Realistic Corrosion Research Articles

An investigation on the collapse pressure prediction of subsea pipelines with realistic corrosion defects

Subsea pipelines are widely used for oil and gas transportation, but they are susceptible to failure due to corrosion. Corrosion in pipelines typically results in defects of varying depths and complex shapes. The computational simulation through the finite element (FE) method is one of the most efficient and accurate tools for assessing the integrity of corroded subsea pipes by allowing the simulation of the nonlinear behavior and assessing the hydrostatic collapse. This paper evaluates the collapse response of subsea pipelines with realistic corrosion defects. The study uses the PIPEFLAW system - developed by the PADMEC (High-Performance Processing on Computational Mechanics) research group from UFPE - which integrates reliable tools for automatic FE model generation and performs nonlinear analyses. After validation based on the experimental tests available in the literature, the effect of realistic corrosion defects on the collapse pressure of subsea pipelines is analyzed in detail. The results are compared to results obtained using a semi-empirical method and numerical results obtained considering idealized FE models, i.e., constant-depth and elliptical-shaped corrosion defects. It is observed that the non-uniformity of defects is an important factor affecting the collapse response of pipes. In addition, the idealized geometry of the corrosion defects, especially when considering constant depth, leads to an excessively conservative prediction of the hydrostatic collapse.

Subset simulation based simplified approach for pipeline with multiple irregular corrosion defects in time-dependent reliability analysis

Pipeline system plays an important role in the natural gas and petroleum transportation, and it is widely employed in the engineering application. However, the pipeline system is subjected to corrosion given the industry environment condition, or soil condition when it is buried. In this case, it is important to assess the remaining life of corroded pipeline. Consequently, it is important to predict the failure probability considering the corrosion growth over time and operating pressure. Nevertheless, the prediction of failure probability in corroded pipeline in not an easy task, due to the fact that a realistic corrosion usually has an irregular geometry, especially, when multiple irregular corrosion is involved in the analysis. To simplify the problem, this work presents a simplified procedure for time-dependent reliability analysis to predict the failure probability in pipeline with multiple irregular corrosion defects, considering two failure modes, the burst and leak mode. The approach is based on Subset Simulation and Weighted Depth Difference method, where the multiple irregular corrosion is treated by a discretization procedure and a weighting coefficient is evaluated in every discretization points. Then, this weighting coefficient is introduced into burst pressure assessment, which is employed by burst failure mode limit state function. In this work, the corrosion growth is modelled by power function corrosion model, and initial corrosion depth is generated randomly. The Subset Simulation is employed to evaluate the failure probability, where the Markov Chain Monte Carlo is adopted to evaluate the conditional probability and Metropolis-Hasting algorithm is employed to solve the problem. Finally, several scenarios with single and multiple irregular corrosion defects are analyzed to demonstrate the effectiveness of presented procedure.

Numerical simulation of oil and gas pipeline corrosion based on single- or coupled-factor modeling: A critical review

Numerical simulation is an effective research approach to assess the condition and predict the remaining service life of process pipelines suffering corrosion hazards. This work comprises a critical review of 182 academic articles to analyze environmental factors affecting the pipeline corrosion process, basic numerical methods for corrosion simulation, and single- and coupled-factor numerical investigations. Numerical simulation of corroded pipelines could combine the electrochemical corrosion processes and structural characteristics of pipelines to obtain more accurate results. Multiphysics-based techniques have been successfully applied to simulate the evolution process of corroded pipelines affected by two or more coupled factors under stray current interference. Through integration with learning-based algorithms, predictive studies are conducted to assess the development of corrosion. The challenge for current research is that the remaining types of corrosion are difficult to describe by numerical methods. Opportunities are proposed to improve the pipeline corrosion simulation model to describe more corrosion types and realistic corrosion morphologies, including time-varying corrosion simulation, random field in the simulation, and microelectrochemical corrosion simulation.

