Monitoring Of Corrosion Damage Research Articles

Acoustic emission testing for multi-scale assessment of reinforcement corrosion in concrete structures

Degradation of existing structures poses a serious threat to our built environment. The aim of this paper is to investigate the use of acoustic emission monitoring in degradation assessment of existing structures, focusing specifically on corrosion damage detection in reinforced concrete structures. Reinforcement corrosion is seen as one of the most significant and costly degradation mechanisms that impact the durability and structural safety of our built infrastructure and Modern heritage buildings. The paper presents a multi-scale experimental approach, from material to structure, focusing on two challenges: (i) monitoring the evolution of the corrosion process itself and the consequential concrete cracking during accelerated corrosion, and (ii) identifying the different AE sources in this complex process. The application of AE testing for rebar corrosion monitoring is investigated on various sample types and scales under accelerated conditions in a lab environment, and from on-site monitoring of a concrete girder bridge. Results show that the developed test setups, data filtering and processing procedures substantially improve AE-based corrosion damage monitoring, and provide a valuable contribution towards on-site application.

Steel corrosion damage monitoring in reinforced concrete structures with the acoustic emission technique: A review

• An in‐depth literature review and discussion on AE‐based corrosion monitoring in RC is presented. • Consistency of parameter‐ and signal‐based AE methods for corrosion monitoring is analyzed. • AE‐based condition assessment of corroded RC elements during load testing is discussed. • An overview on availability of AE data sets for corrosion tests in lab and in‐situ is presented. • Research challenges for in‐situ monitoring of corrosion damage in RC structures are discussed. Corrosion is a major issue in construction and infrastructure management, giving rise to high repair costs, safety concerns and structural failures. Especially reinforcement corrosion in concrete structures is a complex issue. As degradation starts internally, visual inspection lacks efficiency in early stages of the corrosion process. Acoustic Emission (AE) monitoring provides major advantages as this technique enables to detect internal damage in an early stage. However, the use of AE monitoring also comes with certain challenges. The aim of this paper is to review appropriate protocols for AE-based reinforced concrete (RC) corrosion monitoring based on an overview of reported lab experiments, highlighting challenges and pitfalls, and to provide a solid basis for extension of the research focus towards on-site AE-based corrosion monitoring in RC structures. Therefore, this paper firstly discusses AE monitoring during (accelerated) corrosion tests, including methods for data analysis and best-practice protocols. Secondly, application of the AE technique for condition assessment of corroded RC elements during load testing is discussed. Thirdly, an overview is presented of reported on-site AE monitoring studies on corroding RC structures. The paper concludes with a discussion and future research challenges, especially towards on-site monitoring of existing RC structures.

Degradation Monitoring in Reinforced Concrete with 3D Localization of Rebar Corrosion and Related Concrete Cracking

Corrosion of the reinforcement is a major degradation mechanism affecting durability and safety of reinforced concrete (RC) structures. As the corrosion process starts internally, it can take years before visual damage can be noticed on the surface, resulting in an overall degraded condition and leading to large financial costs for maintenance and repair. The acoustic emission (AE) technique enables the continuous monitoring of the progress of internal cracking in a non-invasive way. However, as RC is a heterogeneous material, reliable damage detection and localization remains challenging. This paper presents extensive experimental research aiming at localizing internal damage in RC during the corrosion process. Results of corrosion damage monitoring with AE are presented and validated on three sample scales: small mortar samples (scale 1), RC prisms (scale 2), and RC beams (scale 3). For each scale, the corrosion process was accelerated by imposing a direct current. It is found that the AE technique can detect damage earlier than visual inspection. However, dedicated filtering is necessary to reliably localize AE events. Therefore, AE signals were filtered by a newly developed post-processing protocol which significantly improves the localization results. On the smallest scale, results were confirmed with 3D micro-CT imaging, whereas on scales 2 and 3, results were compared with surface crack width measurements and resulting rebar corrosion levels.

High-Frequency Guided Waves for Corrosion Thickness Loss Monitoring

Abstract Adverse environmental conditions result in corrosion during the life cycle of marine structures such as pipelines, offshore oil platforms, and ships. Generalized corrosion leading to the loss of wall thickness can cause the degradation of the integrity, strength, and load bearing capacity of the structure. Nondestructive detection and monitoring of corrosion damage in difficult to access areas can be achieved using high-frequency guided waves propagating along the structure. Using standard ultrasonic wedge transducers with single-sided access to the structure, specific high-frequency guided wave modes (overlap of both fundamental Lamb wave modes) were generated that penetrate through the complete thickness of the structure. The wave propagation and interference of the guided wave modes depend on the thickness of the structure and were measured using a noncontact laser interferometer. Numerical simulations using a two-dimensional finite element model were performed to visualize and predict the guided wave propagation and energy transfer across the plate thickness. During laboratory experiments, the wall thickness was reduced uniformly by milling of one steel plate specimen. In a second step, wall thickness reduction was induced using accelerated corrosion for two mild steel plates. The corrosion damage was monitored based on the effect on the wave propagation and interference (beating effect) of the Lamb wave modes in the frequency domain. Good agreement of the measured beatlengths with theoretical predictions was achieved, and the sensitivity of the methodology was ascertained, showing that high-frequency guided waves have the potential for corrosion damage monitoring at critical and difficult to access locations.

