Carbon Steel Pipelines Research Articles

Exploring corrosion protection properties of alkyd@lanthanide bis-phthalocyanine nanocomposite coatings.

Organic coatings have been widely used to protect carbon steel pipelines from external corrosion; however, they often suffer from permeability and weak adhesion. Here we show that synthetic lanthanide bis-phthalocyanine complexes, LnPc2 (Ln = lanthanide metal, Pc = C32H16N8 denotes the phthalocyanine ligand) can be used to form new nanocomposite coatings to provide corrosion protection to the underlying carbon steel pipelines. Electrochemical studies (EIS and potentiodynamic polarization) showed that the incorporation of LnPc2 compound (PrPc2, SmPc2 and HoPc2) additives with alkyd coating, leads to a significant increase in the corrosion resistance of carbon steel in 0.5 M HCl solution. The alkyd@LnPc2 nanocomposite coatings absorb very low water volumes, when compared to the neat alkyd coating. LnPc2 compounds allowed enhancing the pull-off adhesion of coatings performance from 3.34 MPa to 19.94 MPa. The efficiency of alkyd@HoPc2 coating appears higher than that of alkyd@PrPc2 and alkyd@SmPc2 coatings. The protective properties of alkyd@LnPc2 coatings were confirmed by SEM, TGA, scratch hardness, impact resistance, bend test and contact angle analysis.

Effect of temperature and fluid speed on the corrosion behavior of carbon steel pipeline in Qatari oilfield produced water

Metals integrity, such as carbon steel used in pipeline network can be seriously damaged by produced water causing serious corrosion problems. This can result in significant threats to safe operation of the oilfield facilities and leads to considerable economic losses. In this study, the effect of produced water from the North oilfield of Ras Laffan in Qatar on corrosion and scaling of carbon steel is investigated using electrochemical methods. The specimen rotation speed ranged from 0 to 2m/s and temperature between 20 and 60°C were used as test parameters for the study. X-ray power diffractometer (XRD) and scanning electron microscopy (SEM) techniques were employed in the analysis of the corroded steel samples. It was found that the corrosion rate increased with increasing temperature and specimen rotation speed. These results also showed that the steel reacted with the corrosive ions at the early stage of its exposure to the produced water leading to the formation of corrosion products on the steel surface in which CaCO3 scale layer were deposited on the surface of the specimen as loose products due to the presence of large amounts of Ca2+ and HCO3− ions contained in the Rass Lafan oilfield produced water. More so, pitting and cracks were observed on the steel surface which increased as the temperature and specimen rotation speeds were increased, suggesting localized corrosion mechanism.

An extended engineering critical assessment for corrosion fatigue of subsea pipeline steels

Abstract Engineering critical assessment (ECA) is widely used to assess the structural integrity in offshore industry. But industry standards provide limited guidance on ECAs of structures subjected to corrosion fatigue (CF). In this paper, a critical stress intensity factor (SIF) derived from a corrosion-crack correlation model is proposed to improve the traditional ECA for steel structures in seawater. The proposed critical SIF extends the traditional ECA for CF in that it accounts for the influence of load frequency and initial crack size on the model selection within current ECA guidelines for the ECA of marine structures under CF. The extended ECA is applied for × 65 carbon pipeline steels subjected to CF. The crack growth curves are built using a three-stage CF crack growth model and the experimental data. Fatigue lives are calculated based on those curves as well as traditional ECA models. Results show that the critical SIF can effectively improve the ECA for × 65 carbon pipeline steels under CF. The extended ECA provides a reasonable assessment with reduced conservatism in contrast to the traditional ECA for CF.

Studies on the Development of New Efficient Corrosion Inhibitors for Crude Oil Pipelines: Electrochemical Impedance Spectroscopy Results for 1,8-Naphthyridines

Five 1,8-naphthyridines were tested as corrosion inhibitors, including three non-previously reported 3-alkyl-1,8-naphthyridines. All were produced via the extended Friedländer synthesis, that for 3-alkyl-1,8-naphthyridines involves the earliest use of aliphatic aldehydes. Fragmentation pattern in MS for 3-alkyl-1,8-naphthyridines shows a remarkable parallel with that exhibited by 3-alkylpyridines. Electrochemical Impedance Spectroscopy (EIS) was used to assess the inhibiting properties of these compounds on samples of API X52 carbon steel pipelines immersed in oilfield-related water. Except for one of the molecules tested, the inhibition efficiency (IE%) values were significantly higher than that calculated for a reference commercial inhibitor.