Efficient numerical algorithms for assessing the mechanical performance of corroded offshore steel sheet piles

Deterioration of offshore steel sheet pile walls subjected to corrosion may significantly affect the structural performance under serviceability and failure. Most steel corrosion studies focused on the mechanism of reflecting the actual corrosion situations to establish a relatively realistic corrosion model. The mechanical performances of the material loss phenomenon in the offshore steel sheet piles are useful for assessing their in-service and life cycle conditions. In this paper, the general power corrosion model is adopted to reflect the changes in the material and section properties of the pile and combine with the p-y curve method to formulate a new pile element to consider the corrosion effect. The Updated-Lagrangian (UL) method and the newly-developed element formulations are integrated into a modified Newton-Raphson method to eliminate the repetitive modelling process when considering the varied mechanical properties under different corrosion levels. After verifying the accuracy of the present numerical method, parametric studies have been considered to explore the effects of the changes of the annual corrosion rates and the trends of corrosion progress on the offshore steel sheet piles. The annual corrosion rate in the immersion zone plays an important role in the mechanical performance of offshore structures in a marine environment.

A hybrid corrosion-structural model for simulating realistic corrosion topography of maritime structures

A multiscale multiphysics model has been developed coupling nonlinear structural behaviour and the corrosion kinetics. This study develops a hybrid mechano-electrochemical corrosion model using finite element method to evaluate long-term topography evolution on carbon steel stiffened plates for marine applications. A parametric study is performed on a stiffened plate (1.5 m × 0.95 m) with different localised corrosion locations (0.75 m × 0.045 m) at different load levels. Stress-based anodic and cathodic surfaces are defined using a level-set function to solve the transport equation, facilitated by the moving boundary technique. Key model insights show broad-pitted corrosion features with benching, closely resembling those found in actual ship inspections and/or surveys.

Advanced corrosion-rate model for comprehensive seismic fragility assessment of chloride affected RC bridges located in the coastal region of india

In this study, a methodology is being proposed for performing seismic fragility analysis of corrosion affected bridges located in the coastal region of India. The study performed adopting this advanced corrosion rate model capturing nonlinearity that necessitates pitting corrosion as a realistic corrosion degradation mechanism rather than conventional uniform corrosion. With the application of advanced corrosion model, a distinct improvement over seismic fragility assessment achieved due to its capability to capture nonlinearity in the overall process of corrosion transport. The proposed model exhibits the corrosion rate accelerates after initial cracking of the concrete cover until at a phase, when severe cracking occurs leading to spalling of concrete. Based on the current degradation mechanism, the study estimates the capacity limit states of deteriorating reinforced concrete (RC) T-girder bridges as well as the impact of bridge degradation on the seismic response assessed using nonlinear time history analysis (NLTHA). However, the NLTHA of the finite element bridge models performed considering erraticism about material properties, geometries, ground motions and corrosion degradation parameters such that the uncertainties associated with the bridge population could be realistically taken into account as per the basic corrosion mechanism. Comparisons are drawn with respect to general and pitting corrosion as well as the adverse effect of pitting corrosion on the bridge service life has been identified. Thus, the output of the seismic fragility analysis would indicate some useful information in understanding the nonlinear crack growth of bridge vulnerability in marine environment, such that proper maintenance strategies could be framed for adequate safety of the highway infrastructure system for its enhanced design life.

Multi-Method Approach to Assess the Corrosion Behavior of a Coated WE43 Mg Alloy

Developing appropriate and functional coatings for Mg alloys, such as WE43, in view of controlling the degradation rate in biodegradable applications, requires a realistic understanding of the corrosion processes. While conventional methods, such as electrochemical measurements, can already give a good estimation about the protectiveness of coatings, immersion tests are also required to simulate a more realistic corrosion scenario (i.e., open-circuit dissolution as a function of time). In the current study, immersion tests at pH 5 were performed in a solution composed of the inorganic Dulbecco’s Modified Eagle’s Medium constituents. For four different types of coatings on WE43, a combined experimental approach was introduced that compares the corrosion rates obtained by the different methods. The strengths and drawbacks of the methods, such as hydrogen evolution and ion release measurements, mass loss, and electrochemical tests, will be discussed. The different monitoring methods all have their advantages; thus, for a profound examination, multiple methods should be used in a complementary manner. For the evaluation of the corrosion protection ability of coated samples, the hydrogen evolution measurements may offer the most advantages.

