CO2-saturated Environment Research Articles

Influence of oxygen on metastable pitting behavior of super 13Cr stainless steel in CO2-saturated environment

This study investigates the effect of oxygen on the metastable pitting corrosion behavior of Super 13Cr martensitic stainless steel in a CO2-saturated environment, which is pertinent to challenging extraction conditions of oil and gas industry. Potentiostatic polarization and comprehensive statistical analysis to assess the corrosion dynamics. The results indicate that the presence of oxygen significantly influences the initiation and progression of metastable pitting. In the 50 % O2 + 50 % CO2 environment, a decrease in the frequency and size of metastable pitting events was observed, along with a reduction in the peak current, pit radius, and stable product, suggesting that oxygen inhibits the transition from metastable to stable pitting.

Imidazoline As a Volatile Corrosion Inhibitor for Mitigation of Top- and Bottom-of-the-Line CO2 Corrosion in Carbon Steel Pipelines.

A fatty acid imidazoline-based inhibitor was synthesized via a facile solvent-free synthesis method between tall oil fatty acid (TOFA) and diethylenetriamine (DETA) under atmospheric conditions with a short reaction time. The as-synthesized imidazoline (S-Imd) acted as an effective inhibitor for reducing or preventing corrosion of carbon steel pipelines at both bottom of the line (BOL) and top of the line (TOL) positions under simulated conditions of a gas pipeline in a CO2-saturated environment. The inhibition efficacy was examined by both weight loss and electrochemical measurements, such as the electrochemical impedance spectrum (EIS), potentiodynamic polarization (PDP), and linear polarization resistance (LPR). The results revealed that the S-Imd, 2-(8-heptadecenyl)-2-imidazoline-1-ethanamin, at 300 ppm exhibited a superior inhibition efficiency of up to 91.6 and 89.9% for BOL and TOL corrosion tests, respectively. The surface morphology of the carbon steel test specimens was also examined using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDAX), and contact angle analysis. It was found that the as-synthesized S-Imd acted as a mixed-type inhibitor that exhibited a decreased surface roughness and oxide layer on carbon steel surfaces. However, the water contact angle was found to increase, implying enhanced hydrophobicity of the surface. Adsorption of the imidazoline molecules on carbon steel surfaces followed the Langmuir adsorption isotherm. The present work provides very promising results in the synthesis and utilization of the studied imidazoline as a volatile corrosion inhibitor (VCI), especially for carbon steel pipelines in petroleum industries.

Exploring the Effectiveness of Natural Food Flavors in Protecting Carbon Steel against CO2-Induced Corrosion.

Two food flavors, furfuryl mercaptan (2-FFT) and difurfuryl disulfide (DFDS), were investigated as green corrosion inhibitors for the N80 steel in a CO2-saturated solution containing 3.5% NaCl. Experimental methods, quantum chemical calculations, and molecular dynamics simulation were employed to evaluate the effectiveness of 2-FFT and DFDS. The results of the study indicate that both 2-FFT and DFDS act as mixed corrosion inhibitors, with a dominant inhibition effect on the cathodic reaction. 2-FFT is physiochemically adsorbed on the steel surface in a tiled form through the furan ring and the - SH groups as adsorption sites. On the other hand, DFDS is chemisorbed on the steel surface through the - S-S- groups in a parallel manner. DFDS exhibits a higher tendency for electron transfer and stronger adsorption to steel compared to 2-FFT. Overall, this study highlights the potential of natural food flavors as effective and environmentally friendly corrosion inhibitors for carbon steel in CO2-saturated environments. The findings of this research can contribute to the development of sustainable and nontoxic corrosion inhibitors for the oil and gas industry.

Investigation of the evolution of an iron carbonate layer and its effect on localized corrosion of X65 carbon steel in CO2 corrosion environments

The general and localized corrosion of X65 carbon steel in CO2-saturated environments conducive to iron carbonate (FeCO3) formation has been studied using electrochemical measurements, together with post-test surface analysis. This research offers new insights into the evolution of FeCO3 layer and its link to the subsequent initiation and propagation of localized corrosion. We identify crevice-like regions forming at boundaries/edges of the FeCO3 crystals, which constitute the crystalline layer, where small cavities filled with electrolyte are restricted between developing crystals. It is apparent that such crevice-like features act as precursors to the localized/pitting corrosion on carbon steel over longer durations. Data availabilityThe raw/processed data required to reproduce these findings cannot be shared at this time as the data also forms part of an ongoing study.