In situ SR-XRD study of FeCO3 precipitation kinetics onto carbon steel in CO2-containing environments: The influence of brine pH

The growth of iron carbonate (FeCO3) on the internal walls of carbon steel pipelines used for oil and gas transportation can reduce internal corrosion significantly. Solution pH can be considered as one of the most influential factors with regards to the kinetics, morphology and protection afforded by FeCO3 films. This paper presents results from a recently developed in situ Synchrotron Radiation-X-ray Diffraction (SR-XRD) flow cell integrated with electrochemistry for corrosion measurements. The cell was used to follow the nucleation and growth kinetics of corrosion products on X65 carbon steel surfaces in a carbon dioxide (CO2)-saturated 3.5wt.% NaCl brine at 80°C and a flow rate of 0.1m/s over a range of solution pH values (6.3, 6.8 and 7). In all conditions, FeCO3 was identified as the only crystalline phase to form. Electrochemical results coupled with post-test surface analysis indicate that at higher pH, larger portions of the surface become covered faster with thinner, more protective films consisting of smaller, denser and more compact crystals. The comparison between XRD main peak area intensities and FeCO3 surface coverage, mass and volume indicates a qualitative relationship between these parameters at each pH, providing valuable information on the kinetics of film growth.

Aislamiento térmico de tuberías de acero que transportan fluidos calientes a partir de recubrimientos elaborados mediante proyección térmica

Se depositaron recubrimientos cerámicos, a partir de polvos comerciales de Al2O3, Al2O3-TiO2, y Al2O3-ZrO2 sobre la superficie exterior de tuberías de acero al carbono ASTM A106 Grado B con y sin capa base de una aleación de níquel, con el fin de reducir las pérdidas de calor contenido en fluidos calientes que son transportados a través de este tipo de ductos. Tanto la capa base como los recubrimientos cerámicos fueron depositados mediante proyección térmica oxiacetilénica y posteriormente se evaluó la transferencia de calor en estado transitorio, para lo cual se introdujo en las tuberías aceite de silicona calentado a 160ºC. La variación de temperatura con el tiempo del aceite de silicona y de la pared externa de cada tubo fue medida, encontrando que además de la baja conductividad térmica de los materiales cerámicos, un mayor espesor y una mayor porosidad del recubrimiento brindan medios efectivos de aislamiento térmico, y que la capa base actúa como una resistencia térmica que consume calor y contribuye a la disminución de la temperatura superficial de la tubería.

Development of a strain based fracture assessment procedure for undermatched pipe girth welds subjected to bending

Structural integrity assessment of pipeline girth welds subjected to high strain levels which arises from the reel-lay method relies on precise crack driving force estimation procedures. Recent developments in subsea technology favor the use of high strength carbon steel pipelines with an internal corrosion resistant layer to increase protection against corrosive fluids. In contrast to homogeneous structural components, the bimetal configuration may induce the occurrence of weld strength undermatch, with a strong impact on the relationship between remote applied load and crack tip constraint. This work explores the development of a crack driving force estimation procedure based on a strain-based version of the EPRI J estimation scheme coupled with the equivalent stress-strain relationship method (ESSRM) and a weld geometry simplification procedure. The proposed framework takes advantage of the displacement controlled nature of the reeling process. Extensive 3D analyses provide a large set of fracture parameters applicable to the strain-based EPRI methodology followed by parametric analyses conducted to assess the accuracy of the new procedure. Subsequently, a case study is performed to determine the tolerable crack sizes in an idealized pipe installation. The procedure shows an overall good agreement to the benchmark analyses and increased accuracy when compared to the recommended approach proposed by DNV.

Pitting and Uniform Corrosion of X65 Carbon Steel in Sour Corrosion Environments: The Influence of CO2, H2S, and Temperature

Localized corrosion of carbon steel pipelines in oilfield environments is a serious concern. In environments containing both CO2 and H2S gases, pitting corrosion of carbon steel is considered to be a common occurrence which is particularly complex and still not fully understood. This paper presents a parametric study investigating the pitting corrosion behavior of carbon steel in CO2-H2S-containing environments. The work presented is divided into two parts. Part one focuses on understanding the impact of changes in three key process parameters (namely: temperature, absence/presence of 10% H2S, and absence/presence of CO2 in the gas phase) on FeS film formation process and overall the corrosion behavior of carbon steel with emphasis on general corrosion of carbon steel in a 3.5 wt% NaCl brine at 30°C and 80°C. Part two focuses on understanding the early and later stages of the pitting corrosion process, with consideration afforded to general corrosion and iron sulfide (FeS) film formation mechanisms, kinet...

