corrosion of galvanized steel in a simulated recirculating cooling tower system

In this study, mixed species biofilm formation including sulphate reducing bacteria (SRB) on the galvanized steel surfaces and also microbiologically influenced corrosion (MIC) of galvanized steel were observed in a model recirculating cooling water system during 10 months. A biofilm which had a heterogeneous structure formed on galvanized steel coupons. The results suggested that galvanized steel was corroded by microorganisms as well as SRB in the biofilm. Extracellular carbohydrate was degraded and quantities of carbohydrate were positively correlated with the weight loss. The concentrations of zinc in the biofilm showed significant correlations with weight loss, carbohydrate amount and SRB count.     

Effect of Geobacter sulfurreducens on the microbial corrosion of mild steel, ferritic and austenitic stainless steels

The influence of Geobacter sulfurreducens was tested on the anaerobic corrosion of four different steels: mild steel 1145, ferritic steel 403 and austenitic steels 304L and 316L. Within a few hours, the presence of cells induced a free potential (E_oc) ennoblement around +0.3 V on 1145 mild steel, 403 ferritic steel and 304L austenitic steels and slightly less on 316L. The kinetics of E_oc ennoblement depended on the amount of bacteria in the inoculum, but the final potential value depended essentially on the nature of the material. This effect was due to the capacity of G. sulfurreducens to create a direct cathodic reaction on steel surfaces, extracting the electrons directly from material. The presence of bacterial cells modified the corrosion features of mild steel and ferritic steel, so that corrosion attacks were gathered in determined zones of the surface. Local corrosion was significantly enhanced on ferritic steel. Potential ennoblement was not sufficient to induce corrosion on austenitic steels. In contrast G. sulfurreducens delayed the occurrence of pitting on 304L steel because of its capability to oxidize acetate at high potential values. The electrochemical behaviour of 304L steel was not affected by the concentration of soluble electron donor (acetate, 1–10 mM) or the amount of planktonic cells; it was directly linked to the biofilm coverage. After polarization pitting curves had been recorded, microscopic observations showed that pits propagated only in the surface zones where cell settlement was the densest. The study evidenced that Geobacter sulfurreducens can control the electrochemical behaviour of steels in complex ways that can lead to severe corrosion. As Geobacteraceae are ubiquitous species in sediments and soils they should now be considered as possible crucial actors in the microbial corrosion of buried equipment.     

Influence of strain Bacillus cereus bacterium on corrosion behaviour of carbon steel in natural sea water

This paper examines the corrosion behaviours of carbon steel immersed in sterile natural sea water with and without strain Bacillus cereus. Electrochemical studies, including Tafel plots and electrochemical impedance spectroscopy (EIS) were performed to evaluate the variation of the corrosion behaviour of carbon steel in medium containing B. cereus as compared to the sterile control samples. The results of Tafel plot measurements showed significant reduction in the corrosion rate in the presence of bacterial biofilm produced by strain B. cereus. The EIS data showed that the charge transfer resistance is greater in a medium containing B. cereus and increases with immersion time.     

Development of microbially influenced corrosion on carbon steel in a simulated water injection system

Microbially influenced corrosion (MIC) on internal pipeline surfaces has become a severe problem during the water injection process in secondary oil recovery. The formation of a biofilm, normally dominated by sulfate‐reducing bacteria (SRB), is believed to be the critical step of the MIC process. A continuously fed biofilm simulating the water injection process was operated to investigate the influence of biofilm development on MIC behavior in the early phase of corrosion development. The development of the corrosion product film and biofilm was monitored for 5 months with electrochemical impedance spectroscopy, linear polarization resistance, scanning electron microscopy, 3D optical profiling, and direct weight measurement. MIC development was found to comprise three phases: initialization, transition, and stabilization. The initialization phase involved the formation of the corrosion product layer and the initial attachment of the sessile microbes on metal surface. In the transition phase, the MIC process gradually shifted from charge‐transfer‐controlled reaction to diffusion‐controlled reaction. The stabilization phase featured mature and compact biofilm on the metal surface, and the general corrosion rate (CR) decreased due to the diffusional effect, while the pitting CR was enhanced at a lower carbon source level, which supported the mechanism of direct electron uptake from the metal surface by SRB.     

