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The research related to subsea inspection, and the prediction of corrosion is a challenging task, and the progress in this area is continuously generating exciting new developments that may be used in subsea inspection. Wall thickness monitoring is an important tool to control and predict corrosion, such as on platforms for the infrastructure of floating offshore wind power production. This study shows the results obtained in marine environments. For this experiment, a steel plate equipped with ultrasound transducers was placed in seawater to corrode naturally. The sensor test setup consisted of 15 ultrasound transducers and 1 temperature sensor, which were installed in the cassette. The data acquisition system was based on a standard industrial computer with software written in Python and MATLAB. The ultrasound signals were collected at regular intervals and processed to calculate the instantaneous wall thickness. The progress of corrosion was evaluated by trend plots of wall thickness versus time, and the change in shape of the ultrasonic back wall reflection waveform measured by each sensor. [ABSTRACT FROM AUTHOR]

Ultrasonic thickness measurement of mechanical structures is one of the most popular and commonly used nondestructive methods for various kinds of process control and corrosion monitoring. With ultrasonic propagation speed being temperature-dependent, the thickness measurement can be performed reliably only when the thermal profile is completely known. Most conventional techniques assume the temperature of the test structure is uniform and at room temperature across its thickness. Such assumptions may lead to large errors in the thickness measurement, especially when there are significant temperature variations across the thickness. State-of-the-art techniques use external temperature measurements or implement iterative methods to compensate for the unknown thermal profiles. However, such techniques produce unsatisfactory results when the heat distribution is complex or varies rapidly with time. In this work, we propose a two-sensors technique, using both compressive and shear excitations, with a non-iterative rapid data processing method for accurate thickness measurement under arbitrary time-variant thermal profile. The independent behavior of shear and compressive waves is used to formulate a real-time thickness estimation technique. The developed technique is experimentally validated on a steel plate with fixed acoustic sensors. Test results show that the error in thickness estimation can be reduced by up to 98% compared to conventional thickness gauging methods. [ABSTRACT FROM AUTHOR]

Mapping corrosion depths along pipeline sections using guided-wave-based tomographic methods is a challenging task. Accurate defect sizing depends heavily on the precision of the forward model in guided wave tomography. This model is fitted to measured data using inversion techniques. This study evaluates the effectiveness of a recursive extrapolation scheme for tomography applications and full waveform inversion. It employs a table-driven approach, with precomputed extrapolation operators stored across a spectrum of wavenumbers. This enables fast modelling for extensive pipe sections, approaching the speed of ray tracing while accurately handling complex velocity models within the full frequency band. This ensures an accurate representation of diffraction phenomena. The study examines the assumptions underlying the extrapolation approach, namely, the negligible reflection and conversion of modes at defects. In our tomography approach, we intend to use multiple wave modes— A 0 , S 0 , and S H 1 —and helical paths. The acoustic extrapolation method is validated through numerical studies for different wave modes, solving the 3D elastodynamic wave equation. Comparison with an experimentally measured single-mode wavefield from an aluminium plate with an artificial defect reveals good agreement. [ABSTRACT FROM AUTHOR]

This paper presents the most typical corrosion mechanisms occurring in the petroleum industry. The methods of corrosion monitoring are described for particular corrosion mechanisms. The field and scope of the application of given corrosion-monitoring methods are provided in detail. The main advantages and disadvantages of particular methods are highlighted. Measurement difficulties and obstacles are identified and widely discussed based on actual results. Presented information will allow the corrosion personnel in refineries to extract more reliable data from corrosion-monitoring systems. [ABSTRACT FROM AUTHOR]

Corrosion under insulation (CUI) is a form of corrosion typically occurring on steel pipes and vessels covered with thermal insulation. CUI is a critical issue in petrochemical and refining industry leading to significant financial losses and severe environmental hazards. State‐of‐the art CUI monitoring system consisting of wireless loggers with flexible resistometric sensors is used to assess the effect of insulation material, position, and presence of a defect on the actual corrosivity toward carbon steel under alternating condensation conditions. All three considered factors together with the climatic parameters and presence of corrosion products are important for the CUI process. Most complex is the role of the insulation material as the properties inhibiting corrosion under intact insulation may be linked to a worse insulating ability. Because of the high sensitivity and immediate response of the sensors, the technique can be applied for timely CUI detection of insulated pipelines in both industrial facilities and laboratory studies. [ABSTRACT FROM AUTHOR]

Corrosion and scaling in metal pipelines are the major issues in the exploitation of geothermal sources. Geothermal fluids are complex mixtures consisting of dissolved gases and high-salinity solutions. This creates very aggressive environments primarily due to the high concentrations of carbon dioxide (CO2), hydrogen sulfide (H2S), chlorides, and other chemical species. Besides, the high temperature of the brines also increases corrosion rates, which can lead to failures related to stress and fatigue corrosion. On the other hand, reinjection of cooled brine exiting the heat exchanger favors the onset of scaling, since the chemicals dissolved in geothermal waters may tend to precipitate promoting inorganic depositions on the casing. Corrosion and scaling phenomena are difficult to detect visually or monitor continuously. Standard techniques based on pH, temperature pressure, electrical resistance measurements, chemistry composition, and physical properties are habitually applied as indirect methods for corrosion rate control. These methods, however, lack enough robustness for accurate and reliable measuring of the corrosion behavior of materials. To address this issue, a novel system has been proposed for the continuous monitoring of corrosion degradation caused by the effect of the geothermal brines. The present work aims to design, develop, and validate a dedicated electrochemical-based test system for online and onsite monitoring of the corrosion rate and scaling growth occurring on different materials exposed to real operating conditions. This system uses non-standard methods based on electrochemical impedance spectroscopy (EIS) to obtain quantitative data related to the material quality. It can be used to track the condition of the pipeline, reducing the operation and maintenance (O&M) costs and shutdown times. By providing early corrosion rate data, this system allows the prediction of failures in critical units of the plant. [ABSTRACT FROM AUTHOR]

