No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
A Mechanistic Model for Carbon Dioxide Corrosion of Mild Steel in the Presence of Protective Iron Carbonate FilmsPart 2: A Numerical Experiment
Abstract
A theoretical carbon dioxide (CO2) corrosion model was used to conduct numerical experiments, which allowed total in- sight into the underlying physicochemical processes. The focus was on factors influencing protective iron carbonate film formation and the effect that these films have on the CO2 corrosion process. It was confirmed that high bulk pH, high temperature, high partial pressure of CO2, high Fe 2+ concen- tration, and low velocity all lead to favorable conditions for protective iron carbonate film formation. The model can be used to identify threshold values of these parameters. Corro- sion rate was not strongly correlated with protective film thickness. The so-called surface film "coverage" effect ap- peared to be more important. Corrosion rates decreased rap- idly as the film density increased. It was shown that in the presence of dense films diffusion of dissolved CO2 through the film is the main mechanism of providing the reactants to the corrosion reaction at the metal surface. It was demon- strated that "detached" films have poor protective properties even when they are very dense. Serious errors in prediction/ reasoning can be made by operating with bulk instead of surface water chemistry conditions. The former is made possible by using advanced models such as the one used in the present study.
... In order to evaluate the iron carbonate precipitation, a useful parameter is the system supersaturation (SS Equation 2) [34]. System supersaturation is the ratio of the product of [Fe 2+ ] and [CO3 2-] and the solubility product Ksp. ...
... Concerning the temperature influence over precipitation, Nesic et al. proposed a numerical simulation of a carbon steel corroding surface in a CO2 solution [34]. In the case illustrated, iron carbonate supersaturation is already attained at room temperature, however, at this temperature, no protective corrosion deposits are formed on the carbon steel surface. ...
... The results show that the corrosion rate is higher for higher oxygen concentration. It is expected especially at 60°C, a temperature that does not allow optimal development of protective scales [34,40,104]. ...
This study is concentrated on the protectiveness of the carbon steel corrosion product scales in CO2 aqueous conditions. At first, a bibliographic study is performed on the characteristics of a corrosion product layer both from the electrochemical perspective and a structural perspective dealing with its morphology and composition. A specific section is dedicated to pseudo-passivation of carbon steels, a particularly protective condition that forms spontaneously in certain environments. Finally, the effect of relevant impurities presents in industrial environments such as chlorides, calcium ions and oxygen, is analyzed in relation to the protectiveness of the scales and the corrosion processes. In order to investigate the scales protectiveness and the changes that some inputs have on them pseudo-passivation, a reference experimental condition is selected. Pseudo-passive scales are composed by siderite; magnetite is observed occasionally and never forming a continuous film between the siderite layer and the carbon steel substrate. The electrochemical reaction mechanism explaining pseudo-passivation is investigated by applying different overpotential and flow conditions on the pseudo-passivated scales. Using the observations obtained with those experiments, an electrochemical impedance model is proposed explaining the behavior of the reactions before and after pseudo-passivity. It is considered that before pseudo-passivation, a simple reduction of the active surface slows down the corrosion of the carbon steel. After the pseudo-passivation, a diffusion limitation attributed to the anodic reaction (going through an adsorbed step process) is proposed. Finally, the effect of oxygen contamination in CO2 aqueous conditions is investigated. Oxygen contamination is introduced in the hundreds of ppb range. O2 changes the corrosion morphology from a uniform corrosion type to a localized one. Inside the localized corrosion features, other phases than siderite such as chukanovite, precipitate. The propagation of the localized corrosion features depth is strongly correlated to the oxygen content of the solution. The propagation of the pits stops when O2 is not present anymore and for our experimental conditions, a protective pseudo-passive layer is rebuilt. Our results could be explained with an O2 contamination model already proposed in the literature.
... In the empirical/semi-empirical models mentioned above, the influence of corrosion product film on corrosion rate is usually presented as an impact factor, which is not related to the ion mass transfer process, and the definition is not clear [30]. Different from the empirical correction constants, Nesic et al. [31] took into account the characteristics of corrosion product layer thickness, porosity and curvature, and introduced the influence of corrosion product film into the mechanistic model. This is a theoretical finding but also a complicated and difficult calculation since we need to solve the mass conservation equation of each species to obtain the concentration of all chemical substances on the steel surface [32]. ...
... If the working conditions change, the influence factor can be calculated according to the actual corrosion rate in the corresponding conditions, which can be taken as the function of temperature, flow rate, pH value, CO 2 partial pressure, ion concentration and others. As shown in Eq. (31). ...
Based on corrosion thermodynamics and kinetics, considering the multi-field coupling effects of fluid flow, electrochemical reaction and mass transfer process, a new corrosion prediction mechanistic model was proposed by introducing the influence factor of corrosion product film on diffusion coefficient of ion mass transfer, which is based on the CO 2 corrosion prediction model proposed by Nesic et al. The influence of temperature, flow rate and pH value on CO 2 corrosion behavior on 20# steel was studied by orthogonal tests. Scanning electron microscopy (SEM) and energy spectrum analysis (EDS) was used to analyze the surface and cross section morphology of the corrosion product film, and the thickness of the corrosion product film was measured. The results show that the introduced influence factor can simplify the ion mass transfer calculation in the presence of corrosion product film, and the relative error between the predicted value of the modified model and the experimental results is satisfactorily controlled less than 10%. Compared with the prediction model without considering the influence of corrosion product film, the influence factor can effectively correct the high prediction value of the mechanistic model under the influence of corrosion product film, improve the accuracy and applicability of corrosion prediction, and provide important theoretical guidance for the design, manufacturing, operation and maintenance of oil and gas production pipelines and related facilities.
... With the development of computer technology, experts have combined computational methods with experimental and theoretical analysis to reveal the mechanism of corrosion and the established mechanism model. We considered the influence of factors such as the pH value, medium flow rate, and temperature on the reduction reaction of hydrogen ions, water, and oxygen at the cathode and the dissolution process of iron at the anode in the mechanism model [9][10][11][12]. In addition, we propose dimensionless film-forming tendency factors based on the circulation experiment to establish a kinetic model of deposition growth for corrosion product films and better understand the corrosion process [13]. ...
