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Brown, Bruce
Effect of Salt Concentration on Uniform Hydrogen Sulfide Corrosion Rate of Pipeline Steel
Sani, Fazlollah Madani (Institute for Corrosion and Multiphase Technology, Ohio University) | Brown, Bruce (Institute for Corrosion and Multiphase Technology, Ohio University) | Nesic, Srdjan (Institute for Corrosion and Multiphase Technology, Ohio University)
Abstract Large amounts of water can be produced during the production of hydrocarbons from underground reservoirs. Salts are always dissolved in these produced waters. The concentration of dissolved salts can be as high as 400 g/l. For the first time, the effect of salt concentration on uniform hydrogen sulfide (H2S) corrosion of carbon steel in aqueous solutions is studied. Linear polarization resistance (LPR) and potentiodynamic polarization (PD) experiments were conducted in aqueous solutions at 20°C and pH 5.00 saturated with an H2S/N2 gas mixture with a total pressure of 1 bar and H2S concentration of 100 ppm(v). Two NaCl concentrations were tested: 1 and 20 wt.%. A rotating cylinder electrode with a rotational speed of 1000 rpm was used as the specimen. LPR corrosion rates indicated that H2S corrosion rate decreased with increasing salt concentration. PD results showed that the corrosion process was under mixed control. Increasing salt concentration retarded both the anodic and the cathodic reactions, and thereby, decreased the rate of uniform H2S corrosion. Introduction Large amounts of water can be produced during extraction of hydrocarbons from underground reservoirs. It is well understood that produced waters usually contain high amounts of dissolved salts, up to 28 wt.%. In addition to salts, dissolved corrosive gases (CO2 and H2S) are present in produced water, which make the mixture a complex corrosive environment for metallic parts and equipment used throughout the production process. Internal H2S corrosion of carbon steel tubulars often occurs in the oil and gas industry, particularly when drilling deeper to search for new oil and gas reservoirs. In contrast to CO2 corrosion, a limited number of studies exist for H2S corrosion. And, to the best knowledge of the authors, no study has been done on the effect of salt concentration on uniform H2S corrosion. It is necessary to understand H2S corrosion mechanisms in high saline solutions to develop a correct corrosion prediction. For the first time, the effect of salt concentration on uniform H2S corrosion of carbon steel in aqueous solutions is presented as part of a wider mechanistic study.
- North America > United States (1.00)
- Asia (1.00)
- Energy > Oil & Gas > Upstream (1.00)
- Government > Regional Government > North America Government > United States Government (0.46)
Corrosion Mechanisms of Mild Steel in the Presence of Formic Acid and Acetic Acid
Ayyagari, Sahithi (Institute for Corrosion and Multiphase Technology, Ohio University) | Eslami, Maryam (Institute for Corrosion and Multiphase Technology, Ohio University) | Brown, Bruce (Institute for Corrosion and Multiphase Technology, Ohio University) | Nesic, Srdjan (Institute for Corrosion and Multiphase Technology, Ohio University)
Abstract The presence of organic acids such as formic acid, acetic acid and propionic acid in oil field brines has been identified as a significant contributor to corrosion of mild steel. Extensive research indicates that corrosion rates of steel are significantly higher in weak acid environments, such as aqueous CO2 or acetic acid, as opposed to fully dissociated aqueous strong acids at the same pH. A general observation is that the increase in corrosion rate is due to increase in cathodic current, which is due to the partial dissociation of the weak acid. Most corrosion research with respect to aqueous organic acid environments has focused on acetic acid as it is a prevalent organic acid found in oil fields; it is also a good representative for higher molecular weight carboxylic acids with similar acid dissociation constants (Ka) values that may be present, e.g., propionic acid. However, the difference in acidity of formic acid as compared to acetic acid emphasizes the need to establish a mechanistic understanding of the role of operational parameters such as pH, temperature, and/or concentration of undissociated acid concentrations on corrosion behavior. A conventional three electrode glass cell equipped with a rotating disc electrode was used to conduct electrochemical measurements (potentiodynamic sweeps, electrochemical impedance spectroscopy, and linear polarization resistance) on an API 5L X65 steel working electrode in a 1 wt.% NaCl electrolyte maintained at constant pH and temperature. It was confirmed that both formic acid and acetic acid have a similar effect on the cathodic reaction rate, wherein their contribution to the corrosion process is through chemical dissociation, which induces the buffering effect. However, while acetic acid has a slight inhibitive effect on the anodic reaction rate, a similar effect was not observed in the presence of formic acid. The effects of concentration of undissociated acid, temperature, pH, rotational speed, and presence of CO2 in the environment on corrosion of mild steel were established.
