Corrosion Defects Research Articles

An Experimental Study on Phased Array Ultrasonic Testing for Internal Inspection of Gas Storage Wells

A reduction in wall thickness, caused by corrosion, of the inner and outer surfaces of underground compressed natural gas storage wells is one of the main causes of failure. Therefore, taking wall thickness measurements is an important task during periodic inspection. This study proposes a corrosion detection technique based on the well’s shape using cylindrical convex ultrasonic phased array and develops a cylindrical convex phased array probe with 512 elements. Using an example well of ∅177 × 10.36 mm, the influences of process parameters such as active aperture, focal length, gain, and gate threshold are studied. In addition, an experiment is conducted on a sample well with artificial defects for parameters optimization. Next, experimental tests are carried out on the well at the test platform according to the optimized parameters. The results show that the proposed technique is of high sensitivity and efficiency for the detection of corrosion defects and is able to detect pitting corrosion of more than ∅2 mm and line corrosion of 1 mm width.

High-Temperature Passivation of the Surface of Candidate Materials for MSR by Adding Oxygen Ions to FLiNaK Salt.

The problem of tailoring the structural materials for MSR is solved by continuously overcoming the shortcomings of widely used materials and finding new ones. The materials commonly used in engineering may not be applicable for MSR due to their high corrosivity. Experiments were carried out to determine the corrosion rate of stainless steel 12Cr18Ni10Ti with different concentrations of oxide ions (by adding lithium oxide to the melt in the concentration range from 0 to 0.8 wt.%) in a FLiNaK melt. The formation of a protective oxygen-containing layer with a thickness of 1 micron has been realized. The corrosion rate decreases by an order of magnitude at the concentration of oxygen anions in the melt, in the range from 0.2 to 0.4% by weight, which may indicate high-temperature passivation of the material due to modification of the composition of the fluoride melt and reduction in its corrosion activity. In addition, the corrosion type of stainless steel in fluoride melts changes from the intercrystalline and pitting that is usually harmful to reactor material structure to total corrosion when lithium oxide is added. This is due to the “healing” of individual corrosion defects formed on the surface of the studied material by oxygen-containing compounds.

Experimental and numerical analysis of ratcheting behavior of A234 WPB steel elbow joints including corrosion defects

In this paper, ratcheting behavior of intact and corroded 90o elbow pipe specimens of A234 WPB steel is investigated at intrados, crown, and extrados positions. A special fixture was designed and constructed to carry out the fatigue experiments. Then, the effects of fatigue loading parameters (mean and amplitude) and defect depth were examined on ratcheting responses of intact and corroded specimens at intrados, crown, and extrados positions. To simulate the ratcheting behavior of specimens, a finite element analysis was performed based on the combined nonlinear isotropic/kinematic hardening model. As a reasonable agreement was found between the finite element (FE) simulation results and experimental data, the influence of constant internal pressure during the cyclic loading was examined on ratcheting responses through FE simulation. Results indicated that decreasing the load amplitude was more effective on decreasing the ratcheting strain than that of the mean fatigue load. Moreover, the most critical ratcheting response was associated with the intrados location of the pipe. For defective specimens, decreasing fatigue loading parameters resulted in a shakedown behavior for a defect placed at extrados, while, for the defects at intrados and crown, an increasing behavior was observed for the ratcheting strain. It was revealed that, at extrados position, the ratcheting behavior was arrested up to 1 mm defect depth. The ratcheting strains were increased at intrados and crown by increasing the internal pressure, while they were decreased at extrados.

A new method for assessment of burst pressure capacity of corroded X80 steel pipelines containing a dent

This work developed a new finite element (FE)-based method to perform pressure capacity assessment on a corroded X80 steel pipe containing a dent, where their mutual interaction and the effect on further corrosion growth were defined. Parametric effects including corrosion depth, dent depth, corrosion length and service time were determined. The presence of a dent at corrosion defect remarkably changes the local stress distribution, elevating stress to plastic range. The mutual interaction between the dent and the corrosion defect depends on both the initial corrosion depth and the initial dent depth. The interaction remarkably changes the local stress level at the dent and must be included in pipeline burst failure assessment.

TECHNOLOGIES FOR MONITORING THE TECHNICAL CONDITION OF TRANSPORT INFRASTRUCTURE OBJECTS BASED ON THE COEFFICIENT OF CORRELATION BETWEEN CRITICAL VALUES OF NOISE AND USEFUL SIGNALS

Transport infrastructure objects are exposed to a large number of loads, which cause the formation of displacements, bends, wear, cracks, breakdowns, corrosion, and other defects. It is shown that at the moment of initiation of malfunctions in objects, the noise of the noisy signals coming from the corresponding sensor takes critical values that correlate with useful signals. Therefore, algorithms are developed for calculating the probability of random noise accepting critical values, a coefficient of correlation between the critical values of the noise and the useful component, and a relay cross-correlation function. Technologies for monitoring the technical condition of transport infrastructure objects are proposed based on the estimates of the developed noise characteristics. Computational experiments are conducted, and the reliability of the developed algorithms and technologies is confirmed.