... The dynamic inertia weight factor is introduced into the velocity update formula of the particle swarm optimization algorithm, as shown in Equation (9). ...
To predict the corrosion failure of carbon steel oil and gas pipelines more accurately, a new corrosion failure prediction model for submarine oil and gas transport pipelines was constructed. A corrosion failure prediction management system was also developed based on the constructed model. To construct the model, corrosion experiments were carried out to analyze the influences of temperature, partial pressure of CO2, pH value, and flow rate acting on the corrosion rate. Based on the analysis results and the corrosion experiment data, a new corrosion failure prediction model containing the time and flow rate for oil and gas pipelines was constructed. The model is based on the existing corrosion prediction model and has a determination coefficient, R2, of 0.9573, which indicates good prediction accuracy. A machine learning prediction model was also used to predict, and the prediction results are compared with that of the proposed model, which further verifies the accuracy and feasibility of the proposed model. A corrosion failure prediction management system for carbon steel oil and gas pipelines was developed based on the constructed model, which makes corrosion failure prediction more convenient and faster and provides a reference for the accurate prediction and efficient control of oil and gas pipeline corrosion failure.
... The key factor for the formation of FeCO 3 is the supersaturation of Fe 2+ and CO 2− 3 ions (Eq. (8)) [70]. In this study, to simulate worst-case corrosion (i.e., when the formation of protective corrosion layers is hindered), the Fe 2+ concentration was kept low (less than 80 ppm which is a critical point for FeCO 3 formation based on the experimental conditions in this study [71]) during the exposure, and this condition is not favorable for FeCO 3 scale formation. ...
... Therefore, the presence of FeCO 3 in the corrosion layer bulk and between the remaining Fe 3 C layers or particles cannot be proven by in this study. Nešic et al. [70] discussed in their study that in CO 2 corrosion, the chemical conditions on the surface of the steel can be completely different than the conditions in the bulk solution. Because of the corrosion process, Fe 2+ ions are produced, whereas H + ions are consumed on the surface of the corroding steel. ...
... Iron carbonate formation in the form of siderite (FeCO 3 ) is the most commonly observed corrosion product in an aqueous NaCl-containing medium saturated with CO 2. This has been proved to be one of the most important factors governing the rate of corrosion [1,10]. The influence of this layer on the corrosion rate of steel has been researched and documented in the literature [11][12][13][14][15]. Indeed, the iron carbonate layer can slow the general corrosion process by acting as a physical barrier to the diffusion of ionic species involved, covering up a portion of the steel surface, and preventing the underlying steel from further dissolution. ...
... The protectiveness of the iron carbonate layer is strongly dependent on several parameters such as CO 2 partial pressure [11][12][13][14], concentration of ionic species [17,18], pH and temperature [19][20][21][22]. Temperature is one of the most crucial parameters that influences the corrosion of mild steel in CO 2 environments. ...
Effects of alkanolamine molecules on the corrosion inhibition of L80-1Cr steel were studied in a CO2-saturated 1 wt% NaCl solution at well downhole temperatures of 20 and 80°C. The electrochemical results showed lower corrosion rates at 20°C, for which corrosion rates were more influenced by the alkanolamine injection. The experimental results and molecular modelling calculations using DFT revealed that alkanolamine adsorption/desorption played a determining role in the kinetics and characteristics of FeCO3 formation. Additionally, the dependency of inhibitor efficiency on both chemical structures and adsorption energy on Fe(110), FeCO3(104) and Fe3C(001) was demonstrated, resulting in the highest efficiency provided by ethanolamine.
... However, temperature fluctuations in tight geologic systems may occur over only long timescales (years to centuries). A temperature decrease could in fact result in an increase in the corrosion rate as corrosion in such complex systems is controlled by the rates of steel oxidation and CPs precipitation [48]. Modelling in pure carbonate systems predicted that the rate of CPs precipitation decreases more rapidly than that of steel oxidation as the temperature decreases towards ambient conditions [48]. ...
... A temperature decrease could in fact result in an increase in the corrosion rate as corrosion in such complex systems is controlled by the rates of steel oxidation and CPs precipitation [48]. Modelling in pure carbonate systems predicted that the rate of CPs precipitation decreases more rapidly than that of steel oxidation as the temperature decreases towards ambient conditions [48]. Such calculations however do not take into account the diffusion of reactants and products in compact clay, which is usually temperature-activated and can significantly influence the corrosion rate [38]. ...
Corrosion of low alloy carbon steel in simulated crevices and in a perforated envelope containing a rod, mimicking the liner-overpack system, was assessed at 90 °C in anoxic water-saturated clay. Corrosion in crevices was limited (< 1 µm/year). The corroded surface exposed magnetite with a fringe of siderite. Internal corrosion of the envelope was heterogeneous due to gradual filling with porewater, and average corrosion depth for the internal rod was limited to 11.5 µm after 76 months. Magnetite was the main corrosion product replacing steel, together with chukanovite, Fe silicate, and outer siderite in areas first bathed with porewater.
... A model of uniform carbon dioxide corrosion of mild steel (MS) has been developed by several researchers [1][2][3][4] in the form of electrochemical models for surface processes or semi-empirical correlations. A major issue for model development has been the effect of insoluble corrosion products on corrosion rate, for example, an iron carbonate [5]. ...
... Description In addition, expect the parameters which are shown in Table also parameters such as Henry's constant, the equilibrium constant of CO 2 hydration, H 2 CO 3 dissociation, dissociation, water dissociation reactions required in this numerical simulation were taken from the literature [1][2][3][4]. Also, the initial concentration of all species in solution (CO 2 , H 2 CO 3 , , , H + , OH -, Fe 2+ ) was calculated using the above mentioned equilibrium constants. ...