Corrosion monitoring of reinforced or prestressed concrete structures has become increasingly important in recent years. Areas of application include components that are no longer accessible after completion or where potential field measurements cannot be carried out due to existing coatings. Corrosion monitoring can also be used to monitor the progress of corrosion in corroding systems, e.g. to prove the success of repair measures according to repair principle 8 in accordance with EN 1504‐9 or repair method 8.3 in accordance with the DIBt repair guideline. It also could be used to prove the functionality of cathodic corrosion protection systems in accordance with ISO 12696. Despite the increasing importance of corrosion monitoring, no guidelines or recommendations existed until 2018. This gap was closed by the English version of specification B12, "Corrosion Monitoring of Reinforced and Prestressed Concrete Structures," of the German Society for Non‐Destructive Testing, which was published in 2021. This article introduces specification B12 by explaining the basic measurement principles and illustrating the potential of corrosion monitoring in new and existing buildings. [ABSTRACT FROM AUTHOR]

The corrosion of reinforced concrete (RC) is one of the most serious durability problems in civil engineering structures, and the corrosion detection of internal reinforcements is an important basis for structural durability assessment. In this paper, the appropriate frequency required to cause excitation signals in the specimen is first analyzed by means of frequency dispersion curves. Subsequently, the effectiveness of five damage indexes (DIs) is discussed using random corrosion in finite elements. Finally, guided ultrasonic wave (GUW) tests are conducted on reinforcement and RC specimens at different corrosion degrees, and the test results are verified using a theoretical corrosion model. The results show that the larger the covered thickness is at the same frequency, the higher the modal order of the GUW in the frequency dispersion curve is, and the smaller the group velocity is. The SAD is the most sensitive to the corrosion state of the reinforcement compared with the other DIs, and it shows a linear increasing trend with the increase in the corrosion degree of the reinforcement. The SAD values of the RC specimens showed a three-stage change with the increase in the corrosion time, and the time until the appearance of corrosion cracks was increased with the increase in the covered thickness. It can be seen that increasing the covered thickness is an effective method to delay the time until the appearance of corrosion cracks in RC specimens. [ABSTRACT FROM AUTHOR]

Ultrasonic thickness measurement of mechanical structures is one of the most popular and commonly used nondestructive methods for various kinds of process control and corrosion monitoring. With ultrasonic propagation speed being temperature-dependent, the thickness measurement can be performed reliably only when the thermal profile is completely known. Most conventional techniques assume the temperature of the test structure is uniform and at room temperature across its thickness. Such assumptions may lead to large errors in the thickness measurement, especially when there are significant temperature variations across the thickness. State-of-the-art techniques use external temperature measurements or implement iterative methods to compensate for the unknown thermal profiles. However, such techniques produce unsatisfactory results when the heat distribution is complex or varies rapidly with time. In this work, we propose a two-sensors technique, using both compressive and shear excitations, with a non-iterative rapid data processing method for accurate thickness measurement under arbitrary time-variant thermal profile. The independent behavior of shear and compressive waves is used to formulate a real-time thickness estimation technique. The developed technique is experimentally validated on a steel plate with fixed acoustic sensors. Test results show that the error in thickness estimation can be reduced by up to 98% compared to conventional thickness gauging methods.

Since the electrochemically integrated multi-electrode array, often referred to as the wire beam electrode, was initially developed for corrosion studies in 1990s, remarkable progresses have been made in its applications for probing and monitoring various forms of localised corrosion that are difficult-to-measure by conventional methods. This paper provides a brief overview of diverse and innovative applications of variously designed and constructed electrode array probes for measuring localised corrosion under complex environmental conditions with particular focus on the discussion of challenges and obstacles that prevent wider applications of electrode arrays. Discussion on future perspectives have included suggestions on the innovative design and fabrication of multi-scale, three-dimensional, complex shaped and patterned electrode arrays for simulating microstructural features of heterogeneous alloys and thoughts on the future integration of corrosion monitoring data and data analytics, machine learning and artificial intelligence for future prediction, modelling and prevention of corrosion in industrial applications. [ABSTRACT FROM AUTHOR]

The evaluation of the corrosion wear rate was carried out using the Norsok Standart M-506 method for oilfield production tubing in Belarus. The method is based on a model that takes into account the speed of the gas-liquid flow, its pH, the volumetric flow rate of water, oil, gas, pressure, temperature, immersion depth, pH, density and viscosity of these media, and diameter and wall thickness of tubing. A feature of the model is the consideration of the friction of the gas-liquid flow on the walls of the tubing and the resulting shear stresses near them, which allows taking into account the corrosion-mechanical component of the metal degradation process of the tubing. The characteristics of well media and operating conditions of equipment in fields are given. Empirical coefficients of the considered model for typical conditions of Belarusian oil fields have been determined and a predictive calculation of the corrosion rate of 32Mn1A tube steel strength group N80 (Q) of the API Specification 5CT has been carried out. Data on actual values of corrosion wear of tubing from more than 100 production wells have been collected. The results indicate a high convergence of calculated and actual data. The adapted Norsok Standart M-506 method of predicting corrosion wear is recommended for use at oil fields in Belarus. It is shown how the proposed approach can be extended to other oil-bearing regions. [ABSTRACT FROM AUTHOR]

Reinforced Concrete Structures (RCS) are a fundamental part of a country's civil infrastructure. However, RCSs are often affected by rebar corrosion, which poses a major problem because it reduces their service life. The traditionally used inspection and management methods applied to RCSs are poorly operative. Structural Health Monitoring and Management (SHMM) by means of embedded sensors to analyse corrosion in RCSs is an emerging alternative, but one that still involves different challenges. Examples of SHMM include INESSCOM (Integrated Sensor Network for Smart Corrosion Monitoring), a tool that has already been implemented in different real-life cases. Nevertheless, work continues to upgrade it. To do so, the authors of this work consider implementing a new measurement procedure to identify the triggering agent of the corrosion process by analysing the double-layer capacitance of the sensors' responses. This study was carried out on reinforced concrete specimens exposed for 18 months to different atmospheres. The results demonstrate the proposed measurement protocol and the multivariate analysis can differentiate the factor that triggers corrosion (chlorides or carbonation), even when the corrosion kinetics are similar. Data were validated by principal component analysis (PCA) and by the visual inspection of samples and rebars at the end of the study. [ABSTRACT FROM AUTHOR]