- Well Completion > Well Integrity > Subsurface corrosion (tubing, casing, completion equipment, conductor) (1.00)
- Reservoir Description and Dynamics > Improved and Enhanced Recovery (1.00)
- Production and Well Operations > Well Intervention (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Materials and corrosion (1.00)
Revisiting the Anodic Dissolution of Pure Iron in Strong Acids
Hariri, Mohiedin Bagheri (Institute for Corrosion and Multiphase Technology, Ohio University) | Brown, Bruce (Institute for Corrosion and Multiphase Technology, Ohio University) | Nesic, Srdjan (Institute for Corrosion and Multiphase Technology, Ohio University)
Abstract The goal of the research reported herein was to accomplish a quantitative mechanistic analysis of iron dissolution in strong acid in a potential range in the proximity of its open circuit potential (OCP), leading to articulation of a revised narrative of BDD mechanism for iron dissolution; additional mechanistic pathways were postulated in addition to the hypothesized mechanisms of BDD and Heusler. Thirty-eight different pathways were investigated here and theoretical Butler-Volmer equations were written for each. The kinetic consequences of each pathway and the corresponding theoretical values of the main kinetic parameters were determined, and the theoretical outcomes were compared to the experimental observations. It was found that in strong acids (pH ≤ 4) in the potential range of ±50 mV vs. OCP, the mechanism of iron dissolution agrees well with three pathways, and all three were explainable within the same framework of BDD mechanism, where the reaction of OH with iron produces the adsorbed intermediate FeOHads. One single dissolution pathway which corresponds to the conversion of FeOHads to Fe(II)sol is dominant in the potential range adjacent to the OCP. Near OCP the effect of hydrogen reduction was taken into account using the linearity of the cathodic potentiodynamic branch to approximately extract the pure anodic data points from both anodic and cathodic sweeps. Introduction Reviewing literature related to corrosion research brings to light the importance of understanding the mechanisms involved, and how this is essential to aid in development of mathematical models for corrosion prediction. The current research documents possible mechanisms for the dissolution of pure iron in strong acid in a potential range in the potential range of ±50 mV vs. OCP, providing explanations for corrosion engineers and researchers working with mild steel. Prediction of corrosion rate relies on the precise understanding of the anodic and cathodic processes at the metal surface in the potential range close to the OCP. In the case of iron dissolution, not far from OCP, there are two common mechanisms in strong acids (pH ≤ 4) reported in the literature; namely, the "catalytic mechanism" proposed by Heusler et al., and the "consecutive mechanism" postulated by Bockris, et al. . which is also known as "BDD mechanism". Heusler’s model is based on the second order dependence on OH- ions and the anodic Tafel slope of 30 mV/decade, while BDD mechanism predicts a first order of dependency on OH- and an anodic Tafel slope of 40 mV/decade. Over a wider range of overpotentials far from the OCP, Keddam, et al., reported that iron dissolution occurs through three different but interrelated dissolution paths in which four adsorbed intermediates are involved in seven elementary steps. Bockris’ approach for elucidation of the mechanism near the OCP was methodical in terms of utilizing the Butler-Volmer equation as a means to reasonably deduce the mechanism since it immediately provides the metrics to prove, or disprove, a particular hypothesis.
