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Metal casings shield the cathodic protection current and detection signals of buried metal pipelines, making the corrosion protection and detection technology of pipelines at the casing one of the challenges for safe operation and integrity evaluation of pipelines. This paper uses the primary current distribution physics interface in the COMSOL Multiphysic simulation software to study the effects of the coating quality of the casing and pipeline, the installation of sacrificial anodes in the casing, the conductivity of the electrolyte, and defects in the pipeline coating in the casing on the pipeline potential. The influence of distribution. The results show that: The coating quality of the outer surface of the casing and the pipe inside the casing has a great influence on the cathodic protection potential of the pipeline. The better the coating quality, the more negative the cathodic protection potential is, and the less cathodic protection current required by the pipeline, so the power consumption of the forced current law is reduced, and the service life of the sacrificial anode is longer. Installing sacrificial anodes in the casing has a positive effect on the cathodic protection of this special pipe section. The conductivity of the electrolyte in the casing has a certain impact on the cathodic protection potential of the pipeline. When the conductivity of the internal electrolyte is greater, the protective potential of the pipeline becomes more negative. However, impurities such as soil, groundwater, and silt make the pipeline more susceptible to corrosion, so keeping the annular space relatively dry is an important prerequisite for anti-corrosion. When there is a coating defect on the inner and outer pipes of the casing, the potential at the damaged point will have a potential peak. The larger the potential peak difference, the more serious the coating defect is.

The paper presents a method of the simulation of the pipeline potential shift produced by D.C. traction stray currents which are stochastic in character. The calculation model presented is based on the deterministic model used in the earth-return circuit theory combined with the non-deterministic approach based on the Monte Carlo procedure. The model of the equivalent rail with current energization and the concept of superposition allow one to consider more complicated D.C. railway systems using a segmental approximation of the complex railway route and taking into account a number of substations and loads at any location. A locomotive position and a load current are assumed to be independent random variables in the non-deterministic approach. Using simulation program developed random characteristics of a pipeline response e.g. maximum, minimum, median and mean values can be obtained. Hence the pipeline regions more exposed to corrosion risk can be determined.

This research aims to study the microstructure characteristics, mechanical properties, and corrosion behaviors of the dissimilar autogenous laser beam welded joint of pipeline steel (X-70) and super duplex stainless steel (sDSS 2507). Pipelines for the transmission of oil and gas and risers for offshore oil and gas drilling require this dissimilar joint. A dissimilar joint must maintain its properties and be defect-free under such challenging operating conditions. The microstructure of the interface, weld zone and heat-affected zone (HAZ) were all investigated thoroughly using optical microscopy (OM) and scanning electron microscopy (SEM) equipped with energy-dispersive spectroscopy (EDS). This dissimilar joint had significant microstructure anomalies in the weld and interfaces. Microstructure inhomogeneity’s effect on welded joint mechanical properties, including microhardness, tensile and impact strength, was also studied. The linear potentiodynamic polarisation test in neutral 3.5 wt.% NaCl solution was used to study this weldment’s corrosion behavior. The corroded surfaces were examined using an OM and SEM for the surface morphology investigation of corroded specimens. The macro-optical investigation has revealed full penetrations in the weld without any inclusions or porosities. The interface between the sDSS 2507 weld zone and the X-70 coarse grain heat-affected zone (CGHAZ) indicated a peak hardness of 418 Hv 0.5 . With an average of 345 Hv 0.5 , the WZ’s hardness variation was reported to be in the 298–420 Hv 0.5 range. The hardness of the X-70/sDSS 2507 weld interface was assessed to be greater than that of the other region of weldments. An untempered martensitic region in WM and the CGHAZ of X-70, and the presence of M-A components are credited with the increase in hardness. The welded joint achieved reasonably excellent strength and ductility and met the marine and offshore standards requirements. The base metals and weldment for X-70 and sDSS 2507 have respective ultimate tensile strengths (UTS) of 610 ± 6 MPa, 995 ± 8 MPa, and 675 ± 10 MPa. The tensile findings revealed that the fracture location for weldment was evident in the X-70 base metal, ensuring that the weld metal was of adequate strength for the laser-weld joints. It was observed that the weldment’s WM had the lowest impact strength. The Charpy impact toughness of the weld metal, however, was higher than both the ASME standard (> 41 J) and the EN 1599:1997 standards (> 47 J). The sDSS 2507 BM (310 ± 4 J) clearly outperforms the weld zones (185 ± 3 J) and X-70 base metal (295 ± 2 J) in terms of impact strength. The electrochemical corrosion test shows the corrosion potential, and the weld zone's corrosion rate is between sDSS 25,070 (− 260 ± 1.3 mV, 0187 ± 0.002 mm/year) and X-70 base metal (− 454 ± 1.8 mV, 0.321 ± 0.017 mm/year). Additionally, the surface morphologies and the electrochemical measurements matched significantly.

