Mechano-electrochemical Interaction Research Articles

Investigation into the mechano-electrochemical interaction of internal and external corrosion defects on pipe surfaces

Revealing the mechanical-electrochemical interactions (M-E) on internal and external defects in pipelines is of paramount importance for ensuring the safe operation of pipelines. The present study establishes a mechano-electrochemical multi-physics coupling model and develops a two-dimensional finite element (FE) model of internal and external defects on the pipe surface to investigate the M-E interaction of X100 steel pipe with corrosion defects on both internal and external surfaces. The results demonstrate that the M-E interaction is significantly influenced by the geometrical shape, relative position, and internal pressure of defects. Moreover, altering a single defect parameter can simultaneously impact the M-E interaction of two defects. As the depth of defects increases, the cross-sectional area between internal and external defects decreases, leading to an intensified interaction between mechanics and electromagnetics and a gradual concentration of M-E interaction at the center of defects. The magnitude of the M-E interaction exhibits a negative correlation with the length of the defect, while the presence of a long defect minimally impacts the M-E interaction on the opposing side. As the external defects gradually distance themselves from the internal defects, the M-E interaction diminishes and the concentration area of M-E interaction shifts in the opposite direction to defect migration, while stress in the non-defect region adjacent to both internal and external defects progressively intensifies. The increase in internal pressure significantly enhances the M-E interaction of internal and external defects, with the M-E interaction primarily focused on the minimum cross-sectional area of radial overlap between these defects. At low internal pressures, however, the M-E interaction becomes negligible.

Mechano-electrochemical interaction of high-strength pipeline steels with Al-Ti deoxidization and Mg-Ca compound treatment

The micro-zone interface of inclusions with the steel matrix of X70 high-strength pipeline steel with Al-Ti deoxidization and Mg-Ca compound treatment in the tropical marine environment was investigated. Results revealed that the Volta potential difference increased in proportion to the residual stress at the interface of inclusions with the steel matrix. The early corrosion behavior of pipeline steel was investigated by immersion testing and corrosion morphology assessment. Three stages of the early corrosion process of pipeline steel were elucidated based on micro mechano-electrochemical (M-E) interaction. Thermodynamic and kinetic models of M-E interactions at the micro-scale were proposed.

Pipeline condition assessment and finite element modeling of mechano-electrochemical interaction between corrosion defects with varied orientations on pipelines

Multiple corrosion defects located in varied orientations are common on pipelines, significantly impacting pipeline conditions. In this work, 3D finite element (FE) based multi-physics field coupling models were developed to model mechano-electrochemical (M−E) interaction between corrosion defects with varied orientations and its effect on pipeline conditions. The effects of the parameters, including defect geometries, operating conditions, and the relative positions and spacings between the defects, were determined. The results demonstrated that, the strongest M−E interaction occurred between defects when the longitudinal or circumferential spacing is 0, causing high-level local stress concentration and the anodic current density (i.e., corrosion rate) at the corrosion defects. As the defects gradually overlapped or separated from each other on the pipe surface, the magnitude of the M−E interaction decreased. The interaction between defects even disappeared when the longitudinal or circumferential spacing between defects reached 96 mm or 72 mm, respectively, and the defects can be assessed separately. An increased internal pressure led to local plasticity deformation and anodic current density concentration occurring at the inner edge of the defects and defect adjacent area. For example, the maximum anodic current density increased by 56.4% when the internal pressure increased from 12 MPa to 17 MPa. It was also observed that M−E interaction between defects disappeared if the defects were shorter than 48 mm or shallower than 8 mm. Sensitivity analysis demonstrated that the degree of M−E interaction was most sensitive to circumferential spacing, followed by defect depth, defect length, longitudinal spacing, and internal pressure.

A Fully Coupled Tribocorrosion Simulation Method for Anchor Chain Considering Mechano-Electrochemical Interaction

This study aims at proposing a fully coupled numerical simulation method of tribocorrosion development on anchor chains during service life, where the mechano-electrochemical interaction is considered in a simplified way. The damage evolution can be realized by a user-defined UMESHMOTION FORTRAN subroutine, where both stress-accelerated corrosion and corrosion-accelerated wear can be considered. Based on this numerical method, the time-variant damage morphology of mooring chain can be obtained. Simulation results obtained by different damage evolution models are shown and compared, and some discussions on the simplified simulation method of reciprocating tribocorrosion are also presented. A systematic parametric study is carried out, and the key factors affecting the tribocorrosion of chain link are revealed. Finally, a modified design method is proposed, and it can be used for optimization of the design of marine anchor chains.