Factors in Galvanic Corrosion between Steel and Iron Sulfides in Acidic Solutions
Abdar, Payman Sharifi (Institute for Corrosion and Multiphase Technology, Ohio University) | Brown, Bruce (Institute for Corrosion and Multiphase Technology, Ohio University) | Nesic, Srdjan (Institute for Corrosion and Multiphase Technology, Ohio University)
Abstract With the increase in producing sour oil and gas fields in the world, mitigation of production related failures due to H2S corrosion is a key challenge. In H2S environments, localized corrosion is the type of attack which contributes to the most failures in oilfields. The main cause of localized attack is the galvanic coupling between steel and iron sulfide corrosion products due to their electrical conductivity. However, the mechanism of the galvanic coupling between steel and iron sulfides and the effect of experimental parameters on it, have not been unraveled yet. The present study investigates the effect of three different experimental parameters: iron sulfide type, cathode to anode surface ratio, and salt concentration, on the galvanic coupling between steel and iron sulfides in acidic solutions. Pyrite and pyrrhotite were selected as iron sulfide specimens since these corrosion products have been mostly found when localized corrosion of mild steel was observed in sour environments. The results show that the cathodic current of pyrrhotite was an order of magnitude higher than the cathodic current of pyrite, leading to a higher galvanic current as well as a higher galvanic potential for coupled steel-pyrrhotite compared to coupled steel-pyrite. In addition, it was found that the increase of cathode to anode surface area ratio as well as the increase of salt concentration to some extent, increased the galvanic current for the coupled materials. Introduction H2S corrosion, also known as sour corrosion, is one of the most researched types of metal degradation in oil and gas transmission pipelines requiring a wide range of environmental conditions and detailed surface analysis techniques. This is because localized or pitting corrosion is known to be the main type of corrosion failure in sour environments which caused 12% of all oilfield corrosion incidents according to a report from 1996. Therefore, control and reduction of this type of corrosion could prevent such failures in oil and gas industries, and significantly enhance asset integrity while reducing maintenance costs as well as eliminating environmental damage. The unpredictability of pitting corrosion in sour media is a complicated challenge in this area as several factors, such as the nature of the corrosion products and the contribution of galvanic coupling, play a role in this type of corrosion.
- Research Report > New Finding (0.66)
- Research Report > Experimental Study (0.48)
- Well Completion > Well Integrity > Subsurface corrosion (tubing, casing, completion equipment, conductor) (1.00)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology > Corrosion inhibition and management (including H2S and CO2) (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Materials and corrosion (1.00)
Development of Methodologies for Continuous and Batch Inhibitor Film Persistency Investigation in the Laboratory
Pan, Mengqiu (Institute for Corrosion and Multiphase Technology, Ohio University) | Bahadori, Kasra Shayar (Institute for Corrosion and Multiphase Technology, Ohio University) | Eslami, Maryam (Institute for Corrosion and Multiphase Technology, Ohio University) | Brown, Bruce (Institute for Corrosion and Multiphase Technology, Ohio University) | Singer, Marc (Institute for Corrosion and Multiphase Technology, Ohio University)
Abstract Organic corrosion inhibitors (CIs) are widely used in the oil and gas industry to mitigate corrosion in pipeline transmission systems. Upstream, there are two distinct internal pipeline corrosion mitigation methods using inhibitors: continuous injection and batch inhibition. Each treatment mode has its own challenges, requiring specific knowledge of inhibitor film persistency (i.e., interrupted continuous injection or irregularity in batch inhibitor application frequency). The performance of applied corrosion inhibitors is typically evaluated in laboratory conditions, prior to field application. This study is focused on development of methodologies to investigate inhibitor film persistency using inhibitor model compounds, possessing only one molecular type, in both continuous and batch inhibition. For persistency studies related to continuous treatment, experiments were divided into three main steps: pre-corrosion, inhibitor addition, and inhibitor dilution. For batch inhibition, an inhibitor testing procedure was developed that can maintain stable water chemistry and avoid O2 contamination, with the potential to be adapted for top-of-the-line corrosion (TLC) environments. Corrosion rates were monitored using linear polarization resistance (LPR) in all experiments (except in TLC conditions). The Langmuir isotherm model was used to calculate adsorption coefficient kA and desorption coefficient kD for benzyldimethylammonium (BDA) inhibitor model compounds, possessing tetradecyl and hexadecyl tails, at different temperatures. Introduction Application of corrosion inhibitors confer many advantages for combatting internal pipeline corrosion in the upstream oil and gas industry. It is known that the associated costs for using corrosion inhibitors are low compared to other mitigation techniques [1]. For continuous injection procedures, water-soluble inhibitors are not expected to form long-lasting films, so they must be continuously injected to maintain their effectiveness. Batch inhibitors are usually higher molecular weight species and oil soluble. They tend to be more tenacious, providing a protective barrier between the water and the metal over a long period of time. For corrosion inhibitors used in the field, the physicochemical characteristics of the inhibitor molecules is of vital importance. These characteristics determine whether the inhibitor is classified as water-soluble or oil-soluble; a major factor relating to effectiveness and the way the inhibitor is applied [2].
