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This study investigates the evolution process of hot corrosion in bi-phase Ti-6.5Al-1.5Zr-3.5Mo-0.3Si (TC11) titanium alloy induced by sodium chloride (NaCl). Through morphological progression and elemental distribution analyses, the integrated processes involved in the onset of internal corrosion during hot corrosion are elucidated, revealing intriguing phenomena that deviate from conventional mechanisms. The development of corrosion can be divided into three stages: First there is the rapid growth of the external corrosion layer induced by Cl; then a Cl and O induced internal corrosion is initiated when the external corrosion layer reaches a critical thickness, at the same time the external corrosion decreases; finally, the chlorine pressure is too low to act as the corrosion depth increases, O becomes a major contributor to deep internal corrosion, leading to O induced internal corrosion. Significant interphase selective corrosion was observed in this internal corrosion zone: the β phase was corroded while the α phase remained uncorroded, challenging the prevailing notion that the β phase is more corrosion-resistant in titanium alloys. This distinctive phenomenon results from the differences in oxygen solubility, element diffusion rates and the reactivity between the α and β phases.

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[Objective] Surface gas transmission pipelines suffer serious internal corrosion. To ensure the service safety of pipelines, it is necessary to accurately predict their internal corrosion rate. [Methods] The main control factors that affect corrosion were screened based on the Rough Set(RS) theory, and the reconstructed data set was used as the input while the corrosion rate was used as the output to train the Kernel Based Extreme Learning Machine(KELM) model. Additionally, the Improved Seagull Optimization Algorithm(ISOA) was used to optimize the model hyperparameters, and a prediction method of internal corrosion rate based on the RS-ISOA-KELM model was proposed. The prediction precision was compared with that of other combination models, and the long-term prediction effect and model universality were analyzed. [Results] The convergence analysis for the ISOA algorithm was conducted on five benchmark functions including Sphere, Schaffer, Rosenbrock, Rastrigin, and Griewank, and it was found that the ISOA algorithm had better performance in terms of solution precision and calculation stability. The model was verified using actual operating data from a gas field block. For the selected data set, the temperature, CO2 partial pressure, H2S partial pressure, flow rate, Cl-content, moisture content, and corrosion inhibitor residual concentration were crucial factors that affect internal corrosion. Among them, H2S partial pressure, flow rate, and corrosion inhibitor residual concentration had the largest weight. The RS-ISOA-KELM model was used to predict the corrosion rate, and its average relative error was 1.498%, root mean square error was 0.002 1 mm/a, and coefficient of determination was 0.999 3, which were all better than other common comparison models. [Conclusion] The combined model has strong generalization performance and high prediction precision. By expanding and updating the original database,it can predict the medium-and long-term corrosion rate of pipelines.With different corrosion parameters,data sizes,and training test ratios,the model still maintains a good prediction effect.

Corrosion monitoring plays a determining role in corrosion management in industries, particularly oil and gas systems. Corrosion's effective monitoring could be achieved through the properly selected monitoring methods, using suitable reassessment intervals as well as application of generated data. When carried out properly, corrosion monitoring can also be served as an early warning system before the onset of corrosion-associated failures. This paper provides a literature review of pipelines' internal corrosion using electrochemical technique. Several electrochemical techniques namely electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR), galvanic sensors, electrochemical noise (ECN), harmonic distortion analysis (HDA) and wire beam electrode (WBE) have been discussed in this review; as well as examples of exploiting these techniques have been presented. The main focus of this paper is reviewing field applications of mentioned techniques rather than laboratory experiments. The same trends can be exhibited through the corrosion rates determined by ECN, LPR, and EIS. Studies have implied that ECN can be a very powerful tool for monitoring corrosion rate and corrosion mechanism. LPR has been mainly utilized for water pipelines or those that have at least 30% free water. HDA has been rarely used due to the complexity of interpretation. Developed galvanic sensor system cannot numerically express the corrosion rate, but it can only provide the information about the presence of corrosion. Reliable EIS measurements could not be obtained with regularity in operating oil and gas pipelines but there some field cases of this technique has been discussed. For studying pitting tendency, WBE is a better and more accurate technique than traditional cyclic potentiodynamic polarization method. Application of potentiodynamic testing in the field is primarily limited to inhibitor evaluations. Results revealed that corrosion rate obtained by using WBE technique has good correlation with other techniques. There are numerous references, which would be very helpful in finding the details of each above-described technique. Finally many case studies for the application of electrochemical techniques in oil and gas pipelines have been gathered and tabulated as a guideline for target users which by comparing the capability and inability of each method can select the best tailored techniques for intended se-rvice. [ABSTRACT FROM AUTHOR]

This investigation focuses on the ranking of pipeline leakage susceptibility of two categories of pipeline systems. One consists of three oilfield water-handling pipeline systems and the other consists of five dry crude systems. Online corrosion monitoring (OCM) method was used for both systems, forthermore, in-line inspection (ILI) method, with Magnetic Flux leakage (MFL) tool, was also used for the dry crude systems. The OCM leakage susceptibility potential is derived from the combined severity of general corrosion, pitting corrosion, fluid corrosivity and sessile bacteria population density in the process streams. The ILI leakage susceptibility potential is derived from the average number of corrosion anomalies greater than 10% of the wall thickness and the maximum depth of the anomalies (as percentage of the wall thickness). In spite of such distinctions, the ranking of pipeline leakage susceptibility for the five dry crude pipeline segments turned out to be identical for the two methodologies. [ABSTRACT FROM AUTHOR]