Assessment by finite element modeling of corrosion in dent on X52 steel pipelines

While corrosion in dent presents a realistic threat to integrity of pipelines, there have been limited methods available to assess the problem and its effect on fitness-for-service of the pipelines. In this work, a method was developed to assess the corrosion in dent on an X52 steel pipe by considering both mechanical and electrochemical corrosion factors and their interaction at an unconstrained dent through finite element modeling. Parametric effects including dent depth, dent size (i.e., open mouth diameter for spherical dents) and internal pressure on distributions of stress, anodic current density and net current density were determined. The stress concentration at the dent accelerates corrosion due to a mechano-electrochemical interaction. As the dent depth increases, the local stress concentration is enhanced, resulting in increased corrosion activity and corrosion rate. The most negative corrosion potential and the maximum anodic current are located at the center of the dent, where the anodic reaction occurs. The cathodic reaction mainly occurs at the dent sides. The internal pressure has a limited effect on the anodic current density. The dent with a smaller open diameter can cause greater local stress concentration and anodic current density. At specific dent depths, small dents tend to accelerate local corrosion at a more rapid speed than bigger dents.

Effect of external wall defect growth on internal wall corrosion of oil pipelines under mechano‐electrochemical interaction

AbstractThe corrosion mechanism of X80 steel in simulated solutions of acid red soil and product oil sediment under mechano‐electrochemical interaction (MEI) was researched to build a new finite element model through multi‐physical field coupling simulation technology. Based on the new model, the effect of external wall defect growth on the internal wall corrosion of oil pipelines was analyzed in detail. The results showed that the distributions of stress and corrosion of the internal wall were extremely affected by the external wall defect depth, and the corrosion rate of the internal wall was enlarged remarkably by the external wall defect growth. Moreover, attributing to the local galvanic cell effect under MEI, the growth rates of corrosion defects in the depth and length directions of the external defect were accelerated because these directions were associated with larger stress and equivalent to the anode, but the corrosion rate in the width direction of the external defect was inhibited because this direction was associated with smaller stress and equivalent to the cathode.

Investigation by numerical modeling of the mechano-electrochemical interaction at a dent-corrosion defect on pipelines

Dent-corrosion combination defect causes the curvature change and wall thickness thinning on the pipeline simultaneously, which poses a higher threat to pipeline integrity than a single type of defect. In this work, a finite element (FE) based multi-physical field coupling model was developed to investigate the mechano-electrochemical (M-E) interaction at the dent-corrosion defect on an operating X80 pipeline. Parameter effects, including internal pressure, the diameter-to-thickness ratio of the pipe, and the geometries of the defect, were determined. Results demonstrate that the local equivalent plastic strain and anodic current density are insensitive to practical operating pressure but highly dependent on the diameter-to-thickness ratio and the geometries. A critical dent depth of 4% of the pipe diameter existed, exceeding which the increase of dent depth hardly affects the maximum equivalent plastic strain of the pipeline. The size of the indenter is negatively correlated with the equivalent plastic strain and the anodic current density at the defect center. There is also a critical threshold of 10% pipe diameter, below which the distribution of equivalent plastic strain and anodic current density at the defect is significantly affected. The effect of the circumferential dent is significant, while that of the axial dent is marginal.

Time variant characteristic of steel cable considering stress-corrosion deterioration

This study aims at proposing a numerical simulation method able to predict the time-variant stress-corrosion damage and the breaking strength of steel cable, where the mechano-electrochemical interaction can be considered in a simplified way. The damage evolution was realized by a user defined FORTRAN subroutine combining with the Arbitrary Lagrangian-Eulerian (ALE) method. Two stress-corrosion model and the engineering method were used, and the simulation results were compared. Besides, the random stress-corrosion was also realized. After model validation, the time-variant corrosion morphology of steel cable was obtained, and the remaining breaking strength was also determined. The influence of damage evolution on force relaxation, the variability of corrosion rate and the pressure-dependent friction coefficient on damage evolution were also investigated and discussed.