- North America > United States (1.00)
- Asia (1.00)
- Well Completion > Well Integrity > Subsurface corrosion (tubing, casing, completion equipment, conductor) (1.00)
- Reservoir Description and Dynamics (1.00)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology > Corrosion inhibition and management (including H2S and CO2) (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Materials and corrosion (1.00)
A Quantitative Study of FeCO3 Solubility in Non-Ideal Solutions
Gao, Xin (Institute of for Corrosion and Multiphase Technology Ohio University) | Sani, Fazlollah Madani (Institute of for Corrosion and Multiphase Technology Ohio University) | Ma, Zheng (Institute of for Corrosion and Multiphase Technology Ohio University) | Brown, Bruce (Institute of for Corrosion and Multiphase Technology Ohio University) | Singer, Marc (Institute of for Corrosion and Multiphase Technology Ohio University) | Nesic, Srdjan (Institute of for Corrosion and Multiphase Technology Ohio University)
Abstract The effect of NaCl concentration (non-ideality) was investigated on the solubility of FeCO3 layer. After a layer of FeCO3 was formed on a gold coated crystal, NaCl was incrementally added into the solution and the mass change of the FeCO3 layer was measured with an Electrochemical Quartz Crystal Microbalance (EQCM). It was found that the mass of the precipitated FeCO3 layer did not change with increasing NaCl concentration even though the saturation value of FeCO3 (SFeCO3.) was far below 1 and dissolution of FeCO3 was expected. It was hypothesized that the calculation of SFeCO3 was incorrect due to inaccurate equations for dissociation equilibrium constants or solubility product constant (Ksp). Therefore, the equations for dissociation equilibrium constants taken from Oddo & Tomson 1982 and the Ksp equation borrowed from Sun et al. 2009 were revisited. New equations were proposed for carbonic acid first dissociation equilibrium constant (Kca) and Ksp. (equation) The predicted pH and SFeCO3 values at low pressures over a temperature range of 30°C to 80°C and anionic strength range of 0 to 4.95 M were in good agreement with the experimental results. The new equations could justify the observations for the effect of NaCl concentration on FeCO3 solubility. Introduction Iron carbonate (FeCO3) formed on the internal surface of oil and gas pipelines plays an important role in protecting these pipelines from further corrosion. Whether precipitation of FeCO3 is thermodynamically favorable is determined by a parameter called saturation of FeCO3, SFeCO3. In CO2 corrosion, ferrous ions, coming from the dissolution of the steel matrix, combine with carbonate ions to form FeCO3. Precipitation of FeCO3 occurs when SFeCO3 is larger than one. If the precipitated FeCO3 covers the steel surface evenly, it can form a compact and protective layer. This acts as a diffusion barrier hindering the mass transfer of corrosive species to the surface, which enhances the resistance of mild steel to further uniform CO2 corrosion. SFeCO3 is inversely proportional to the FeCO3 solubility limit constant, Ksp. Therefore, it is important to be able to calculate Ksp accurately, which is a function of temperature and ionic strength. There are several studies that investigated the effect of temperature and ionic strength on Ksp. When Sun, et al. reviewed literature associated with FeCO3 solubility, they found studies of Ksp at room temperature and very low ionic strength, studies of solubility limit dependence on temperature, as well as studies of solubility limit dependence on ionic strength. Sun et al. combined the equations from Greenberg and Tomson for temperature and Silva et al. for ionic strength to obtain a new equation for calculating the iron carbonate solubility product constant as a function of both temperature and ionic strength as follows: (equation) Where TK is temperature in Kelvin and I is ionic strength in mol/L.