Guided ultrasonic wave tomography of a pipe bend exposed to environmental conditions: A long-term monitoring experiment

Continuous monitoring of corrosion damage in pipelines requires sensor systems that can achieve high precision (repeatability) to detect and size subtle wall thickness (WT) losses. In fact, corrosion typically progresses at a rate of 1 mm per year or less which poses very demanding performance requirements if the state of the pipe has to be assessed on a weekly or even monthly basis. Guided ultrasonic wave tomography (GUWT) has emerged as an attractive approach for continuous monitoring owing to its ability to map WT losses over an extended pipe section. This is possible because GUWT employs ultrasonic waves that are guided by the pipe wall to travel a large distance from the source transducer. Defects along the path of the guided wave cause a perturbation of the signal which is then interpreted by model-based inversion schemes to determine the WT loss. In addition to damage, there is a vast number of time-dependent operational and environmental (O & E) factors that can perturb the signal also when damage is not present. To achieve high precision, it is therefore essential that GUWT can detect the changes in the signal due to damage and suppress those caused by other benign factors such as temperature variations. Although numerous studies have been conducted to estimate the accuracy of various implementations of GUWT, precision has received less attention due to the challenges associated with reproducing realistic O & E conditions in the lab. This work focuses on the effect of temperature and presents the results of a continuous monitoring experiment conducted on a pipe bend kept outdoors and exposed to weather conditions for a period 21 months. It is shown that the pipe undergoes a relatively severe temperature cycling with typical daily peak-to-trough variations of 20∘C that cover the range from -15∘C to +51∘C as the seasons alternate. The effect of temperature is suppressed by exploiting the spatial diversity of array measurements and combining multiple datasets measured during the monitoring period. The maximum WT loss is estimated with high precision exhibiting a standard deviation not exceeding 0.4% of the nominal WT.

Corrosion issues in structural health monitoring of aircraft

Last couple of decades have seen significant progress in the paradigm of structural health monitoring (SHM) which is expected to provide enhancements in the levels of safety and mission readiness of an aircraft or a fleet of aircraft at an affordable cost. These developments comprise, broadly, (1) a diagnosis part which deals with detection of structural damage through various sensing technologies, (2) a prognosis part which attempts to forecast the performance with the current damage state under anticipated future loading environments and (3) a damage mitigation strategy for dealing with the identified damage. Much of the research and developmental effort on these three fronts has focused on mechanical damage such as cracks and similar flaws in metals and impact damage and delaminations in composites and on their growth under operational loads through processes such as fatigue. Relatively less attention has been devoted to problems of metal corrosion, which has been also a bothersome factor in ensuring structural integrity of airframe structures. This paper makes an attempt to highlight some of the issues that are being faced or may be faced while bringing in corrosion into the SHM framework for aircraft. Towards this objective, a review of the current state of the art on various aspects of monitoring of corrosion damage is presented. Beginning with the phenomenon of corrosion (especially in Al alloys) to identify parameters that may be helpful for its monitoring, the review covers important aspects of corrosion damage, sensing concepts and technologies. Five categories of techniques are described: (1) direct monitoring of corrosion damage, (2) monitoring the state of corrosion through coupons and surrogates through physical means, (3) electrochemical techniques, (4) monitoring the corrosivity of the environment as an indirect assessment of corrosion and (5) monitoring the degradation in corrosion prevention coatings as a means to infer underlying corrosion. A special subsection is devoted to use of optical fibres in corrosion sensing. Instances of actually using all such sensors in aircraft are briefly mentioned. An overall discussion of the current state of the art is provided. It is emphasised that corrosion sensing and monitoring are increasingly using developments in “smart technology”, such as smart coatings, thin-film technology, smart materials such as magneto-resistive and magneto-optical, smart polymers and microdevices fabrication. It is expected that the issues highlighted here will be of relevance not only for ageing aircraft but also for new aircraft under design or in operation.

An algebraic reconstruction imaging approach for corrosion damage monitoring of pipelines

In this paper, an algebraic reconstruction technique is presented for corrosion damage monitoring in steel pipes by using helical guided ultrasonic waves. To validate the proposed approach, numerical simulations as well as experimental tests were carried out. For the numerical simulations, a finite element model was created using ABAQUS software to simulate wave propagation in a steel pipe. The model simulates corrosion damage by reducing the thickness of the pipe in a selected location. Experimental tests were conducted on a steel pipe instrumented with a network of six low-profile piezoelectric transducers. Reconstructed images from both the numerical simulations and experimental tests accurately localized the simulated damages. These results suggest that the proposed imaging algorithm has the potential to be effectively used for continuous monitoring of pipelines.

