Aerobic Corrosion Research Articles

Reactive transport modelling of iron bentonite interaction in the FEBEX in situ experiment

The evolution of steel/bentonite interfaces in engineered barrier systems of radioactive waste disposal is governed by the corrosion of the steel and the interaction of corrosion products with the bentonite. In the early post-closure phase of the repository, the transition from aerobic to anaerobic corrosion in combination with evolving temperature conditions and chemical gradients due to the hydration of the bentonite take place. In situ tests in underground laboratories provide a high degree of representativeness for the early transient evolution of the interfaces. Complex Fe-bentonite interaction patterns have been observed, which include a concave Fe accumulation front and distinct coloured halos around the corroding steel. A reactive transport model for the FEBEX in situ test is presented, which describes the transition from aerobic to anaerobic corrosion, the transport of O2 in the gas and liquid phase and the chemical evolution of the steel/bentonite interface during the 18 years of the experiment. The model successfully reproduces the major steps of the interface evolution: an aerobic corrosion phase characterized by accumulation of goethite in the corrosion layer, and an anaerobic corrosion phase, where Fe(II) and Fe(II)/Fe(III) corrosion products form, including a gradual re-dissolution of the aerobic corrosion products. In the anaerobic corrosion phase, some of the Fe(II) diffuses into the bentonite, where it partly reacts with remaining O2 to form Fe(III) precipitates or interacts with the clay minerals via surface complexation or cation exchange. Two different approaches for the implementation of a potential electron transfer from sorbed Fe(II) to structural Fe(III) are presented, but the lack of experimental data does not allow evaluation of their representativeness for the FEBEX in situ experiment. The model calculations qualitatively reproduce the concave shape of the Fe accumulation front in the bentonite and a distinct zonation with an iron-oxide precipitation dominated zone adjacent to the steel and a Fe(II) sorption dominated zone further into the bentonite. Sensitivity cases with respect to the hydration of the bentonite and the transport parameters point to the importance of the fast O2 diffusion in the gas phase for the formation of these characteristic interface features. The calculated thickness of the Fe-bentonite interaction zone varies from 1 to 4 cm, which is smaller than observed in some areas of the experiment, where locally this zone extended >10 cm into the bentonite. It is possible that this difference is due to a more complex flow pattern in the in situ experiment that is not captured by the model or due to an additional decoupled electron transport across oxide rich layers.

Integrated modeling, surface, electrochemical, and biocidal investigations of novel benzothiazoles as corrosion inhibitors for shale formation well stimulation

Three novel benzothiazole-based structures (BTPM series) were investigated for their anticorrosion and biocidal effectson N80 carbon steel alloys. BTPM series molecules were tested against the acidization stimulation process of shale formations oil wells, as well as their antibacterial performance as biocidal agents against water fracturing well stimulation. The anticorrosion evaluation used gravimetric and electrochemical techniques in 1 mol·dm−3 (9.86 wt%) HCl solution. Benzothiazole derivatives, namely, (E)-N-(benzo[d]thiazol-2-yl)-1-phenylmethanimine (H-BTPM), (E)-N-(6-methylbenzo[d]thiazol-2-yl)-1-phenylmethanimine (Me-BTPM), and (E)-2-(benzylideneamino) benzo[d]thiazole-6-thiol (SH-BTPM), were studied using chemical and electrochemical techniques. Experimental data showed that the inhibition efficiency of H-BTPM, Me-BTPM, and SH-BTPM for 1 × 10−2 mol·dm−3 reached 78%, 82%, and 90%, respectively. The tested compounds were found to comply with Langmuir adsorption isotherm. Quantum chemical calculations were performed to provide a rationalization for the obtained experimental data. Results of the microbial assay revealed the excellent bioactivity of the BTPM series against selected isolated bacterial strains known for their aerobic corrosion effect, emphasizing the role of these novel structures as potential biocides.

