Low-cost technologies used in corrosion monitoring

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.The authors are indebted to the projects PID2021‐126405OB‐C31 and PID2021‐126405OB‐C32 funded by FEDER funds—A Way to Make Europe and Spanish Ministry of Economy and Com‐petitiveness MICIN/AEI/10.13039/501100011033/, project PID2019‐106555RB‐I00 and project IDEAS 2.14 from Ports 4.0. It should also be noted that funding for this research was provided for Seyed‐milad Komarizadehasl by the European Social Fund and the Spanish Agencia Estatal de Investi‐gación del Ministerio de Ciencia Innovación y Universidades, grant (PRE2018‐083238).Peer ReviewedPostprint (published version

Detection of reinforcement corrosion by an acoustic technique

Corrosion of reinforcing steel is a major serviceability issue with reinforced concrete structures, often resulting in significant section and bond loss. However, current non-destructive diagnostic techniques do not allow corrosion to be reliably detected at the very early stages of the process, before damage to the concrete occurs. This research describes the development of an Acoustic Emission (AE) technique as a practical tool for the early detection of corrosion of reinforcing steel embedded in concrete. The study falls into three main areas: (i) determining the influential material parameters of reinforced concrete that affect the magnitude of the acoustic emissions; (ii) investigating the influence of diurnal and seasonal temperature variations on corrosion rate and thus the rate of acoustic emissions; and (iii) developing a testing and evaluation procedure that combines the findings of the first two stages with existing knowledge about corrosion and deterioration of concrete structures. In the first phase of the research material parameters such as cover thickness, compressive strength and rebar diameter were investigated to ascertain the influence of varying these factors on the magnitude of AE Energy obtained per gram of steel loss. The experimental results confirmed that early age corrosion, verified by internal visual inspection and mass loss measurements, can be detected by AE before any external signs of cracking. Furthermore results show that compressive strength was the primary influential parameter, indicating an exponential, empirical relationship between compressive strength and AE Energy. An increase in temperature usually induces an increase in corrosion activity, which should be measurable using the AE technique. Consequently the influences of seasonal and diurnal temperature variations were investigated to determine their impact on undertaking AE measurements. This phase of the research demonstrated that seasonal variations in temperature impart a negligible influence on measured AE Energy. However measurement of AE Energy per hour followed trends in the diurnal temperature and corrosion rate evolution, these being in a state of constant flux. Therefore AE measurements of corrosion in reinforced concrete are more responsive to a change in temperature, and so corrosion rate, as opposed to a specific and constant corrosion rate. In the final phase practical experience with AE from site trials and laboratory work were coupled with leading research and existing knowledge of corrosion in concrete and structural deterioration, to develop a testing and evaluation procedure for on-site application. This rigorous procedure enables reliable corrosion measurements to be undertaken on reinforced concrete structures using AE technology and enabling an assessment of the rate of corrosion induced damage to be made. As far as the author is aware this is the first site testing procedure for detecting corrosion in reinforced concrete using AE. Future research in this area might involve more site testing with a view to improving accuracy and analysis of on-site data, underpinning the developed procedure

Techniques for In Situ Monitoring the Performance of Organic Coatings and Their Applicability to the Pre-Finished Steel Industry: A Review

A review is carried out in this paper into techniques that currently exist for, of have the potential to be used for, monitoring the performance of organic coating. Specific attention is paid to the applicability of each method to pre-finished steel used in the construction industry as these are rarely monitored in situ and their expected performance is often only estimated from lab-based accelerated corrosion testing. Monitoring could allow more accurate estimates of building cladding lifespan and required maintenance schedules; provide customers with active performance data; additionally, with a better understanding of performance, more appropriate coatings or coating weights could be selected for a construction project, offering economic benefits as part of smart building developments. An introduction to coatings, their use for corrosion protection, failure mechanisms, and relevant monitoring techniques is given before current assessment techniques are described in terms of their working principles. Examples of recent work are presented for the techniques that have been investigated for monitoring or directly relatable purposes. The review concludes that there are several good reasons why an optimum corrosion monitoring technology does not currently exist, however, promising research is emerging in the field of wireless and embedded sensor design which is providing optimistic results

