X80 Steel Research Articles

Imidazoline behavior as corrosion inhibitor in the electrochemical characterization of SCC behavior of an API X70 steel exposed to brine solution

Abstract The effect of concentration of an organic imidazoline as inhibitor on internal stress corrosion cracking (SCC) behavior of an API X70 pipeline steel exposed to a brine solution was studied. The SCC process using simultaneously the slow strain rate stress test (SSRT) and electrochemical measurements was performed. Fracture surface analysis and secondary cracking were observed through a scanning electron microscopy (SEM). According to SEM fractography and SSRT results, the steel showed high SCC susceptibility with a brittle fracture and several secondary cracks without addition of inhibitor, whereas the addition of inhibitor to brine solution was effective to increase the SCC resistance of steel at concentrations of inhibitor of 50 and 100 ppm. A further addition of concentration of inhibitor had a negative effect on the mechanical properties of the steel. Electrochemical measurements results are in accordance with the SCC susceptibility, indicating that corrosion inhibitor film suppressed the anodic and cathodic reactions increasing the resistance to SCC until concentration of 100 ppm. Further addition of inhibitor aggravated the localized corrosion due to local desorption of inhibitor molecules. The Hilbert–Huang transform (HHT) analysis revealed the contribution of different corrosion process contained in the electrochemical current noise (ECN) signals at several inhibitor concentrations.

Corrosion of X80 steel in the co-existence of sulfate reducing bacteria and permeating hydrogen

PurposeThis study aims to shed light on the corrosion behavior of X80 steel when sulfate-reducing bacteria (SRB) and permeating hydrogen interact.Design/methodology/approachIn this study, electrochemical tests were conducted between 25 and 55 °C, and the surface morphology of the specimen was observed using scanning electron microscopy and three-dimensional photos. The composition of the oxide film was characterized by X-ray photoelectron spectroscopy (XPS).FindingsUnder the condition of 6 MPa simulated natural gas (15% H2), the content of S-containing compounds (FeS and FeSO4) in the corrosion products on the surface of the specimen decreases from 60.8% to 54.4%. This finding indicates that hydrogen permeation inhibits the metabolic processes of SRB in this environment. By comparing the hydrogen-uncharged specimen, it was found that under the condition of 6 MPa simulated natural gas (15% H2) hydrogen charging, the uniform corrosion on the X80 surface was weakened, and the protection of the oxide film on the specimen surface in this environment was better than that without hydrogen charging.Originality/valueTo the best of the authors’ knowledge, most of these existing studies have focused on the effect of hydrogen on the mechanical properties of materials and very little is known about corrosion behavior in the hydrogen environment. In this study, a self-designed small gas phase hydrogen charging device was used to study the X80 surface corrosion behavior in the environment of the H2-doped natural gas pipeline.

Inhibition Effect of Pseudomonas stutzeri on the Corrosion of X70 Pipeline Steel Caused by Sulfate-Reducing Bacteria.

Microbiologically influenced corrosion (MIC) is a common phenomenon in water treatment, shipping, construction, marine and other industries. Sulfate-reducing bacteria (SRB) often lead to MIC. In this paper, a strain of Pseudomonas stutzeri (P. stutzeri) with the ability to inhibit SRB corrosion is isolated from the soil through enrichment culture. P. stutzeri is a short, rod-shaped, white and transparent colony with denitrification ability. Our 16SrDNA sequencing results verify the properties of P. stutzeri strains. The growth conditions of P. stutzeri bacteria and SRB are similar, and the optimal culture conditions are about 30 °C, pH 7, and the stable stage is reached in about seven days. The bacteria can coexist in the same growth environment. Using the weight loss method, electrochemical experiments and composition analysis techniques we found that P. stutzeri can inhibit the corrosion of X70 steel by SRB at 20~40 °C, pH 6~8. Furthermore, long-term tests at 3, 6 and 9 months reveal that P. stutzeri can effectively inhibit the corrosion of X70 steel caused by SRB.