Study on aerobic corrosion characteristics of gas injection pipe wall in oil field under dry / wet interaction condition

By studying the corrosion behavior of oilfield pipelines in different oxygen content and corrosive medium under simulated ambient air/air foam flooding environment, the dry/wet interaction between the surface and the interface of the service casing is caused by the air displacement/air foam flooding, which greatly aggravates the aerobic corrosion process. The corrosion process changed from localized corrosion to uniform corrosion with the increase in dry and wet cycles. Pitting corrosion occurs in the early stages of dry and wet cycles, and the increase in chloride concentration and oxygen content will accelerate the initiation and development of pitting.

Degradation of PCB67 in soil using the heterogenous Fenton process induced by montmorillonite supported nanoscale zero-valent iron

Montmorillonite supported nanoscale zero-valent iron (MMT-nZVI) was prepared and proved to be able to induce the heterogenous Fenton process for better removal of 2,3′,4,5-tetrachlorobiphenyl (PCB67) in a long-term polluted soil. PCB67 removal depended highly on the dosages of MMT-nZVI and H2O2, and the initial pH, with the highest removal rate of 76.38% at conditions of H2O2 45.99 g·kg−1, MMT-nZVI 29.88 g·kg−1 and initial pH 3.5 after 80 min of reaction. Furthermore, PCB67 could be removed in a wider pH range (from 3.5 to near neutrality), with a loss of 13.6% in removal rate at neutral pH. With an activation energy of 21.4 kJ·mol−1, the degradation of PCB67 was an endothermic and diffusion-controlled process and followed the pseudo-first-order kinetics. That Fe2+ was supplied through aerobic corrosion of MMT-nZVI to activate H2O2 for·OH production was the possible mechanism of PCB67 degradation, leading to complete mineralization of PCB67 through two proposed pathways, with the intermediates of ethylbenzene and 3-hepten-2-one, as well as dibutyl phthalate and butyl acetate respectively.

Enhanced microbial corrosion of stainless steel by Acidithiobacillus ferrooxidans through the manipulation of substrate oxidation and overexpression of rus.

Acidithiobacillus ferrooxidans cells can oxidize iron and sulfur and are key members of the microbial biomining communities that are exploited in the large-scale bioleaching of metal sulfide ores. Some minerals are recalcitrant to bioleaching due to the presence of other inhibitory materials in the ore bodies. Additives are intentionally included in processed metals to reduce environmental impacts and microbially influenced corrosion. We have previously reported a new aerobic corrosion mechanism where A. ferrooxidans cells combined with pyrite and chloride can oxidize low-grade stainless steel (SS304) with a thiosulfate-mediated mechanism. Here we explore process conditions and genetic engineering of the cells that enable corrosion of a higher grade steel (SS316). The addition of elemental sulfur and an increase in the cell loading resulted in a 74% increase in the corrosion of SS316 as compared to the initial sulfur- and cell-free control experiments containing only pyrite. The overexpression of the endogenous rus gene, which is involved in the cellular iron oxidation pathway, led to a further 85% increase in the corrosion of the steel in addition to the improvements made by changes to the process conditions. Thus, the modification of the culturing conditions and the use of rus-overexpressing cells led to a more than threefold increase in the corrosion of SS316 stainless steel, such that 15% of the metal coupons was dissolved in just 2 weeks. This study demonstrates how the engineering of cells and the optimization of their cultivation conditions can be used to discover conditions that lead to the corrosion of a complex metal target.

Study on inner corrosion behavior of high strength product oil pipelines

Pipeline transportation is one of the five major modes of transportation. Inner corrosion problems in product oil pipelines are widespread but have not received attention, and high strength product oil pipelines are rarely used in China. In this paper, morphology and composition analysis and electrochemical methods were used to study the corrosion behaviors and characteristics of API 5L X65, X70 and X80 steel product oil pipelines. The feasibility of using high strength product oil pipelines in the transportation environment of product oil under the condition of inner corrosion is discussed, and the support for the safe operation of product oil pipelines is provided. The research results show that X80 pipeline steel has advantages over X65 and X70 pipeline steel. In the simulated liquid system of sediments in product oil pipeline, as the immersion time increases, the corrosion rate of X65, X70 and X80 pipeline steels shows a trend from high to low. Morphological analysis and electrochemical analysis showed that X80 pipeline steel showed better performance and adaptability to the environment, and its aerobic corrosion reaction was slower than that of X65 and X70 pipeline steel. X-ray photoelectron spectroscopy (XPS) results show that the three pipeline steels have the same corrosion mechanism, and all of them form Fe2O3, FeOOH, FeCO3, and FeS. The corrosion process is similar but the speed is different. This is attributed to the more corrosion-resistant trace elements in the X80 pipeline steel composition and the structure more compact. The application of high strength API 5L X80 steel in the product oil pipeline is still in its infancy, and it will be more practical to accelerate the development of API 5L X80 steel to make it more applicable to the construction of product oil pipelines.