The impact of corrosion-stress interactions on the topological features and ultimate strength of large-scale steel structures

Aged marine structural analysis often relies on simplified corrosion modelling. Empirical or statistical methods are used to predict a uniform thickness reduction over time. Although convenient, this approach cannot incorporate the corrosion evolution or the rough surfaces in the damaged area. This is fundamentally due to the lack of representation of the underlying corrosion mechanisms in service environments. To better understand how structural response changes based on corrosion under service loads, this paper presents a series of finite element analyses which consider the coupling relationship between the surface mechanical stresses and the resulting change of corrosion rate. The coupling provide complex corrosion-stress interaction depending on the experimental datasets. The quantification of this interaction is based on in situ experimental measurements of corrosion kinetics at different stress levels. The simulations show the stress effect results in the generation of more realistic corrosion patterns on the structural surface, based on a two-bay/two-span large-scale panel model subject to uniaxial compression. In addition, the incorporation of corrosion experiments allows the modelling of corrosion evolution based on physical observations instead of empirical assumptions. The irregular surface damage leads to a change in structural buckling mode, and up to 8% reduction in ultimate strength compared to models without considering the stress effect.

A finite element model for estimating time-dependent reliability of a corroded pipeline elbow

PurposeThe aim of this paper is to investigate the failure probability in an irregular area in pipeline (elbow) over its lifetime. The reliability analysis is performed by using of an enhanced first-order reliability method / second-order reliability method (FORM/SORM) and Monte Carlo simulation methods: a numerical model of a corroded pipeline elbow was developed by using finite element method; also, an empirical mechanical behavior model has been proposed. A numerical case with high, moderate and low corrosion rates was conducted to calculate the deferent reliability indexes. The found results can be used in an application case for managing an irregular area in pipeline lifetime. Hence, it is necessary to ensure a rigorous inspection for this part of a pipeline to avoid human and environmental disasters.Design/methodology/approachThe present paper deals a methodology for estimating time-dependent reliability of a corroded pipeline elbow. Firstly, a numerical model of corroded elbow is proposed by using the finite element method. A mechanical behavior under the corrosion defect in time is studied, and an empirical model was also developed.FindingsThe result of this paper can be summarized as: a mechanical characterization of the material was carried out experimentally. A numerical model of a corroded pipeline elbow was developed by using the finite element method. An empirical mechanical behavior model has been developed. The reliability of a corroding pipe elbow can be significantly affected by corrosion and residual stress. A proportional relationship has been found between probability of failure and corrosion rate. The yield stress and pressure service have an important sensitivity factor.Originality/valueAiming to help Algerian gas and oil companies' decision makers, the present paper illustrates a methodology for estimating time-dependent reliability of a corroded pipeline elbow over its lifetime using numerical models by applying the finite element method. Firstly, a numerical model of a corroded pipe elbow was developed and coupled with an empirical mechanical behavior model, which is also proposed. A probabilistic is then developed to provide realistic corrosion parameters and time modeling, leading to the real impact on the lifetime of an elbow zone in pipeline. The reliability indexes and probability of failure for various corrosion rates with and without issued residual stress are computed using Monte Carlo simulation and FORM.

Development of corrosion flaws for the production of realistic test specimens

Abstract To produce realistic test specimens with realistic flaws, it is necessary to develop appropriate procedure for corrosion flaw production. Tested specimens are made from steels commonly used in power plants, such as carbon steels, stainless steels and their dissimilar weldments. In this study, corrosion damage from NaCl water solution and NaCl water mist are compared. Specimens were tested with and without mechanical bending stress. The corrosion processes produced plane, pitting and galvanic corrosion. On dissimilar weldments galvanic corrosion was observed and resulted to the deepest corrosion damage. Deepest corrosion flaws were formed on welded samples. The corrosion rate was also affected by the solution flow in a contact with the specimens, which results in a corrosion-erosive wear. Produced flaws are suitable as natural crack initiators or as realistic corrosion flaws in test specimens.

Impact of corrosion product removal to depth of corrosion damage in weldment joint

Abstract Corrosion flaws in pipelines can caused severe financial losses and also can be dangerous for people. One of the most frequently damaged parts are dissimilar pipe welds. We would like to understand how corrosion process reacts on corrosion product removal. Outputs from experiment will be used for production of test specimens. For testing we chose standard dissimilar weldment used in Czech power plants. It is joint with 08Ch18N10T and 22K (GOST) steel. Joint is cut to 24 same specimens. There are exposed to flowing water solution of 5% NaCl. Half of the specimens are regularly mechanically cleaned. The joint is metallographically observed and parts with and without corrosion products are compared. Water salt solution increased pH from 7,25 to 7,86 during 31 days test and conductivity varies around 74 mS cm−1. Metallographic observation indicates that corrosion under corrosion products layer is locally speed up and causes pitting corrosion. Cleaned specimens indicate plane corrosion with lower depth. These results indicate that slag in pipeline could locally speed up corrosion depth penetration. On the other hand, solutions with abrasive particles (which can wipe out the corrosion product) will probably facilitate plane corrosion damage on pipeline walls. This test brings us another knowledge, how to simulate realistic corrosion damage for production of NDT qualification test pieces.