In recent years, pipeline transportation has become an indispensable way of oil and gas transportation in China. However, with the frequent occurrence of pipeline accidents, the corrosion of natural gas gathering and transmission pipeline has become a great threat to the sustainable development of natural gas. Taking shale gas gathering pipeline as an example, a variety of corrosive substances such as CO2, dissolved oxygen, SRB and Cl- were detected in the transported gaseous and liquid substances, resulting in a very harsh corrosive environment, which caused varying degrees of corrosion damage to the gas gathering pipeline, and even led to rapid perforation of multiple gas gathering pipelines, resulting in serious economic losses and threatening the personal safety of staff. The direct evaluation of internal corrosion of shale gas wet gas pipeline can provide favorable guarantee for the safe operation of the pipeline. Therefore, based on the multiphase flow theory and the operating conditions of shale gas wet gas gathering and transmission pipeline in a gas field, the internal corrosion direct evaluation process was carried out according to MP-ICDA. The multiphase flow simulation and calculation were conducted by OLGA software to indirectly evaluate the corrosion in the pipeline. The corrosion sensitive areas in the pipeline were determined to be low-lying areas and uphill sections. The internal corrosion should be directly evaluated after the excavation detection should be conducted at the high-risk position of the pipeline. Excavation detection was conducted in high-risk locations of pipelines to verify the direct evaluation of internal corrosion. The post evaluation of the pipeline should be completed according to the detection results, and the re-evaluation time should be determined.

Testing of the reagent method of water treatment with the use of corrosion control devices was performed at the district boiler house of Kyiv city. Corrosion rate probes were installed on the straight and return pipelines of the heating network, and on the feed line. The anti-scale efficiency of the reagent was determined by measuring the change in the hardness of water before and after the heating equipment. Corrosion monitoring showed that the corrosion rate in the heating network is maintained at 0.1 mm/year. The corrosion rate on the feed line due to reagent water treatment was reduced to 0.03 mm/year in non-deaerated water. The calculation of economic efficiency has shown that the reagent method of water treatment for heating networks is by 13% cheaper than traditional approach and can serve as an alternative to the traditional one, especially regarding energy conservation. [ABSTRACT FROM AUTHOR]

In order to improve the prediction accuracy on internal corrosion rate of multiphase flow pipelines, the combined model of Improved Gravitational Search Algorithm(IGSA) and Random Forest Regression(RFR) was adopted, the number of decision trees and division characteristics of RFR model were optimized by IGSA, the influence of iteration times on prediction accuracy was discussed, the accuracy of model was verified by introducing the statistical indicators, and the characteristic variables affecting the corrosion rate were ranked. The results show that the variables other than pressure have great influence on the internal corrosion rate. The mean-square error of IGSA-RFR combined model in the same test set is 0.000 016 5, which is 2 orders of magnitude smaller than that of other models. Besides, its mean absolute percentage error is 0.524 1, which is 1 order of magnitude smaller than that of other models, and the coefficient of determination R2 is 0.999 6,which is the closest to 1 in all models. Hence, IGSA-RFR model is better than other models in terms of prediction accuracy and suitable for the research on prediction of internal corrosion rate of multiphase flow gathering pipelines.

Abstract Unrefined and highly corrosive upstream petroleum resources and complex operating environments pose a significant threat to the integrity and safety of gathering pipelines. The present study proposed a novelty method to perform a risk assessment for gathering pipelines. The use of historical failure data developed a fishbone diagram model of hazard factors. The risk index system was developed based on the KENT method, including failure likelihood and failure consequence coefficient models. Information entropy theory was used to determine the weight of each indicator. Combined with the area-level safety design coefficient, The welding institute (TWI) method was improved to perform risk classification for different areas. The proposed method was applied to 81 gathering pipelines. Results demonstrated that the proposed method could meet the actual conditions of gathering pipelines, improving upstream energy security.

Copyright of Natural Gas & Oil is the property of Editorial Department of Natural Gas & Oil and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Internal water pipe corrosion is a complicated problem due to the interaction of water quality parameters with pipe wall. This study presents investigations of internal pipe surface corrosion mechanisms related to water physicochemical. Samples of water and corrosion-damaged ductile cast iron (30+ years) and galvanized steel pipe (15-20 years) were collected at in-situ condition from Addis Ababa city water distribution system. Scanning electron microscopy and optical microscopy were used to examine the pipes' corrosion morphology and microstructures, respectively. Additionally, Mountains 9 surface analysis software was used for further pitting corrosion characterization.To identify the causes of internal pipe corrosion, water physicochemical analyses were conducted by using inoLab pH 7310P, DR 900, Palintest Photometer 7100, and Miero 800. Water physicochemical test indicates: CaCO3 is 77 - 215 ppm, pH is 7.05 – 7.86, total dissolved solids (TDS) is 84.10 -262.8 ppm, ClO2 is 0 – 0.5 ppm, and dissolved oxygen (80-81 ppb). From water test results, major causes of internal pipe corrosion damage mechanisms were identified as dissolved oxygen, CaCO3, TDS, ClO2,and resistivity of water which initiates a differential cell that accelerates pipe corrosion. Using Mountain 9 surface analysis software, corrosion morphology and pitting features were characterized. The outputs of this paper will be helpful for water distribution and buried infrastructure owners to investigate corrosion damage mechanisms at early stage. To manage corrosion mechanisms, water supply owners need to conduct frequent inspections, recording of pipe data, testing of water quality, periodic pipelines washing, and apply preventative maintenance.