COMPARATIVE STUDY AND ANALYSIS OF CARBON STEEL CORROSION IN CO2 SATURATED ENVIRONMENT.

Carbon steel is arguably one of the most efficient, reliable and safer kind of steel used in petroleum and gas industry for production, distribution and transmission of products. Acetic acid (HAc), is also one of the impurities in oil and gas during transportation from the well sites to the refineries. It is formed in the formation water, which also present in oil and gas production and transportation processes. Acetic acid aids corrosion in pipelines and as a result causes environmental degradation. It has been observed that high concentration of HAc increases the rate of corrosion of carbon steel in CO2 environment. Corrosion slows down production of oil and gas and thereby reduces revenue. In this work, a comparative study and analysis of carbon steel corrosion in the presence of HAc was carried out at 25oC and 80oC in CO2 saturated environment. Weight loss and surface analysis methods (XRD, EDX and SEM) were used to characterize the corrosion layers of the carbon steel samples at different conditions. The weight loss results show that the corrosion rate increased initially with the increase in the concentration of HAc and attained a maximum, and then gradually decreased. At 25oC with 500ppm of HAc, the corrosion rate is 1.35 mm/yr, and 1.80 mm/yr when 1000ppm of HAc was added to the solution. At 80oC and 500ppm HAc, the corrosion rate was 1.80 mm/yr and 2.70 mm/yr with 1000ppm of HAc. A further increase was observed at 3.45 mm/yr when 2500ppm of HAc was added to the system. This increase in corrosion rate is attributed to increase in temperature as increased temperature increases the rate of all reactions. The XRD analysis confirmed that the iron is formed in the absence of HAc while siderite (FeCO3), which is an ore of iron is observed on the materials with HAc. The SEM and EDX results confirmed that a fairly dense material of FeCO3 was formed in the absence of HAc and the layers became porous on addition of HAc to the solution. Key Words: Corrosion, Acetic acid, Carbon steel, CO2, Environment

Modeling and experimental study on the effects of temperature on the corrosion of API carbon steel in CO2-Saturated environment

This paper presents the results of a corrosion study conducted in carbonated brine (2% NaCl solution). All experiments were performed for a one-week duration at a total pressure of 41.37 MPa. The main test variables were temperature (38, 71, and 107 °C) and specimen material type (T95, C110, and Q125). The weight loss technique is used to assess the average corrosion rate (ACR). To detect the presence of localized corrosion, the actual load-carrying capacity (LCCT) of specimens was measured and compared with the one predicted from weight loss (LCCuc). Besides this, corrosion scale and specimen surface were examined using a digital microscope to investigate the presence of localized corrosion and explain ACR and LCCT measurements. To forecast corrosion under a CO2 saturated environment, a new model has been formulated considering a scale-forming condition.Results demonstrate the strong impact of temperature on the CO2 corrosion of API grade carbon steels (T95, C110, and Q125). Regardless of the material type, the highest corrosion rate was observed at 38 °C. Q125 displayed the highest CO2 corrosion resistance. All tested materials were prone to localized corrosion at high temperatures (71 and 107 °C). Model predictions show reasonable agreement with measurements displaying a discrepancy of mostly below 20%.

CO2 Corrosion of Carbon Steel: The Synergy of Chloride Ion Concentration and Temperature on Metal Penetration