There is a great importance in investigating and measuring microbial corrosion in the cooling tower of thermal power plants, especially in the case of open cycles. Moreover, this issue becomes more important in the situation where the source of water supply for cooling tower is river or sea water. In this research, the cooling tower water for Ramin Power Plant, which is supplied from the Karun River, is examined as a point of of microbial growth. For this purpose, microbial tests including TBC (general test) and specific bacteria tests such as APB, FP, IRB, NRB, Aero, SRB and TRB, physicochemical tests (conductivity, salinity, pH, turbidity) and the amount anions and cations, are carried out in the water sample of the cooling tower. In the TBC test, the approximate number of bacterial colonies is 107 cfu/ml, which is in a very heavy range. The results of APB and IRB test indicate the value is much higher than the permissible limit and the presence of Aero bacteria. On the other hand, in the analysis of anion and cation, sulfate and chlorine species have a very high concentration of more than 1000 ppm. Therefore, to deal with microbial factors, and as a solution in the first priority, the method of chlorination with water shock is recommended. The second priority includes the general method based on oxidizers such as ozonation and bromination. Selective removal of sulfate and nitrate ions is suggested as the third priority solution due to the high concentration of these ions and the intense activities of SRB and NRB bacteria.

Mapping corrosion depths along pipeline sections using guided-wave-based tomographic methods is a challenging task. Accurate defect sizing depends heavily on the precision of the forward model in guided wave tomography. This model is fitted to measured data using inversion techniques. This study evaluates the effectiveness of a recursive extrapolation scheme for tomography applications and full waveform inversion. It employs a table-driven approach, with precomputed extrapolation operators stored across a spectrum of wavenumbers. This enables fast modelling for extensive pipe sections, approaching the speed of ray tracing while accurately handling complex velocity models within the full frequency band. This ensures an accurate representation of diffraction phenomena. The study examines the assumptions underlying the extrapolation approach, namely, the negligible reflection and conversion of modes at defects. In our tomography approach, we intend to use multiple wave modes—A0, S0, and SH1—and helical paths. The acoustic extrapolation method is validated through numerical studies for different wave modes, solving the 3D elastodynamic wave equation. Comparison with an experimentally measured single-mode wavefield from an aluminium plate with an artificial defect reveals good agreement.

This paper presents the most typical corrosion mechanisms occurring in the petroleum industry. The methods of corrosion monitoring are described for particular corrosion mechanisms. The field and scope of the application of given corrosion-monitoring methods are provided in detail. The main advantages and disadvantages of particular methods are highlighted. Measurement difficulties and obstacles are identified and widely discussed based on actual results. Presented information will allow the corrosion personnel in refineries to extract more reliable data from corrosion-monitoring systems.

Abstract Interculturally, corrosion has been counted as one of the most expensive factors toward the retrogression of concrete and metallic structures resulting in huge monetary losses and unanticipated loss of life. To a large extent, corrosion-related catastrophes can be avoided by having the ability to monitor corrosion before structural integrity is jeopardized. This paper critically reviews the various accustomed electrochemical techniques utilized for corrosion monitoring in terms of their definition, timeline, experimental set-up, advantages, and shortcomings. Additionally, literature exploiting these techniques as their corrosion detection technique has been focused on here. Furthermore, a comparison between recently reported methods has been made to provide better insights into the research progress in this arena. [ABSTRACT FROM AUTHOR]

The assessment of infrastructure conditions is at present a topic of great interest and importance, as well as great challenge. This paper presents a case study of the Samuel De Champlain Bridge (Montreal, QB, Canada), an outstanding stay cable bridge equipped with a comprehensive monitoring system (SHM). Among other SHM features, particular attention was paid to implementation of a strategic corrosion monitoring system. This paper intends to describe the concept design, implementation and data interpretation. Here corrosion sensors have been embedded during construction stage to monitor long term evolution of key electro‐chemical parameters for controlling deterioration of materials. Furthermore, these sensors measure stray current interference generated from the rail system that can cause corrosion. In both cases, abnormal values would warn the owner of the associated increased risk of corrosion. This gives them the possibility to take corrective measures to protect the structure before corrosion becomes a serious threat. [ABSTRACT FROM AUTHOR]

Corrosion of steel in concrete is a complex process with many factors influencing its kinetics. Especially under on‐site condition, the prediction of corrosion rates is a challenge since many influencing factors such as the temperature change constantly. The whole corrosion process is the concert of three sub‐processes: (i) the anodic reaction rate, (ii) the cathodic reaction rate and (iii) the electrolytic conductivity of the concrete. Each of the processes show temperature dependency and existing corrosion monitoring systems record either data to evaluate part of the processes or the resulting corrosion rate. For service life estimates, prediction of corrosion rates is necessary. Consequently, the knowledge on the temperature effect on the corrosion rate is crucial, especially in view of rising temperatures due to climate change. This paper presents an overview on the existing knowledge on the temperature dependency on the corrosion rates; highlights the analysis of temperature data and provides guidance for service life prediction. [ABSTRACT FROM AUTHOR]