Impact of the correlation between random variables on the reliability assessment of the corroded pipelines

In the present work, an Algerian pipeline made of API X70 steel, used for transporting gas and subjected to corrosion attack for three decades, was investigated. Using an intelligent inspection tool, the sizes and orientations of the defects were determined to analyze and improve the accuracy of reliability and/or probability of failure estimates for the damaged pipelines. A probabilistic methodology has been developed to assess the reliability index and the sensitivity of each random variable, within the limit state function, of a gas-transporting steel pipeline that has been corroded for three decades. The reliability analysis utilizes the Second Order Reliability Method, which is based on the BFGS algorithm. In addition, the corrosion defect depth, pipe wall thickness, and corrosion defect length are the most dominant variables within the limit state function, followed by ultimate stress and operating pressure, respectively. Meanwhile, for a failure scenario, thus, it is essential to include a potential parameter such as the correlation coefficient between random variables within the objective function during reliability assessment. For instance, not taking into account the correlation between random variables can lead to an overestimation of the reliability index by 8.89% for a defect depth to wall thickness ratio d/t of 20%. This overestimation increases to 19.16% when the d/t ratio increases to 70%. If the correlation coefficient is significant, it can cause an increase of 8.86% in the error of reliability index assessment for a defect with a depth to wall thickness ratio of 20%, and an increase of 14.58% for a defect with a ratio of 50%. Besides, these avoid the conservative practice resulting from the negligence of the existing correlation between random variables within the limit state function. Hence, considering the correlation coefficients during reliability assessment contributes to setting optimal maintenance schedules for pipelines made of steel under localized corrosion attack.

Piezomagnetic Behavior Corresponding to the Variations of the Toughness of X70 Steel Under Cyclic Loadings

The goal of this study is to investigate magnetic field characteristics corresponding to variations of the toughness of X70 pipeline steel under cyclic loading. After a series of stress-controlled cyclic loadings, the specimens were subjected to static tensile tests. Changes in the magnetic field were recorded simultaneously during the test. The results suggest that cyclic loadings will reduce the toughness of the material. The initial value and slope of the magnetic field-strain curve obtained in the static tensile test are related to the number of cyclic loadings. The evolutions of magnetic field and the stress-strain curve can reflect variations in the toughness of materials. Compared with the stress-strain curve, the magnetic field demonstrates the fatigue degradation process more markedly. The high sensitivity of the magnetic field to toughness may be used to estimate the degree of fatigue damage of steel.

An analysis of electrochemical corrosion on pipeline steel in silty soil under salt-temperature coupling environments

The initial corrosion evolution process of X80 steel exposed to silty soil mixed with NaCl at increasing salinities and temperatures was investigated. Based on the electrochemical testing and microscopic observations, the analysis results indicate dissolution rate is limited by cathodic processes in moist soil. The migration and accumulation of Cl− ions on the oxide film surface are driven by soil water potential after soil freezing, resulting in the decomposition of the film. The release of Fe2+ accelerates the passivation rate. The growth of salt and ice water crystals on the steel-soil interface expands the void between the soil particles, thereby further increasing the diameter of the corrosion pit.

Temperature Effect on the Corrosion Inhibition of Carbon Steel by Polymeric Ionic Liquids in Acid Medium

In the present research work, the temperature effect on the corrosion inhibition process of API 5L X60 steel in 1 M H2SO4 by employing three vinylimidazolium poly(ionic liquid)s (PILs) was studied by means of electrochemical techniques, surface analysis and computational simulation. The results revealed that the maximal inhibition efficiency (75%) was achieved by Poly[VIMC4][Im] at 308 K and 175 ppm. The PILs showed Ecorr displacements with respect to the blank from -14 mV to -31 mV, which revealed the behavior of mixed-type corrosion inhibitors (CIs). The steel micrographs, in the presence and absence of PILs, showed less surface damage in the presence of PILs, thus confirming their inhibiting effect. The computational studies of the molecular orbitals and molecular electrostatic potential of the monomers suggested that the formation of a protecting film could be mainly due to the nitrogen and oxygen heteroatoms present in each structure.