Characterization of corrosion morphologies from deteriorated underground cast iron water pipes

AbstractFollowing the completion of the Advanced Condition Assessment and Pipe Failure Prediction project in Australia, it has emerged that cast iron pipes normally experience corrosion damages extending over the large spatial area that resemble a patch, and structural failures are commonly associated with these patches. In this study, we defined a corrosion patch as a cluster of individual defects within or less than the one‐wall‐thickness distance of each other and conducted a morphometric study on patches from several deteriorated cast iron pipes. It was found that the size parameters, viz., the patch length, width, area, and volume potentially attain steady‐state progression over long‐term deterioration and are consistent with current understanding in underground corrosion. The rectangularity, convex deficiency, and solidity shape parameters were found to be related to each other and could be described by power‐law functions. Moreover, the analysis of two‐dimensional (D2D) and three dimensional (D3D) fractal dimension parameters revealed that they serve as useful proxies for different patch properties. In particular, the D3D revealed linear trends with the patch aspect ratio and an ability to delineate between failed and in‐service pipes. It is expected that the results from this study will serve as important baseline information for future works aiming to generate and implement realistic corrosion patches for pipe structural integrity analysis.

Reliability analysis of irregular zones in pipelines under both effects of corrosion and residual stress

In this work, both effects of corrosion and residual stress on the irregular zones of a pipeline is investigated. A finite element model of a corroded elbow area, butt welding area and flange area is proposed, coupled with usual residual stress models. The probabilistic is then developed to provide a realistic corrosion parameters and time modeling, leading to the real impact on the lifetime of a burred pipeline. The failure probability and reliability index of various corroded areas are computed by using Monte Carlo simulations. A numerical case study with three different corrosion rates (low, moderate and high corrosion rate) allows us to estimate the impact of various factors on the reliability of the corroded pipes. The obtaining result shows that it is necessary to ensure the inspection of the irregular areas in pipelines in order to better manage their lifetimes.

Ultrasonic Wave-Speed Diffraction Tomography With Undersampled Data Using Virtual Transducers

Ultrasonic diffraction tomography offers a way to achieve high-resolution imaging of the wave-speed map, and hence, has strong potential applications in medical diagnosis and nondestructive evaluation. Ideal images can be obtained with a complete array of sensors surrounding the scatterer, provided that the measurement data are fully sampled in space, obeying the Nyquist criterion. Spatial undersampling causes the image to be distorted and introduce unwanted circular artifacts. In this paper, we propose an iteration approach using virtual transducers to achieve high-resolution tomographic imaging with undersampled measurements. At each iteration stage, the extent constraint estimated from the shape of the object of interest is applied on the image space to obtain a regularized image, based on which the ultrasonic measurement data at virtual transducers are calculated using a forward model. The full data set composed of original and virtual measurements is then used for tomography in the next stage. A final image with sufficiently high resolution is obtained only after a few iterations. The new imaging method yields improvements in the robustness and accuracy of ultrasonic tomography with undersampled data. We present numerical results using complicated wave-speed maps from realistic corrosion profiles. In addition, an experiment using guided ultrasonic waves is performed to further evaluate the imaging method.

A non-uniform corrosion model and meso-scale fracture modelling of concrete

Corrosion-induced concrete cracking is a significant durability problem for reinforced concrete structures. Considerable research has been carried out in the last few decades to understand and model the expansion mechanism of the corrosion products around the reinforcing bar and simulate the cracking behaviour of the concrete cover. In this paper, a new corrosion model based on non-uniform corrosion expansion is formulated and validated against experimental data. A meso-scale fracture model, consisting of aggregates, cement paste/mortar and ITZ, is established for the cases of both middle and side reinforcing bars. Under the developed corrosion and concrete fracture model, the cracking phenomena of the concrete cover are accurately simulated. It has been found that the non-uniform corrosion model can be used to express the realistic corrosion rust progression around the reinforcing bar, with the best accuracy. It has also been found that some microcracks occur before they are connected to form the dominating discrete crack which usually appears on the concrete surface. Moreover, the effects of the corrosion variables, as well as other key material and geometric parameters, on surface cracking of concrete are investigated.