Corrosion and scaling in metal pipelines are the major issues in the exploitation of geothermal sources. Geothermal fluids are complex mixtures consisting of dissolved gases and high-salinity solutions. This creates very aggressive environments primarily due to the high concentrations of carbon dioxide (CO2), hydrogen sulfide (H2S), chlorides, and other chemical species. Besides, the high temperature of the brines also increases corrosion rates, which can lead to failures related to stress and fatigue corrosion. On the other hand, reinjection of cooled brine exiting the heat exchanger favors the onset of scaling, since the chemicals dissolved in geothermal waters may tend to precipitate promoting inorganic depositions on the casing. Corrosion and scaling phenomena are difficult to detect visually or monitor continuously. Standard techniques based on pH, temperature pressure, electrical resistance measurements, chemistry composition, and physical properties are habitually applied as indirect methods for corrosion rate control. These methods, however, lack enough robustness for accurate and reliable measuring of the corrosion behavior of materials. To address this issue, a novel system has been proposed for the continuous monitoring of corrosion degradation caused by the effect of the geothermal brines. The present work aims to design, develop, and validate a dedicated electrochemical-based test system for online and onsite monitoring of the corrosion rate and scaling growth occurring on different materials exposed to real operating conditions. This system uses non-standard methods based on electrochemical impedance spectroscopy (EIS) to obtain quantitative data related to the material quality. It can be used to track the condition of the pipeline, reducing the operation and maintenance (O&M) costs and shutdown times. By providing early corrosion rate data, this system allows the prediction of failures in critical units of the plant.

Bacterial biocementation has been shown to have the unique capability of healing cracks in concrete. However, there is a concern that the materials used in biocement may cause corrosion. This paper reports the performance of bacterially healed reinforced concrete when exposed to chloride-induced reinforcement corrosion. Cracks in reinforced concrete specimens were healed using two different calcium sources. After healing, the samples were subjected to 3.5% sodium chloride exposure to salt water for 120 days. The state of corrosion was assessed through standard electrochemical techniques such as half-cell and linear polarization methods as well as ultrasonic-guided waves. After the exposure period, the bars were extracted from concrete, and mass loss and tensile tests were conducted. It was found that electrochemical measurements indicated corrosion activity in the cracked specimens, but the uncracked specimen did not indicate corrosion during the entire exposure period. The presence of electrolytes in the healing fluid seems to have influenced the electrochemical measurements and gave a misleading indication of corrosion. The ultrasonic-guided waves that assess both effects of corrosion, loss of metal and bar-concrete interfacial debonding, were found to realistically assess the state of corrosion in all the samples. The rate of corrosion had slowed down significantly as a result of healing. [ABSTRACT FROM AUTHOR]

Corrosion under disbonded coatings (CUDC) remains a major unsolved issue and a prime risk to underground steel structures such as buried gas pipelines. CUDC could not be effectively mitigated by conventional cathodic protection (CP) or be detected through usual inspection and survey technologies due to CP shielding. This article provides a brief review of recent progresses made through laboratory and field probing of CUDC and its influence factors. Discussions on CUDC processes and mechanisms are made based on results from an extensive laboratory and field-testing program using electrode array-based corrosion probes. It is shown that CUDC is affected not only by well-known factors such as the CP level, but also by coating disbondment geometry and soil conditions especially the seasonal dry-wet changes in soil saturation status. These findings have led to improved understanding of CUDC, and could lead to the development of better CUDC mitigation and control methods. [ABSTRACT FROM AUTHOR]

Corrosion induced thickness loss in metallic structures is a common and crucial problem in multiple industries. Therefore, it is important to accurately monitor the corrosion amount of the structure. Traditional corrosion monitoring methods are mainly based on electrochemical methods, and most of them are unable to quantify the corrosion amount. In our previous work, a new type of corrosion sensing mechanism based on the electromechanical impedance instrumented circular piezoelectric-metal transducer was proposed, in which the peak frequencies in the conductance signatures decrease linearly with the increase of the corrosion induced thickness loss. However, only the uniform corrosion with even metal thickness decrease was considered in the previous study. In this paper, the capability of the proposed sensing mechanism for the quantification and prediction of pitting corrosion was investigated using one-dimensional convolutional neural networks (1D CNN). Finite element modeling of the pitting corrosion was performed and the probability distribution of the corrosion pits was considered. In the experimental setup, corrosion pits were generated on the corrosion sensor using mechanical drilling. The 1D CNN was adopted to explore the regression relationship between the EMI signatures of the sensor and the mass loss induced by pitting corrosion. The results show that the proposed method has achieved high accuracy in the quantitative prediction of pitting corrosion. This paper lays the technical foundation for real-time and quantitative monitoring of pitting corrosion for metallic structures. [ABSTRACT FROM AUTHOR]

Based on high-stress characteristics of prestressed anchor cables, this paper develops an axial-distributed testing method to test corrosion damage of prestressed anchor cables. The positioning accuracy and corrosion range of an axial-distributed optical fiber sensor is studied, and its mathematical model between corrosion mass loss and axial fiber strain is established. The experimental results show that the fiber strain from an axial-distributed sensor enables one to reflect the corrosion rate along a prestressed anchor. Moreover, it has a greater sensitivity when an anchored cable has a higher stress. The mathematical model between corrosion mass loss and axial fiber strain is determined to be ε = 4723.64 ρ + 2592.95 . The corrosion location along the anchor cable is characterized by axial fiber strain. Therefore, this work provides an insight for cable corrosion. [ABSTRACT FROM AUTHOR]

Electromagnetic techniques are widely employed for corrosion detection, and their performance for inspection of corrosion is well established. However, limited work is carried out on the development and reliability of smart corrosion monitoring devices for tracking internal or buried thickness loss due to corrosion remotely. A novel smart magnetic corrosion transducer is developed for long-term monitoring of thickness loss due to corrosion at critical locations. The reliability of the transducer is enhanced by using a dissimilar active redundancy approach. The improved corrosion monitor has been tested in the ambient environment for seven months to evaluate the stability against environmental factors and degradation. The monitor is found to show great sensitivity to detect defects due to corrosion. Detection of anomalous patterns in the time series data received from the monitors is accomplished by using Pearson's correlation coefficient. The critical component of the monitor is identified at the end of the test. Research findings reveal that, compared to the existing corrosion monitoring techniques in the industry, the detection and isolation of faulty sensor features introduced in this study can contribute to reliable monitoring of thickness loss due to corrosion in ferromagnetic structures over an extended period of time. [ABSTRACT FROM AUTHOR]