In this work corrosion of mild steel affected by carbon dioxide was studied using a simulation model developed by Nordsveen M. and Nesic S. Using this comprehensive model of the uniform corrosion made possible to predict of corrosion rate of steel in the carbonic acid medium and the influence of different conditions on the anticorrosive property of coated electrode has been investigated. 1D model of corrosion process includes Butler-Volmer and Tafel equations and takes into account both the kinetics of anodic dissolution of an iron and electrochemical discharge of carbonic acid, water and hydrogen ions. The model has been created in COMSOL Multiphysics software and further improvement of this model allowed studying the influence of parameters such as solution composition, the partial pressure of CO2, temperature and flow velocity of the solution on the corrosion rate of the steel. The results of numerical simulation demonstrate that the use of conductive polymerpolypyrrole/ SiO2 composite as an anti-corrosive resin coating reduces the corrosion rate of mild steel by 7 times or more, depending on pH, temperature and flow rate. Furthermore, increasing of flow velocity from 0.1 to 10 m/s affects to the removal of corrosion products from the surface of mild steel and as a result corrosion rate raises from 0.3 to 0.45 mm/year at a temperature of 80 °C and pH=4.
... Numerous researchers have looked into the mechanism of CO 2 corrosion of carbon steel [6][7][8][9][10] and the effect of protective FeCO 3 (siderite) precipitation on the corrosion process is very well established qualitatively [11][12][13][14]. However, various CO 2 corrosion models exists within the oil and gas industry and across them, there is no consensus on exactly how the protective scale is formed or how the scale structure quantitatively controls the corrosion rate [15,16]. ...
... As explained above, there are various techniques that can be used to solve the co-diffusion equations, Eqs. 12 and 13, some of them analytical and others numerical. 12,18,20,[25][26][27][28][29][30] The numerical techniques are generally effective but do not result in explicit expressions that can be readily used in electrochemical models. On the other hand, the existing analytical methods 3,18-20,28-30 proposed in the past cannot cope with the chemical reaction terms such as those given in Eqs. 12 and 13. ...
The limiting current density for the hydrogen evolution reaction in aqueous saturated carbon dioxide solutions needed revisiting, as the basic understanding of the underlying reaction mechanism in weak acids has changed over the past few years. We now know that the direct reduction of undissociated carbonic acid on a metal surface in aqueous carbon dioxide solutions is not significant, as was thought before, and that there is only a single dominant pathway for hydrogen evolution: reduction of free hydrogen ions. The main role of weak carbonic acid is to provide additional hydrogen ions via buffering. Therefore, a new mathematical model was needed for calculation of the limiting current density for hydrogen ion reduction, that accounts for both hydrogen ion diffusion in the boundary layer and simultaneous buffering provided by dissociation of weak carbonic acid. The new model relies on analytically solving the co-diffusion of hydrogen ions and carbonic acid in the mass transfer boundary layer, with simultaneous homogenous chemical reactions. The new expression for the limiting current density takes the form:
iLim = F*sqrt(Deff*kf*c_CO2*c_H)*coth(Delta_m/Delta_r)
The performance of the new model was successfully validated by comparing it with experimental data over a broad range of conditions.
... At higher exposure temperatures, the faster reaction kinetics result in greater local release of Fe 2+ and greater consumption of H + ions during corrosion. Thus, the local pH near the steel surface can be increased when the corrosion process initiates [41][42][43]. Even if the bulk solution is undersaturated, the increased local pH results in an increase in supersaturation at the steel surface, with probable FeCO 3 precipitation on the steel surface. ...
The effect of cooling rate-induced microstructural changes on the corrosion resistance in a CO2-saturated 3.5 wt.% NaCl solution have been explored for an API L80-1Cr steel. The corroded layer majorly contains siderite, akagenite, and undissolved cementite. The amount of FeCO3 in this layer is larger for the water-cooled sample with a martensitic structure, whereas the furnace-cooled sample with a ferritic-pearlitic structure contains a larger amount of akagenite. The retained cementite and the microrough surface of the furnace-cooled sample provide greater anchoring to the scale. Comparing samples cooled at different rates, the furnace-cooled condition appears to provide better CO2 corrosion resistance.
... Being an assist gas in oil and gas fields, carbon dioxide accelerates corrosion of the pipeline metal. The detailed reviews devoted to carbon dioxide corrosion [1][2][3][4][5] demonstrated that dissolved СО 2 can both serve as the depolarizer promoting the corrosion (for example, at the reduction of Н + , and Н 2 CO 3 ions) and make easier the formation of protective oxide-carbonate films on the metal surface [6][7][8]. The former effect can be explained by the direct involvement of H + , and Н 2 CO 3 in the cathodic process [9][10][11][12] and also by the buffering properties of carbonic acid which maintains the constant concentration of protons in the near-surface region [12]. ...
... The enhanced current density was attributed to the promotion of anodic reactions via the following reactions [3,40,41]: ...
A combination of an in-situ microzone injection test and ab-initio DFT calculations was employed to investigate the effect of H⁺ and Cl⁻ ions on the degradation of the FeCO3 corrosion products. The experimental results show that an acidic environment promoted the dissolution kinetics of the FeCO3 scales while the presence of Cl⁻ ions induced FeCO3 surface reconstruction. The DFT calculations validate the experimental results and indicate that both H⁺ and Cl⁻ corroded FeCO3 surface through weakening of the Fe-O bond and increased the corrosion active sites.
... Corrosion losses affect many sectors, such as in petroleum installations, production equipment, processing, storage tanks, transportation, and other facilities. Severity of corrosion depends on many operating conditions, such as temperature, flow conditions, type of corrosive aqueous solution, etc. Water containing salts and saline solutions represent one of these aggressive media [1,2]. This salty water is naturally produced with oil. ...
The behavior of the corrosion inhibition of mild steel in a brine produced water saturated with carbon dioxide using 1, 3, 5, 7-tetraazaadamantane (TAA) as a heterocyclic organic inhibitor was investigated. Gravimetrical and electrochemical methods were used to determine corrosion rates and the experimental work were mathematically designed using Doehlert experimental design (DED). Corrosion rate was optimized as a function of TAA dosage, temperatures, and rotation rate. Maximum corrosion inhibition efficiency was 92% at optimum conditions. TAA was adsorbed chemically and spontaneously on metal surface according to Langmuir isotherm. These results were confirmed by scanning electron microscopy (SEM), optical microscopy, UV–Vis spectral, and FTIR techniques. Quantum chemical analysis was used as a theoretical tool. It was found that the protonated state of TAA was more efficient than the ground state.