Study of the initiation and propagation phases of chloride induced corrosion in reinforced concrete structures

Il est communément admis que la corrosion des aciers par les chlorures est la cause principale de la détérioration des structures en béton armé. L'objectif de cette thèse est de contribuer à l'amélioration de la compréhension de la corrosion induite par les chlorures dans le béton pendant la phase de transition entre l'initiation et la propagation et pendant la phase de propagation de la corrosion. Traditionnellement, la corrosion induite par les chlorures est initiée lorsque la teneur en chlorure atteint une valeur critique appelée seuil critique en chlorure ou Ccrit. Malgré de nombreuses recherches dans ce domaine, il n'existe toujours pas d'accord sur une méthode précise pour la détermination de la valeur seuil initiant la corrosion. Le premier objectif de ce travail était de développer un nouveau montage expérimental prenant en compte le caractère localisé de la corrosion initiée par les chlorures. Cette approche se basait sur une séparation physique entre l'anode contaminée par des chlorures et la cathode sans chlorure. Le protocole expérimental permettra de quantifier le courant de corrosion galvanique, permettant ainsi de déterminer, dans un deuxième temps, les valeurs de seuils critiques en chlorure. Le critère d'initiation de la corrosion était un courant de corrosion seuil défini comme un courant indépendant du rapport de surface cathode/anode et, par la suite, indépendant de la surface de l'acier passif. Ce critère a été considéré comme un contrôle anodique de la corrosion pendant la phase de transition de la phase d'initiation à la phase de propagation. Ce protocole d'essai a été appliqué à des formulations de mortier et de béton avec plusieurs types de liants (ciment CEM I, ciment CEM III et CEM I avec fumée de silice), différents rapports eau/liant, incorporant des barres d'acier HA torsadés avec différentes conditions de surface d'acier (tels que reçus, nettoyés chimiquement et nettoyé chimiquement puis oxydé avec humidité ou à haute température). Il a été constaté que le protocole expérimental est rapide et applicable à toutes les formulations. Les résultats expérimentaux permettent de comprendre l'influence du type de liant, du rapport E/L et de la porosité sur la sensibilité de l'acier à l'initiation de la corrosion induite par les chlorures. Il a été constaté que l'état de la surface de l'acier avait un effet global important sur l'initiation de la corrosion, mais cet effet dépend du type de liant utilisé. Plusieurs études de la littérature ont considéré que le déclenchement de la corrosion induite par les chlorures est sous contrôle anodique, ce qui pourrait signifier que la corrosion est contrôlée par les paramètres électrochimiques de l'acier. Les paramètres de l'acier passif peuvent être directement dérivés des mesures expérimentales grâce à l'état passif uniforme des barres d'armature. Cependant, en raison de la nature non uniforme de la corrosion induite par les chlorures dans le béton, il n'est pas possible d'obtenir expérimentalement de l'acier uniformément actif. Dans cette thèse, la détermination des propriétés électrochimiques de l'acier actif a été réalisée sur la base d'une modélisation numérique inverse se concentrant sur la dépendance de ces propriétés vis-à-vis de la contamination par les chlorures. Toutes les observations expérimentales associées à l'approche de modélisation numérique ont mis en évidence la dépendance des propriétés électrochimiques de l'acier actif sur la teneur en chlorure. Lorsqu'il s'agit de la corrosion par macro pile, il est crucial de prendre en compte la géométrie et la taille de la structure, y compris la distance mobilisable cathode-anode et le rapport surfacique cathode/anode. Dans ce travail, la distance mobilisable cathode-anode a été étudiée. Il a été constaté que le courant de corrosion par macro pile pouvait être fourni par des barreaux de cathode éloignés de l'anode, cette distance dépendant de la résistivité électrique de la structure. Ces résultats confirment l'hypothèse selon laquelle la corrosion dans la zone submergée avec un manque d'oxygène pourrait être due au couplage avec la zone cathodique dans les parties aérées de la structure et non nécessairement au phénomène de piqûre lié à la réduction de l'eau suite à un potentiel très négatif en zone submergée. La propagation de la corrosion est influencée par plusieurs paramètres comme la résistivité électrique connue, selon plusieurs études empiriques rapportées, par sa relation inversement proportionnelle à la vitesse de corrosion. Cette relation inversement proportionnelle entre le courant de macro pile et la résistivité a également été trouvée dans nos investigations expérimentales qui consistaient en une technique de permutation de cathode dans laquelle la même anode était connectée à deux cathodes différentes avec des résistivités électriques différentes. Enfin, il a été observé expérimentalement que l'acier dans des mortiers composés de taux de substitution élevés en laitier (80%) présentait un comportement particulier. Des potentiels fortement négatifs ont été mesurés malgré l'absence de chlorures, ce qui a été considéré comme une indication de l'absence d'oxygène à l'interface acier/mortier. On a supposé que ces potentiels négatifs étaient associés à la réaction de réduction de l'eau, alors qu'en présence d'oxygène, la réaction est la réduction de l'oxygène. Lors du couplage galvanique entre des cathodes fortement négatives et des anodes contaminées par des chlorures, les courants de corrosion étaient, dans certains cas, négatifs puis positifs. Le changement de signe du courant mesuré a toujours été associé à l'augmentation des potentiels des cathodes à des valeurs plus positives. Ce qui a été considérée comme une indication de l'oxydation du fer avec une polarisation importante pour un courant faible et donc une réduction rapide du courant galvanique. En effet à un potentiel aussi faible, la couche passive a disparu mais la polarisation anodique de la cathode a conduit à la fois à l'augmentation du potentiel de la cathode et à la reformation de la couche passive. Ces déclarations ne sont que des hypothèses et nécessitent des investigations supplémentaires. Enfin, une partie du travail de thèse a été consacrée au développement d'un modèle empirique simplifié pour l'ingénieur utilisé pour la prédiction de la durée de propagation de la corrosion induite par les chlorures dans les structures en béton armé non fissurées. Ce modèle était principalement basé sur les résultats expérimentaux obtenus au cours de la thèse. La durée de la période de propagation de la corrosion acceptable a