Medium carbon steel is widely consumed by various industrial sectors due to its attractive set of mechanical properties and low cost, but it experiences deterioration when exposed to a corrosive environment. In the present study, Aloe Vera plant extract was studied as a green corrosion inhibitor for medium carbon steel in an acidic medium. The presence of inhibitive compounds in Aloe Vera plant extract was determined by FTIR. Moreover, the inhibition efficiency was determined through gravimetric analysis and electrochemical analysis. The results show that the Aloe Vera plant extract provided inhibition efficiency of more than 90% in both gravimetric and electrochemical analyses. Furthermore, the shift in polarization curves depicts that this plant extract is a mixed type inhibitor acting as an anodic and cathodic inhibitor. Overall, Aloe Vera plant extract provides excellent corrosion inhibition to medium carbon steel in the H2SO4 environment and can be used as a green corrosion inhibitor for mitigating internal corrosion of pipelines and storage tanks.

The hot corrosion behavior of Ni‐based superalloys induced by NaCl at 600°C, 650°C, and 700°C in a marine‐like environment was investigated. The results show that the corrosion scale on the IN718 alloy includes two distinct layers, of which the outer layer is mainly composed of NiFe2O4 and NiO, while the inner layer contains FeCr2O4 and NiCr2O4. The HCl(g) as a catalyst significantly accelerated the corrosion of the samples. The formation of the Cr‐depletion layer was analyzed. The O2 in the atmosphere can diffuse to the substrate surface through the corrosion product layer, leading to internal corrosion. The hot corrosion behaviors of the corroded samples have been discussed in detail. [ABSTRACT FROM AUTHOR]

Unrefined and highly corrosive upstream petroleum resources and complex operating environments pose a significant threat to the integrity and safety of gathering pipelines. The present study proposed a novelty method to perform a risk assessment for gathering pipelines. The use of historical failure data developed a fishbone diagram model of hazard factors. The risk index system was developed based on the KENT method, including failure likelihood and failure consequence coefficient models. Information entropy theory was used to determine the weight of each indicator. Combined with the area-level safety design coefficient, The welding institute (TWI) method was improved to perform risk classification for different areas. The proposed method was applied to 81 gathering pipelines. Results demonstrated that the proposed method could meet the actual conditions of gathering pipelines, improving upstream energy security. [ABSTRACT FROM AUTHOR]

• An analysis of damage to a grate made of duplex cast steel after one year of operation was presented. • The formation and removal of a two-zone scale on the surface of the grate were observed. • Intergranular corrosion in the grate due to corrosion in molten salts was observed. • The processes of precipitation of Cr 23 C 6 , G and σ phase occurred as a result of long-term heating. • Recommendations regarding the choice of material have been presented. The paper presents findings on the mechanisms and consequences of high-temperature corrosion in a waste incineration plant, particularly focusing on the corrosion of gratings made of duplex cast steel. The structure is crucial for corrosion resistance. Symptoms of this corrosion include scale formation and removal, characterized by a two-zone composition: an outer part containing elements such as magnesium, calcium, aluminium, silicon, and oxygen, and an inner part consisting of chromium oxide and iron oxide. Melting traces caused by corrosion in molten salts are also observed on the surface of the scale, and intergranular corrosion and internal oxidation are observed on the cross-section of the grating. Additionally, precipitation processes occur due to long-term heating, leading to the formation of Cr 23 C 6 , G and σ phases. These findings underscore the challenges posed by high-temperature corrosion in industrial settings and highlight the complex mechanisms involved in the degradation of materials under such conditions. [ABSTRACT FROM AUTHOR]

Internal water pipe corrosion is a complicated problem due to the interaction of water quality parameters with the pipe wall. This study presents investigations of internal pipe surface corrosion mechanisms related to water physicochemical. Samples of water and corrosion-damaged ductile cast iron (30+ years) and galvanized steel pipe (15-20 years) were collected under in-situ condition from Addis Ababa city water distribution system. Scanning electron microscopy and optical microscopy were used to examine the pipes' corrosion morphology and microstructures, respectively. Additionally, Mountains 9 surface analysis software was used for further pitting corrosion characterization. To identify the causes of internal pipe corrosion, water physicochemical analyses were conducted by using inoLab pH 7310P, DR 900, Palintest Photometer 7100, and Miero 800. Water physicochemical test indicates: CaCO3 is 77-215 ppm, pH is 7.05 - 7.86, total dissolved solids (TDS) is 84.10-262.8 ppm, ClO2 is 0-0.5 ppm, and dissolved oxygen (80-81 ppb). From water test results, major causes of internal pipe corrosion damage mechanisms were identified as dissolved oxygen, CaCO3, TDS, ClO2,and resistivity of water which initiates a differential cell that accelerates pipe corrosion. Using Mountain 9 surface analysis software, corrosion morphology and pitting features were characterized. The outputs of this paper will be helpful for water distribution and buried infrastructure owners to investigate corrosion damage mechanisms at an early stage. To manage corrosion mechanisms, water supply owners need to conduct frequent inspections, recording of pipe data, testing of water quality, periodic pipelines washing, and apply preventative maintenance. [ABSTRACT FROM AUTHOR]