Assessment of general and localized corrosion behavior of X65 and 13Cr steels in water-saturated supercritical CO2 environments with SO2/O2

To mitigate the corrosive effect encountered in carbon steel pipelines during dense phase CO2 transport the general consensus is that the CO2 stream must be sufficiently dehydrated. Although such a process will undoubtedly help prevent the breakout of free water, it can contribute significantly towards the handling costs, particularly in the context of offshore installations. As opposed to drying the CO2 stream to excessive levels, one alternative option is the application of corrosion resistant alloys such as 13Cr. This paper performs a comparison between X65 carbon steel and 13Cr in pure and impure CO2, evaluating the influence of SO2 and O2 on the general and localized corrosion rate of both materials at 80bar and 35°C. The results show that 13Cr is able to perform exceptionally well in comparison to X65 in pure CO2 as well as when SO2 and O2 are present in the system individually, producing no localized corrosion and general corrosion rates below 0.02mm/y. However, when SO2 and O2 were combined, the formation of sulfuric acid was permitted which proved detrimental to 13Cr, producing excessive localized attack much greater than that observed on X65. Raman spectrosopy, XRD and SEM/EDX are used to analyse the corrosion products.

Bio-corrosion of carbon steel by sulfate reducing bacteria consortium in oil and gas pipelines

This research is aimed to give an overview of the impact of bio-corrosion on carbon steel grade API 5L X-70 immersed in growth medium and exposed to SRB consortium. Simulation of anaerobic corrosion conditions was carried out in a laboratory for 28 days. Raw crude oil gathered from the Baram Delta Operation Terminal was cultured in broth number 1249 (Modified Barr’s Medium) to study the effect of bacteria growth upon metal loss. Carbon steel coupons grade X70 were cut to approximately 10mm x 20mm x 5mm and immersed in the cultured broth. During the experiment, the planktonic SRB were enumerated using a counting chamber (direct cell count method) under the electronic microscope at 200x magnification. Results indicated that the optimum pH and temperature for the respected SRB consortium genes were 8.5 and 37 °C, respectively. Metal loss of the corrosion specimen was measured and recorded after retrieval from the immersion period in the medium on a weekly basis prior to SRB inoculation for further analysis. The metal loss values supported that SRB activity can increase the metal loss of carbon steel against time of exposure. Additionally, the FESEM image showed the biofilm formations on the corrosion specimen. Thus, the results could conclude that biocorrosion caused by particular local SRB consortium can be considered as a threat to carbon steel pipelines. Besides, the effect of SRB activity and response towards metallic materials in a dynamic environment is an interesting topic to be studied upon in the future.

Effects of Thermally Degraded Monoethylene Glycol with Methyl Diethanolamine and Film-Forming Corrosion Inhibitor on Gas Hydrate Kinetics

Gas hydrate blockage and corrosion are two major flow assurance problems associated with transportation of wet gas through carbon steel pipelines. To reduce these risks, various chemicals are used. Monoethylene glycol (MEG) is injected as a hydrate inhibitor while methyl diethanolamine (MDEA) and film-forming corrosion inhibitor (FFCI) are injected as corrosion inhibitors. A large amount of MEG is used in the field, which imposes the need for MEG regeneration. During MEG regeneration, rich MEG undergoes thermal exposure by distillation to remove the water. This study focuses on analyzing the kinetics of methane gas hydrate with thermally exposed MEG solutions with corrosion inhibitors at 135–200 °C. The study analyses the hydrate inhibition performance of three different solutions at selected concentrations and pressures (50–300 bar), using a PVT cell and isobaric method. Results established that thermally degraded solutions cause hydrate inhibition drop. However, the inhibition drop was found to be lower...