... Les observations visuelles montrent un recouvrement de l'acier par une couche de produits de corrosion, après 100 heures d'immersion, dont le spectre Raman montre la présence de sidérite. La communauté scientifique s'accorde à dire que cette couche est majoritairement constituée de sidérite FeCO3 [108]- [110]. Dans certaines conditions de pH et de températures, des fragments de magnétite ont été détectés sous la couche de sidérite [25] [111] mais aucune analyse complémentaire n'a été effectuée dans le cadre de la thèse. ...
Ce travail s’inscrit dans le cadre du projet SCCoDRa (Suivi et Contrôle de la corrosion des Composant métalliques pour le stockage des Déchets Radioactifs). L’étude vise à contribuer à des propositions de combinaisons de techniques capables d’apporter des informations complémentaires pour la détection et le suivi de la corrosion localisée et uniforme d’un acier au carbone. Dans un premier temps, les potentialités du Bruit Electrochimique (BE) et de l’Emission Acoustique (EA) ont été étudiées pour la détection, l’identification et le suivi de la corrosion localisée d’un acier au carbone. Des milieux Ca(OH)2, sat et NaHCO3 contenant des ions chlorure ont été utilisés afin d’activer cette corrosion et d’obtenir des sites corrodés de taille millimétrique sur des temps d’immersion courts. Les essais effectués dans ces milieux ont permis de définir l’apport et les limites de chaque technique. Dans un deuxième temps, plusieurs techniques électrochimiques telles que l’Analyse des Harmoniques (HDA – Harmonic Distorsion Analysis), le bruit électrochimique, la Résistance de Polarisation Linéaire (RPL) et la Spectroscopie d’Impédance Electrochimique (SIE) ont été utilisées pour suivre la vitesse de corrosion uniforme d’un acier au carbone lorsqu’il est immergé dans une solution saline sous atmosphère CO2.
... As a process of mechanical and electrochemical interaction, SCC was closely related to water chemical environment. In the formation water, Table 3 The effect factor of CO 2 pressure, temperature and the synergistic effect of the two on the SCC susceptibility (I ψ ). the equilibrium reactions during the CO 2 dissolution process and corresponding reaction equilibrium constants were listed as follows (reaction (7)- (11)) [38][39][40][41], ...
The stress corrosion cracking of HP-13Cr stainless steel in the geothermal environment was studied by experimental measurements and modeling calculations. The stress corrosion cracking susceptibility of HP-13Cr stainless steel increases with both temperature and CO2 pressure, and shows a synergistic effect greater than the temperature or CO2 pressure does singly. The fracture morphologies presented quasi-cleavage fracture characteristic in the geothermal environment. The stress corrosion cracking mechanism is dominated by the anodic process. The critical stress intensity factor for stress corrosion cracking was measured and the pitting-to-cracking process was clarified by a mechanism model.
... • Experimental database for validating the model is usually scarce. Example (Nesic et al., 2003, Vitse et al., 2003, Zhang et al., 2007 ...
It is essential for infrastructure managers to predict the remaining service life of buried pipelines since their structural failure impact the social, environmental and financial aspects of the country. Corrosion is known to be one of the major contributors to the failure of the pipeline. Reliability analysis methods are widely used for predicting the future structural integrity of pipeline subjected to corrosion. Incorporating the realistic corrosion modelling techniques based on the random-field theory into the reliability analysis methods enables Spatio-temporal reliability assessment of corroding pipes. Implementation of Spatio-temporal reliability analysis methods, however, requires calibration of the correlation structure that exists over the geometry of the pipe corroding surface with the real data. It has been shown that incorporating the finite element models of corroding surfaces into the Spatio-temporal reliability analysis methods provides a comprehensive structural integrity assessment of corrosion affected structures. The existing models for corroding surfaces, however, do not consider both the spatial and temporal variations of corrosion altogether. Throughout the literature, the reliability of interconnected pipes is studied through the structural system reliability concept. It has been shown that the matrix-based system reliability (MSR) outperforms other methods due to its unique features. To account for the correlation between components, the MSR requires fitting a Dunnett-Sobel class (DS-class) correlation matrix to the general correlation coefficient matrix which can be a challenging task, especially for a large number of common source random variables.
In this research, a semi-empirical time-dependent correlation length model is proposed to model the evolutions of the correlation structure of the pipe corroding surface over time. The model is developed based on the data collected from failed cast-iron water pipes buried in Melbourne suburbs. Moreover, this research proposes a FEM-based Spatio-temporal reliability analysis method based on copulas and gamma process. The method is fed with the developed correlation length model to provide an ever-realistic framework for Spatio-temporal reliability analysis of corroding pipes at the component level. As for the system reliability analysis, the research proposes a copula-based MSR that eliminates the need for DS-class matrix fitting. The results show that the proposed method is not only more accurate than the traditional method, but it is easier to set up.
Finally, as a case study, this research shows the application of the proposed methodology for reliability analysis of a pipeline network with unknown failure history. The result enables for ranking the pipe segments based on the predicted time of failure and, therefore, finding the location and time of failure in a buried pipeline network with unavailable failure history.
Moreover, the results indicate the necessity of the corrosion correlation structure calibration when attempting Spatio-temporal reliability analysis at both the component and the system level. The results of the proposed methodology allow asset managers to plan an accurate maintenance strategy for the pipeline. The maintenance strategies are mainly involved in finding a balance between the probability of failure and the cost of reducing the risk. Therefore, an optimal maintenance strategy can be obtained using the probability of failure estimation from the proposed method in this research and cost information which is determined by stakeholders.
... It is understood to be incorrect but no other expression of the equilibrium constants is available. This is not the case with FeCO 3 where both the solubility constant as well as the dissociation constants are a function of ionic strength (NaCl concentration) [45]. ...
A parametric study defined a window of conditions leading to pitting of mild steel in marginally sour environments: temperatures between 30°C and 60°C, pH2S from 0.02 mbar to 0.15 mbar, bulk pH below 6, and sodium chloride concentrations between 1 and 10 wt. %. A 100∼300 nm porous layer containing both mackinawite and magnetite was observed by transmission electron microscopy. Pitting initiated when the mackinawite layer was broken-down and exposed the steel surface to highly corrosive H2CO3. Pitting propagated due to the galvanic coupling between the exposed steel surface and the rest surface area covered by the conductive mackinawite.