Globally, corrosion is the costliest cause of the deterioration of metallic and concrete structures, leading to significant financial losses and unexpected loss of life. Therefore, corrosion monitoring is vital to the assessment of structures' residual performance and for the identification of pathologies in early stages for the predictive maintenance of facilities. However, the high price tag on available corrosion monitoring systems leads to their exclusive use for structural health monitoring applications, especially for atmospheric corrosion detection in civil structures. In this paper a systematic literature review is provided on the state-of-the-art electrochemical methods and physical methods used so far for corrosion monitoring compatible with low-cost sensors and data acquisition devices for metallic and concrete structures. In addition, special attention is paid to the use of these devices for corrosion monitoring and detection for in situ applications in different industries. This analysis demonstrates the possible applications of low-cost sensors in the corrosion monitoring sector. In addition, this study provides scholars with preferred techniques and the most common microcontrollers, such as Arduino, to overcome the corrosion monitoring difficulties in the construction industry. [ABSTRACT FROM AUTHOR]

The use of fibers in Reinforced Concrete (RC) elements changes their cracking pattern, leading to narrower and more closely spaced cracks. In addition, the presence of fibers can improve the steel‐to‐concrete bond behavior reducing the steel‐to‐concrete interface damage after cracking. Cracks and steel‐to‐concrete interface damage work like paths, for aggressive agents, to reach the rebar in cracking elements, reducing the initiation period of the corrosion process, and favoring the corrosion at the intersection between cracks and reinforcement. In this context, this article discusses an experimental program on tension ties mechanically cracked and exposed to a chloride‐rich environment with the purpose to check and eventually adequate the typical electrochemical measurements, used in the case of RC elements, for Steel Fiber Reinforced Concrete (SFRC). Adjustments related to degradation morphology and interference of steel fibers are proposed and used on Fiber Reinforced Concrete (FRC) elements for monitoring the influence of cracks and fibers on corrosion propagation. Finally, these proposed modifications were checked and validated against the results obtained by monitoring SFRC beams in the cracked stage. [ABSTRACT FROM AUTHOR]

The corrosion of reinforced concrete (RC) is one of the most serious durability problems in civil engineering structures, and the corrosion detection of internal reinforcements is an important basis for structural durability assessment. In this paper, the appropriate frequency required to cause excitation signals in the specimen is first analyzed by means of frequency dispersion curves. Subsequently, the effectiveness of five damage indexes (DIs) is discussed using random corrosion in finite elements. Finally, guided ultrasonic wave (GUW) tests are conducted on reinforcement and RC specimens at different corrosion degrees, and the test results are verified using a theoretical corrosion model. The results show that the larger the covered thickness is at the same frequency, the higher the modal order of the GUW in the frequency dispersion curve is, and the smaller the group velocity is. The SAD is the most sensitive to the corrosion state of the reinforcement compared with the other DIs, and it shows a linear increasing trend with the increase in the corrosion degree of the reinforcement. The SAD values of the RC specimens showed a three-stage change with the increase in the corrosion time, and the time until the appearance of corrosion cracks was increased with the increase in the covered thickness. It can be seen that increasing the covered thickness is an effective method to delay the time until the appearance of corrosion cracks in RC specimens.

Atmospheric corrosion monitoring and evaluation are important means for studying the mechanism and behavior of atmospheric corrosion of metals. In view of the long cycle, cumbersome process, and poor data quality of the traditional outdoor hanging method, an innovative atmospheric corrosion data monitoring system has been designed to detect atmospheric environment data and metal corrosion data on site, and display the detection data of the equipment’s service location to users in real-time in the form of a “dynamic corrosion map”. This can provide a differentiated design for the anti-corrosion of important equipment such as power grid transmission and transformation engineering components Provide effective data support for engineering life prediction and operation and maintenance. At present, the system has been piloted and promoted in some network provinces, achieving good social and economic benefits.

Water distribution systems at KGHM S.A. are of great importance for the efficient production of copper and environmental protection. For failures leading to perforation and leakage, the corrosion processes are responsible. This paper aims to assess corrosion on the basis of the analysis of the exposure of the Hydrotechnical Plant pipelines. To this end, the system of transfer and deposition of post-flotation waste as well as the circulation of industrial water in the process of copper ore enrichment are described. Water sources as well as inflows and outflows in the water system are indicated; corrosion hazards are determined. Water is obtained from mines; it is often contaminated during the copper ore mining process. The chemical analysis of industrial (technological) water and sludge water resulting from the sedimentation of post-flotation waste showed a high concentration of inorganic salts which are responsible for the corrosive processes. Furthermore, tests were carried out to determine the corrosion rate.Additionally, possible methods to reduce corrosion have been proposed, i.e., a corrosion monitoring system has been described as a tool for reducing production interruptions and environmental pollution.

The protective behaviour of ZrO2-3%molY2O3 sol–gel coatings, deposited with an immersion coating technique on 9Cr-1Mo P91 steel, was evaluated with corrosion monitoring sensors using the electrochemical impedance spectroscopy technique. The tests were carried out in contact with solar salt at 500 °C for a maximum of 2000 h. The results showed the highly protective behaviour of the coating, with the corrosion process in the coated system being controlled by the diffusion of charged particles through the protective layer. The coating acts by limiting the transport of ions and slowing down the corrosive process. The system allowed a reduction in the corrosion rate of uncoated P91 steel. The estimated corrosion rate of 22.62 μm·year−1 is lower than that accepted for in-service operations. The proposed ZrO2-3%molY2O3 sol–gel coatings are an option to mitigate the corrosion processes caused by the molten salts in concentrated solar power plants. [ABSTRACT FROM AUTHOR]