Metal Surface Defect Detection Method Based on TE01 Mode Microwave.

With the aim of addressing the difficulty of detecting metal surface cracks and corrosion defects in complex environments, we propose a detection method for metal surface cracks and corrosion defects based on TE01-mode microwave. The microwave detection equations of cracks and corrosion defects were established by the Maxwell equations when the TE01 mode was excited by microwaves, and the relationship model between the defect size and the microwave characteristic quantity was established. A finite integral simulation model was established to analyze the influence of defects on the microwave electric field, magnetic field, and tube wall current in the rectangular waveguide, as well as the return loss at the defect; an experimental platform for the detection of metal surface cracks and corrosion defects was built. The absolute value of the return loss of the microwave reflected wave increased, and with the increase of the defect width, the microwave detection frequency at the defect decreased. The TE01-mode microwave has good detection ability for metal surface cracks and corrosion defects and can effectively detect cracks with a width of 0.3 mm.

Experiment and simulation on testing steel plate with corrosion defects via magnetic flux leakage method

The testing of corrosion defects of steel components in engineering is critical to ensure the service safety of structures in civil engineering. Although some research of the corrosion of steel components using magnetic flux leakage (MFL) testing has been carried out, the quantitative evaluation of corrosion parameters has not been achieved due to the lack of quantitative analysis on the relationship between corrosion parameters (action zone, corrosion amount) and the MFL signal. In this paper, the steel plate is taken as the specimens of nondestructive testing. The MFL testing technology was used to measure the change laws of the MFL signal and its characteristic with under different lengths of the action zone and corrosion amount. The finite element simulation of the corrosion testing shows a good correlation with the MFL testing experiment. Combined with finite element simulation and experimental data, a detailed process for quantitative evaluation of the corrosion length and corrosion amount is established based on the corrosion signal characteristic. Based on the analysis of the signal characteristics measured by the experiment, it is confirmed that the evaluation accuracy of the corrosion amount of the steel plate can be guaranteed to be about 1.0 g, which demonstrates the feasibility of quantitative evaluation of corrosion parameters based on the MFL signal.

Failure assessment of corroded ultra-high strength pipelines under combined axial tensile loads and internal pressure

The failure of corroded ultra-high-strength steel (X100 and X120) pipelines under combined axial loads and internal pressure is investigated numerically by finite element analyses, and an empirical model is proposed for burst strength prediction. The finite element structural models are constructed with uniformly oriented axial defects and consider material non-linearity. After validating the finite element models against test data of intact and corroded ultra-high-strength pipes, they are used to study the effect of axial tensile force on burst strength. Extensive parametric analyses are then conducted to investigate the influence of corrosion defect parameters on the burst strength under combined loading. The results revealed that both axial tension and corrosion defect can significantly reduce the burst strength of UHS pipe. Later, the results of the parametric analysis are used to develop an empirical model for burst strength prediction of ultra-high-strength steel corroded pipelines subjected to combined loading. Finally, the model's prediction capability is validated by comparisons with other available models.

Finite element-based parametric and forensic analysis of corrosion-induced structural deterioration in prestressed concrete bridge girders

To study corrosion effects on real structures, three prestressed concrete (PC) girders salvaged from a decommissioned 27-year-old bridge in Alberta, Canada, were studied numerically and compared to experimental tests. Nonlinear finite element (FE) models were developed to simulate the degraded flexural and shear behaviour of PC girders. The FE models were used to infer the possible unknown deterioration conditions (i.e., forensic analysis) by comparing FE-predicted and experimental behaviour of the girders. Based on the developed FE models, comprehensive parametric studies considering various corrosion-induced deteriorations at a wide range of corrosion levels were also conducted. Insights gained from the parametric study assisted assessing other girders under similar conditions. It was found that corrosion defects, such as reinforcement area loss, prestress force loss, and bonding loss in the end anchorage, affect PC girder behaviour significantly and the developed FE models of corroded PC girders can assist girder condition assessment.