Electrochemical stability of hot dip galvanised steel in an acid environment containing Thiobacillus Ferrooxidans

Abstract

Hot dip and non-hot dip galvanised steel specimens were immersed in a 9K medium containing Thiobacillus ferrooxidans and the weight change and variation in potential with time measured. After this period, the surfaces of the specimens were observed using a scanning electron microscope and analysed by energy dispersive analysis by X-rays (SEM-EDX). Both specimens showed increased weight changes after immersion in the 9K medium with T. ferrooxidans, but did not show any significant difference in potential in the solution with T. ferrooxidans and that without the microorganisms. However, SEM-EDX analysis of the specimens immersed in the microbially infected solution showed the presence of dark areas that exhibited high concentrations of phosphorous and sulphur. This suggests the existence of biofilm on the specimen surface, which is implicated in microbially influenced corrosion (MIC) of the steel surface.     

Evaluation of effective biocides for SRB to control microbiologically influenced corrosion

The effects on microbiologically induced corrosion (MIC) of mild steel resulting from the presence of corrosion products in the biofilm of sulphate‐reducing bacteria (SRB) have been investigated. The culture‐media‐containing sulphide of biogenic origin was used to find out the effect of metal‐sulphide layers developed. The SRB were isolated from the Ennore brackish water (Chennai, India). Biocides with different concentrations were used to inhibit the metabolic activity of bacteria. Open circuit potentials (OCP) followed by potentiostatic polarisation measurements were carried out for the specimens with and without the biofilm. Electrochemical impedance spectrometry (EIS) and scanning electron microscopy (SEM) were used to study the accumulation of the biofilms. The corrosion rates and the mechanism of corrosion processes were understood from the investigation.     

Corrosion behavior of low-alloy steel in the presence of Desulfotomaculum sp.

The objective of this study was to determine the effect of sulfate-reducing Desulfotomaculum sp. bacteria isolated from a crude oil field on the corrosion of low-alloy steel. The corrosion rate and mechanism were determined with the use of Tafel slopes, mass loss method and electrochemical impedance spectroscopy (EIS). The formation of the biofilm and the corrosion products on the steel surface was determined with scanning electron microscopy (SEM) micrographs and energy dispersive X-ray spectra (EDS) analysis. It was observed from the Tafel plots that the corrosion potential exhibited a cathodic shift that verifies an increase in the corrosion rates. The semicircles tended to open at lower frequencies in the Nyquist plots which indicates the rupture of the protective film. The corrosion current density reached its maximum value at the 14th hour after the inoculation and decreased afterwards. This was attributed to the accumulation of corrosion products on the surface.     

Anticorrosive Influence of <Emphasis Type="Italic">Acetobacter aceti</Emphasis> Biofilms on Carbon Steel

Microbiologically influenced corrosion (MIC) of carbon steel infrastructure is an emerging environmental and cost issue for the ethanol fuel industry, yet its examination lacks rigorous quantification of microbiological parameters that could reveal effective intervention strategies. To quantitatively characterize the effect of cell concentration on MIC of carbon steel, numbers of bacteria exposed to test coupons were systematically controlled to span four orders of magnitude throughout a seven-day test. The bacterium studied, Acetobacter aceti, has been found in ethanol fuel environments and can convert ethanol to the corrosive species acetic acid. A. aceti biofilms formed during the test were qualitatively evaluated with fluorescence microscopy, and steel surfaces were characterized by scanning electron microscopy. During exposure, biofilms developed more quickly, and test reactor pH decreased at a faster rate, when cell exposure was higher. Resulting corrosion rates, however, were inversely proportional to cell exposure, indicating that A. aceti biofilms are able to protect carbon steel surfaces from corrosion. This is a novel demonstration of corrosion inhibition by an acid-producing bacterium that occurs naturally in corrosive environments. Mitigation techniques for MIC that harness the power of microbial communities have the potential to be scalable, inexpensive, and green solutions to industrial problems.     