Removal of Uranium from waste water by in-situ formation of magnetite from aerobic corrosion of mild steel

ABSTRACTIncreased concentration levels of uranium (U) in ground water from nuclear applications and use of fertilizers, is of concern as it may enter human body through drinking water and food. Removal of the heavy metal from such large volumes of environmental waste water as well as from tap water demands development of efficient, simple and cost effective technologies. Amongst others, adsorption of U by magnetite shows great promise. In the present study, a novel approach has been made for separation of the heavy metal by in-situ generated magnetite from aerobic corrosion of mild steel.

Characterization of Corrosion Behavior of Irradiated X65 Low Carbon Steel in Aerobic and Unsaturated Gaomiaozi Bentonite

2.98 kGy/h (1007 h) gamma irradiation and 90 °C (2000 h) thermal aging were exerted to X65 grade low carbon steel buried in Gaomiaozi bentonite containing 17 wt% Beishan groundwater. The average corrosion rate of X65 low carbon steel was measured. The elemental and phase distribution on cross section was characterized by using electron probe micro-analysis, high-resolution X-ray diffraction, and micro-X-ray diffraction. The following conclusions can be made: the average aerobic corrosion rate of the carbon steel is (45.16 ± 1.53) μm/year. Taking the original surface as boundary, the corrosion scale is divided into an internal dense product layer (DPL) mainly composed of Fe3O4 with segregated FeCO3 at the corrosion front and an external DPL mainly composed of Fe3O4 with segregated α-Fe2O3 and bentonite at some relics. Si, S, and Cl are concentrated at the corrosion front of the internal DPL, while Si and Al are concentrated at the external DPL.

Anaerobic Corrosion of 304 Stainless Steel Caused by the Pseudomonas aeruginosa Biofilm.

Pseudomonas aeruginosa is a ubiquitous bacterium capable of forming problematic biofilms in many environments. They cause biocorrosion of medical implants and industrial equipment and infrastructure. Aerobic corrosion of P. aeruginosa against stainless steels has been reported by some researchers while there is a lack of reports on anaerobic P. aeruginosa corrosion in the literature. In this work, the corrosion by a wild-type P. aeruginosa (strain PAO1) biofilm against 304 stainless steel (304 SS) was investigated under strictly anaerobic condition for up to 14 days. The anaerobic corrosion of 304 SS by P. aeruginosa was reported for the first time. Results showed that the average sessile cell counts on 304 SS coupons after 7- and 14-day incubations were 4.8 × 107 and 6.2 × 107 cells/cm2, respectively. Scanning electron microscopy and confocal laser scanning microscopy corroborated the sessile cell counts. The X-ray diffraction analysis identified the corrosion product as iron nitride, confirming that the corrosion was caused by the nitrate reducing biofilm. The largest pit depths on 304 SS surfaces after the 7- and 14-day incubations with P. aeruginosa were 3.9 and 7.4 μm, respectively. Electrochemical tests corroborated the pitting data.