Analysis of the scaling mechanism and characteristics of a double-defects screen based on data from Hafaya oilfield

Corrosion defects of screen occurred frequently in sand control process due to the influence of formation factors. The main purpose of this study was to analyze screen scaling based on field data with CFD technology under different sizes, quantities and distribution modes of corrosion defects. A full presentation of turbulent Kinetic Energy contours, wall shear stress contours, fluid velocity and temperature on the screen surface are presented and discussed in the process of scaling. The distribution characteristics of CaCO3 in the scaling model were used to characterize the scaling characteristics. Furthermore, prediction model of scaling thickness was established to systematically evaluate the results. The conclusion of numerical analysis showed that with other conditions unchanged, the scale of radial distribution is larger than that of axial distribution. More over, the larger the defect width and distance, the less obvious scaling. However, the defect depth indicated the opposite results, which meant that the size factor has the greatest influence on scaling. Keeping the environmental conditions changed, velocity and temperature showed obvious influence on particle scaling. It reveals that the velocity of produced liquid has a great influence on the defect screen with different distribution modes.When the size condition of the defect were kept remained, the scaling amount of screen increases obviously with the increase of velocity. The influence of temperature on the two different distribution patterns of defects was not obvious. With the increased of the temperature, the amount of scaling in the pipe also increased similarly. Considering the results, this research could be used as basis to offer safe operating guidelines to reduce the scaling in the screen due to corrosion defects in oil production. To mitigate the impact of this factor on production, scaling can be addressed by reasonably increasing the velocity of the produced liquid and lowering the temperature with the defects exist.

Reactive Oxygen Species Formed by Metal and Metal Oxide Nanoparticles in Physiological Media-A Review of Reactions of Importance to Nanotoxicity and Proposal for Categorization.

Diffusely dispersed metal and metal oxide nanoparticles (NPs) can adversely affect living organisms through various mechanisms and exposure routes. One mechanism behind their toxic potency is their ability to generate reactive oxygen species (ROS) directly or indirectly to an extent that depends on the dose, metal speciation, and exposure route. This review provides an overview of the mechanisms of ROS formation associated with metal and metal oxide NPs and proposes a possible way forward for their future categorization. Metal and metal oxide NPs can form ROS via processes related to corrosion, photochemistry, and surface defects, as well as via Fenton, Fenton-like, and Haber–Weiss reactions. Regular ligands such as biomolecules can interact with metallic NP surfaces and influence their properties and thus their capabilities of generating ROS by changing characteristics such as surface charge, surface composition, dissolution behavior, and colloidal stability. Interactions between metallic NPs and cells and their organelles can indirectly induce ROS formation via different biological responses. H2O2 can also be generated by a cell due to inflammation, induced by interactions with metallic NPs or released metal species that can initiate Fenton(-like) and Haber–Weiss reactions forming various radicals. This review discusses these different pathways and, in addition, nano-specific aspects such as shifts in the band gaps of metal oxides and how these shifts at biologically relevant energies (similar to activation energies of biological reactions) can be linked to ROS production and indicate which radical species forms. The influences of kinetic aspects, interactions with biomolecules, solution chemistry (e.g., Cl− and pH), and NP characteristics (e.g., size and surface defects) on ROS mechanisms and formation are discussed. Categorization via four tiers is suggested as a way forward to group metal and metal oxide NPs based on the ROS reaction pathways that they may undergo, an approach that does not include kinetics or environmental variations. The criteria for the four tiers are based on the ability of the metallic NPs to induce Fenton(-like) and Haber–Weiss reactions, corrode, and interact with biomolecules and their surface catalytic properties. The importance of considering kinetic data to improve the proposed categorization is highlighted.

Critical Evaluation of Building Defects Research: A Scientometric Analysis

The architecture, engineering, and construction (AEC) industry is a major contributor to national economic development across the world. However, this industry’s development has been threatened by several issues, including defects. Building defects (BDs) can cause several problems including risks posed to life, personal safety, health, and project financial conditions. This review aimed to outline scholarly works that have examined various aspects of BDs and highlight the gaps in knowledge. The study presents the first comprehensive scientometric study evaluating contemporary research on BDs and their management. This research uses the science mapping method to analyze 712 bibliographic records extracted from Scopus for the last three decades. The study showed that there is a spike in the number of BD-related publications in the last decade. The results also indicated that the finite-element method and nondestructive examination have been the most widely used BD assessment methods. The study also found that cracks, corrosion, and surface defects have been the most commonly addressed topics. The primary value and uniqueness of this study lie in it being the first in providing an up-to-date inclusive, big picture of the literature on BD management. This research adds value to the AEC literature through visualizing and understanding trends and patterns identifying main research interests, journals, institutions, and countries, and how these are linked within now-available studies on BD. The findings of this research bring forward the gap in the current research and provide directions for future research, where they indicated that future research opportunities lie in exploring human factors on defects, thermal effects, and the root causes of defects in the building services, particularly in plumbing and drainage works. For the world of practice, the study offers a readily available point of reference for practitioners, policy-makers, and research and development bodies. This study, therefore, raises the level of awareness of BD management in the AEC industry.