This paper investigates the synergy of chloride ion concentration and temperature on the general and pitting corrosion of carbon steel in CO2-saturated environments. Experiments were conducted over 168 h in different concentrations of NaCl brines (1 wt%, 3.5 wt%, and 10 wt%) and temperatures (30°C, 50°C, and 80°C) with the aim of elucidating the combined effect of changes in chloride ion concentration and temperature on overall metal degradation, taking into consideration general and pitting corrosion. This also includes a correlation with the formation and properties of FeCO3 corrosion products. Linear polarization resistance was implemented to monitor the electrochemical responses. Corrosion product characteristics and morphologies were studied through a combination of scanning electron microscopy and x-ray diffraction. Pitting corrosion evaluation was conducted through the application of 3D surface profilometry to study pit geometries such as the depth and diameter. The results show that general and pitting corrosion are strongly correlated to the synergistic effects of changing chloride ion concentration and temperature in carbon steel as a result of their combined influence on ferrite (Fe) dissolution and FeCO3 formation. This represents a paradigm shift from the already established mechanisms on chloride ion and temperature effects on passive alloys such as stainless steel. Increasing chloride ion concentration and temperature up to 10 wt% NaCl and 50°C to 80°C, respectively, is observed to increase the rate of Fe dissolution and formation of semiprotective FeCO3 corrosion products, leading to the increased manifestation and severity of pitting corrosion. The results also show that a “threshold chloride concentration” exists at 30°C, above which there is no significant increase in corrosion rate. However, such “threshold effects” were not observed at higher temperatures evaluated in the range of chloride concentration considered in this study.

Performance evaluation of an imidazoline corrosion inhibitor in a CO2-saturated environment with emphasis on localised corrosion

The ability of an imidazoline inhibitor to provide corrosion protection to X65 carbon steel in a CO2-saturated sodium chloride (NaCl) solution at 80ºC was evaluated. The performance of the inhibitor was investigated with respect to both generalised and localised corrosion behaviour using in-situ electrochemical measurements, ex-situ scanning electron microscopy (SEM) and non-contact surface profilometry. We demonstrate that the optimum inhibitor concentration required to minimise generalised corrosion is significantly lower than that required to minimise localised corrosion. This highlights the importance of systematic, post-test topographical measurements in the selection and optimisation of inhibitor dosage.

THE EFFECT OF INSIDE CIRCUMSTANCE OF THE HAZARDOUS WASTE LANDFILL ON THE LEACHING BEHAVIOR OF HARMFUL HEAVY METALS

In Japan, among three landfill classes, the hazardous waste landfill is used for disposing ofhazardous waste of which leaching of heavy metal exceeds its criteria. To prevent the emission of ahazardous substance to the surrounding environment, the hazardous waste landfill is required to beconstructed with a robust concrete wall and base, and the top must be capped. Because of the containmentstructure, rainwater infiltration and air intrusion hardly occur. This means the leaching potential of hazardousheavy metals in waste remains forever. But considering long term safety, their leaching potentials must bebetter reduced. In this study, the influence of interior condition in the hazardous waste landfill on theleaching of heavy metals was examined from the accelerated weathering experiments for dust which isdisposed of at the hazardous waste landfill. As the results, a decrease in the leaching amount of Cd, Pb, Mn,and Zn was confirmed in a wet environment where adsorbed water was present on the particle surface. Onthe other hand, in the dry and CO2 saturated environment, an increase in the leaching amount was observed.The former phenomenon was thought to be the formation of hydroxide at the particle surface, and the latterwas considered to be the influence of adsorption of CO2 to Fe3O4 and ZnO. Though further scientificverification is required for each phenomenon, the findings obtained in this study indicate that the leaching ofheavy metals from wastes in the hazardous waste landfill may change over time depending on the interiorcondition.

Cracking mechanism in API 5L X65 steel in a CO2-saturated environment – Part II: A study under cathodic polarisation

The aim of this work is to achieve a better understanding of hydrogen effect in CO2 environments, isolating its contribution by imposing cathodic polarisation on Hydrogen Permeation (HP) and Slow Strain Rate Tests (SSRTs). The influence of Fe3C and FeCO3 layers on hydrogen embrittlement (HE) susceptibility was a specific focus of this study. The results indicate that CO2 environment generates hydrogen, which permeates through steel, although in lower amount compared to H2S environments. Moreover, in Fe3C-rich surface, the HP current achieves values higher than in wet-ground surface. Furthermore, in FeCO3-filmed surface HP current is higher at the beginning of the test but decreases over time. The results of SSRT show the loss of ductility of the steel under cathodic polarisation that was driven by hydrogen and the embrittlement effect magnitude depends on the surface condition, indicating that a pre-corroded steel surface can raise the HE susceptibility in a CO2 environment.