été définie comme celle correspondant à l'apparition des premières fissures de corrosion. L'approche développée permettra de prédire la durée de la phase de propagation, selon les critères de limite de service choisis, dans le cas de nouvelles structures en béton armé exposées au risque de corrosion induite par les chlorures.It is commonly accepted that chloride-induced corrosion of steel is one of the most documented causes leading to the deterioration of reinforced concrete structures. The Ph.D. study aimed at the improvement of the understanding of chloride-induced corrosion in concrete during the transition phase between initiation and propagation and during the corrosion propagation phase. Traditionally, chloride-induced corrosion is initiated when the chloride content reaches a threshold value called critical chloride content or Ccrit. In spite of much research invested in this domain, there is still no agreement on an accurate method for the determination of the chloride threshold value initiating corrosion. The first objective of this work was to develop a new test set-up that considers the localized character of corrosion initiated by chlorides. This approach was based on a physical separation between the anode, contaminated with chlorides, and the cathode, which is chloride free. The experimental protocol will allow quantifying the galvanic corrosion current, making it possible to determine, in a second step, the chloride threshold values for corrosion initiation. The criterion for corrosion initiation was a threshold corrosion current defined as a current that is independent of the cathode/anode surface ratio and subsequently independent of the area of passive steel. This criterion was considered as an anodic control of corrosion during the transition stage from the initiation phase to the propagation phase. This test protocol was applied to mortar and concrete formulations with several types of binders (CEM I cement, CEM III cement and CEM I with silica fume) with different water/binder ratios embedding ribbed steel bars with different steel surface conditions (as received, chemically cleaned, chemically cleaned than oxidized with humidity or high temperature). It was found that the test protocol is rapid and applicable to all formulations. The experimental results provide an understanding of the influence of binder type, w/b ratio and porosity on the susceptibility of steel to chloride-induced corrosion initiation. The steel surface condition was found to have an important overall effect on corrosion initiation but this effect is dependent on the type of binder used. Several literature studies considered that chloride-induced corrosion initiation is under anodic control which could mean that corrosion is controlled by the electrochemical parameters of steel. The parameters of passive steel can be directly derived from experimental measurements owing to the uniform passive state of rebars. However, because of the non-uniform nature of chloride-induced corrosion in concrete, it is not possible to experimentally obtain uniformly active steel. In this thesis, the determination of the electrochemical properties of active steel was achieved based on inverse numerical modeling focusing on the dependence of these properties on chloride contamination. All the experimental observations coupled with the numerical modeling approach highlighted the dependency of the electrochemical properties of active steel on chloride content. When dealing with macrocell corrosion, it is crucial to consider the geometry and size of the structure, including the mobilizable cathode-anode distance and the cathode to anode surface ratio. In this work, the mobilizable cathode-anode distance was investigated. It was found that macrocell corrosion current could be provided by cathode bars at large distances from the anode, the distance being dependent on the electrical resistivity of the structure. These findings support the assumption that corrosion in the submerged zone with lack of oxygen could be due to coupling with a cathodic zone in the aerated parts of structures and not necessarily associated with pitting phenomenon linked to water reduction under very negative potential in submerged area. Corrosion propagation is affected by several parameters like electrical resistivity which is known to be inversely proportional to the corrosion rate according to several empirical reported studies. An inversely proportional relationship between macrocell current and electrical resistivity was also found in our experimental investigations which consisted of a cathode permutation technique where the same anode was connected to two different cathodes with different electrical resistivity. Last but not least, it was experimentally observed that steel embedded in mortar with a high substitution level of slag (80%) presented a particular behavior. Highly negative potentials were measured despite the absence of chlorides which was considered as an indication of the absence of dissolved oxygen at the steel/mortar interface. It was assumed that these negative potentials were associated with the reaction of water reduction, while, in the presence of oxygen the reaction is the reduction of oxygen. During the galvanic coupling between highly negative cathodes and chloride contaminated anodes, corrosion currents were, in some cases, negative and then became positive. The change in sign of the measured current was always associated with the increase in the potentials of cathodes to more positive values which was considered as an indication of the oxidation of iron with a significant polarization for a weak current and therefore a rapid reduction of the galvanic current. Indeed at such low potential, the passive layer has disappeared but the anodic polarization of cathode led to both the increase of the potential of the cathode and the reformation of the passive layer. These statements were only assumptions and needed further investigations. Finally, a part of the thesis work was devoted to the development of a simplified empirical model of relevance to the engineer used for the prediction of corrosion propagation duration in the case of chloride-induced macrocell corrosion in uncracked reinforced concrete structures. This model was mainly based on the experimental results obtained during the thesis. The duration of the acceptable corrosion propagation period was defined as the one corresponding to the appearance of the first corrosion cracks. The developed approach will allow predicting the duration of the propagation phase, according to the chosen service limit criteria, in case of new reinforced concrete structures under the risk of chloride-induced corrosion