... In recent years, CO 2 corrosion has been extensively investigated to understand the fundamental corrosion mechanism, whereas corrosion prediction models have also been developed to predict the CO 2 -induced corrosion for various steels [11]. The current prediction models, including empirical models [34,35], semi-empirical models [36][37][38], and comprehensive mechanistic models [39][40][41], mainly focus on CO 2 -induced general corrosion of mild steel. It should be noted that the pitting corrosion plays a major role in the failure of wells. ...
A multi-degree of freedom mechanistic-chemometrics model for predicting the pitting damage of HP-13Cr stainless steel is developed by combining the mechanistic models and chemometrics method. The mechanistic model is reconstructed by considering the effect of single factors, such as high temperature, high CO2 pressure, flow rates and complex stress distribution. The single mechanistic models are combined together considering the weight coefficients of variable interaction using the chemometrics method. Finally, the predicted results are validated by six-year-served field data, which indicates that the newly developed mechanistic-chemometrics model is accurate and highly reliable.
A numerical exploration of a comprehensive mechanistic aqueous carbon dioxide (CO2) corrosion model is conducted across a range of temperatures (273-313 K), CO2 partial pressures (0.1-1 bar), and bulk pHs (5-6.5). Contour plots are produced to examine the impact on corrosion rate, surface pH, and surface saturation index of iron carbonate (FeCO3). Two response patterns are identified depending upon the limiting behaviour of the system, with a transition from charge-transfer control to mass-transport control as temperature is increased and partial pressure is reduced. FeCO3 surface saturation shows a strong correlation with the release of Fe2+ and increase in bulk pH.
The recent failures in flexible pipes have motivated the exhaustive research of corrosion mechanisms on high-strength carbon steel armor wires that are the main structural compounds of those structures that mostly operate in seawater environments in the presence of carbon dioxide (CO2) and confined spaces. Recently, the literature reported discoveries about electrolyte properties (as Fe⁺²(aq)/HCO3⁻(aq.) ratio) and supersaturation, near neutral pH inside the confined space, multiphase reactions of contaminants present in CO2 gas, the formation and dissolution mechanism of FeCO3 film, and interaction of CO2 gas impurities with the corrosion scale. Therefore, this review is aimed at presenting an up-to-date narrative of the CO2 corrosion phenomenon in carbon steel, connecting background fundamentals with current data studies.
A failure analysis of API X52 steel pipeline was conducted. The investigation included complete material characterizations using tensile and hardness testing, optical microscope, SEM, and EDS. The main failure occurred in the downstream pipe located near the welded joint at the elbow outlet instead of elbow which was interesting. The main mechanism of failure was found to be erosion-corrosion mechanism that caused breakdown of the protective FeCO3 film, thinning of the downstream pipe, and finally failure. It is believed that the erosion-corrosion was induced by sand impingement due to turbulent flow that was promoted by sudden change in the flow cross section between the elbow inlet and upstream pipe and poor welding quality of joint at the elbow outlet.
Carbon capture and storage (CCS) technology is considered to be one of the key technologies to reduce CO 2 emissions. This paper reviews the industry corrosion accidents of CCS transportation system, in which the pipeline corrosion risk is analyzed, and the pipeline corrosion theory is summarized. Also, the effect of impurities on gas phase properties is discussed. We analyze the corrosion mechanism of multicomponent impurities on metals in a supercritical CO 2 environment from the aspects of corrosion rate and corrosion products. We also describe the mechanism of pitting and stress corrosion of metals in a supercritical CO 2 environment. Besides, the formation mechanism of FeCO 3 protective layer and the research status of corrosion resistant alloys in supercritical CO 2 are reviewed and analyzed. Finally, a series of shortcomings and prospects of the current research are put forward.
Corrosion is one of the most severe operational problems in CO2 absorption processes, which use aqueous solutions of alkanolamines, especially when carbon steel is used for plant construction. Corrosion inhibitors are widely applied used in this process to suppress severe corrosion to an acceptable level. However, currently available corrosion inhibitors are heavy metals, which are toxic to human health and the environment, making solvent handling and waste disposal more difficult and costly. This work evaluated a low-toxic corrosion inhibitor, copper carbonate (CuCO3), as a replacement
for toxic corrosion inhibitors. An inhibition evaluation was performed on copper
carbonate by examining its parametric effects on the corrosion rate and corrosion behavior of carbon steel.
Results show that CuCO3 is an anodic corrosion inhibitor which suppresses the corrosion of carbon steel by raising the system's potential to the passive region where the passive film of hematite (Fe2O3) is formed on the metal surface and acts as a barrier between the bulk solution and metal surface. CuCO3 offers satisfactory corrosion inhibition under typical service conditions in the CO2 absorption process. The corrosion rate of carbon steel is held below 0.254 mmpy and its inhibition efficiency is at least 80%. The inhibition performance of CuCO3 is affected by partial pressure of 02, CuCO3
concentration, CO2 loading in solution, solution velocity, solution temperature, MEA concentration, cleanliness of the metal surface (pre-corrosion duration) and degradation products including reversible products and heat-stable salts. Dissolved oxygen (02) is required for effective corrosion inhibition by CuCO3.
One of the important industrial issues is corrosion of carbon and low alloy steels exposed to a wet environment where CO2 and/or H2S are dissolved. In case of carbon and low alloy steels, mainly iron-based corrosion products such as iron carbonate and iron sulfides can form depending on the condition. Microalloys added in small amounts to carbon steel can change the water chemistry near the steel surface due to dissolution of the microalloys, which may also alter the corrosion resistance of the steel and corrosion morphology. In this study, the individual microalloying effects of small amount (1 mass%) of Cr and Mo added in carbon steel were investigated in a wet CO2 and H2S environment, where the formation of mackinawite (FeS) are considered to be the dominant iron-based corrosion product. The variation of corrosion rate and corrosion potential of the microalloyed steels was monitored in the NaCl solution aerated with CO2 - 10% H2S gas by linear polarization resistance (LPR) measurements. The corrosion product formed on the steel surface was also analyzed by SEM, EDS, XRD, TEM and XPS. The experimental results show that the addition of a small amount of Cr improves corrosion resistance by forming a dense film of FeS on the surface, while the addition of a small amount of Mo delays the formation of FeS on the surface and the corrosion resistance behavior is similar to that of steel with no additions.