Cracking mechanism in API 5L X65 steel in a CO2-saturated environment

Hydrogen charging in low alloy steels poses a significant problem in the oil and gas industry. Detrimental hydrogen effects are not commonly expected in CO2 aqueous environments. However, the acid nature of these environments and the high corrosion rates expected justify the assessment of cracking susceptibility of carbon steel in a CO2-saturated environment as presented in this work. The focus of this investigation is to understand how different surface films/corrosion products influence the hydrogen permeation and cracking mechanism of an API 5L X65 carbon steel in a saturated CO2 environment. The experiments were carried out to assess hydrogen permeation at open circuit potential on steel samples which were either wet-ground, or pre-filmed with iron carbide (Fe3C) rich or iron carbonate (FeCO3) layers. Tafel measurements were also performed to determine the effect of the surface composition on the cathodic reactions. Slow strain rate tests (SSRT) were conducted in order to evaluate the effects of hydrogen on the cracking mechanisms of the steel in this sweet environment. Results indicated that at open circuit conditions, Fe3C was able to increase the steady state hydrogen permeation current due to accentuation of the cathodic hydrogen-evolution reaction. Although FeCO3 suppressed the cathodic reaction at the steel surface, the development of the protective and densely packed crystalline layer increased hydrogen uptake marginally from that of the ground steel reduced. SSRT indicated a very moderate loss of ductility in wet-ground and FeCO3 steel surface conditions. However, a more significant reduction in area was observed in the tests carried out on Fe3C rich samples. These results imply that a corroded API 5L X65 steel surface in a CO2 rich environment can enhance the hydrogen embrittlement (HE) susceptibility and as such, hydrogen permeation susceptibility needs to be considered in material selection.

CO2 Corrosion of Low Carbon Steel Under the Joint Effects of Time-Temperature-Salt Concentration

The time-dependent effect of temperature and salt (NaCl) concentration on the corrosion behavior of carbon steel in CO2-saturated environments were explored using various electrochemical techniques coupled with XRD, Raman spectroscopy and SEM/FIB examinations. At constant salt level, corrosion rate increased and stabilized when temperature was below 60 °C. When temperature was higher than 60 °C, corrosion rate firstly increased, reached an apex, and then started decreasing continuously. The magnitude of the decrease is inversely proportionally to the salt concentration, which is then attributed to the microstructure of dual-layer FeCO3 scale. Polarization experiments indicate the anodic process is more affected by salt concentration than temperature while the opposite is true for the cathodic kinetics. Although chloride is not detected in the corrosion scale, it is regarded to have significant influence on the nucleation and growth of FeCO3 and therefore the properties (e.g., thickness and compactness) of the corrosion scales. Lastly, a mechanism is proposed for the evolution of corrosion scales on carbon steel in CO2 saturated environment as a function of temperature and salt concentration.

Crevice corrosion of N80 carbon steel in CO2-saturated environment containing acetic acid

Crevice corrosion of N80 carbon steel in CO2-saturated environment containing acetic acid (HAc) was studied by electrochemical measurements and surface analysis. No obvious corrosion is observed on the half-electrode outside crevice while severe corrosion occurs on the half-electrode inside crevice, and deep corrosion groove appears at the crevice mouth. Crevice corrosion of carbon steel is triggered by the galvanic effect between the two half-electrodes inside and outside crevice. Crevice corrosion is promoted by increasing the HAc concentration because the galvanic effect between the two half-electrodes inside and outside crevice is strengthened with the increase of HAc concentration.

The Influence of pH on Localized Corrosion Behavior of X65 Carbon Steel in CO2-Saturated Brines