A leaf spring caliper is a device used to detect the geometry and defects of the inner wall of oil and gas pipelines. The detection principle involves installing strain gauges on the detecting arm, which can be bent elastically. The strain gauge signal is connected to the voltage-detecting equipment to detect the inner wall of the pipeline through the voltage signal. This equipment has the advantages of high detection accuracy and small structure size. However, the detection arm of the leaf spring caliper works via contact detection, and the detection arm will be worn out when working, thus reducing the detection accuracy. This paper establishes a wear model of the leaf spring caliper and constructs a wear test system based on the model. The wear test system simulates wear between the detection arm material 51CrV4 (ISO 683-2-2016) and the oil pipeline material L555Q (ISO 3183:2012). By changing the coating material of the detection arm, such as nickel-phosphorus coating, epoxy acrylic resin coating, or polytetrafluoroethylene (PTFE) coating, the wear pattern of the detection arm is explored and the experimental results are analyzed and summarized to select the most suitable coating material. A polynomial fit to the test data, followed by a Reye–Archard wear model fit, was performed to finally derive the wear function for leaf springs with different coating materials. A prediction algorithm was used to predict the wear pattern of the detector arm, and the extended wear length was calibrated. The results show that the average error between the predicted data and the actual observed data is in accordance with the experimental expectations. Therefore, the wear prediction model and its corresponding wear function can be applied to wear error correction to improve the detection accuracy of leaf spring calipers.

Unanticipated sabotage of two underwater pipelines in the Baltic Sea (Nord Stream 1 and 2) happened on 26 September 2022. Massive quantities of natural gas, primarily methane, were released into the atmosphere, which lasted for about one week. As a more powerful greenhouse gas than CO 2 , the potential climatic impact of methane is a global concern. Using multiple methods and datasets, a recent study reported a relatively accurate magnitude of the leaked methane at 0.22 ± 0.03 million tons (Mt), which was lower than the initial estimate in the immediate aftermath of the event. Under an energy conservation framework used in IPCC AR6, we derived a negligible increase in global surface air temperature of 1.8 × 10 −5 °C in a 20-year time horizon caused by the methane leaks with an upper limit of 0.25 Mt. Although the resultant warming from this methane leak incident was minor, future carbon release from additional Earth system feedbacks, such as thawing permafrost, and its impact on the methane mitigation pathways of the Paris Agreement, warrants investigation.

In the present study, the implementation of a comprehensive mechanistic predictive model for corrosion of mild steel in the oil and gas transmission pipelines is described. The present model simultaneously accounts for all major corrosion scenarios, including CO2 corrosion, H2S corrosion, and corrosion in the presence of organic acid and also incorporates the effect of corrosion product layer formation, including iron carbonate and iron sulfide. With this approach, the present model mechanistically reflects the mainstream understanding of corrosion in such environments and can be readily used to predict the corrosion rates in industrial applications. The model was implemented by using a generalized mathematical and programming approach that has built-in flexibility to add new chemical species and additional reactions in the future. The model was designed to make it easy to extend and cover an even broader range of conditions than it currently does, such as higher temperatures and pressures, nonideal solutions, etc. The mechanistic nature of the model allows it to be readily coupled with other applications such as computational fluid dynamics codes, multiphase flow simulators, process design simulators, etc. In order to demonstrate the capabilities of this model, the calculated corrosion rates were compared with the experimental corrosion rate data across a broad range of environmental conditions and brine chemical compositions.