Progress in developing realistic corrosion models

The quality of life-cycle assessments and civil and structural engineering reliability analyses depends much on the quality of the models on which they are based. Models for loads and material properties are well-established. For structural or material deterioration, including corrosion, good quality models are still being developed. Empirical models exist but often have large uncertainty and extrapolation is problematic. High quality models must be based closely on fundamental scientific principles and observations and be calibrated to real-world data. This approach has been exploited for some years to develop corrosion models for steels in marine environments, including the use of data from field experiments and selected laboratory observations. This work is reviewed and the effect of various influencing factors described, including that of microbiological corrosion. The approach has been extended to cast iron, aluminium and copper-nickels. Two practical application examples are described.

Computational analysis of the early stage of cuprous oxide sulphidation: a top-down process

ABSTRACTThe initial steps of Cu2O sulphidation to Cu2S have been studied using plane-wave density functional theory at the PBE-D3+U level of sophistication. Surface adsorption and dissociation of H2S and H2O, as well as the replacement reaction of lattice oxygen with sulphur, have been investigated for the most stable (111) and (100) surface facets under oxygen-lean conditions. We find that the (100) surface is more susceptible to sulphidation than the (111) surface, promoting both H2S adsorption, dissociation and the continued oxygen–sulphur replacement. The results presented in this proceeding bridge previous results from high-vacuum experiments on ideal surface to more realistic corrosion conditions and set the grounds for future mechanistic studies. Potential implications on the long-term final disposal of spent nuclear fuel are discussed.This paper is part of a supplement on the 6th International Workshop on Long-Term Prediction of Corrosion Damage in Nuclear Waste Systems.

Bayesian approach for the reliability assessment of corroded interdependent pipe networks

Pipelines under corrosion are subject to various environment conditions, and consequently it becomes difficult to build realistic corrosion models. In the present work, a Bayesian methodology is proposed to allow for updating the corrosion model parameters according to the evolution of environmental conditions. For reliability assessment of dependent structures, Bayesian networks are used to provide interesting qualitative and quantitative description of the information in the system. The qualitative contribution lies in the modeling of complex system, composed by dependent pipelines, as a Bayesian network. The quantitative one lies in the evaluation of the dependencies between pipelines by the use of a new method for the generation of conditional probability tables. The effectiveness of Bayesian updating is illustrated through an application where the new reliability of degraded (corroded) pipe networks is assessed.

Simple and easy-operated method for filtering eco-friendly corrosion inhibitors

Purpose – The purpose of this paper was to find a simple and easy-operated method for filtering eco-friendly corrosion inhibitors. Design/methodology/approach – The molecular structures and atomic electronegativities of the four kinds of natural reagents, iota-Carrageenan, sodium alginate, sodium dodecanesulphonate (SDS) and sodium dodecylbenzene sulfonate were calculated by Gaussian and Natural Bond Orbital, and the corrosion inhibition rates were forecasted by the calculated results. Then, the realistic corrosion inhibition efficiency were confirmed by electrochemical impedance spectroscopy and potentiodynamic polarization tests in 3.5 Wt.% sodium chloride corrosive solutions. At the same time, the function of pefloxacin mesylate (PM) was explored in this paper polarization tests in 3.5 Wt.% sodium chloride corrosive solutions. Findings – Results showed that the order calculated by the chemical software was correct, and the corrosion inhibition of SDS was the best. Optimum addition of PM not only can reduce microbial corrosion but also can improve the corrosion inhibition by spatial cooperation. Practical implications – This method can be used to filter eco-friendly corrosion inhibitors quickly. PM can be also used to improve the corrosion inhibition rate of corrosion inhibitors. Originality/value – The present method to filter corrosion inhibitors was time-consuming, which needed lots of experiments to verify the corrosion inhibitive efficiency. The calculated method was simpler than others, which need complicated calculation process.

Prediction of Corrosion Processes on Weathering Steel Bridges

The paper describes the basic attributes of the new developed analytical method used for the calculation of corrosion losses on structural elements designed from weathering steels. The calculation takes into account the locality of the structure, type of the weathering steel, position and location of a surface in the structure and compliance with structural and maintenance requirements. The methodology for experimental testing of the realistic corrosion rates is introduced in this paper as well.