Pitting and localized corrosion of carbon steel is considered to be a complex process influenced by a wide range of parameters such as temperature, bulk solution pH, and chloride ion concentration. Solution pH is known to influence corrosion product characteristics and morphology in CO2- and H2S-containing corrosion systems. However, from the perspective of pitting corrosion in CO2-saturated environments, the extent to which bulk pH of solutions and the presence of corrosion products influence localized attack is still not clearly understood. This paper presents an investigation into the role of pH on the characteristics of corrosion product and pitting corrosion behavior of X65 carbon steel (UNS K03014) in CO2-saturated brine. Pitting corrosion studies were conducted over 168 h at 50°C in 3.5 wt% NaCl solutions at different bulk pH (buffered to pH values of 6.6 and 7.5 in some cases) in order to understand and correlate the role of pH on corrosion product morphology, chemistry, initiation, and propagation of pits within each distinct environment. Corrosion product composition and morphology are identified through a combination of electrochemical and surface analysis techniques, which include scanning electron microscopy and x-ray diffraction. The extent of corrosion damage of the carbon steel is evaluated through the implementation of surface interferometry to study discrete pit geometry, namely the size, depth, and aspect ratio. Results indicate that the process of pit initiation and propagation of carbon steel in CO2 corrosion environment is different depending upon bulk solution pH. At low pH (pH values starting at 3.8), pitting initiates faster and propagates steadily along with significant uniform corrosion resulting from the formation of an “amorphous” form of FeCO3. At higher pH, uniform corrosion is significant, while pitting initiates with increasing protection from crystalline FeCO3. At a pH value of 7.5, pitting corrosion initiation occurs after and/or during pseudo-passivation is achieved as a result of the formation of a “protective and pseudo-passivating” FeCO3 film.

Biomimetic Sequestration of CO2 Using Carbonic Anhydrase from Calcite Encrust Forming Marine Actinomycetes

Background: CO2 in the environment has been a burning issue and aggravated the threats of global warming. Various strategies are being used to decrease the level of releasing CO 2 . Biosequestration is a one of the available nontoxic, robust and eco-friendly approaches but still less evaluated. This study reports the role of microbial Carbonic Anhydrase (CA) in the formation of calcite by utilizing CO2. Methods: The marine Nocardiopsis lucentensis was studied for intracellular microbial CA. Isolate grown optimally at 2.5% CO2 saturated environment and procedure the calcium carbonate encrust in the presence of CaCl2. Results: The enzyme was found to catalyze the reaction in a wide range of pH and temperature with an optimum at 7.0 pH and 25°C. The 50 mM NaCl, KCl and MgCl2 were found to support the enzyme activity and 50 mM ZnCl 2 increases activity 1.5 fold. CA was able to withstand against sulphanilamide inhibitor and stable over prolonged incubation at 4 and 37°C. Conclusion: Calcite formation was evaluated with and without enzyme using marine water as a source of calcium ions. The result of SEM and EDX indicated the formation of larger flower-shaped particles compare to the small cubic particles formed without enzyme. The results suggest that the robustness of enzyme and suitability in the CO2 capture reactor.

Assessment of combined scale/corrosion inhibitors – A combined jar test/bubble cell

Abstract The formation of calcium carbonate scale and the occurrence of CO2 corrosion are both widespread phenomena observed within pipework during oil and gas production. The most common form of treatment for both processes is the application of chemical inhibition through corrosion and/or scale inhibitors. Surface scaling of pipework rarely occurs in environments where no corrosion exists, yet techniques used to develop and assess the performance of scale inhibitors tend to focus on assessing and reducing solely bulk/surface scaling, without affording consideration towards corrosion, whilst corrosion inhibitors are frequently evaluated in non-scaling environments. Furthermore, both chemicals tend to be evaluated independently meaning that any potential antagonistic effects between the chemicals can go unrecognised. This paper addresses this very issue by presenting a unique setup and methodology to enable the occurrence of scale and corrosion to be monitored simultaneously in a CO2-saturated environment in the presence and absence of combined scale and corrosion inhibitors. The test cell focuses on evaluating four key parameters which are quantified either throughout the duration of the test, or from the implementation of post-test surface analysis techniques. The multiple assessment of (i) bulk scale precipitation, (ii) surface scaling, (iii) general corrosion and (iv) localised corrosion permits a full assessment of the chemical blends propensity to mitigate both scaling and corrosion. Non-inhibited tests were initially conducted at 60 °C to form a baseline for comparison. Four combined scale/corrosion inhibitors were subsequently used at low concentrations in order to understand their mechanisms and highlight any competitive effect which existed in reducing either scale or corrosion. The results demonstrate that the methodology implemented is effective at assessing the efficiency of combined inhibitors in reducing both corrosion and scale in environments where both processes occur simultaneously. The limitations of conducting solely bulk scaling or corrosion tests in non-scaling environments are discussed relative to the results obtained in this work. The results of each individual inhibitor are discussed and markedly different behaviour is observed according to the concentration administered, as well as the particular blend of chemicals applied.