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Materials and corrosion (0.86)
- Well Completion > Well Integrity > Subsurface corrosion (tubing, casing, completion equipment, conductor) (0.68)
- Well Drilling > Drilling Fluids and Materials > Drilling fluid selection and formulation (chemistry, properties) (0.55)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology > Corrosion inhibition and management (including H2S and CO2) (0.54)
Calculation of Surface Speciation on Mild Steel Under Applied Polarization
Ma, Zheng (Institute for Corrosion and Multiphase Technology (ICMT), Ohio University) | Brown, Bruce (Institute for Corrosion and Multiphase Technology (ICMT), Ohio University) | Nesic, Srdjan (Institute for Corrosion and Multiphase Technology (ICMT), Ohio University) | Singer, Marc (Institute for Corrosion and Multiphase Technology (ICMT), Ohio University)
Abstract The rates of electrochemical and precipitation reactions taking place on the steel surface are dependent on the chemistry of the aqueous phase in contact with the substrate. While the bulk speciation is often used to characterize the severity of the environment, large differences can exist between bulk and surface chemistries, leading to inaccurate representation of the corrosion phenomena. This issue requires a better understanding of the surface speciation. Given the fact that directly measuring surface speciation is a very challenging task, corrosion models must be employed to calculate these surface parameters based on the bulk chemistry. In the present work, an electrochemical model was developed for that exact purpose and used to predict corrosion behavior not only at the corrosion potential, but also under applied polarization, where surface and bulk chemistries differ greatly. This model has been extensively calibrated against experimental results in both corrosion product free conditions as well as in conditions where corrosion product layers form. INTRODUCTION It has been well understood that corrosion product layers can precipitate on the surface of mild steel in both sweet corrosion (CO2 dominated) and sour corrosion (H2S dominated) environments. However, all the current kinetics models focused on corrosion product layer formation are proposed based on bulk speciation. This situation is understandable: most of kinetics related parameters used in these models can either be measured directly from the bulk solution, or can be estimated through a simple bulk water chemistry model; not to mention the fact that the predictions from some of the bulk speciation-based kinetics models have been proven accurate within an acceptable rage. To separate the effects from "precipitation" and "corrosion", the two processes that normally occur simultaneously during corrosion product formation, a cathodically protected iron substrate and an actively corroding iron substrate were used for corrosion product layer precipitation in the authors previous study. For experiments using the cathodically protected substrate, a cathodic polarization ( −50∼−100 mV vs. OCP) was applied to ensure that substrate corrosion was minimized and the precipitation of corrosion product layer was the dominant process during measurement; for experiments using the actively corroding substrate, both the precipitation and spontaneous iron corrosion were taking place at the substrate surface. Figure 1 compares predictions and measured data at 50°C (the lowest experiment temperature) on the left and 80°C (the highest experiment temperature) on the right. The results from two different substrates do not completely overlap with each other, yet they are similar in magnitude, and most of the results from the actively corroding surface are lower than the results from the cathodically protected surface within a factor of two. This means the surface speciation did not affect FeCO3 precipitation kinetics significantly, at least in these tested conditions.