Comparative study on the crack growth behaviours of E690 steel and heat-affected zone microstructures under cathodic potential in artificial seawater based on mechano-electrochemical effect at crack tip

The crack growth behaviours of E690 steel and HAZ microstructures under cathodic potential in artificial seawater were investigated and compared. The crack growth behaviours of three HAZ microstructures and basic metal are determined by mechano-electrochemical interaction at crack tip, and growth paths are different due to the change of microstructures. As cathodic potential negatively decreases, the crack growth rates (CGRs) of four microstructures first decrease and then increase with the minimum CGR at − 750 mV, which depends on the variation of hydrogen concentration. Applying cathodic potential is impossible to restrain crack growth, but can slow the CGR at an optimized potential.

Time-variant burst strength of pipe with corrosion defects considering mechano-electrochemical interaction

This study aims at assessing the time-variant burst strength of pipe with corrosion defects under high internal pressure. A new numerical model was developed, where the mechano-electrochemical interaction was considered in a simplified manner. The damage evolution of corrosion, which was governed by a stress corrosion model, was realized by a user defined UMESHMOTION subroutine. The time-variant corrosion morphology and burst strength can be obtained using the numerical model. The proposed method avoids the disadvantages of the conventional method, where the damage form and size at a given moment are presumed and history-independent. Based on this simplified method, the effect of a single and two adjacent local corrosion defects on the burst strength of the pipe was investigated. Moreover, a new method was proposed that can consider the time-variant reliability of the pipe along with the randomness of the corrosion rate, geometry, and material strength. The predicted value of the deterministic method was also compared with that obtained by the stochastic method. Furthermore, systematic parametric studies were also conducted.

Assessment by finite element modelling of the mechano-electrochemical interaction at corrosion defect on elbows of oil/gas pipelines

The assessment of corrosion defects to determine their effect on pipeline integrity is essential for pipe managers to develop a scientific maintenance strategy. In this work, a nonlinear finite element (FE) model coupled with multi-physical fields was developed to study the mechano-electrochemical (M-E) synergistic effect at an external corrosion defect on X100 pipeline elbow. The results indicated that bending radius has an apparent effect on the burst pressure of the corroded pipe elbow. However, anodic and cathodic reactions was insensitive to bending radius under normal working pressures. Pipes elbows with corrosion defects located in the intrados have a lower burst pressure than those in the extrados and central line crowns. When the deformation or stress generated at the corrosion defect was elastic, the synergistic mechano-electrochemical interaction effect was insignificant. However, when the depth of the defect or the applied internal pressure of the elbow was sufficient to produce a local plastic strain in the corroded region, the corrosion reaction of the local steel at the defect was remarkably enhanced. Under multiaxial stress, the corrosive behaviour of steel in the defective area involved numerous local galvanic batteries, with the anode located in the high-stress zone and the cathode in the lower-stress zone. Anodic polarisation was found to occur in high-stress zone, which accelerated local corrosion.

Mechano-electrochemical interaction for pipeline corrosion: A review

Engineering structures such as pipelines usually operate under stressing conditions. When corrosion occurs on the structures in service environments, the stress and corrosion reactions synergistically result in a so-called mechano-electrochemical (M-E) interaction, adversely affecting the structural integrity. This work reviewed the fundamentals of the M-E interaction for pipeline corrosion, where both corrosion thermodynamics and kinetics were derived by incorporating the effect of stress and strain applied on the pipelines. Under an elastic deformation, the M-E interaction for pipeline corrosion is usually negligible, while a dynamic elastic stress can degrade the integrity of corrosion scale on the steel and slightly accelerates the steel corrosion. However, plastic deformation results in an appreciable M-E interaction, remarkably changing both corrosion potential and corrosion rate of pipeline steels. Based on the M-E interaction theory, a multi-physics field coupling model with finite element analysis was developed to assess corrosion defects on pipelines for failure prediction. Perspectives of the M-E interaction in pipeline corrosion research and preventive management were analyzed.