Mechanical Response of a Buried Pipeline to Permafrost Thawing Based on Sequential Coupling Method

Thawing permafrost has affected the structural integrity of buried warm pipelines in cold regions and poses an ongoing threat in the context of climate change. Therefore, characterizing variation in the engineering properties of pipeline foundation permafrost and its effect on the mechanical behavior of pipeline is important. In this paper, the ground temperature distributions around a buried warm pipeline and mechanical response of the pipeline to differential thaw settlement of foundation permafrost are investigated using thermal–mechanical sequential coupling simulation, based on the observational data collected from a selected monitoring site along the China-Russia crude oil pipelines in northeastern China. The results indicate that the thaw-induced settlement of pipeline foundation permafrost develops quickly with the formation and expansion of the thaw bulb in the first 10 years, and then increases slowly when the thaw bulb extends to the weathered granite. Differential thaw settlement will cause a significant change in the deformation and stress of the pipeline near the interface of strong and weak thaw settlement zones. When the length ratio of strong and weak thaw settlement zones is 1, the maximum stress of the pipeline with a thickness of 16 mm is approximately 45% of the allowable stress of X65 steel, and the pipeline remains safe for 30 years. However, the potential failure of the pipeline should be considered due to the continued ground thawing and warming and pipe material aging. Forthcoming research on this topic is needed to evaluate more carefully the structural integrity of buried pipelines in cold regions.

Stress-based hydrogen damage model of X80 pipeline steel and its damage risk assessment under cathodic interference

In this paper, the crack propagation behaviors of X80 pipeline steel under different cathodic current conditions were investigated by constant displacement loading experiment of double cantilever beam (DCB) samples, and the subsurface hydrogen concentration rules were obtained by hydrogen permeation test. A hydrogen damage model based on the threshold stress intensity factor of hydrogen-induced cracking arrest was established for X80 pipeline steel. The hydrogen permeation data showed that in 0.5 mol/L H2SO4 + 0.2 g/L CH4N2S solution, the relationship between subsurface hydrogen concentration C0 and applied current density i satisfied the expression of C0/L∝ i when the current density was 1–10 mA/cm2. The relationship between the threshold stress intensity factor of hydrogen-induced cracking arrest KHSC and the subsurface hydrogen concentration C0 satisfied the expression of KHSC ∝ -lnC0. An analytical model of KHSC = -0.4648lnC0-1.5040 was proposed for the API X80 steel pipe used in the experimental. The KHSC value under cathodic interference was calculated according to the C0 value in the soil simulation solution, and the risk of crack growth was analyzed under service conditions.

A synthesized pyrimidine derivative with highly efficient long-term corrosion protection for API X60 steel in CO2-saturated NACE brine ID196 under hydrodynamic condition

This research investigates the CO2 corrosion inhibition characteristics of a synthesized pyrimidine derivative whose molecular structure is embellished with nitrogen-based functional groups with the intention of achieving highly effective and stable film formation, at low doses, after prolonged corrosion period under turbulent hydrodynamics. For this purpose, 5-(4-(dimethylamino)phenyl)-2,7-dithioxo-2,3,5,6,7,8-hexahydropyrimido[4,5-d]pyrimidin-4(1H)-one (DPP) was synthesized using the one-pot method, and investigated as inhibitor against the corrosion of API X60 steel after instantaneous and prolonged (72 h) immersion in CO2-saturated NACE ID196 brine under 1000 rpm rotation speed. Results from potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) measurements show that DPP is a mixed-type inhibitor which lowers the double layer capacitance and rate of charge transfer across the steel-solution interface with 97% efficiency. Its instantaneous adsorption blocks the steel surface from any noticeable microstructural damage, based on scanning electron microscopy (SEM) characterization. After prolonged exposure (72 h), the uninhibited steel experiences enhanced resistance, which inversely depreciated the DPP efficiency to > 73%. With DPP, however, the steel is significantly protected against surface microstructural degradation, based on SEM assessment. Computational modeling with density functional theory (DFT) and molecular dynamics simulation (MDS) provided molecular-level confirmation of the experimental results.