- Asia (1.00)
- North America > United States > Texas (0.28)
- Europe > Norway > Norwegian Sea (0.24)
- Energy > Oil & Gas > Upstream (1.00)
- Government > Regional Government > Asia Government (0.93)
Adhesion of Corrosion Product Layers Formed in Dewing Conditions
Prieto, Claudia (Institute for Corrosion and Multiphase Technology) | Brown, Bruce (Institute for Corrosion and Multiphase Technology) | Singer, Marc (Institute for Corrosion and Multiphase Technology) | Young, David (Institute for Corrosion and Multiphase Technology)
Abstract Engineers in the oil and gas industry frequently rely on the formation of protective corrosion product layers to mitigate internal pipeline corrosion. However, their protectiveness can be compromised if such layers, iron carbonate formed during CO2 corrosion for example, are mechanically removed from the metal. Partial loss of a corrosion product layer has the potential to result in localized attack and loss of containment. In sour environments, this partial loss can lead to particulate (black powder in case of commercial gas pipelines) entrainment, which can cause multiple problems downstream in the pipeline. Consequently, the study of adhesion forces between iron carbonate, iron oxide or iron sulfide layers and their associated metal substrate is essential to the industry. In the current work, adherence characteristics of iron carbonate layers grown in dewing conditions (condensing water conditions) were mechanically characterized via scratch testing by measuring the critical force to produce a removal of the layer. With the use of critical frictional forces (tangential forces parallel to the surface that produce the removal of the corrosion product) and the projected area of the indenter, the shear stress associated with the removal of the layer was calculated. This mechanical assessment was extended to layers grown in bulk aqueous conditions for comparative purposes. The results indicated that the critical shear stress for the removal of iron carbonate in dewing conditions was 3 orders of magnitude lower than for iron carbonate grown in aqueous environments. Finally, the critical shear stress for iron sulfide produced in dewing conditions indicated that the layer was significantly more adherent than the iron carbonate layer grown in similar conditions. In addition to understanding corrosion phenomena, this work has significance relating to black powder formation and resultant erosion. INTRODUCTION The oil and gas industry produces a large variety of products essential to everyday life, such as gasoline, diesel, and natural gas as fuels as well as petrochemical feedstocks used to make a wide range of products. To transport refined products as liquids or gases to customers, the oil and gas industry frequently uses transmission pipelines. One of the operational problems associated with gas transmission pipelines is the formation of black powder. As its name suggests, black powder is blackish dust that can impact the performance of transportation pipelines due to its accumulation, even resulting in pipelines potentially becoming blocked1,. This blockage affects the flow of gas, thereby reducing the amount that is delivered to the end user. In terms of pipeline integrity, black powder causes erosion of the internal pipe wall, compromises the functioning of critical components (e.g., sensors, valves), and induces pressure drop due to the variation of internal diameter. Gas turbine blades are also susceptible to damage caused by black powder accumulation due to excessive wear and erosion. Therefore, understanding mechanisms of spallation are essential so that conditions at which corrosion products form black powder can be avoided, predicted, or mitigated.
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Mineral > Sulfide > Iron Sulfide (0.47)
Use of Quartz Crystal Microbalance in Study of Inhibitor Adsorption
Singla, Kushal (Institute for Corrosion and Multiphase Technology (ICMT)) | Perrot, Hubert (Sorbonne Université, CNRS) | Sel, Ozlem (Sorbonne Université, CNRS) | Brown, Bruce (Institute for Corrosion and Multiphase Technology (ICMT)) | Nesic, Srdjan (Institute for Corrosion and Multiphase Technology (ICMT))
Abstract Although inhibitor adsorption and inhibition mechanisms have been studied extensively using various electrochemical techniques, these electrochemical techniques only provide an indirect estimate of inhibitor adsorption. Quartz crystal microbalance (QCM) has been shown to be a powerful acoustic technique which can be effectively used to evaluate net mass adsorption of inhibitors, adsorption rates and kinetic coefficients. In the present study, calibration of QCM by electrochemical deposition of copper on gold-coated quartz crystal resonator was done to evaluate the minimum mass change that can be determined using these devices. Sensitivity coefficient was measured within 5% accuracy for QCM-D equipment vs. within 20% accuracy for oscillatory circuit based-QCM equipment. Also, a different oscillatory circuit based-QCM equipment was used with flow cell to investigate the adsorption of tetra-decyl-dimethyl-benzyl-ammonium (Q-C14) inhibitor model compound on gold-coated quartz crystal resonator. Analysis of experimental data indicated that the inhibitor was adsorbed on the gold surface within a few minutes and the net amount of inhibitor adsorbed depends upon the bulk inhibitor concentration. However, the rate of frequency change for adsorption and desorption processes did not vary much for two inhibitor concentrations (50 ppm(w) and 100 ppm(w)) used for this study. This calls for further investigation of inhibitor adsorption at different concentrations. Introduction Corrosion is a material degradation process, mostly related to metals, after exposure to adverse environmental conditions. It leads to huge economic losses, environmental damage and possible risks to human life. According to a report published in 2016, economic losses due to corrosion were estimated to be US$ 2.5 trillion which is approximately equivalent to 3.4% of the global Gross Domestic Product (2013). Corrosion of carbon steel pipelines in oil and gas industry is a major contributor to corrosion related losses. The majority of oil and gas transportation structures are made of low alloy carbon steel, which has poor resistance to corrosion. Hence, pipelines are often prone to internal corrosion in service environments. Any structural failure directly implies significant economic burdens and associated risk to the environment and human life. Therefore, corrosion as a process, becomes a key factor in structural design and material selection in energy applications.