EIS study on aerobic corrosion of copper in ground water: influence of micro-organisms

The nuclear waste disposal concept in Finland and Sweden is based on a multi-barrier system, where the solid spent fuel is placed in a cast iron container that is further enclosed in a copper canister. The copper canisters will be placed vertically in holes drilled in a deep bedrock which are then filled with a bentonite clay. The near-field environment of bentonite clay and groundwater is then expected to maintain integrity of the copper canisters for at least 100 000 years. The ground water at the final disposal depth contains micro-organisms with a vast metabolic potential, and it is known that micro-organisms may induce or accelerate the corrosion of metals. Therefore, it is of vital importance to understand the surface interactions of copper and the expected near-field environment. In this study, the results from two types of experiments that investigate the corrosion of copper in oxic ground water environment with and without micro-organisms and electrochemical impedance spectroscopy (EIS) as one of the key research methods are reported. First, long-term immersion experiments with a range of in-situ electrochemical measurements were designed to simulate the initial oxic stage of the deep geological nuclear waste repository in the presence of bentonite. Second, electrochemical laboratory tests were planned to improve understanding on the interactions between copper and the micro-organisms in ground water environment: copper specimens were incubated with micro-organisms for different time periods and then subjected to electrochemical measurements to provide data. The results collected from these two test series are reported and discussed here by focusing on the EIS data and its role in interpreting the surface processes. It is evident that EIS helps in understanding the influence of micro-organisms on the copper degradation process.

Contaminant Removal from Source Waters Using Cathodic Electrochemical Membrane Filtration: Mechanisms and Implications.

Removal of recalcitrant anthropogenic contaminants from water calls for the development of cost-effective treatment technologies. In this work, a novel electrochemical membrane filtration (EMF) process using a conducting microfiltration membrane as the cathode has been developed and the degradation of sulphanilic acid (SA) examined. The electrochemical degradation of SA in flow-by mode followed pseudo-first-order kinetics with the degradation rate enhanced with increase in charging voltage. Hydrogen peroxide as well as oxidants such as HO• and Fe(IV)O2+ were generated electrochemically with HO• found to be the dominant oxidant responsible for SA degradation. In addition to the anodic splitting of water, HO• was formed via a heterogeneous Fenton process with surface-bound Fe(II) resulting from aerobic corrosion of the steel mesh. In flow-through mode, the removal rate of SA was 13.0% greater than obtained in flow-by mode, presumably due to the better contact of the contaminant with the oxidants generated in the vicinity of the membrane surface. A variety of oxidized products including hydroquinone, p-benzoquinone, oxamic acid, maleic acid, fumaric acid, acetic acid, formic acid, and oxalic acid were identified and an electrochemical degradation pathway proposed. These findings highlight the potential of the cathodic EMF process as an effective technology for water purification.

Soil‐induced corrosion of ancient Roman brass – A case study

This work focuses on the study of the solid state processes on naturally corroded ancient brass artefact. The object, recovered from burial in the Tiber riverbed in Italy, has been characterised from a morphological, chemical and microstructural point of view. The artefact probably originates from a Roman brass coin or medal and the alloy substrate was identified as a leaded brass (85% copper, 12.8% zinc and 2.2% lead). A combination of XRF, SEM coupled with EDS spot analyses and elemental mapping, Raman spectroscopy and OM observations were employed in order to describe the corrosion processes that created the heterogeneous, multi‐layer corrosion product stratification. The identification of copper sulphide layers and the precipitation of some, rarely reported, basic copper and zinc phosphates are among the most important findings of this work. Two phases of anaerobic and aerobic corrosion emerged from the analyses. The object has undergone dezincification at early stages and decuprification later on. However, the most crucial action was the environmental elements activity, which determined the corrosion rate and the nature of the corrosion product layers. The results are critically discussed and correlated with the environmental conditions of the burial context. The study is supported by an extensive literature review.

High-throughput corrosion quantification in varied microenvironments

Harsh conditions ranging from those of biomedical implants to industrial oilfield applications prompt rapid assessment of whether and to what extent corrosion will occur. Here, we describe and demonstrate a novel high-throughput approach to quantify corrosion susceptibility based upon electrical resistance and colorimetric outputs. We illustrate this capability by quantifying aerobic corrosion rates of steel alloys within hours, and by comparing anaerobic microbiologically influenced corrosion (MIC) conditions over several days. Such methods can be extended to rapidly assess conditions that will accelerate corrosion, to compare corrosion mitigation scenarios, and to explore biofilm formation and MIC mechanisms through robust replicate conditions.