Medium carbon steel is widely consumed by various industrial sectors due to its attractive set of mechanical properties and low cost, but it experiences deterioration when exposed to a corrosive environment. In the present study, Aloe Vera plant extract was studied as a green corrosion inhibitor for medium carbon steel in an acidic medium. The presence of inhibitive compounds in Aloe Vera plant extract was determined by FTIR. Moreover, the inhibition efficiency was determined through gravimetric analysis and electrochemical analysis. The results show that the Aloe Vera plant extract provided inhibition efficiency of more than 90% in both gravimetric and electrochemical analyses. Furthermore, the shift in polarization curves depicts that this plant extract is a mixed type inhibitor acting as an anodic and cathodic inhibitor. Overall, Aloe Vera plant extract provides excellent corrosion inhibition to medium carbon steel in the H2SO4 environment and can be used as a green corrosion inhibitor for mitigating internal corrosion of pipelines and storage tanks. [ABSTRACT FROM AUTHOR]

Medium carbon steel is widely consumed by various industrial sectors due to its attractive set of mechanical properties and low cost, but it experiences deterioration when exposed to a corrosive environment. In the present study, Aloe Vera plant extract was studied as a green corrosion inhibitor for medium carbon steel in an acidic medium. The presence of inhibitive compounds in Aloe Vera plant extract was determined by FTIR. Moreover, the inhibition efficiency was determined through gravimetric analysis and electrochemical analysis. The results show that the Aloe Vera plant extract provided inhibition efficiency of more than 90% in both gravimetric and electrochemical analyses. Furthermore, the shift in polarization curves depicts that this plant extract is a mixed type inhibitor acting as an anodic and cathodic inhibitor. Overall, Aloe Vera plant extract provides excellent corrosion inhibition to medium carbon steel in the H2SO4 environment and can be used as a green corrosion inhibitor for mitigating internal corrosion of pipelines and storage tanks. [ABSTRACT FROM AUTHOR]

For the operation mode of the production, gathering and transmission pipelines is diversified in the Changqing Gas Field, and the flow state and corrosion environment vary greatly, there is a large error between the actual detection and the detection using the prediction model specified in the technical standard of internal corrosion direct assessment. Considering the characteristics of the operating conditions of the gathering and transmission pipelines in Changqing Gas Field, a three-dimensional flow pattern distribution map was plotted based on the gas set, water-gas ratio and pipeline inclination with the Fluent and SolidWorks softwares. In addition, a corrosion prediction model suitable for the actual operating condition parameters was established and optimized based on the De WarrD and SwRI models. Through the detection and verification at 31 excavation points along 9 pipelines, it is shown that the prediction coincidence degree of the detection points is up to 86.67%, which basically satisfies the requirement of pipeline corrosion risk discrimination, and the measures to enhance the accuracy of pipeline elevation-mileage data and reduce the locating error of excavation, etc., are helpful to improve the prediction coincidence degree.

• A comprehensive analysis of root causes for the accelerated internal corrosion in steel saltwater pipes coated with fusion bonded epoxy. • Cathodic delamination of the epoxy lining is identified as the primary cause of early internal corrosion failure. • Dynamic cyclic load has a greater chance for crack propagation in the epoxy lining compared to static load. • Development of recommendations and precautions based on the results of failure analysis. Effective functioning of saltwater supply system is essential to Hong Kong government agencies. However, it has been frequently observed that steel saltwater pipes suffered from severe internal corrosion and consequently early burst accidents, which may cause high economic loss and safety concerns to the public. Therefore, by taking a sample saltwater pipe made of DN450 mild steel with internal and external walls coated with fusion bonded epoxy in Hong Kong, this paper investigates the root causes and failure mechanism for the internal corrosion of this failed steel saltwater pipe through laboratory experiments and numerical simulation analysis. Two hypotheses are proposed and validated: (1) cathodic delamination of the epoxy lining, and (2) delamination of the epoxy lining due to external mechanical loads. The results verify that the sample saltwater pipe failed due to the cathodic delamination of the epoxy lining, and the electrochemical corrosion of the inner pipe wall. Moreover, it can be concluded that external mechanical load has few significant impacts on the damage of the epoxy lining for this sample pipe. This study exemplifies the importance of an in-depth analysis on the internal corrosion of steel water pipes, especially in a highly-corrosive internal environment. [ABSTRACT FROM AUTHOR]

This paper describes a non-intrusive method for collecting data about internal corrosion damages in AISI-304 stainless steel plates and classifying them according to severity. The mapping of the electric potential gradient is derived using the potential drop technique, which is then analyzed using image processing techniques including edge enhancement and segmentation. Simulations were run using finite element modeling to produce examples of damaged plates, with four types of defects that can be considered part of pitting corrosion. The image processing stage plays the role of an extractor of features that, when employed as inputs of machine learning algorithms, make it possible to determine the damage severity. With the Gradient Boosting regressor, the maximum absolute error of 0.879 mm was obtained in the estimate of the depth of the defects. Additionally, with the application of a Convolutional Neural Network, an accuracy of 94.84% was achieved to classify of the severity of the damages. [ABSTRACT FROM AUTHOR]