Rainbow fringes around crevice corrosion formed on stainless steel AISI 316 after ennoblement in seawater

The crevice corrosion occurrence probability of stainless steel (SS) AISI 316 was increased under ennoblement condition due to chemically added H₂O₂ into seawater. The H₂O₂ was used to simulate the important factor causing ennoblement in natural marine biofilm. Morphology of the crevice corrosion was observed using an incident‐light source microscopy. Some interesting “rainbow” fringes were observed around micro‐crevices. The mechanism was discussed from the ions diffusion and potential distribution during the crevice formation. This result shows that under ennoblement condition the colored fringe is a distinct characteristic of the morphology of localized corrosion for stainless steel.     

Mechanism of a MIC probe

Interaction of bacterial biofilms with stainless steel is expected to alter electrochemical behaviour compared with that obtained under sterile conditions and under non-biological deposits. In principle, electrochemical signals can monitor biofilm formation and microbial activity. In this study, attempts were made to understand the mechanism by which an electrochemical sensor using periodic mutual polarisation of two similar stainless steel electrodes responds to biofilm formation. This probe is believed by others to respond to cathodic depolarisation by the biofilm, but the present study using natural fresh water showed that an increase in the galvanic and applied currents of two similar, coupled AISI Type 304 SS electrodes took place only after biofilms had initiated corrosion on the anodically polarised electrode. Comparison of electrodes with natural biofilms and deposited rust layers showed that both the films showed evidence of crevice action, but with a lower ionic resistance than a conventional crevice, therefore permitting rapid propagation of localized corrosion even in dilute chloride media.     

海洋环境下金属材料微生物腐蚀研究进展

海洋环境下的微生物易附着在金属材料表面形成生物膜,进而导致金属材料表面的微生物腐蚀(MIC)。分析了海洋环境下常见的易导致腐蚀的微生物种类及其特征,如硫酸盐还原菌(SRB)、铁氧化细菌(IOB)、产酸菌(APB)与产粘液菌(SPB)等,归纳了船舶与海洋平台涉及的微生物腐蚀及其与材料摩擦磨损的协同作用。在此基础上,重点综述了近年来碳钢、不锈钢与铜合金在海洋环境下的微生物腐蚀研究进展,包括溶解氧(DO)浓度、胞外聚合物(EPS)、生物膜微观形态等因素对碳钢MIC的影响,不锈钢在MIC过程中钝化膜与Cr元素化合物形态与含量变化,微生物抵抗Cu离子毒性机制以及铜合金在MIC过程中出现的脱合金成分腐蚀。对比了碳钢、不锈钢与铜合金表面在MIC中由生物膜、腐蚀产物与钝化膜形成的复合表面层结构差异。并从阴极去极化理论与微生物电化学腐蚀理论的角度解释了MIC,总结了两种理论间的关联性与局限性,指出了一些亟待解决的问题。     

The effect of cathodic polarization on the corrosion behavior of X65 steel in seawater containing sulfate-reducing bacteria

Sulfate-reducing bacteria (SRB) are one of the main reasons for the accelerated corrosion of steel. Cathodic polarization has been reported as an effective and economic method against marine corrosion, including microbiologically induced corrosion. However, the interaction between cathodic polarization and microbial activity has not been well defined. In this study, a fluorine-doped tin oxide electrode is used to study the effect of cathodic current on SRB cells. Fluorescence microscopy results clearly show that the attachment degree of SRB is dependent on the electric quantity and current intensity. The large electric quantity and high cathodic current (400 mA/m² × 30 h) can effectively inhibit bacterial attachment and subsequent biofilm formation. Furthermore, the effect of cathodic potential on the corrosion behavior of X65 steel in the presence of SRB is systematically investigated. Results show that the impressed charges, the increase of pH, and the formation of calcareous deposits on the electrode surface at the cathodic potential of −1,050 mV/SCE inhibit the attachment of SRB. In turn, the presence of SRB also interferes with the electrochemical reactions that occur during the polarization process, thus increasing the cathodic current. The interaction between SRB-induced corrosion and the process of preventing corrosion by various cathodic potentials is discussed.     