Evaluation of pH and redox conditions in subsurface disposal system for assessing influence of metal corrosion

The properties of metal corrosion, such as the corrosion rate and corrosion expansion rate, are key factors for assessing the long term performance of the subsurface disposal system. In this study, transient changes in pH were first simulated using a finite difference computer code. In the second step, the consumption times of the residual oxygen in the facility after the backfill were calculated. Finally, the supply of dissolved oxygen in the groundwater to the engineered barrier and the corrosion amount resulting from it were estimated. A high pH of around 12·5 would persist at least for 105 years inside the low permeability layer (LPL). In addition, the results suggest that the rate of oxygen supply in the form of dissolved oxygen in the groundwater was very small due to the restriction of mass transport by the LPL and the low diffusivity layer. Thus, the environment in which aerobic corrosion extremely limited was found to be of long duration. This strongly suggests that, for assessing the long term performance of the engineered barrier system, anaerobic corrosion will have to be evaluated carefully.

Microbiological and abiotic processes in modelling longer-term marine corrosion of steel

Longer term exposure of mild steel in natural (biotic) waters progresses as a bimodal function of time, both for corrosion mass loss and for pit depth. Recent test results, however, found this also for immersion in clean fresh, almost pure and triply distilled waters. This shows chlorides or microbiological activity is not essential for the electrochemical processes producing bimodal behaviour. It is proposed that the first mode is aerobic corrosion that eventually produces a non-homogeneous corroded surface and rust coverage sufficient to allow formation of anoxic niches. Within these, aggressive autocatalytic reduction then occurs under anoxic abiotic conditions, caused by sulfide species originating from the MnS inclusions typical in steels. This is consistent with Wranglen's model for abiotic anoxic crevice and pitting corrosion without external aggressive ions. In biotic conditions, metabolites from anaerobic bacterial activity within and near the anoxic niches provides additional (sulfide) species to contribute to the severity of corrosion. Limited observational evidence that supports this hypothesis is given but further investigation is required to determine all contributor(s) to the cathodic current for the electrochemical reaction. The results are important for estimating the contribution of microbiological corrosion in infrastructure applications.

The effect of aerobic corrosion on anaerobically-formed sulfide layers on carbon steel in dilute near-neutral pH saline solutions

• The corrosion rate is low when steel is exposed to anaerobic conditions (pH = 8.9). • An anaerobic corrosion with sulfide to aerobic switch increases the corrosion rate. • Aerobic conditions leads to corrosion and oxide deposition beneath FeS. • Continual air exposure leads to the blistering of the original FeS film. The aerobic corrosion of pipeline steel was investigated in an aqueous sulfide solution by monitoring the corrosion potential and periodically measuring the polarization resistance. The properties and composition of the corrosion product deposits formed were determined using scanning electron microscopy, energy dispersive X-ray analysis, and Raman spectroscopy. The establishment of aerobic conditions leads to corrosion and (oxyhydr)oxide deposition beneath the anaerobically-formed mackinawite film originally present on the steel surface. This leads to blistering and spalling of the sulfide film. Chemical conversion of the mackinawite to Fe(III) (oxyhydr)oxides also occurs but is a relatively slow reaction.

The effect of sulfide on the aerobic corrosion of carbon steel in near-neutral pH saline solutions

Severe corrosion damage may occur when gas transmission pipelines are exposed, at disbonded coating locations, to trapped waters containing sulfide followed by secondary exposure to air. Aerobic corrosion with sulfide was investigated in a long-term corrosion experiment in which corrosion was monitored by measurement of the corrosion potential and polarization resistance obtained from linear polarization resistance measurements. The properties and composition of the corrosion product deposits formed were determined using scanning electron microscopy, energy dispersive X-ray analysis, and Raman spectroscopy. A switch from aerobic to aerobic-with-sulfide corrosion doubles the relative corrosion rate.