In order to study the residual strength of buried pipelines with internal corrosion defects in seasonally frozen soil regions, we established a thermo-mechanical coupling model of a buried pipeline under differential frost heave by using the finite element elastoplastic analysis method. The material nonlinearity and geometric nonlinearity were considered as the basis of analysis. Firstly, the location of the maximum Mises equivalent stress in the inner wall of the buried non-corroded pipeline was determined. Furthermore, the residual strength of the buried pipeline with corrosion defects and the stress state of internal corrosion area in the pipeline under different defect parameters was analyzed by the orthogonal design method. Based on the data results of the finite element simulation calculation, the prediction formula of residual strength of buried pipelines with internal corrosion defects was obtained by SPSS (Statistical Product and Service Solutions) fitting. The prediction results were analyzed in comparison with the evaluation results of B31G, DNV RP-F101 and the experimental data of hydraulic blasting. The rationality of the finite element model and the accuracy of the fitting formula were verified. The results show that the effect degree of main factors on residual strength was in order of corrosion depth, corrosion length, and corrosion width. when the corrosion length exceeds 600 mm, which affects the influence degree of residual strength will gradually decrease. the prediction error of the fitting formula is small and the distribution is uniform, it can meet the prediction requirements of failure pressure of buried pipelines with internal corrosion defects in seasonally frozen soil regions. This method may provide some useful theoretical reference for the simulation real-time monitoring and safety analysis in the pipeline operation stage. [ABSTRACT FROM AUTHOR]

Under the coupling effect of the defects inside and around pipes, the shear displacement of the joints of old concrete pipes fallen into disrepair usually shows an accelerated deterioration trend, and its excessive value can lead to structural damage or fluid leakage. Therefore, developing a prediction model for the maximum shear displacement of concrete drainage pipe joints with preexisting defects is of crucial significance. To this end, this work selects internal corrosion and erosion voids as the typical defects inside and around old pipes, establishes 300 sets of three‐dimensional fine finite element (FE) models of the concrete drainage pipes with corrosion and void, and verifies the reliability of the developed FE model by the full‐scale tests. Based on the verified FE data, a prediction model is successfully proposed for the assessment of the maximum shear displacement of the concrete drainage pipe joints with corrosion and void defects. Moreover, parameter sensitivity analysis is carried out to reveal their relative contribution to the maximum shear displacement of pipe joints. The results show that the model proposed herein has the ability to accurately predict the maximum shear displacement of the pipe joints. The maximum and minimum relative error between the value predicted by the proposed model and the one computed by the FE model is also 12.4% and 4.8% respectively. Moreover, the traffic load with a contribution of 28.7% has the greatest impact on the maximum shear displacement of pipe joints. [ABSTRACT FROM AUTHOR]

Copyright of Coatings & Protection / Tuceng yu Fanghu is the property of Coating & Protection Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to monitor, prevent and control the corrosion in in-service product pipelines, the value of the first-run inline inspection data was further mined, and the analysis idea was proposed in such a way that, the internal corrosion sensitive area should be semi-quantitatively located through differential analysis of the dispersion of the absolute depth of internal corrosion in the watershed region, combined with the relative positions between the internal corrosion and the pipe fittings such as welds, bends and the like, as well as the pipeline process operation data information. Taking one product pipeline as example, the corrosion conditions of two pipeline sections were analyzed, and it was found that the corrosion accumulation in the pipeline was formed by the gradual development of internal corrosion generated during the pipeline construction. The corrosion-sensitive pipeline sections with pipeline joints as basic units were located, and the in-line inspection data were suggested to be included in the key data of engineering construction quality evaluation. It is suggested that the newly-built pipeline should be pigged as soon as possible to facilitate in-line inspection, the pigging frequency should be increased, the rust in the pipeline should be removed earlier, and subsequently, routine pigging operations can be carried out to effectively slow down the development of internal corrosion.

Regular internal and external detection on oil and gas pipelines is helpful for timely and accurate detection of pipeline corrosion defects, and to take appropriate maintenance and replacement measures and effectively reduce the occurrence probability of corrosion accidents. Focusing on the problems of external corrosion, internal corrosion, stress corrosion cracking, and external corrosion of crossing sections, the development status of corrosion detection technology and related standards for oil and gas pipelines was elaborated, the principles and engineering applications of trenchless detection technologies such as transient electromagnetic detection, ultrasonic guided wave detection, and magnetic stress detection were introduced, the problems existing in the application and management of corrosion detection technology for oil and gas pipelines in China were summarized, and the demands for future development were discussed from the aspects of management improvement and technology upgrading. In terms of management improvement, it was proposed to build a unified technical specification, data management platform and professional corrosion detection efficiency evaluation team. As for technology upgrading, it was suggested to continuously carry out research on stress corrosion cracking detection and assessment technology, initiate research on microbial corrosion mechanism and detection technology, carry out research on pinhole corrosion defect detection and verification technology, and develop combined internal and external detection tools.

In this work, the maximum potential difference on the surface of the pipeline while in contact with various phases of the oil-water emulsion was established. Potential measurements were made under static conditions in a medium that simulates the separation of water in the pipeline, on the metal surface of a piece of steel pipe 20. The study showed that the controlling step of corrosion is differential aeration, which contributes to a significant potential difference in the surface of the metal in contact with the different phases of the oil-water emulsion. The potential difference in different sections of the metallic surface in corrosive medium No. 3 varied from 0,3 to 0,5 V, which meant the development of a galvanic cell, and that the anode section is formed on the metallic surface located in the accompanying oil water.