The corrosivity of carbon dioxide (CO2) corrosion and iron carbonate (FeCO3) layer formation in sodium chloride (NaCl) solutions (1 – 12 % w/v) were investigated through electrochemical experiments and modelling. Relying on electrochemical measurements (Potentiodynamic polarisation) and simplified current density expressions (employing only H⁺ activity), reaction enthalpies (ΔH) and rate constants (Kr) for Fe dissolution, H2 evolution and H2O reduction reactions were estimated over a temperature range of 40 – 80 °C. Additionally, a revised FeCO3 precipitation rate expression was developed based on a newly derived FeCO3 solubility product (Ksp), integrating the effects of temperature and ionic strength (using activity coefficients). Collectively, this yielded a new CO2 corrosion prediction model accounting for the presence of a developing layer of FeCO3 in NaCl solutions. The model was validated over a broad range of conditions (pH, temperature, pressure and NaCl concentrations) by employing the corrosion rate and FeCO3 characteristics as metrics. Notably, it was shown that the activities of dissolved CO2 and Cl⁻ were not essential to predict the electrochemical response of anodic processes. Furthermore, it was demonstrated that increasing NaCl concentration resulted in a complexly evolving environment where porous, less protective FeCO3 layers were formed.
Corrosion represents a threatening and expensive problem for every industrial sector. To address this issue, several predictive models were developed and categorized in empirical, semiempirical and mechanistic, according to their underlying hypotheses, their representation of major physicochemical phenomena, and their applicability limits. In this work, a mechanistic model strongly based on the theory of kinetics of electrochemical corrosion is presented and validated. The model, called Tafel-Piontelli, was firstly proposed in 2017 as a tool for the calculation of the corrosion rate of active metals in acidic environments, characterized by hydrogen evolution as the dominant cathodic process. Starting from its initial version, the base-equation of the model has been revised and the theoretical architecture improved. The model was validated according to the experimental data collected for a variety of strong acids in a wide range of temperature and pH sets. The kinetic parameters of the equation, such as the cathodic Tafel slope and the hydrogen evolution exchange current density, were determined via cathodic potentiodynamic polarization tests (Tafel extrapolation method), while the iron ion activity and the corrosion rate were determined from mass loss tests and application of the Faraday law. The results show a remarkable improvement in the representation of the iron ion activity and of its exponential dependence on pH and temperature with respect to the original formulation. Additionally, the estimated corrosion rates accurately capture the dynamics observed in the empirical data, thus confirming the validity of the model.
This chapter covers the protocols for collecting, preserving, and analyzing water samples. Many of the analytical procedures used for analysis have been approved by federal authorities and organisations such as the Environmental Protection Agency (EPA). Obtaining analytical data that precisely depict the chemical composition of the water in situ is emphasized throughout and the methods implemented for analyzing are briefly presented. It covers the various analytical techniques implemented to determine the organics, inorganics, and radioactive materials. It also covers the toxicity test systems, requirements, evaluation, and their implementation.
This chapter discusses the post‐treatment of desalinated water using conventional as well as recent technologies for remineralization of permeate produced by desalination systems. Desalted water produced by desalination facilities are unpleasant, unhealthy, and they are corrosive, cannot be utilised directly. Because of the requirement for high‐quality water, remineralization of desalinated water as part of the post‐treatment process has gotten a lot of attention recently. It gives insights on examining remineralization requirements and restrictions in terms of corrosion control, human health, and agricultural needs. The chapter also provides an summary of alternative disinfection systems and guidance for their use in desalination applications.
Desalination brine is highly saline and contains a variety of chemical pollutants, making its disposal a key issue for desalination around the world. For the long‐term management of desalination brines, environmentally benign and economically viable technologies are required. This chapter presents the methods to manage the brine/waste product from desalination methods. It covers the recovery of useful products from waste brine that are available for economic or societal use.
This chapter explains the thermodynamic phase equilibrium and kinetic modeling of hydrate formation in seawater through the gas hydrate‐based desalination process. The literature review of the proposed models reveals that the production of gas hydrate is affected not only by gas composition and free water concentration, but also by temperature and pressure. Further application of artificial intelligence in desalination efficiency is also discussed. A literature review based on kinetic models for hydrate formation has been discussed. Hybrid machine learning techniques are suggested for finding the optimum process parameters, such as pollutant removal efficiency and higher water recovery.
This chapter focuses on the various additives used by conventional techniques to treat wastewater. It also gives an overview of the favorable conditions to determine the hydrate formers in the hydrate‐based desalination process. Using additives to enhance hydrate formation has been proven as an effective technique to advance the use of hydrate technology during the last two decades, and typically consists of kinetic promoters and thermodynamic promoters. It gives insights into the potential hydrate formers for hydrate‐based desalination that can enhance the rate of hydrate formation.
Corrosion is a naturally occurring phenomenon through which a material can transform into its more chemically stable form. Microbial influenced corrosion, a major concern in industries, is a category of corrosion caused by microorganisms that change the media chemistry through their own metabolic activities. Fundamental concerns about MIC remain unresolved despite intensive research and several publications. In many industrial systems, microbial corrosion remains unnoticed, resulting in considerable waste and increased operational expenses. One metal that is highly corrosive and yet immensely famous in the industries due to a wide range of applications is mild steel. Corrosion inhibition is important now more than ever. The use of corrosion inhibitors is the easiest and most economical method of corrosion protection of the metal. A myriad of inhibitors are currently in use for the protection of mild steel against microbial corrosion and the following article provides a comprehensive review of them.
A variety of polymeric surfaces, such as anti-corrosion coatings and polymer-modified asphalts, are prone to blistering when exposed to moisture and air. As water and oxygen diffuse through the material, dissolved species are produced, which generate osmotic pressure that deforms and debonds the coating. These mechanisms are experimentally well-supported; however, comprehensive macroscopic models capable of predicting the formation osmotic blisters, without extensive data-fitting, is scant. Here, we develop a general mathematical theory of blistering and apply it to the failure of anti-corrosion coatings on carbon steel. The model is able to predict the irreversible, nonlinear blister growth dynamics, which eventually reaches a stable state, ruptures, or undergoes runaway delamination, depending on the mechanical and adhesion properties of the coating. For runaway delamination, the theory predicts a critical delamination length, beyond which unstable corrosion-driven growth occurs. The model is able to fit multiple sets of blister growth data with no fitting parameters. Corrosion experiments are also performed to observe undercoat rusting on carbon steel, which yielded trends comparable with model predictions. The theory is used to define three dimensionless numbers which can be used for engineering design of elastic coatings capable of resisting visible deformation, rupture, and delamination.