Experimental studies of the effect of irradiation on the anaerobic corrosion of carbon steel in relation to the Belgian supercontainer concept

This paper describes recent results from an investigation of the effects of -radiation on the anaerobic corrosion of carbon steel in cement, in relation to the Belgian Supercontainer Concept for radioactive waste disposal. Anaerobic corrosion rates were measured by monitoring hydrogen evolution and the corresponding electrochemical behaviour was investigated by measuring open circuit potential and linear polarisation resistance. The test medium was alkaline simulated porewater, at -irradiation dose rates of 0 and 25 Gy hr −1 , temperatures of 25 ◦ C and 80 ◦ C and chloride concentrations of 0 and 100 mg/l. The effects of radiation on the corrosion behaviour were found to be small. The reference design for the Belgium Supercontainer for disposal of high-level nuclear waste and spent fuel consists of a 30 mm thick carbon steel cylindrical vessel ('the overpack') surrounding 309 grade stainless steel waste canisters. The overpack will be surrounded by a cementitious buffer material, which may or may not be encased in a stainless steel vessel ('the envelope'). This paper is concerned with the anaerobic corrosion processes that may affect the carbon steel overpack within the Supercontainer. The carbon steel will be exposed to alkaline porewater in the cementitious buffer or in the alkaline material which may be used as a filler in the annulus between the cementitious buffer and the overpack. After a relatively short period the interface between the steel and alkaline porewater will become anoxic as residual oxygen in the repository is consumed by aerobic corrosion and microbial activity. Low concentrations of chloride (typically 100 ppm) from the groundwater may penetrate the buffer and reach the surface of the overpack. Following a review of the corrosion issues affecting the Supercontainer design an experimental programme was initiated to investigate (i) the possible effect of gamma radiation on the anaerobic corrosion rate of carbon steel in cementitious porewaters and on the nature of the corrosion products formed, and (ii) the effect of radiation on the electrochemical and corrosion behaviour of carbon steel corroding anaerobically in simulated concrete porewater conditions. Previous publications have reported earlier results from this programme (1, 2) for both gas generation and electrochemical measurements. The aim of this paper is to provide an update on this work programme, with the main focus being on the results of the electrochemical measurements, although the results from the gas generation experiments are also shown for comparison. In essence the work programme involved setting up test cells containing representative corrosion systems and exposing them to controlled gamma radiation

Nominally Anaerobic Corrosion of Carbon Steel in Near-Neutral pH Saline Environments

Abstract Gas transmission pipeline corrosion commences when coatings disbond, exposing the steel to groundwater. When this occurs, a number of anaerobic and aerobic corrosion scenarios can be envisaged. The initial nominally anaerobic corrosion period has been investigated by applying a combination of electrochemical methods (i.e., corrosion potential, linear polarization resistance, and electrochemical impedance spectroscopy [EIS] measurements) and surface analytical techniques (scanning electron microscopy, energy-dispersive x-ray spectroscopy, and Raman spectroscopy). An evolution in film properties was observed and attributed to the entry of adventitious oxygen into faults within the preformed film. This leads to an increase in overall corrosion and a change in properties of the film as detected by EIS and Raman analysis. This article describes the mechanism involved in this transition, and provides a basis for a more extensive study of the corrosion process encountered on switching between anaerobic ...

Recent Advances in Electron Transfer Between Biofilms and Metals

Microbial biofilms produce electrochemical interactions with metal surfaces by following a wide variety of different electron exchange pathways. Reviewing the mechanisms identified in the biocorrosion of steels leads us to distinguish direct and indirect mechanisms for biofilm-catalysed cathodic reactions. Indirect mechanisms are due to the production of metal oxides or hydrogen peroxide (aerobic corrosion) or metal sulphides (anaerobic corrosion), which further react with the metal surface. Direct mechanisms involve adsorbed biocompounds, generally enzymes or their active sites, which catalyse the cathodic reduction of oxygen for aerobic biocorrosion or the proton/water reduction in anaerobic processes. Recent studies dealing with the role of hydrogenases in anaerobic corrosion have shed light on the important role of phosphate species via so-called cathodic deprotonation. Advances in the development of microbial fuel cells have also resulted in new concepts, mainly for oxidation processes. Some microbial cells have been shown to be able to produce their own electron mediators. Others can transfer electrons directly to electrodes through membrane-bound electron shuttles or achieve long-range transfer through conductive pili.