Modeling of mechano-electrochemical interaction at a corrosion defect on a suspended gas pipeline and the failure pressure prediction

Suspension effect poses a big threat to the integrity and safety of corroded pipelines. In this work, a finite element (FE) based multi-physics field coupling model was developed to determine the mechano-electrochemical (M-E) interaction at an external corrosion defect on a suspended X100 steel pipe and predict its failure pressure. Theoretical calculations were used for model validation. Parameter effects including the defect location on the pipe, geometry of the defect, suspension length and pipe burial depth were determined. Results demonstared that, generally, the M-E effect at corrosion defect caused an increased stress concentration and anodic current density (i.e., corrosion rate), decreasing the failure pressure of the pipeline. The effect became more apparent when the pipe was in suspension. Both the stress and the anodic current density at the corrosion defect were dependent on the defect geometry, especially the defect depth. When the depth was up to 40% of pipe wall thickness, the von Mises stress exceeded the yield stress of the steel, causing local plastic deformation. A critical defect length of 20Dt (D is the outer diameter of the pipe and t is pipe wall thickness) existed, below which the von Mises stress and the anodic current density at the corrosion defect increased with increased defect length. When the defect length exceeded the critical value, the effect was not obvious. An increased suspension length of the pipe would elevate the local stress and anodic current density at the corrosion defect, reducing the failure pressure of the pipe. A critical pipe burial depth of 2.5 m was identified, exceeding which the failure pressure of the pipe decreased rapidly with the increased burial depth. When the burial depth was smaller than 2.5 m, the effect was marginal. The location of the corrosion defect on the pipe did not affect the local stress, anodic current density and failure pressure at an appreciable level, and could be ignored in defect assessment on suspended pipelines.

Modeling of mechano-electrochemical interaction between circumferentially aligned corrosion defects on pipeline under axial tensile stresses

Defect assessment on oil/gas pipelines has been used for fitness-for-service determination. However, the mechano-electrochemical (M-E) interaction of adjacent corrosion defects is usually ignored. In this work, a finite element-based model was developed to determine the M-E interaction between adjacent, circumferentially aligned corrosion defects on an X46 steel pipe, which has been widely servicing in West Canada, under axial tensile stresses, simulating the stressing condition induced by pipe-soil interaction. Distributions of von Mises stress, corrosion potential and anodic current density at the corrosion defects were determined. A new criterion is proposed to define the threshold condition that a mutual M-E interaction exists between adjacent circumferential corrosion defects, i.e., the ratio of the anodic current density at the middle of two defects to the anodic current density of uncorroded area on the pipe. For corrosion defects with a width of 0.025πD, 0.05πD and 0.1πD (where D is the pipe outer diameter), the critical circumferential spacing between them is 0.08πD, 0.09πD and 0.09πD, respectively, exceeding which a mutual interaction between the defects is negligible.

Mesoscale Elucidation of Electrodeposition in All-Solid-State Lithium Batteries

Lithium metal anodes, owing to their theoretical promise have been considered decisive towards the development of next-generation battery systems with higher power and energy densities. Compared to the liquid counterparts, solid electrolytes proffer enhanced safety and dendrite suppression features due to the non-flammability and mechanical stiffness. However, the electrodeposition dynamics at a solid-solid interface is quite intricate, involving coupled transport, mechanical and kinetic processes, which are closely related to the interfacial heterogeneities. Furthermore, the mechanical properties of the solid electrolyte, lithium metal and externally applied pressure influence the mechano-electrochemical interaction and hence the interfacial stability. In this work, a mechanistic understanding of the mesoscale underpinnings in the electrodeposition stability at solid-solid interfaces for all-solid-state lithium batteries will be presented.

Assessment by finite element modelling of the mechano-electrochemical interaction at double-ellipsoidal corrosion defect with varied inclinations on pipelines

In this work, a 3-dimensional finite element model was developed to assess the double-ellipsoidal corrosion defect on an X100 steel pipe exposed to a near-neutral pH solution, where the double-ellipsoidal defect is more representative than the usually used ellipsoid of the realistic defects generated on the pipelines. Results confirm that the axial lengths of the two ellipsoidal defects affect the local stress and anodic current density distributions, and the effect depends on the inclination of the defect on the pipeline. When the primary axis of the corrosion defect is perpendicular to the axial direction of the pipeline, the maximum stress and anodic current density happen at the defect’s deepest site, which is not necessarily the defect center. The reduced ratio of the axial lengths of the two ellipsoids, i.e., the increased difference of the axial lengths, remarkably increases the local stress concentration and anodic current density at the deepest site of the defect, making it the location of the fastest corrosion growth. When the corrosion defect is parallel to the axial direction of the pipeline, the maximum stress and anodic current density is always located at the center of the defect. The reduction in the axial length ratio does not obviously affect the stress and anodic current density.