Corrosion Inhibition Behavior and Adsorption Mechanism of Ethyl Acetate Extract from Scorzonera Undulata for Carbon Steel in 1 M HCl Solution.

For carbon steel X70 in a 1 M hydrochloric acid solution, Scorzonera undulata acetate extract (SUAc) was investigated as an ecological corrosion inhibitor. The anti-corrosion effect of Scorzonera undulata extract is studied using potentiodynamic polarization analysis and electrochemical impedance spectroscopy (EIS). The polarization curves clearly show that the extract is an excellent mixed inhibitor. Our findings show that the maximum inhibition efficiency of 83% has been found with inhibitor concentration up to 400 mg/L at 298 Kelvin. The Langmuir isotherm is followed by the inhibitor's adsorption on the steel surface and physical adsorption was discovered to be the mechanism. To understand the inhibitory mechanism, thermodynamic parameters (∆G°ads) and activation parameters (Ea, ∆Ha, and ∆Sa) were determined. Scanning electron microscopy (SEM) and X-ray photoelectron spectrometry studies of the surface chemistry and morphology are included to this investigation. The results obtained from chemical and electrochemical measurements, confirm that a protective film is formed on the carbon steel surface.

Chasew (Anacardium Occidentale) Leaves Extract as Green Corrosion Inhibitor of API 5L X52 in Acidic Media

Chasew leaves extract has been investigated as green corrosion inhibitor to inhibit the corrosion process of API 5L X52 in acidic media. The inhibition effect of cashew leaves was analyzed using electrochemical measurement such as Tafel Polarization and Electrochemical Impedance Spectroscopy (EIS). FTIR, polyphenol content and phytochemical analysis were also employed to ensure the chemical compound of cashew leaves extract. Concentration of cashew leaves extract was varied for electrochemical measurement i.e. 0, 100, 200, 300, 400 and 500 ppm. Furthermore, immersion time variation (0, 30 and 60 min) was used prior to electrochemical measurement. The electrochemical measurement results indicate that cashew leaves extract work effectively as green corrosion inhibitor of API 5L X52 in acidic media. The performance of this green corrosion inhibitor was optimum at concentration of 500 ppm and 60 min of immersion time. Cashew leaves extract was mixed-type inhibitor because the corrosion potential value shifted less than 85 mV. The Increasing of surface resistance value and the decreasing in the capacitance of double layer due to the adsorption process of cashew leaves extract molecules on the API 5L X52 steel surface. HIGHLIGHTS Cashew (Anacardium Occidentale) leaves extract as green corrosion inhibitor is a novelty of this research Cashew leaves extract delivers up to 96 % inhibition efficiency with 500 ppm of concentration and 60 min of immersion time ElS has confirmed that cashew leaves extract inhibits the corrosion process of API 5L X52 in acidic media by boosting the impedance Cashew leaves extract contains active corrosion inhibiting agents such as polyphenol, tannin, flavonoid and alkaloid The adsorption mechanism of cashew leaves extract obeys the Langmuir isotherm GRAPHICAL ABSTRACT

Effect of Alcaligenes sp. on corrosion behavior of X65 steel in simulated offshore oilfield-produced water.

In this paper, the effect of Alcaligenes sp. on the corrosion process of X65 steel was investigated by using non-targeted metabolomics techniques for comprehensive characterization of metabolites, combined with surface analysis techniques and electrochemical testing. The results showed that the organic acids produced by Alcaligenes sp. accelerated the corrosion process of X65 steel in the early stage, and the presence of Alcaligenes sp. promoted the deposition of stable corrosion products and minerals in the middle and late stages. In addition, proteoglycans and corrosion inhibiting substances were enriched on the metal surface, which enhanced the stability of the film. The combined effect of multiple factors makes the mixed film of biofilm and corrosion products more dense and complete, which effectively inhibits the corrosion of X65 steel.