A predictive model for pitting corrosion in buried pipelines is proposed. The model takes into consideration the chemical and physical properties of the soil and pipe to predict the time dependence of pitting depth and rate. Maximum pit depths were collected together with soil and pipe data at more than 250 excavation sites over a three-year period. The time dependence of the maximum pit depth was modeled as dmax = κ(t − t0)ν, where t is the exposure time, t0 is the pit initiation time, and κ and ν are the pitting proportionality and exponent parameters, respectively. A multivariate regression analysis was conducted with dmax as the dependent variable and the pipeline age, and the soil and pipe properties as the independent variables. The dependence of κ and ν on the predictor variables was found for the three soil textural classes identified in this study: clay, clay loam, and sandy clay loam. The proportionality parameter κ was found to be primarily influenced by the redox potential, pH value, soil resistivity, and the dissolved ion concentrations. In contrast, the pitting exponent ν was found to be influenced mainly by the pipe-to-soil potential, water content, bulk density, and the pipe coating type. A real-life pipeline integrity assessment is used as a case study to illustrate the application of the proposed model and to show how it can have a positive impact on integrity management programs.

This study conducts a computational fluid dynamics (CFD)-based assessment of internal corrosion risk in wet sour gas pipeline systems, focusing on developing a predictive framework for pipeline integrity. Using the L415 X60 steel pipeline as a reference, the analysis revealed an extreme Corrosion rate of 68,595.942 mm/year, leading to total wall failure in under 12 min. The model was validated through a case study of the Kashagan 28-inch offshore pipeline, known for early failures due to internal corrosion and sulfide stress cracking. Mitigation strategies were evaluated, including corrosion-resistant alloys (CRAs), coatings, liners, inhibitors, H₂S scavengers, and dehydration. A 3 mm CRA cladding, particularly Inconel 625, reduced the corrosion rate from 63711 to 0.055 mm/year due to its Nickel-Molybdenum composition and barrier properties. Hastelloy C-276 showed the lowest corrosion rates. Polymeric liners (Polyethylene of Raised Temperature Resistance, Polyamide12), epoxy coatings, and imidazole-based inhibitors further suppressed corrosion, while complete dehydration eliminated it. These results support CFD-driven models for optimizing corrosion control in sour gas pipelines.

Mixed steel/polyethylene gas distribution pipelines are increasingly used in congested urban environments where conventional layouts are restricted by existing underground utilities, safety constraints, and site-specific construction conditions. In such systems, buried steel transition sections may become particularly vulnerable to electrical perturbation and corrosion, especially when installed near electrified transport infrastructure. This paper presents a field case study on a recently installed mixed steel/polyethylene gas distribution pipeline located on Lunca Street, Petroșani, Romania, approximately parallel to an electrified railway. Electrical and electrochemical investigations were carried out eight months after installation and included 24 h monitoring of pipe-to-soil potential versus Cu/CuSO4, 24 h monitoring of alternating current pipe-to-soil voltage, mixed alternating current and direct current signal visualization, and coating insulation resistance measurements. The results showed that alternating current pipe-to-soil voltage was present at all monitored points, with weighted mean values ranging from 0.41 to 1.23 Vrms, while pipe-to-soil potential values ranged from −0.120 to −0.238 V versus Cu/CuSO4. Although the measured average coating insulation resistance remained relatively high, the combined electrical and electrochemical data indicate that alternating current interference associated with the nearby electrified railway is the most plausible dominant contributing source of the recorded electrical perturbation. Within the analyzed site perimeter, no other nearby electrical infrastructures with comparable interference potential were identified. The highest alternating-current exposure and the least favorable electrochemical values were recorded on the longer metallic segment, showing that metallic length and local configuration strongly influenced the severity of the effect. A mitigation strategy based on polarized electrical decoupling and dedicated grounding is proposed as a practical means of improving electrical safety and reducing corrosion risk in the exposed and buried steel sections.

Corrosion is an important cause of oil and gas pipeline failure, and with the continuous development of social economy and the rising demand for energy, the problem of corrosion of oil and gas transportation pipelines is becoming more and more obvious. The finite element model of axial section of X65 pipeline steel is established by electrochemical parameters obtained from experiments in near-neutral soil simulation solution, and the corrosion defects produced by the effect of uneven microstructure distribution are analyzed. Based on this, the behavior and failure time of X65 pipeline steel corrosion under pressure and electrochemical coupling are further investigated. The results show that there is a significant effect on the corrosion of X65 pipeline steel between different defects. In addition, the corrosion at the defects of X65 pipeline steel under double defects will be weakened compared with single defects, and the corrosion at the defects of X65 pipeline steel under triple defects is the most serious. This study mainly analyzes the effect of single and multiple defects on the corrosion behavior of X65 pipeline steel, which provides a reference for the corrosion protection and pipeline safety of X65 pipeline steel under near-neutral soil.