Oil–water two-phase flow is common in the ocean engineering, petroleum, and chemical industries, among others. In the transportation process, the elbow system – as a paramount component – usually suffers from internal corrosion. In order to investigate the corrosion-prone characteristics of elbow systems, the volume of fluid (VOF) method and the renormalization group (RNG) k-ε model were used to study the oil–water flow in three different elbow configurations. The results indicate that the maximum wall shear stress and mass transfer coefficient are located at the intrados of the elbow for all flow configurations. Nevertheless, for horizontal-upward and horizontal-horizontal elbow flows, water does not come into direct contact with the intrados of the elbow, meaning it is much less susceptible to corrosion. Thus, a multiparameter model which also takes into account the water-volume fraction is necessary for characterizing the corrosion process. When this was combined with an analysis of the water wetting process, the horizontal-downward elbow flow was found to exhibit the largest corrosion risk among the three configurations examined, the horizontal-upward elbow flow was the least susceptible and the horizontal-horizontal elbow flow was in the middle.

In order to study the residual strength of buried pipelines with internal corrosion defects in seasonally frozen soil regions, we established a thermo-mechanical coupling model of a buried pipeline under differential frost heave by using the finite element elastoplastic analysis method. The material nonlinearity and geometric nonlinearity were considered as the basis of analysis. Firstly, the location of the maximum Mises equivalent stress in the inner wall of the buried non-corroded pipeline was determined. Furthermore, the residual strength of the buried pipeline with corrosion defects and the stress state of internal corrosion area in the pipeline under different defect parameters was analyzed by the orthogonal design method. Based on the data results of the finite element simulation calculation, the prediction formula of residual strength of buried pipelines with internal corrosion defects was obtained by SPSS (Statistical Product and Service Solutions) fitting. The prediction results were analyzed in comparison with the evaluation results of B31G, DNV RP-F101 and the experimental data of hydraulic blasting. The rationality of the finite element model and the accuracy of the fitting formula were verified. The results show that the effect degree of main factors on residual strength was in order of corrosion depth, corrosion length, and corrosion width. when the corrosion length exceeds 600 mm, which affects the influence degree of residual strength will gradually decrease. the prediction error of the fitting formula is small and the distribution is uniform, it can meet the prediction requirements of failure pressure of buried pipelines with internal corrosion defects in seasonally frozen soil regions. This method may provide some useful theoretical reference for the simulation real-time monitoring and safety analysis in the pipeline operation stage.

In this work, the pulsed thermography process applied to inspect and analyze the internal corrosion defect in a pipe. The study carried out in two stages, the first one characterizes the control of the pipe at a standstill by considering the air inside the pipe, and the second one characterizes the control during operation by introducing a turbulent flow of seawater into the simulation. For this purpose, a 3D model of a fluid pipe containing three forms of internal rust defects performed using finite element software. The influence of parameters such as the size and penetration of rust into the tube evaluated by analyzing the contrast of the corresponding thermal images and the temporal and spatial variation of the temperature. The tube thickness introduced as a parameter influencing detection. [ABSTRACT FROM AUTHOR]

CO2 and H2S are two popular internal corrosion medias in pipeline, when CO2 and H2S coexistence, the corrosion behavior is much more complicated than CO2 or H2S existing independently. Even if a small amount of H2S will have significant impact on CO2 corrosion, which can damage the ground equipment seriously,and even cause equipment malfunction and safety accidents. The corrosion rule is very complex and difficult to control when CO2 and H2S are coexistence, because it is completely different from the single existence of the two factors. The abroad studies of this corrosion began in the late 1980s, and domestic studies started relatively late. After 30 years study, we find that the corrosion progress depends on the content of CO2 and H2S, medium temperature, pressure, flow rate and other factors. According to the gas properties and operating conditions of East Sichuan gas field, this paper carried on experimental research and theoretical induction analysis, then obtained the internal corrosion affecting factors and corrosion effect weights of their interaction under the coexistence of CO2 and H2S in the surface gathering system. On this basis, using normalization method, the corrosion risk weights of high sulfur gas wells in Chongqing Gas Distric were calculated, and the gas wells and pipelines with high corrosion sensitivity were selected, which need special attention. [ABSTRACT FROM AUTHOR]

Oil–water two-phase flow is common in the ocean engineering, petroleum, and chemical industries, among others. In the transportation process, the elbow system – as a paramount component – usually suffers from internal corrosion. In order to investigate the corrosion-prone characteristics of elbow systems, the volume of fluid (VOF) method and the renormalization group (RNG) k-ε model were used to study the oil–water flow in three different elbow configurations. The results indicate that the maximum wall shear stress and mass transfer coefficient are located at the intrados of the elbow for all flow configurations. Nevertheless, for horizontal-upward and horizontal-horizontal elbow flows, water does not come into direct contact with the intrados of the elbow, meaning it is much less susceptible to corrosion. Thus, a multiparameter model which also takes into account the water-volume fraction is necessary for characterizing the corrosion process. When this was combined with an analysis of the water wetting process, the horizontal-downward elbow flow was found to exhibit the largest corrosion risk among the three configurations examined, the horizontal-upward elbow flow was the least susceptible and the horizontal-horizontal elbow flow was in the middle. [ABSTRACT FROM AUTHOR]