Damping Effect on the Wave Propagation in Carbon Steel Pipelines Under Fluid Hammer Conditions

A sudden reduction of the fluid flow yields a pressure shock, which travels along the pipeline with a high-speed. Due to this transient loading, dynamic hoop stresses are developed that may cause catastrophic damages in pipeline integrity. The vibration of the pipe wall is affected by the flow parameters as well as by the elastic and damping characteristics of the material. Most of the studies on dynamic response of pipelines: (a) neglect the effect of the material damping and (b) are usually limited to harmonic pressure oscillations. The present work is an attempt to fill the above research gap. To achieve this target, an analytic solution of the governing motion equation of pipelines under moving pressure shock is derived. The proposed methodology takes into account both elastic and damping characteristics of the steel. With the aid of Laplace and Fourier integral transforms and generalized function properties, the solution is based on the transformation of the dynamic partial differential equation into an algebraic form. Analytical inversion of the transformed dynamic radial deflection variable is achieved, yielding the final solution. The proposed methodology is implemented in an engineering example; and the results are shown and discussed.

Effect of dissolved copper ions on erosion–corrosion synergy of X65 steel in simulated copper tailing slurry

Erosion-corrosion is studied in the context of carbon steel pipelines transporting copper tailings with focus on the influence of dissolved copper ions present in the slurry. API 5L X65 steel is exposed to flow of slurry in rotating cylinder electrode (RCE) simulating flow conditions typical of a slurry pipe. Degradation is evaluated by means of electrochemical and gravimetric techniques, and the worn surfaces are analyzed by scanning electron microscope equipped with focused ion beam. It is found that 500ppm of dissolved copper ions increases the total weight loss by at least 30% and the increase is attributed to the combined contributions of corrosion and the erosion-corrosion synergy, with the underlying mechanism being galvanic coupling of steel with the reduced copper ions deposited on steel surface.

Novel hydrophobic PVDF/APTES-GO nanocomposite for natural gas pipelines coating

Polyvinylidene fluoride (PVDF) nanocomposites were successfully prepared by solvent casting approach using graphene oxide (GO) and 3-aminopropyltriethoxysilane-graphene oxide (APTES-GO) as nanofillers. Field emission scanning electron microscope (FESEM) revealed that the PVDF nanocomposites exhibited features of symmetric membrane. Incorporation of 0.4 wt% of APTES-GO into the PVDF matrix led to a significant decrease in wettability with water contact angle (CA) of 102° as compared to 62° for 0.4 wt% GO and 80° for neat PVDF. PVDF/APTES-GO has increased 2350% in tensile modulus as compared to 75% increased in PVDF/GO nanocomposite. Carbon steel plate, which has similar properties with commercial carbon steel pipelines was used in the salt spray and acid immersion tests. PVDF/APTES-GO nanocomposite coating was found to exhibit excellent corrosion protection and good adhesion property than other coatings in corrosive environments.

Cathodic protection monitoring of buried carbon steel pipeline: measurement and interpretation of instant-off potential

ABSTRACTThe criterion used to verify the cathodic protection condition of a structure is based on structure-to-electrolyte potential measurement, which can include an ohmic drop contribution. Among the available techniques, the use of potential probes with internal reference electrode and of corrosion coupons with a so-called soil-access tube represents the most appropriate way to measure the IR-free potential, eliminating the ohmic drop contribution. An alternative is represented by on-off technique if equalising, galvanic or stray currents are not present. Laboratory tests have been carried out in soil-simulating solution on cathodically protected carbon steel in order to evaluate the effectiveness of off-potential for the assessment of cathodic protection. Instant-off potential is not reliable in overprotection condition; moreover, the accuracy of the measurement is strongly influenced by the presence of external current as galvanic or equalising currents. The effect of low-pass filter in the data acquisition system on the potential reading is discussed.

Effectiveness of Imidazoline in Mitigating Transport Pipeline Corrosion

The detrimental effects of corrosion in transportation pipelines have been a primary issue for the oil and gas industry for many years. Every year, millions of dollars are invested into corrosion inhibitors in order to minimise corrosions implication on flow assurance. Imidazoline and its derivatives have been a prevalent corrosion inhibitor owing to its good adsorption characteristics and film forming capabilities; however, there remains some uncertainty in literature pertaining to the effect of temperature on its performance. GULP simulation software was used to study the effect of temperature on the thermodynamic properties of imidazoline in carbon steel pipelines. Entropy, heat capacity, Helmholtz free energy, entropy and Gibbs free energy were influenced by changes in temperature. An optimal operating range was found to exist between 298K and 333K. Within this range, spontaneous chemisorption was occurring and the imidazoline molecules possessed enough kinetic energy to displace any bound water on the metal surface to permit the preferential adsorption of the imidazoline head group. However, beyond 333K, the kinetic energy of the system hindered the steady formation of the protective barrier, reducing its inhibitive potential. This study agrees with previous literature on the effect of temperature on the ability of imidazoline as a corrosion inhibitor, however further studies into the effect of pipeline conditions and imidazoline molecular structure are needed in order to affirm the optimal applicability of imidazoline as a corrosion inhibitor.