Modelling of mechano-electrochemical interaction at overlapped corrosion defects and the implication on pipeline failure prediction

Defect assessment is essential at determination of fitness-for-service of pipelines. While various codes and methods have been developed, none of them focuses on overlapped corrosion defects, especially the investigation of local mechanical-chemical interaction at the overlapped defects. In this work, a finite element-based multi-physics one-way coupling model was developed to simulate and determine the mechano-electrochemical (M-E) interaction at overlapped corrosion defects on an X46 steel pipeline. It is found that the presence of overlapped corrosion defects results in a local stress concentration and enhanced M-E interaction effect on corrosion defect growth. The maximum stress always generates at the corner of the bottom defect. The enhanced M-E interaction causes an accelerated corrosion at the bottom defect, resulting in the rapid defect growth to cause pipeline leaking. The geometry of corrosion defects, especially the defect depth and length, affects local stress concentration and the M-E interaction. With the increasing length and depth of either top or bottom corrosion defects, the overall stress level increases, but the effect is more apparent at the bottom defect. Similarly, the increased M-E interaction due to the increasing length and depth of the corrosion defects results in a more accelerated corrosion at the bottom defect than the top one.

Sodiation Driven Mechano-Electrochemical Interaction in Alloy Electrodes

The abundance of alkaline sodium (Na) is promising toward achieving a better, cheaper and more efficient energy storage system for renewable energy integration into the electric grid. However, the intercalation-based anode materials of Na-ion battery are inadequate in storing bulky Na ions which raises the concern about efficient reversibility. Desirable alternatives are alloy-based anode material such as tin (Sn), which has relatively high theoretical capacity of 847 mAh/g (for complete conversion of Na15Sn4). However, rapid volume expansion, which strains basic Sn skeletons, coupled with more frequent and extreme noxious events linked to electrolyte decomposition exacerbates the Na-Sn cycling properties and deteriorate the reversibility. The goal of this study to is to wade through different combinations of binders and electrolytes and extract kinetic and transport properties of Sn based Na-ion chemistry and to elucidate mechano-electrochemical underpinnings thereof.

Investigation by numerical modeling of the mechano-electrochemical interaction of circumferentially aligned corrosion defects on pipelines

In this work, a finite element based multi-physics field coupling model was developed to investigate the mechano-electrochemical (M-E) interaction between adjacent, circumferentially aligned corrosion defects on an X46 steel pipeline. The M-E effect existing between the defects results in a high local stress concentration, a negative corrosion potential and a large anodic current density at the defect adjacency, contributing to an increased corrosion of the pipeline steel in service environments. At increased internal pressures, local stress concentration and plasticity occur primarily at the corrosion defects, while the effect on the adjacent area between the defects is slight. With the increase of the defect spacing, the interaction between the defects disappear, and the defects can be treated separately. The increased internal pressure caused a shift of corrosion potential more negatively and a more rapid increase of the anodic current density at the corrosion defects than the adjacent area. The ratio of the anodic current density at the middle of the defect adjacency to that of the uncorroded region is used as to define the separation of adjacent corrosion defects which can be considered as non-interacting. The critical ratio depends on the defect geometry under a given internal pressure.

Modelling of mechano-electrochemical interaction of multiple longitudinally aligned corrosion defects on oil/gas pipelines

Assessment of corrosion defects and their effect on integrity of oil/gas pipelines are critical to the burst strength capability and safe operation of pipeline systems. In this work, a 3-dimensional finite element-based model was developed to investigate the mechano-electrochemical (M-E) interaction of multiple, longitudinally aligned corrosion defects on an X46 steel pipeline in a soil solution. A multi-physics field coupling technique was employed to derive the distributions of stress, strain, corrosion potential and anodic current density at the defects. For multiple corrosion defects, a critical spacing exists, below which there is an interaction between them to enhance the local corrosion. From this work, this value is between 100 mm and 150 mm. The maximum interacting spacing increases as the defect length increases. As the defect spacing reduces, there is a strong interaction between them, resulting in a high plastic stress at the defects. Under the identical defect spacing, the hoop stress condition causes an enhanced E-C interaction between adjacent corrosion defects, while the effect due to the uniaxial stress is ignorable. The interaction between multiple corrosion defects exists not only in the mechanical stress field, but also in the electrochemical corrosion field. An increase of the defect length, while keeping its depth fixed, enhances the local stress at the defects, shifts the corrosion potential negatively, and increases the anodic current density at both the defect and the adjacent area.