Empirical Failure Pressure Prediction Equations for Pipelines with Longitudinal Interacting Corrosion Defects Based on Artificial Neural Network

Conventional pipeline failure pressure assessment codes do not allow for failure pressure prediction of interacting defects subjected to combined loadings. Alternatively, numerical approaches may be used; however, they are computationally expensive. In this work, an analytical equation based on finite element analysis for the failure pressure prediction of API 5L X52, X65, and X80 corroded pipes with a longitudinal interacting corrosion defect subjected to combined loadings is proposed. An artificial neural network (ANN) trained with failure pressure obtained from finite element analysis (FEA) of API 5L X52, X65, and X80 pipes for varied defect spacings, depths and lengths, and axial compressive stress were used to develop the equation. Subsequently, a parametric study on the effects of the defect spacing, length, and depth, and axial compressive stress on the failure pressure of a corroded pipe with longitudinal interacting defects was performed to demonstrate a correlation between defect geometries and failure pressure of API 5L X52, X65, and X80 pipes, using the equation. The new equation predicted failure pressures for these pipe grades with a coefficient of determination (R2) value of 0.9930 and an error range of −10.00% to 1.22% for normalized defect spacings of 0.00 to 3.00, normalized effective defect lengths of 0.00 to 2.95, normalized effective defect depths of 0.00 to 0.80, and normalized axial compressive stress of 0.00 to 0.80.

Understanding the effect of tensile stress on erosion-corrosion of X70 pipeline steel

The pipelines in the oil and gas industry may simultaneously suffer damage from tensile stress and erosion at the internal surface, which could cause the pipeline failure easily. In this work, the combined effect of tensile stress and erosion on the corrosion of X70 pipeline steel was studied in a loop system coupled with a stress loading device. The general corrosion and localized corrosion under the combination of tensile stress and erosion was comprehensively investigated using finite element simulation analysis, potentiodynamic polarization curve, electrochemical impedance spectroscopy, scanning electron microscope as well as 3D ultra-depth microscope. The results show that both tensile stress and erosion can promote general corrosion independently. Furthermore, the combination of tensile stress and erosion can generate a synergistic effect on general corrosion of steels through reducing the compactness of corrosion products layer, accelerating the mass transfer process and improving the reaction activity of the steel, with a changed corrosion current density of 37.54 μA/cm2, even exceeding the influence of tensile stress (17.76 μA/cm2). For localized corrosion, erosion can enhance the inside-out diffusion of metal cations in the metastable pit and dilute the pit anolyte, while tensile stress may generate stress concentration on corrosion defects. Therefore, erosion shows a suppression on localized corrosion, but an enhancement effect from tensile stress.

Origins of wear-induced tungsten corrosion defects in semiconductor manufacturing during tungsten chemical mechanical polishing

During chemical mechanical polishing (CMP) process optimization, a unique corrosion defect was identified in the tungsten (W) contact plugs, which were investigated to develop practical solutions to improve CMP mass productivity. The corrosion defect occurred in the absence of external incident energy and was observed to occur only at the W plugs connected to the P+/n-well close to the wafer edge. To examine the root cause of the corrosion, a series of experiments was carried out at each W CMP step, using in-line defect inspection. Additional experiments were conducted using on-line inductively coupled plasma mass spectrometry (ICP-MS) to understand pH- and potential-dependent electrochemical dissolution behaviors of W. Experimentally, W corrosion was confirmed to be exacerbated if the surface oxide of the W plugs is removed by the deionized water (DIW) rinsing step under wafer pressurization, then exposed to DIW and alkaline cleaning solution. Although the DIW rinsing step is commonly performed to clean polishing pads right after the main polishing, a small amount of applied pressure (0.5 psi) without slurry supply can lead to corrosion defects. This wear-induced corrosion of the W plugs can be prevented by removing the applied pressure during the post DIW rinsing step of W CMP.