Quantitative corrosion imaging of pipelines using multi helical guided ultrasonic waves

This paper presents a multi helical ultrasonic imaging approach for quantitative corrosion damage monitoring of cylindrical structures. The approach consists of two stages. First a multi helical ultrasonic imaging (MHUI) algorithm is used to provide qualitative images of the structure of interest. Then, an optimization problem is solved in order to obtain quantitative damage information, such as thickness map. Experimental tests are carried out on a steel pipe instrumented with six piezoelectric transducers to validate the proposed approach. Three thickness recesses are considered to simulate corrosion damage. The results show the efficiency of the proposed approach for quantifying corrosion location, area and remnant thickness.

J044031 SI-F法を用いた配管構造の減肉損傷モニタリングにおけるセンサ設置箇所の最適化検討([J04403]知的材料・構造システム(3))

J044031 SI-F法を用いた配管構造の減肉損傷モニタリングにおけるセンサ設置箇所の最適化検討([J04403]知的材料・構造システム(3))

Quantitative Corrosion Monitoring Using Wireless Electromechanical Impedance Measurements

This article presents an experimental study for wireless monitoring of corrosion damage that might frequently occur in metallic structures. A simple beam structure made from an aluminum alloy was selected for corrosion-monitoring testing and a small lead-zirconate-titanate (PZT) patch-type sensor was surface-mounted to the structure. To obtain an electromechanical impedance data at the PZT sensor, a wireless impedance sensor node that consists of a miniaturized impedance-measuring chip, a microprocessor, and a radio frequency (RF) telemetry was employed. Three different corrosion cases with a different corroded area were artificially inflicted on the beam structure using hydrochloric (HCI) acid, and the electromechanical impedance data were collected in sequence from the wireless impedance sensor node. To quantify the corroded area, the variations of the resonant frequency that represents structural dynamic information were continuously tracked during all the damage cases. Conclusively, it has been found that the amount of the resonant frequency shift got increased when the corroded area got increased. The above experimental results verified that the proposed approach using the amount of resonant frequency shift at the measured electromechanical impedance can be effectively utilized for quantitative analysis of the corroded area in metallic structures.

Evaluation of Methods for Detecting and Monitoring of Corrosion Damage in Risers

Offshore pipeline failure statistics have been collected for more than 30 years now and illustrate that the riser predominantly fails as a result of corrosion. The consistent wetting and drying in the splash zone combined with defects in the coatings are the usual contributors to the problem. Risers are inspected at some determined frequency and can be done by internal and external methods. Inspecting by either means brings into account caveats and limitations from the technology used as well as human factors. For example, external inspections can be inefficient and inaccurate with some tools missing defects in areas of coating disbondment. In addition, internal inspections sometimes create false positives and can miss defects. These inaccuracies in the technologies or the techniques used may miss defects that eventually lead to failure. On the other hand, using corrosion mapping and fitness-for-service (FFS) assessment from the data collected, along with the inherent conservatism of this data from limited measurement accuracy, may result in the premature replacement of risers. A literature search is being conducted to review existing riser inspection methods and identify candidate nondestructive methods for riser inspection. These methods should be capable of detecting and monitoring general corrosion, localized corrosion pitting, and stress-corrosion cracking (sulfide or hydrogen induced) as external or internal corrosion damage. Thus far, this search has found that assessing the remaining service life of aging risers is largely dependent on the accuracy of analyzing corrosion damage to the riser surface in the atmospheric, splash (tidal), submerged, and buried environmental zones. The accuracy of each technology was analyzed. The capabilities and limitations of each method/technique used for riser inspection are summarized. The investigation is focused on long- and short-range ultrasonic techniques used for initial screening and corrosion mapping. These techniques can be deployed to detect a significant reduction in wall thickness using guided and torsional waves or to map accurately a corrosion damage using single/multiple transducers and phased-array probes in manual or automated mode. A pulsed eddy-current technique that uses a stepped or pulsed input signal for the detection of corrosion areas under insulation (CUI) is also being evaluated. This allows the detection of wall-thinning areas in the riser without removing the outside coatings. In addition, it is found that filmless, real-time, and digital radiography can be used to find internal and external corrosion defects in an insulated splash zone while the riser remains in service. A survey of nondestructive evaluation (NDE) manufacturing companies, NDE inspection companies, and operating companies was completed to collect information about current instrumentation and inspection/operators’ experience for riser inspection. Examples of advanced riser inspection instrumentation and field results are included. The ability of the candidate technologies to be adapted to riser variations, the stage of standardization, and costs are also discussed.