- Materials (1.00)
- Energy > Oil & Gas > Upstream (1.00)
- Government > Regional Government > Asia Government (0.68)
- Energy > Oil & Gas > Midstream (0.66)
- Well Completion > Well Integrity > Subsurface corrosion (tubing, casing, completion equipment, conductor) (1.00)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology > Corrosion inhibition and management (including H2S and CO2) (1.00)
- Health, Safety, Environment & Sustainability > Environment (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Materials and corrosion (1.00)
Note on Selecting DC Potentials for EIS Measurements: an Example of Determining the Diffusion Coefficient of Hydrogen Ion in Aqueous Solutions
Moradighadi, Negar (Institute for Corrosion and Multiphase Technology, Ohio University) | Brown, Bruce (Institute for Corrosion and Multiphase Technology, Ohio University) | Nesic, Srdjan (Institute for Corrosion and Multiphase Technology, Ohio University)
Abstract Electrochemical impedance spectroscopy (EIS) is a powerful technique that can detect and provide information about different phenomena that occur on the corroding surface using alternating current signals. Several electrochemical reactions and associated phenomena, such as mass transfer and chemical reactions happening at and near the metal surface, occur simultaneously. Therefore, the EIS data conducted at a specific DC potential often contain mixed information about several of those reactions, while at other potentials the EIS data are dominated by a single electrochemical reaction. To be able to focus on a single electrochemical reaction and its associated phenomena, it is important to identify the DC potential at which the EIS data provide the most relevant information about this reaction, otherwise, the analysis of the impedance data becomes very difficult. This work aims to show an example of how to select the DC potential range at which the hydrogen evolution reaction is dominant. Following this step, the EIS data can be used to determine the diffusion coefficient of hydrogen ion in a strong acid aqueous solution. Introduction EIS is a powerful tool, yet a challenging technique for studying of a corrosion electrochemical system. It can provide a broad range of information by decoupling the phenomena that occur at or near the metal surface . In the study of corrosion of mild steel in a strong acid solution, the main electrochemical reactions are anodic dissolution of iron and the cathodic reduction of hydrogen ions and water (at lower potentials). In EIS studies of these electrochemical reactions, choosing the appropriate DC potential is of great importance. For example, to study the hydrogen reduction reaction, which is often controlled by the mass transfer of hydrogen ions, a DC potential must be chosen at which the EIS response provides mostly information about the hydrogen reduction reaction and the influence of other reactions on measured impedance is minimized. It is well known that at potentials below the open circuit potential (OCP), the measured current is dominated by hydrogen ion reduction. We are compelled to conclude that the impedance at these same potentials below the OCP is also dominated by the hydrogen reduction reaction? But, is this always the case?
- Asia > China (0.46)
- Europe > United Kingdom > England (0.28)
- Energy > Oil & Gas > Upstream (1.00)
- Government > Regional Government > Asia Government (0.68)