The monitoring of internal corrosion of pipelines is a critical element of the pipeline maintenance programs. A benchmarking study of enhanced techniques for real-time corrosion monitoring such as Linear Polarization Resistance and Harmonic Distortion Analysis was performed, enhanced Electrical Resistance in conjunction with standard metal coupon. The transition of the corrosion processes occurring in metals immersed in corrosive electrolytes at the onset of inhibitor action after its injection was found a revealing item for study. This study considered a 3% NaCl solution with and without 10% diesel, saturated with CO2 at 50 °C and standard AISI 1018 coupons. A set of generic corrosion imidazoline-based inhibitors was studied. The benefits of employing real-time corrosion monitoring devices include shortened test times, increased number of inhibitors evaluated, and an increase in data quality and quantity. Results show that the corrosion rates from linear polarization resistance in the solution without inhibitor were overestimated, while the Harmonic Distortion Analysis and enhanced Electrical Resistance presented similar results to Standard Coupon. The enhanced electrical resistance monitoring also proved to be a good device to reveal the onset of corrosion protection after the inhibitor is applied. [ABSTRACT FROM AUTHOR]

The deterioration of early-age concrete performance caused by SO42− internal diffusion in concrete is a critical factor of concrete durability. In this study, the mechanical properties, heat of hydration, and pore structure of early-age cast-in-situ concrete with different sodium sulfate (Na2SO4) concentrations were studied. The mechanism of SO42− internal corrosion was evaluated by measuring the dynamic elastic modulus, compressive strength, and heat of hydration rate. Scanning electron microscopy, energy dispersive spectroscopy, X-ray computed tomography, X-ray diffraction, thermogravimetry-derivative thermogravimetry, and differential scanning calorimetry were applied to analyze microstructural variations and complex mineral assemblages of concrete samples. The results indicated that during the hardening process of cast-in-situ concrete, Na2SO4 first promoted and then hindered the hydration rate of cement, and also hindered the early strength development of the cement. As the concentration of Na2SO4 solution increases, the corrosion products of ettringite (AFt) and gypsum (Gyp) gradually increase, causing cross cracks in the concrete. The proportion of small and medium pores first increases and then decreases, and the large pores first decrease and then increase. The mechanical properties of concrete gradually decrease and diminish the mechanical properties of the concrete (thereby accelerating the damage to the concrete).

Corrosion in the oil and gas industry represents one of the major problems that affect oil production and transportation processes. Several corrosion-inspection technologies are in the market to detect internal and external corrosion of oil storage tanks, but inspection of storage tanks occurs every 3 to 7 years. In between inspection interval, aggressive corrosion can potentially occur, which makes the oil and gas industry vulnerable to accidents. This study proposes a new internal corrosion detection sensor based on the magnetic interaction between a rare-earth permanent magnet and the ferromagnetic nature of steel, used to manufacture oil storage tanks. Finite element analysis (FEA) software was used to analyze the effect of various sensor parameters on the attractive force between the magnet and the steel. The corrosion detection sensor is designed based on the FEA results. The experimental testing of the sensor shows that it is capable of detecting internal metal loss due to corrosion in oil storage tanks within approximately 8 mm of the internal surface thickness. The sensor showed more than two-fold improvement in the detection range compared to previous sensor proposed by the authors. Furthermore, the sensor of this paper provides a monitoring rather than occasional inspection solution.

The aggressive behavior of carbon dioxide dissolved in water considers as one of basic reasons behind corrosion failure in oil and gas processes. Simulation study using HYSYS program employed to predict CO 2 corrosion in natural gas gathering pipelines system. This work examines the effect of operating pressure, temperature, pH solution, pipeline length, flow regime, and pipe inclination on the CO 2 corrosion. Based on the simulation results, following highlights were identified: increasing operating pressure results in increases CO 2 partial pressure and promotes corrosion rate. Temperature affects formation of protective layer, where maximum CO 2 corrosion rate reached 2.96 mm/year at 40° C for this simulation conditions. After 40° C , the protective layer consists and becomes more dense and reduces corrosion rate. In addition, lower pH enhances the solubility of carbonate, reduces participation rate, and enhancing CO 2 corrosion. Dissolved CO 2 concentration decreases along the pipeline length and the corrosion rate reduces as result. High velocity means efficient mixing which leads to prevent the formation of the protective layer and increases CO 2 corrosion. Pipeline inclination affects the velocity of flow where positive elevation change reduces fluid velocity, while minus elevation change promotes fluid velocity. Frequently, these factors depend on each other and sharing the effects on the CO 2 corrosion. The prevention of CO 2 corrosion in natural gas gathering pipelines starts by understanding the effects of the operation conditions. • Presence of CO 2 and water in natural gas that can causes corrosion. • Operating pressure affects the CO 2 partial pressure and the type of protective scale. • The temperature of natural gas influences the formation of protective layer in great extent. • PH has direct effect on the solubility of carbonate and the corrosion rate as result. • CO 2 corrosion rate decreases as the pipeline length increase. • High velocity prevents the formation of protective layer and increasing corrosion rate as result. [ABSTRACT FROM AUTHOR]