Modification of Caster Oil and Study Its Efficiency as Corrosion Inhibitors in Formation Water Media

The present study relates to preparation corrosion inhibiter from caster oil for carbon steel pipeline by two steps; the first step includes sulfonation of caster oil and the second step includes amination the sulfonic caster oil with ammonia solution the final product characterized by FTIR. The effectiveness of the synthesized compounds is studied as corrosion inhibitors for carbon steel; in formation, water was investigated by electrochemical techniques using Tafel plot methods. The synthesized compounds showed enhancement in inhibition efficiencies, and then studied the effect of temperatures on inhibition efficiency.

Can Thermally Sprayed Aluminum (TSA) Mitigate Corrosion of Carbon Steel in Carbon Capture and Storage (CCS) Environments?

Transport of CO2 for carbon capture and storage (CCS) uses low-cost carbon steel pipelines owing to their negligible corrosion rates in dry CO2. However, in the presence of liquid water, CO2 forms corrosive carbonic acid. In order to mitigate wet CO2 corrosion, use of expensive corrosion-resistant alloys is recommended; however, the increased cost makes such selection economically unfeasible; hence, new corrosion mitigation methods are sought. One such method is the use of thermally sprayed aluminum (TSA), which has been used to mitigate corrosion of carbon steel in seawater, but there are concerns regarding its suitability in CO2-containing solutions. A 30-day test was carried out during which carbon steel specimens arc-sprayed with aluminum were immersed in deionized water at ambient temperature bubbled with 0.1 MPa CO2. The acidity (pH) and potential were continuously monitored, and the amount of dissolved Al3+ ions was measured after completion of the test. Some dissolution of TSA occurred in the test solution leading to nominal loss in coating thickness. Potential measurements revealed that polarity reversal occurs during the initial stages of exposure which could lead to preferential dissolution of carbon steel in the case of coating damage. Thus, one needs to be careful while using TSA in CCS environments.

Fatigue crack growth modelling for pipeline carbon steels under gaseous hydrogen conditions

A corrosion-crack correlation model is proposed for the hydrogen embrittlement (HE) influenced fatigue crack growth modelling of pipeline carbon steels under gaseous hydrogen conditions. The model is developed primarily based on the correlation of environment-affected zone (EAZ) and plastic zone. In the model, fatigue crack growth rate is predicted by Forman equation to take into account the influence from fracture toughness. The critical frequency and the “transition” stress intensity factor (SIF) are derived based on stress-driven hydrogen diffusion and Hydrogen-Enhanced De-cohesion (HEDE) hypothesis, which provides reasonable explanation on the frequency dependence of fatigue crack growth for pipeline carbon steels in hydrogen gas. Furthermore, an approximation formula involving threshold the SIF range and the stress ratio is established to describe the phenomenon of crack growth rate plateau. In addition, a formula is proposed to estimate the equilibrium fracture toughness according to the equilibrium between crack growth and hydrogen delivery rates. A series of experimental data from different grades of carbon pipeline steels (including high-strength grades such as X70 and X80) are utilized for demonstrate the validity of the proposed formulae and model effectiveness. The comparison between model predictions and experimental data shows that the proposed model is capable of capturing the essence of pipeline carbon steels’ fatigue crack growth process under gaseous hydrogen conditions.

Failure analysis of a carbon steel pipeline exposed to wet hydrogen sulfide environment

Abstract Stress Corrosion Cracking (SCC) is one of the most common failure phenomena in the wet hydrogen sulfide environment. In this paper, the fracture failure of a fuel gas pipeline during operation has been analyzed. Through service environmental investigation, crack morphology detection, and stress analysis of fuel gas pipeline, the fracture has the morphology and characteristic of wet hydrogen sulfide SCC in the welding joint between pipeline and flange. The analysis shows that the abnormal martensitic microstructure in the pipeline has provided the advantage for SCC.