In-situ monitoring of CO2 corrosion of carbon steel and FeCO3 precipitation, under continuous replenishing of condensed water conditions, was investigated using a newly developed electrochemical probe. Comparable results were obtained using electrochemical and non-electrochemical methods that validated the design and efficacy of the probe for monitoring corrosion processes such as those that occur in top-of-the-line corrosion. Electrochemical impedance spectroscopy (EIS) combined with cross-sectional analysis identified three stages of corrosion and film formation, namely; active dissolution, formation of a porous film and formation of a more protective film. The protective film consisted of two layers, an inner layer containing a mixture of FeCO3 and Fe3C and an outer layer of FeCO3. During the three stages of corrosion, the corrosion rate increased with time to a maximum value which then declined to minimum values that remained steady with time.
NH4Cl corrosion failure often occurs in petroleum refinery processing units such as the hydrotreatment unit overhead systems where failure is accompanied by CO2−-induced corrosion. In this paper, EIS and potentiodynamic polarization techniques along with SEM, XRD, and EDS studies are performed to evaluate the effects of temperature, pH, and partial pressure of CO2 on the corrosion behavior of carbon steel in 0.5 mol% NH4Cl solution with CO2. The results reveal the formation of the protective FeCO3 film on the carbon steel surface in this environment. The maximum resistance of FeCO3 film (588.3 Ω cm2) and the minimum corrosion rate of carbon steel (0.734 mm/y) are found at 60 °C. Furthermore, the anodic current curves of the steel move toward the lower values as the pH decreases from 6 to 2. The proposed FeCO3 film formation model successfully predicts the protection of FeCO3 film in the NH4Cl/CO2 medium.
Based on corrosion thermodynamics and kinetics, considering the multi-field coupling effects of fluid flow, electrochemical reaction and mass transfer process, a new corrosion prediction mechanistic model was proposed by introducing the influence factor of corrosion product film on diffusion coefficient of ion mass transfer, which is based on the CO2 corrosion prediction model proposed by Nesic et al. The influence of temperature, flow rate and pH value on CO2 corrosion behavior on 20# steel was studied by orthogonal tests. Scanning electron microscopy (SEM) and energy spectrum analysis (EDS) was used to analyze the surface and cross section morphology of the corrosion product film, and the thickness of the corrosion product film was measured. The results show that the introduced influence factor can simplify the ion mass transfer calculation in the presence of corrosion product film, and the relative error between the predicted value of the modified model and the experimental results is satisfactorily controlled less than 10%. Compared with the prediction model without considering the influence of corrosion product film, the influence factor can effectively correct the high prediction value of the mechanistic model under the influence of corrosion product film, improve the accuracy and applicability of corrosion prediction, and provide important theoretical guidance for the design, manufacturing, operation and maintenance of oil and gas production pipelines and related facilities.
Protective corrosion product layers, such as iron carbonate, can govern pipeline corrosion; their formation being associated with operational conditions (high [Fe²⁺], pH > 6.0, T > 70 °C). Brines contain Ca²⁺ that can incorporate as a substitutional cation in the iron carbonate lattice, potentially compromising the mechanical integrity of the protective layer. This work utilized scratch testing as an analytical technique that provides more information on layer adherence than indentation methods. It was demonstrated that the presence of iron calcium carbonate layers contributes to the formation of a protective and mechanically stable iron carbonate layer adjacent to the steel surface.
Metal(loid) oxyanions in groundwater, surface water, and wastewater can have harmful effects on human or ecological health due to their high toxicity, mobility, and lack of degradation. In recent years, the removal of metal(loid) oxyanions using zerovalent iron (ZVI) has been the subject of many studies, but the full scope of this literature has not been systematically reviewed. The main elements that form metal(loid) oxyanions under environmental conditions are Cr(VI), As(V and III), Sb(V and III), Tc(VII), Re(VII), Mo(VI), V(V), etc. The removal mechanism of metal(loid) oxyanions by ZVI may involve redox reactions, adsorption, precipitation, and coprecipitation, usually with one of these mechanisms being the main reaction pathway and the other playing auxiliary roles. However, the removal mechanisms are coupled to the reactions involved in corrosion of Fe(0) and reaction conditions. The layer of iron oxyhydroxides that forms on ZVI during corrosion mediates the sequestration of metal(loid) oxyanions. This review summarizes most of the currently available data on mechanisms and performance (e.g., kinetics) of removal of the most widely studies metal(loid) oxyanion contaminants (Cr, As, Sb) by different types of ZVI typically used in wastewater treatment, as well as ZVI that has been sulfidated or combination with catalytic bimetals.
Carbon capture and storage (CCS) technology is considered to be one of the key technologies to reduce CO 2 emissions. This paper reviews the industry corrosion accidents of CCS transportation system, in which the pipeline corrosion risk is analyzed, and the pipeline corrosion theory is summarized. Also, the effect of impurities on gas phase properties is discussed. We analyze the corrosion mechanism of multicomponent impurities on metals in a supercritical CO 2 environment from the aspects of corrosion rate and corrosion products. We also describe the mechanism of pitting and stress corrosion of metals in a supercritical CO 2 environment. Besides, the formation mechanism of FeCO 3 protective layer and the research status of corrosion resistant alloys in supercritical CO 2 are reviewed and analyzed. Finally, a series of shortcomings and prospects of the current research are put forward.
In this work, a numerical model, which involves mass transfer process, electrochemical corrosion at the steel/solution interface, homogeneous chemical reactions, evolution of FeCO3 film on the steel surface, was developed to predict the corrosion evolution of N80 carbon steel in the supercritical CO2 containing oilfield produced water. Meanwhile, the evolution of the physical parameters of the FeCO3 film, such as the film thickness and porosity, and their influences on the corrosion process of steel are incorporated into the model. Different from the existed CO2 corrosion models, this model could not only predict the time-dependent corrosion rate, but also track the transient movement of corroding surface and depositing interface via the arbitrary Lagrangian-Eulerian technology. Through finite element calculation, the numerical results, especially the corrosion rate and FeCO3 film thickness, show a good agreement with the experimental data. This model aims to provide a deep insight into the complicated interaction between the corrosion of steel and the evolution of protective FeCO3 film under supercritical CO2 conditions.