Comparison between a predicted and an experimentally measured residual stress field generated by side-punching of API X65 steel

A residual stress field was generated by a circular, flat-ended, rigid punch indenting a thick test specimen extracted from X65 grade-controlled-rolled pipeline steel. Laboratory X-ray diffraction was used to measure residual stress field the near-surface, whereas the contour method and neutron diffraction were used to quantify the through-thickness residual stress field. A numerical method was proposed to account for gauge volume variation which allowed a direct comparison of the Finite Element prediction with the experimental measurements. A good agreement between the measurements and prediction was observed, showing that the through-thickness compressive residual stress reaches the highest magnitude in the centre of the specimen. The validated results can be used with confidence for residual stress-crack interaction studies in single-edge notched bend SEN(B) and single-edge notched tension SEN(T) fracture specimens which are common in the oil and gas industry due to the inherited close level of constraint experienced in a pipe.

Alloy design for microstructural-tailored boron-modified ferritic stainless steel to ensure corrosion and wear resistance

Ferritic stainless steels armored with borides had their endurance tested in demanding both abrasive and corrosive environment. The degradation was investigated through a very aggressive plate-on-cylinder wear test in water-based drilling mud containing chlorides, which was designed to simulate, in laboratorial scale, the corrosive tribosystem found in the wear of risers and casings used in deep water oil exploitation. A commercially-grade 430 ferritic stainless steel containing boron content far beyond its solubility limity, namely 1.2 and 3.5 wt.%, was processed by spray-forming to induce a ferritic stainless steel matrix protected by a boride skeleton. Additional corrosion assessment was performed by potentiodynamic polarization and electrochemical impedance spectroscopy in 0.27 M KCl solution, since KCl is a common clay swelling inhibitor. For comparison, API 5L X80 steel was also included since this material is used in risers and casings manufacture. The addition of boron (1.2 and 3.5 wt.%) led to the formation of microstructures composed of an α-ferrite matrix with homogeneously distributed M2B-type borides of different morphologies. Electrochemical tests revealed high corrosion resistance of the alloy with 1.2 wt.% B. However, the alloy with 3.5 wt.% B showed a considerable decrease in corrosion resistance due to Cr-depletion of the ferritic matrix given the M2B formation richer in Cr. Therefore, the alloy with 1.2 wt.% B offered the best tribocorrosion resistance.

The mechanism of inhibitive effect on hydrogen permeation of X70 steel by lanthanum microalloying: Enhanced kinetics of desorption

In this work, electrochemical hydrogen permeation tests were carried out to obtain the steady-state hydrogen permeation current of X70 pipeline steel in acid environment and alkaline electrolyte with applied cathodic overpotentials simulating the service conditions of pipelines. It is shown that La-microalloying can efficiently reduce the steady-state hydrogen permeation current density while maintaining the same mechanical performance. The experimental permeation data were fitted with Iyer-Pickering-Zamanzadeh (IPZ) and surface effect model to analyze the inhibitive mechanism on hydrogen permeation, and the results depicted that La element on the material surface greatly facilitates the desorption process of hydrogen atoms. In addition, the calculated hydrogen diffusion coefficient was found smaller after La microalloyed, which can be ascribed to the larger hydrogen trap density. It is suggested that La-microalloying can mitigate hydrogen damage of X70 pipeline steel in both acidic environment or under cathodic protection.