Concrete structures are considered as durable construction material, but corrosion of the embedded steel reinforcement occurs under chloride exposure as concrete has porous properties. Herein, a cyclic drying–wetting test was performed for two years using saltwater to accelerate steel corrosion in a reinforced concrete (RC) member. The open-circuit potential (OCP) was measured using a newly developed and replaceable agar sensor. The corrosion potential was measured considering the chloride concentration, water-to-cement (w/c) ratio, and cover depth at three levels. Furthermore, its relationships with influential parameters were evaluated using averaged OCP results. The measured OCP showed a linear relationship with the cover depth, and this tendency was more distinct with increasing retention period and higher chloride concentration. For the highest w/c ratio (0.6), values below −100 mV were monitored after only six months regardless of the cover depth, and values below the critical potential level (−450 mV) were evaluated at lower cover depths (30 and 45 mm). The results of regression analysis considering the exposure environment showed a clear relationship in the case of high chloride concentration (7.0%). A linear relationship between cover depth and OCP was derived with a reasonable determination coefficient ranging from 0.614 to 0.771. [ABSTRACT FROM AUTHOR]

A moving electrochemical probe technique is developed for probing coating damages on underground pipelines installed by horizontal directional drilling (HDD) and for assessing the efficiency of cathodic protection (CP) through measuring local polarisation currents and local electrochemical impedance spectroscopy (EIS). The capability and accuracy of the probe in detecting coating defects have been evaluated, and compared with current techniques, using a simulated HDD pipe in a borehole. Results show that the probe is able to detect the locations of coating defects over the HDD pipe and that the capacitance of coating defects calculated from EIS data is a rather accurate parameter for defect size determination. The probe has also been used to apply local CP over coating defects for enhancing local corrosion protection. Preliminary field testing on a section of simulated HDD pipe has also shown reasonable accuracy of the probe in determining coating defect locations and sizes. [ABSTRACT FROM AUTHOR]

The conventional way of studying corrosion in marine environments is by installing corrosion coupons. Instead, this paper presents an experimental field study using an unattended corrosion sensor developed on the basis of ultrasound (US) technology to assess the thickness loss caused by general atmospheric corrosion on land close to the sea (coastal region). The system described here uses FPGA, low-power microcontroller, analog front-end devices in the sensor node, and a Beaglebone black wireless board for posting data to a server. The overall system is small, operates at low power, and was deployed at Gran Canaria to detect the thickness loss of an S355 steel sample and consequently estimate the corrosion rate. This experiment aims to demonstrate the system's viability in marine environments and its potential to monitor corrosion in offshore wind turbines. In a day, the system takes four sets of measurements in 6 hour intervals, and each set consists of 5 consecutive measurements. Over the course of 5 months, the proposed experiment allowed for us to continuously monitor the corrosion rate in an equivalent corrosion process to an average thickness loss rate of 0.134 mm/year. [ABSTRACT FROM AUTHOR]

The influence of liquid aggressive medium on a polyurethane paint coating (PC) is studied by the method of digital speckle pattern interferometry. For this purpose, we developed an experimental installation based on the Twyman–Green interferometer for the corrosion monitoring of PC. The installation was used for recording and subsequent processing of the difference patterns of speckle interferograms (SI) of the coating surface under the action of a 3% NaCl solution for 7, 14, and 21 days. It is shown that the difference patterns of SI can be used to analyze the time dependences of the deformed state of the PC surface and the growth rates of corrosion defects and exfoliations. [ABSTRACT FROM AUTHOR]

Quantitative monitoring of steel corrosion plays a crucial role in evaluating structural safety and predicting structural performance. The electromechanical impedance (EMI) technique has already emerged for uniform corrosion monitoring. This study explores its potential for pitting corrosion monitoring. Specifically, two EMI-based sensor designs were proposed, namely the cylinder and the tube structures. Finite element models were developed to analyze the influence of the pit's location, morphology parameters, as well as the random distribution of multiple pits, on the conductance peak frequency of sensors. The computer numerical controlled processes were employed to create random pits on sensors. Experimental results revealed that different distributions of pits correspond to distinct conductance peak frequencies, even with the same mass loss. Additionally, the tubular sensor exhibited reduced sensitivity to pits distribution compared to the cylindrical sensor. This is beneficial for accurately predicting mass loss induced by random pitting. This paper enhances the capability of EMI-based sensors for quantitatively monitoring pitting corrosion by focusing on structural design aspects. [Display omitted] • The quantitative corrosion monitoring capability of EMI-based sensors under pitting corrosion was investigated. • The finite element models of the sensors with random pitting corrosion were established and validated by experiment. • The prediction accuracy of the sensor for mass loss was improved by optimizing its structure. [ABSTRACT FROM AUTHOR]

The multifunctional optimization of traditional coating materials represents a pivotal strategy for expanding their applicability. Herein, we introduce terbium as an electrolyte additive during the plasma electrolytic oxidation process for alumina coating fabrication, aimed at refining both the porous structure and overall performance of the coating. Notably, the core reaction concludes in just 10 min. The resultant terbium-enhanced alumina coating exhibits a more homogeneous and denser surface structure, showcasing superior corrosion resistance compared to conventional coatings. Additionally, the incorporation of terbium endows the coating with anticipated photoluminescent properties. This advantageous combination of corrosion resistance and photoluminescence makes the coating ideal for protecting metallic materials from corrosion and shows great potential for monitoring corrosion in extreme conditions on-site. The incorporation of Tb not only significantly enhances the corrosion resistance of the PEO coating but also imparts photoluminescent properties to it. This dual functionality holds promising potential for the coating's application in in-situ corrosion monitoring. [Display omitted] • A luminescent coating was grown in-situ on AA 1060 substrate through plasma electrolytic oxidation. • The core reaction involved in the synthesis process of the coating took no more than 10 min. • The introduction of Tb improved the microstructure and corrosion resistance of the PEO coating. • The Tb-reinforced coating shows its potential applications in in-situ corrosion monitoring. [ABSTRACT FROM AUTHOR]