Potential of biocorrosion in Danish district heatings sytems

Danish district heating (DH) systems utilise water with unique characteristics that include low conductivity, high pH, nutrient poor and anaerobic (oxygen free) conditions in order to reduce corrosion rates. This survey was carried out in order to investigate the potential for biofilm formation and biocorrosion in these systems. Determination of total bacterial numbers in water samples were performed in 29 DH systems and showed a range of 10²–10⁵ cells · ml^?1. The potential for biofilm growth was further examined in corrosion monitoring units located at 6 DH locations. Total bacterial numbers in biofilm on mild steel were found in the range of 10⁴–10⁶ cells · cm^?2. The mild steel coupons were examined for general corrosion rates based on weight loss together with an investigation of pitting corrosion. The general corrosion rates were up to 12 μm · year^?1, while the pitting analysis showed pit depths up to 90 μm for half a year of exposure. Presence of sulphate reducing bacteria (SRB) was found in all systems tested with corrosion monitoring units, whereas sulphide was found to different extents in the biofilms on all mild steel coupons. It was shown that DH systems with the highest number of bacteria in the biofilm generally had the most pronounced corrosion. The results show that despite the nutrient poor environment in the DH systems the potential for biofilm formation and biocorrosion was present.     

Identification of steel corrosion associated with sulfate-reducing bacteria by electrochemical noise technique

Deterioration of steel structures in natural waters can result from microbiologically influenced corrosion (MIC) such as that caused by sulfate-reducing bacteria (SRB). Corrosion pits associated with MIC have been recently observed in submerged steel bridge piles and there is renewed interest to assess their deterioration. Conventional electrochemical techniques to identify MIC have been complicated due to the effects of the surface films and the mechanism for charge transfer by the bacteria on the steel surface. An electrochemical noise (EN) technique to identify steel corrosion in an aqueous solution has been developed and the method ideally can identify the onset of local pitting, but complications and limitations relating to data acquisition, filtering, and interpretation exist. EN analysis was shown to differentiate SRB and corrosion activity including initial biofilm development, pitting corrosion development, and diminution of SRB activity. Electrochemical behavior, environmental characteristics, SRB activity, and corrosion modality provided consistent correlation to EN and localized corrosion development.     

Effect of marine Pseudoalteromonas sp. on the microstructure and corrosion behaviour of 2205 duplex stainless steel

The effects of isolated marine Pseudoalteromonas sp. on the microstructure and corrosion behaviour of 2205 duplex stainless steel were investigated using electrochemical and surface analysis methods. Electrochemical studies demonstrated a negative shift in corrosion potential and an increase in corrosion current density in the presence of bacteria. EDS results showed a high concentration of chloride ions in the biofilm structure and a decrease in Cr content beneath the biofilm layer and near cracks. These results could lead to localised corrosion on metal surfaces. FESEM images illustrated the process of bacterial attachment on the metal surfaces at different exposure times.     

Preconditioning of AISI 304 stainless steel surfaces in the presence of flavins—Part II: Effect on biofilm formation and microbially influenced corrosion processes

Biofilm formation and microbially influenced corrosion of the iron-reducing microorganism Shewanella putrefaciens were investigated on stainless steel surfaces preconditioned in the absence and presence of flavin molecules by means of XANES (X-ray absorption near-edge structure) analysis and electrochemical methods. The results indicate that biofilm formation was promoted on samples preconditioned in electrolytes containing minute amounts of flavins. On the basis of the XANES results, the corrosion processes are controlled by the iron-rich outer layer of the passive film. Biofilm formation resulted in a cathodic shift of the open circuit potential and a protective effect in terms of pitting corrosion. The samples preconditioned in the absence of flavins have shown delayed pitting and the samples preconditioned in the presence of flavins did not show any pitting in a window of −0.3- to +0.0-V overpotential in the bacterial medium. The results indicate that changes in the passive film chemistry induced by the presence of minute amounts of flavins during a mild anodic polarization can change the susceptibility of stainless steel surfaces to microbially influenced corrosion.