Assessing the influence of shear stress and particle impingement on inhibitor efficiency through the application of in-situ electrochemistry in a CO2-saturated environment

An investigation was conducted to assess the performance of a commercially available high shear carbon dioxide (CO2) corrosion inhibitor in a series of flow-induced corrosion and erosion–corrosion environments. The purpose of the study was to understand the role that high shear stress and sand particle impingement play in influencing the in-situ corrosion rate of API 5L X65 carbon steel in blank and inhibited conditions. Tests were conducted at 45°C in CO2-saturated conditions using a rotating cylinder electrode (RCE) for low shear stress tests (18–260Pa) and a submerged impinging jet (SIJ) for high shear environments (104–740Pa). The inhibitor was studied at concentrations of 0, 25, 50, 75 and 100ppm. The application of computational fluid dynamics to model the SIJ and the use of ring shaped samples allowed for an accurate prediction of shear stress across the specimen surface that could be correlated with in-situ corrosion rate and inhibitor efficiency over a range of concentrations. The incorporation of 500mg/L of sand to the system helped to quantify the increase of the in-situ corrosion rate due to the impingement of the particles. All corrosion rates were determined through the application of linear polarization measurements throughout the duration of the test. Post-test analysis of the material degradation mechanisms was examined using scanning electron microscopy (SEM).

The influence of high shear and sand impingement on preferential weld corrosion of carbon steel pipework in CO2-saturated environments

Preferential weld corrosion (PWC) has proved problematic for the oil and gas industry for a number of years. Although the effect of high flow rates on PWC in inhibited CO2-saturated solutions has been studied by authors, the consideration of a higher, localised turbulence over the weld material and the implications this has on PWC appears minimal. This work considers this very effect, along with developing an understanding of the threats posed to weld integrity by sand particle presence in the process fluid using a submerged impinging jet (SIJ) apparatus.Experiments were conducted using a commercially available film-forming oilfield corrosion inhibitor which was evaluated in both flow-induced corrosion and erosion–corrosion environments in its ability to control PWC. The SIJ setup allowed control over the individual flow velocities at each nozzle, meaning shear stress could be intensified over the 1% Ni–0.25% Mo weld material to simulate localised turbulence at the sample surface. Galvanic current and mixed potential measurements were performed to ascertain changes in galvanic interactions between the two materials. The work demonstrates that localised turbulence over internal weld beads and the presence of sand within oil and gas systems can influence PWC in certain environments.

Erosion–corrosion of engineering steels—Can it be managed by use of chemicals?

One significant contributory factor in the degradation of both pipelines and downhole tubulars in the oil and gas industry is erosion–corrosion. An erosion–corrosion investigation was carried out with three different steels—carbon steel, martensitic stainless steel and superduplex stainless steel. The materials were chosen to represent “active” and “passive” corrosion materials and are the same materials used in completions. Tests were carried out under three different regimes spanning a range of fluid velocities to simulate the severity of the mechanical erosion effect. A commercial corrosion inhibitor was used to investigate the inhibitor ability to reduce damage due to erosion–corrosion. In each of the conditions, pure corrosion and combined erosion–corrosion were studied by electrochemical and gravimetric techniques. The experiments were conducted using a jet impingement rig capable of producing jet velocities up to 20 m/s in a CO 2-saturated environment with sand. Erosion–corrosion mechanisms were determined from microstructural studies by SEM and inhibitor adsorption tests. The paper shows that the inhibitor effectively reduced erosion–corrosion damage for carbon steel; it was only in severe erosion–corrosion conditions that inhibitor has any noticeable effect for martensitic stainless steel and there were no conditions where the inhibitor offered a benefit for the superduplex stainless steel.

Some Observations on Corrosion of Carbon Steel in Aqueous Environments Containing Carbon Dioxide

Abstract Experimental results and analyses are reported on the corrosion of carbon steel in CO2-saturated environments that typically represent producing well waters encountered in natural gas rese...