Risk Classification of Shale Gas Gathering and Transportation Pipelines Running through High Consequence Areas

Shale gas gathering and transportation pipeline poses significant risk due to special geographical conditions and different climatic conditions in high consequence areas such as Sichuan and Chongqing. The risks become critical as gas pipelines run through high consequence areas such as hospital, market, and scenic areas. This study presents a risk classification method for the pipelines running through high consequence areas. The proposed method considers different failure scenarios including third-party damage, corrosion, design and construction defects, mis-operation, and natural disasters. The method uses subjective and objective data from different sources. To minimize the subjectivity and data uncertainty, an improved fuzzy analytic hierarchy process was used to process data. The estimated risk is used to classify different risk zones. After the failure of shale gas pipelines in HCAs, in order to reduce the adverse impact of emergencies, personnel should immediately organize an evacuation to a safe area, focusing on the diagnosis and analysis of risk factors that are more likely to lead to pipeline leakage. The developed classes are verified using field data. The study observes that risk levels classified using the proposed method provide realistic assessments of hazard zoning. Risk zoning will help develop effective risk management strategies.

Intergranular corrosion effect on fatigue behavior of dissimilar 6005A‐5083 aluminum alloys weld joints

AbstractThe effects of the intergranular corrosion (IGC) defect depth on the high circle fatigue performance of tungsten inert gas (TIG)‐welded joints of 6005A–5083 dissimilar aluminum alloys were investigated. After soaking in different IGC solutions for 72 h, corrosion defects of different depths were generated in various areas of the specimen surfaces. It was found that the 5083 base metal exhibited the poorest corrosion resistance, while the welded metal displayed the best corrosion resistance. Fatigue tests carried out after precorrosion revealed that when the IGC depth was shallow, the weld defects on the weld metal were the main source of cracking for fatigue extension. However, when the IGC depth in the 5083 base metal was >248 μm, the corrosion defect acted as the origin of the fatigue crack, and the fatigue life of the sample was significantly reduced. This was attributed mainly to the local high‐stress field at the tip of the corrosion defect. Finally, a corrosion fatigue crack expansion model was established to analyze the influence of the corrosion defect depth on the fatigue lives of welded joints.

Assessment by finite element modeling of pipelines with corrosion defects based on River-Bottom Profile model

This paper presents a new methodology for the prediction of pipelines failure pressure that uses axisymmetric modeling of pipelines which uses the River Bottom Profile (RBP) of the corrosion defect. This new tool is practical because, typically, the length of the corrosion defect is much larger than its width (L>W) and therefore the width has little influence on the failure pressure. In addition, for pipe models without corrosion defects, the circumferential stress is approximately twice the longitudinal stress. This new methodology allows oil and gas industry piping engineers to assess pipeline integrity quickly and accurately. The quality of the proposed methodology is attested by an average deviation of about 3% from experimental results, for the specimens shown in this article.

CFRP Strengthening and Rehabilitation of Inner Corroded Steel Pipelines under External Pressure

The objective of this study was to investigate the performance of pipelines repaired with carbon-fibre-reinforced polymer (CFRP) under external pressure. The repaired pipeline experienced defects in terms of thinning of its local inner wall. The three-dimensional finite element method was used to analyse the collapse pressure of repaired pipes with internal corrosion defects. The traction–separation law and interlaminar damage criterion were applied to simulate the collapse process of repaired pipes. The results show that the collapse pressure of the composite-repaired pipe increased and the CFRP significantly reduced the strain in the defect region. It was observed that the ovality of the corrosion defect region was reduced and that the repair effectiveness mainly depended on the length, thickness, and interlayer cohesion.

Failure Pressure Prediction of Medium to High Toughness Pipe with Circumferential Interacting Corrosion Defects Subjected to Combined Loadings Using Artificial Neural Network

Assessment of a corroded pipe is crucial to determine when it must be repaired or replaced. However, the conventional corrosion assessment codes for the failure pressure predictions of corroded pipes with circumferentially aligned interacting defects are conservative (underestimations of more than 40%), resulting in premature repair or replacements of pipelines. Alternatively, numerical approaches may be used, but they are time consuming and computationally expensive. In this study, an analytical equation based on finite element analysis for the failure pressure prediction of API 5L X52, X65, and X80 corroded pipes with circumferentially aligned interacting corrosion defects subjected to combined loadings is proposed. An artificial neural network trained with failure pressure obtained from the finite element analysis of the three pipe grades for varied defect spacings, depths and lengths, and axial compressive stress were used to develop the equation. Subsequently, a parametric study on the effects of these parameters on the failure pressure of a corroded pipe with circumferential-interacting defects was conducted using the equation to determine the correlation between the defect geometries and failure pressure of the pipe. The new equations predicted failure pressures for these pipe grades with an R2 value of 0.99 and an error range of −9.92% to 0.98% for normalised defect spacings of 0.00 to 3.00, normalised effective defect lengths of 0.00 to 2.95, normalised effective defect depths of 0.00 to 0.80, and normalised axial compressive stress of 0.00 to 0.60.