Residual strength prediction of X80 steel pipelines containing group corrosion defects

As subsea oil and gas pipelines are corroded by moisture, soil, and other external factors, their surfaces develop groups of corrosion defects, which are prone to stress concentration and affect the residual strength of the pipeline. To this end, a finite element (FE) model of an X80 pipeline containing group corrosion defects is established here using ABAQUS. Considering the influence of various defect sizes on the residual strength of the pipe, 46 sets of failure data for group corrosion pipes with different geometries and 364 sets of maximum von Mises stresses versus internal pressure for different operating conditions were obtained. The accuracy of the FE model was verified using burst tests. The residual strength prediction model of the pipes was obtained by 1stopt software. The results show that the key factor affecting the residual strength of pipes containing group corrosion defects is the depth of the deepest defect and the strength of the interaction between the group corrosion defects. Based on the DNVRP-F101 standard, a more accurate method for calculating the failure pressure of group corrosion pipes was obtained by introducing correction factors. The results of this study can provide theoretical support for the safe management of group corrosion X80 pipelines.

Corrosion inhibition of Q235 and X65 steels in CO2-saturated solution by 2-phenyl imidazoline

This study examined 2-phenyl imidazoline (2-PI) as an eco-friendly corrosion inhibitor for Q235 and X65 steels with various microstructures in CO2-saturated solution. The inhibition performances of the 2-PI inhibitor for both steels were comparatively studied through electrochemical tests, weight-loss method, wire beam electrode (WBE) technique as well as surface analysis. The results demonstrate that the 2-PI compound acts as a mixed-type inhibitor and exhibits effective and durable inhibition performance against general and localized corrosion. The adsorption of 2-PI molecules on steel surfaces is exothermic, spontaneous and follows the Langmuir isotherm model. Furthermore, the steel microstructure strongly influences the adsorption behavior of 2-PI inhibitor, the Q235 steel with a higher pearlite/ferrite ratio promotes the physical adsorption of the protonated 2-PI molecules at lower concentrations, and the X65 steel with a lower pearlite/ferrite ratio enhances the chemical adsorption of the unprotonated 2-PI molecules at higher concentrations. Additionally, the adsorption mechanism was also discussed based on the evaluated thermodynamic data and the results of X-ray photoelectron spectroscopy (XPS) analysis.

Corrosion behavior and mechanism of X80 pipeline steel welded joints under high shear flow fields

The internal-pipeline local corrosion in the welded joint region has been a widely concerning issue, particularly under the synergistic effect of high shear stress and electrochemical corrosion, which can easily result in pipeline rupture. Classical electrochemical testing techniques and wire beam microelectrode (WBE) are used to investigate the local corrosion behavior of X80 steel welded joints in a CO2-saturated NACE solution at different flow rates (velocities of 3 m/s, 5 m/s and 7 m/s), and the corrosion product composition and characteristics are analyzed via scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), X-ray diffraction (XRD), and three-dimensional (3D) measuring laser microscopy. The results show that different welded joint zones exhibit different corrosion degrees. The heat-affected zone (HAZ) shows the worst corrosion resistance, whereas the base metal (BM) and weld metal (WM) show similar corrosion resistances. The HAZ is an anode that corrodes unsatisfactorily at high flow rates, and the enhanced wall shear stresses peel off part of the dense corrosion product film, promoting the development of local corrosion. Therefore, the HAZ zone is a weak link in the X80 steel welded joints. This study provides scientific guidelines for the corrosion protection of long-distance oil & gas pipelines.

Measurements by SKPFM and Finite‐Element Modeling of Hydrogen Atom Diffusion and Distribution in Ferrite and Bainite Contained in X80 Steel

Herein, the diffusion and distribution of hydrogen (H) atoms in ferrite and bainite contained in an X80 pipeline steel is studied by both scanning Kelvin probe force microscopy and finite‐element modeling. The effect of metallurgical microphases on H‐atom accumulation in the steel is analyzed. The results show that H‐charging elevates the electrochemical dissolution activity of both ferrite and bainite contained in the steel, as indicated by the increased Volta potential and thus the decreased work function. The H atoms tend to accumulate at ferrite, making the local H‐atom concentration much greater than the concentration at bainite. The results imply that, compared with bainite, ferrite is the location to accumulate more H atoms initiating hydrogen‐induced cracks once the local H‐atom concentration reaches a threshold value.