A Nonlinear Regression Analytical model was used to simulate the corrosion rate of CO 2 flowing through a pipeline at different operating conditions. The model was formed by applying the simple current-resistance relationship which was further simplified to obtain an appropriate expression for estimating the corrosion rate of a pipeline in relation to the partial pressure of the gas at different temperatures (30–37 °C). Field conditions were validated against simulated results and based on the findings, the model proved to be an accurate tool for determining the corrosion rate of CO 2 for curvilinear pipe of 3 km length transporting fluids having similar gas composition. Based on the estimated corrosion rates, the model's accuracy lies in the range of 96–99%. Also, from the results, there seem to be an approximate linear relationship/positive correlation between the corrosion rate of CO 2 and, the system temperature and CO 2 partial pressure. • Corrosion rates in flow lines as a function of temperature and CO 2 concentration were predicted. • Effect of operating temperature on pipe corrosion was determined. • The pipe under consideration is curvilinear. • A Nonlinear Regression model was used to simulate CO 2 corrosion rate under different conditions. • A simple current-resistance equation was modified and used to calculate pipe corrosion rates in relation to gas partial pressure at 30–37 °C. [ABSTRACT FROM AUTHOR]

Abstract Internal corrosion of pipeline is often observed at the pipe bottom, especially at the pipe elbow, which may bring great threat to personnel safety and cause serious environmental pollution once the pipeline perforation happens. The pipe wall will get thinned by corrosion when it is wetted by produced water dissolved with various corrosive media. Therefore, it is essential to predict the water distribution in pipelines and determine the continuous phase that wets the pipe wall when analyzing the internal corrosion of crude oil pipelines. This paper aims to study key parameters, such as water cut, mixture velocity, oil viscosity and inclination angle of pipes, that dominate water distribution and the phase that wets the wall of pipe bottom by applying computational fluid dynamics. The results of numerical simulation are proved to coincide well with the available experimental results. Highlights • The entrainment of water by oil in upward inclined pipes with different inclination angles was studied. • Flow pattern changes in inclined pipes under the effect of different factors were explained by water wetting model. • It was explained that how key parameters dominate water distribution and water wetting of the pipe bottom wall. • The simulation method can be applied to predict the wetting transition line of hydrophilic pipe surface. [ABSTRACT FROM AUTHOR]

Gas pipeline systems are one of the largest energy infrastructures in the world and are known to be very efficient and reliable. However, this does not mean they are prone to no risk. Corrosion is a significant problem in gas pipelines that imposes large risks such as ruptures and leakage to the environment and the pipeline system. Therefore, various maintenance actions are performed routinely to ensure the integrity of the pipelines. The costs of the corrosion-related maintenance actions are a significant portion of the pipeline’s operation and maintenance costs, and minimizing this large cost is a highly compelling subject that has been addressed by many studies. In this paper, we investigate the benefits of applying reinforcement learning (RL) techniques to the corrosion-related maintenance management of dry gas pipelines. We first address the rising need for a simulated testbed by proposing a test bench that models corrosion degradation while interacting with the maintenance decision-maker within the RL environment. Second, we propose a condition-based maintenance management approach that leverages a data-driven RL decision-making methodology. An RL maintenance scheduler is applied to the proposed test bench, and the results show that applying the proposed condition-based maintenance management technique can reduce up to 58% of the maintenance costs compared to a periodic maintenance policy while securing pipeline reliability.

Based on the actual operational parameters of a subsea multiphase pipeline, an experimental study on the internal corrosion of a subsea multiphase pipeline was conducted in a dynamic, high-temperature autoclave, which had a similar environment to an actual field environment, using the partial pressure of CO2 (PCO2), velocity of the corrosion medium, temperature, corrosion time, and corrosion inhibitor as variables. The results show that CO2 resulted in severe localized corrosion and that the corrosion rate increased as the PCO2 and velocity increased; the corrosion rate first increased and then decreased with increasing temperature. The corrosion rate peaked at approximately 65 °C and then decreased continuously afterwards; the corrosion rate decreased as the duration of the experimental period increased. Under the operational conditions of the selected subsea pipeline, localized corrosion caused by CO2 was still the primary corrosion risk. Several types of corrosion inhibitors could inhibit the occurrence of localized corrosion for a short time period; however, most corrosion inhibitors could not completely inhibit localized corrosion.

In this present paper, failure analysis is conducted for a pipe used in fire water applications. In petroleum industries many failures were observed in API 5 L grade steel pipes. The past inspection history records were observed, which reveals that failed pipeline is poorly maintained since construction. Visual inspection, macroscopic and microscopic examinations were conducted for the failed pipe. The microscopic analysis reveals that the pitting corrosion is a root cause of failure which perforates the wall thickness at 6′o′ clock pipe position. The mechanism of pitting corrosion is correlated with ferrite matrix dissolution. The Cu, Co & Zn ions were detected in scale deposits reveals that the fire water is severely contaminated by various makeup water sources which results in under deposit corrosion. The various sources of foreign elements are discussed in detail. The copper deposits identified at suspected location attributed to galvanic corrosion. Moreover, the severity of pitting is aggravated by grain boundary attack which acts as an anode during corrosion process. Based on various experimental evidences, the conclusions were drawn and further recommendations are discussed to mitigate the corrosion failure. [ABSTRACT FROM AUTHOR]