Reinforced Concrete Structures (RCS) are a fundamental part of a country’s civil infrastructure. However, RCSs are often affected by rebar corrosion, which poses a major problem because it reduces their service life. The traditionally used inspection and management methods applied to RCSs are poorly operative. Structural Health Monitoring and Management (SHMM) by means of embedded sensors to analyse corrosion in RCSs is an emerging alternative, but one that still involves different challenges. Examples of SHMM include INESSCOM (Integrated Sensor Network for Smart Corrosion Monitoring), a tool that has already been implemented in different real-life cases. Nevertheless, work continues to upgrade it. To do so, the authors of this work consider implementing a new measurement procedure to identify the triggering agent of the corrosion process by analysing the double-layer capacitance of the sensors’ responses. This study was carried out on reinforced concrete specimens exposed for 18 months to different atmospheres. The results demonstrate the proposed measurement protocol and the multivariate analysis can differentiate the factor that triggers corrosion (chlorides or carbonation), even when the corrosion kinetics are similar. Data were validated by principal component analysis (PCA) and by the visual inspection of samples and rebars at the end of the study.

Monitoring the corrosion of steel rebars is paramount to ensuring the safety and serviceability of reinforced concrete (RC) structures. Conventional electro-chemical techniques can provide an overall estimate of the extent of corrosion. However, a detailed account of the extent of corrosion would help in understanding the residual strength of corroding RC structures. A passive wave-based technique such as acoustic emissions can identify the location of corrosion but always requires the presence of transducers on the structure. In active wave-based techniques, the structure is excited through a pulse excitation and their subsequent response to this excitation is measured. Thus, for active techniques, the transducers need not always be present in the structure. In guided wave ultrasonics, the excitation pulse is imparted through a waveguide to determine the state of corrosion. This technique relies on parameters such as time of flight or attenuation of the incident signal to predict the state of corrosion. These parameters can be susceptible to uncertainties in the transducer of ultrasonic coupling. In the present study, concrete specimens with embedded steel bars have been subjected to accelerated corrosion. They have been monitored with a combination of active and passive techniques. The received signals are analyzed through a modified S-Transform-based time-frequency approach to obtain a range of modes that propagate through the specimen. The changes in the modal composition of the guided wave signals due to corrosion are parameterized and correlated to various stages of corrosion. A holistic understanding of the stages of corrosion is developed by the inclusion of acoustic emission hits to guided wave parameters. Based on the Guided Wave Ultrasonics and acoustic emission parameters, corrosion has been classified into Initiation, Intermediate, and Advanced. Subsequently, destructive tests have been performed to measure the residual strength of the corroded bars. Thus, this paper presents a novel proof of concept study for monitoring corrosion with Guided Wave Ultrasonics and acoustic emissions. [ABSTRACT FROM AUTHOR]

The sulfuric acid attack is a common form of degradation of reinforced concrete in contact with industrial wastewater, mine water, acid rain, or in sewage treatment stations. In this work, new pH-sensitive IrOx electrodes were developed for monitoring the pH inside mortar or concrete. To test their ability, the pH sensors were embedded in mortar samples at different depths and the samples were exposed to sulfuric acid solution. In another set of experiments, iron wires were placed at the same depths inside similar mortar samples and their corrosion was monitored as the acid attacked the mortar. Severe acid attack led to cement dissolution and formation of gypsum. The new pH sensors succeeded in measuring the pH changes inside the mortars. The pH gradient, from the high acid environment to the high alkaline mortar interior, occurred in a narrow region. Corrosion of the iron electrodes started only when the acidic solution was in their close vicinity. [ABSTRACT FROM AUTHOR]

Various corrosion monitoring methods are used in order to monitor the corrosion state of gas object equipment. The main parameter for evaluation is corrosion rate. In addition to the main gravimetric method, two more determination methods are used: an electrical resistance ER-method, and linear polarization resistance LPR-method. In the course of testing ER- and LPR-probes the possibility of their use in corrosive-aggressive conditions of hydrocarbon processing facilities, as well as the influence of various factors on the data obtained for corrosion rate are evaluated. [ABSTRACT FROM AUTHOR]

Reinforcement corrosion is a major culprit that undermines the service life of reinforced concrete (RC) structures. It costs billions of dollars each year in the US alone and negatively impacts safety, reliability, resilience, and environmental performance of RC infrastructure. Corrosion monitoring of steel rebar is critical to provide early warning of deficiency, enable timely and effective maintenance strategies, and prevent catastrophes associated with premature failure of RC structures. To improve corrosion monitoring in the engineering practice, this work comprehensively reviews the state of the art of five major types of techniques, that is, electrochemical sensors, optical fiber sensors, sensors based on elastic wave methods, sensing based on electromagnetic methods, and untouched sensors. Each type of technique is systematically divided into sub-categories based on the sensing principle and key characteristics. For each sensor type, its maturity, application range, and the problems that hinder its application are discussed, aimed to provide guidance in selecting the appropriate sensors for specific engineering applications. This work concludes with an overview of opportunities and challenges, including the following six aspects for future research: spatial resolution, sensitivity, and measurement range; reliability and interpretation of the measurement; sensor selection based on three corrosion stages of steel rebar; long-term stability and service life; cost-efficiency of the sensing system; and monitoring of existing structure. [ABSTRACT FROM AUTHOR]