This study summarizes the chemical effects that can occur during the corrosion process of carbon steel in a CO2‐saturated aqueous environment. Particularly, it focuses more on the results that small chemical contaminations in the environment have on the corrosion process. Underground waters present complex chemistry with several different dissolved ions (chlorides, carbonates) even in high concentrations that impact substantially the corrosion rates of these materials. Moreover, gas impurities present in the gas mixture, such as oxygen in carbon capture and storage applications, constitute a supplementary form of significant contamination in the CO2‐saturated aqueous environment. In particular, the effect on both electrochemical reactions and corrosion product layer is examined for several chemical species that are commonly present either in the gas mixture or in underground waters.
This paper presents the investigation on the effect of calcium on the corrosion behavior of 1Cr carbon steel under various levels of initial CaCO3 saturation () of the bulk solutions. All the experiments were performed at 80°C in 1 wt% aqueous NaCl solution saturated with CO2. Four initial levels were investigated, namely 0, 0.6, 2, and 10. The corrosion process was followed using linear polarization resistance, potentiodynamic sweeps, and electrochemical impedance spectroscopy. The surface morphology of the corrosion products was analyzed with scanning electron microscopy and structural information using X‐ray powder diffraction. Precipitation of a substitutional solid solution of FexCayCO3 (x + y = 1) was found on the steel surface. The growth of this layer was delayed by Ca2+ ions in the solution, but its protectiveness was not affected and was comparable with the pure FeCO3 corrosion product. No signs of localized corrosion were detected on the material. This paper presents an electrochemical investigation on the effect of calcium ions on the formation and protectiveness of the FeCO3 precipitated layer. Experiments are performed in an aqueous solution saturated with CO2 at 80°C. Results show that calcium ions delay the precipitation of FeCO3 but do not alter its protectiveness.
A mechanistic model of uniform carbon dioxide (CO 2) corrosion is presented that covers the following: electrochemical reactions at the steel surface, diffusion of species between the metal surface and the bulk including diffusion through porous surface films, migration due to establishment of potential gradients, and homogenous chemical reactions including precipitation of surface films. The model can predict the corrosion rate as well as the concentration and flux profiles for all species involved. Comparisons with laboratory experiments have revealed the strengths of the model such as its ability to assist in understanding complex processes taking place during corrosion in the presence of surface films.
Local breakdown of protective corrosion films may result in rapid local attack or mesa corrosion attack during CO2 corrosion of carbon steel. The factors affecting formation and local breakdown of protective corrosion films were studied in a series of flow loop experiments performed at 40 - 80 °C with pH 5.8, 1.8 bar CO2 partial pressure, high iron content in the water and flow rates 0.1 - 7 m/s. Carbon steels with or without chromium and nickel additions up to 1 % were tested. Addition of 0.5 % chromium in the steel was found to reduce the tendency for severe mesa attack in carbon steels during CO2 corrosion significantly. Deep mesa attack did not occur in steels with 0.5-1 % Cr in experiments at 80 °C and pH 5.8. Protective corrosion films reform more easily in the chromium containing steels, making localized attack less dangerous in chromium containing steels than in unalloyed carbon steels.
The initiation and development of mesa corrosion attack during CO2 corrosion of carbon steel has been studied in flow loop experiments performed at 80 °C and pH 5.8. Video recordings of growing mesa attacks have been performed in a test section with a glass window in the corrosion loop. These observations have shown that the mesa attack can grow both laterally and in depth below a lid of original corrosion film before the film is torn away stepwise by the flow. Possible mechanisms for initiation of mesa corrosion attack are discussed based on the observations from the video recordings. Mesa attacks can result from several small local attacks growing together into one large mesa attack.
In carbon dioxide (CO2) corrosion of steels, the bicarbonate ion (HCO3-) is simultaneously the buffer for carbonic acid (H2CO3), the source of iron carbonate (FeCO3) precipitation, and the product of the cathodic reaction. In addition to spatial separation of the production of Fe2+ and HCO3-, galvanic coupling between the steel and cementite (Fe3C) layers is the principal cause of internal acidification in these layers, since the HCO3- ions are removed front the steel surface by electromigration. This can facilitate localized corrosion by lateral galvanic coupling. This mechanism explains the role of traces of free acetic acid (CH3COOH, or HAc) and the existence of multiple steady states. Transposition to corrosion of iron by hydrogen sulfide (H2S) or to corrosion of copper is discussed.
A predictive model was developed for uniform carbon dioxide (CO2) corrosion, based on modeling of individual electro- chemical reactions in a water-CO2 system. The model takes into account the electrochemical reactions of hydrogen ion (H + ) reduction, carbonic acid (H2CO3) reduction, direct water reduction, oxygen reduction, and anodic dissolution of iron. The required electrochemical parameters (e.g., exchange current densities and Tafel slopes) for different reactions were determined from experiments conducted in glass cells. The corrosion process was monitored using polarization resistance, potentiodynamic sweep, electrochemical imped- ance, and weight-loss measurements. The model was calibrated for two mild steels over a range of parameters: temperature (t) = 20°C to 80°C, pH = 3 to 6, partial pressure of CO2 (PCO2) = 0 bar to 1 bar (0 kPa to 100 kPa), and v = 0 rpm to 5,000 rpm (vp = 0 m/s to 2.5 m/s). The model was applicable for uniform corrosion with no protective films present. Performance of the model was validated by compar- ing predictions to results from independent loop experiments. Predictions also were compared to those of other CO2 corro- sion prediction models. Compared to the previous largely empirical models, the model gave a clearer picture of the corrosion mechanisms by considering the effects of pH, temperature, and solution flow rate on the participating anodic and cathodic reactions.
- J W Mullin
J.W. Mullin, Crystallization, 3rd ed. (Oxford, U.K.: Oxford
Press, 1993).