Collecting data from corrosion sensors in reinforced concrete structures demands intensive labor work, therefore measurements are only performed occasionally. A low-cost Wireless Sensor Network/Node (WSN) will eliminate the need for manual work and allow for continuous measurements if needed. For a distributed WSN over a large area, a concerning issue is how to power such devices. This paper, therefore, investigates the use of a reinforced concrete battery for powering WSNs. Results obtained from a real-world immersed tunnel, which has hundreds of electrochemical based corrosion sensors embedded into the reinforced concrete structure, shows that sufficient energy can be harvested from the sensors, to perform wireless transmission of corrosion data to a base-station. With an open circuit potential of 975 mV, the maximum harvested output power is $12.4~\mu \text{W}$ , while the minimum measured output power is $1~\mu \text{W}$. The results also show that $8.82~\mu \text{W}$ , with an open circuit potential of 727 mV, can be directly harvested from the reinforcement steel itself. Due to the fact that the steel volume can work as a large battery anode, a longer lifetime for the energy source is expected. Furthermore, we show that the harvested energy from the corrosion sensors will induce a galvanic corrosion rate of only $3.7~\mu \text{m}$ /year, when transmitting the corrosion data once a month. This indicates that there is no risk to the structural integrity when using this energy source. [ABSTRACT FROM AUTHOR]

Offshore wind turbines operating in harsh marine environments are at risk of corrosion. Thickness loss and perforation caused by corrosion can lead to component failure or structure collapse. An environmental test setup was constructed to simulate various marine corrosion zones. Several experimental studies were conducted on Q355 steel, commonly used in offshore wind turbines. The mass loss and electrochemical properties of the steel specimens were analyzed, including electrochemical impedance spectra and polarization curves. The results indicate that corrosion remains stable in the immersion and tidal zones, whereas corrosion in the splash zone is the most severe, with a corrosion rate as high as 0.70 mm/a. A significant macroscopic corrosion cell effect was observed on the vertical steel strip, accelerating corrosion in the splash zone and at the low tide line. The corrosion product compositions and corrosion morphology of each corrosion zone were characterized and analyzed. Furthermore, a corrosion monitoring sensor based on electromechanical impedance was proposed. A prediction model for the mass loss rate of vertical steel strips was developed based on the conductance peak frequency. This study elucidates the corrosion evolution of wind turbine structural steel and proposes a comprehensive steel corrosion monitoring solution. • The corrosion evolution of Q355 steel under various corrosion zones was elucidated. • Macroscopic corrosion cell effects on vertical steel strips were revealed. • A quantitative corrosion monitoring method for offshore wind turbines was proposed. [ABSTRACT FROM AUTHOR]

Corrosion probes designed based on an electrochemically integrated multi-electrode array have been evaluated in an extensive field and laboratory evaluation program in order to identify their capabilities in visualizing and probing critical forms of buried steel corrosion, in particular, corrosion under disbonded coatings (CDC) and stray current corrosion. Probes of different designs were installed in the pipeline field to simulate and measure the influence of stray currents and cathodic protection (CP) deficiency on corrosion as well as CDC. Accelerated laboratory tests were also performed, where electrochemical measurements can be taken more frequently and the corrosion condition can be more precisely controlled. Corrosion patterns and rates were calculated with a sensitivity in the order of 10 µm/year. Testing results correlated reasonably well with long-term pipeline corrosion behavior. On the other hand, single element electrical resistance probes were not able to simulate or measure CDC occurring on pipeline surfaces. These results demonstrate the capability and some unique advantages of the electrode array probes for monitoring pipeline corrosion.

Based on high-stress characteristics of prestressed anchor cables, this paper develops an axial-distributed testing method to test corrosion damage of prestressed anchor cables. The positioning accuracy and corrosion range of an axial-distributed optical fiber sensor is studied, and its mathematical model between corrosion mass loss and axial fiber strain is established. The experimental results show that the fiber strain from an axial-distributed sensor enables one to reflect the corrosion rate along a prestressed anchor. Moreover, it has a greater sensitivity when an anchored cable has a higher stress. The mathematical model between corrosion mass loss and axial fiber strain is determined to be ε=4723.64ρ+2592.95. The corrosion location along the anchor cable is characterized by axial fiber strain. Therefore, this work provides an insight for cable corrosion.

Electromagnetic techniques are widely employed for corrosion detection, and their performance for inspection of corrosion is well established. However, limited work is carried out on the development and reliability of smart corrosion monitoring devices for tracking internal or buried thickness loss due to corrosion remotely. A novel smart magnetic corrosion transducer is developed for long-term monitoring of thickness loss due to corrosion at critical locations. The reliability of the transducer is enhanced by using a dissimilar active redundancy approach. The improved corrosion monitor has been tested in the ambient environment for seven months to evaluate the stability against environmental factors and degradation. The monitor is found to show great sensitivity to detect defects due to corrosion. Detection of anomalous patterns in the time series data received from the monitors is accomplished by using Pearson’s correlation coefficient. The critical component of the monitor is identified at the end of the test. Research findings reveal that, compared to the existing corrosion monitoring techniques in the industry, the detection and isolation of faulty sensor features introduced in this study can contribute to reliable monitoring of thickness loss due to corrosion in ferromagnetic structures over an extended period of time.

This article proposes a new technique of monitoring neutral axis positions and deflection of Reinforced Concrete (RC) beam during corrosion of steel reinforcement using macro-strain measurements of distributed long-gauge sensors. A different group of distributed long-gauge Packaged Carbon Fiber Line (PCFL) sensors with self-compensation and effective packaging system is installed on the compression and tension fibers of the concrete surface and steel reinforcements of RC beam to verify the proposed method experimentally. An accelerated corrosion method utilizing a salt solution and the constant current was used to achieve the required corrosion levels. The estimated deflection measured by the developed method is compared with the results using Linear Variable Displacement Transducer (LVDTs). It has been demonstrated that long-gauge PCFL sensors could provide the same accuracy. The distributed measured strains were utilized to evaluate the deterioration of the structure's health with the advance of corrosion. Based on corrosion monitoring experimental results, it can be confirmed that using distributed PCFL sensors mounted on steel reinforcements or concrete surface, the locations and progress of the damage with corrosion time can be detected effectively. The maximum error in the estimated deflection from PCFL sensors mounted on the concrete surface compared to the LVDTs before the onset and after 24 h of accelerated corrosion was 0.5% and 2.5%, respectively. [ABSTRACT FROM AUTHOR]