Effect of Cold Galvanizing Zinc Coating as a Cathodic Protection on Corrosion Rate and Bond Strength of Reinforced Concrete

This study focuses on the corrosion rate of steel in reinforced concrete and its effect on the steel rebar physical properties: Rockwell hardness, Vickers hardness, tensile strength, and yield strength. It was no noticeable effect of the corrosion rate of steel rebar on the physical properties. Tafel test was carried out to analyze the effect of pH and salinity on the corrosion rate of the reinforcement steel. Corrosion rate of reinforced concrete for uncoated and cold galvanized zinc coated steel were investigated at different pH and salinity by using weight loss method. The maximum sheer stress required to pull out the steel samples from the concrete was studied at different pH and salinity solutions by bond strength test. The results showed that at low pH ranges (acidic medium), the corrosion rate of the reinforced concrete was higher than at high pH ranges (alkaline medium), i.e. the corrosion rate is inversely proportional to pH. The corrosion rate of reinforced steel is positively proportional to the salinity until a certain salinity concentration, and then inversely proportional to the salinity due to limited oxygen diffusion. It can be concluded that the corrosion rate of the embedded rebar in reinforced concrete affects its structural performance in two ways, either by reducing its cross-section area or by deteriorating the strength of bonds between the steel and concrete.School of Chemical Engineerin

Development of Local and Global Corrosion Sensing Technique to Monitor Structural Behavior of Prestressed Concrete Structures

Corrosion of steel rebar in reinforced concrete structures is a concern for highway bridge owners. According to 2002 study by the Federal Highway Administration, ~15% of the highway bridges in the US are structurally deficient due to corrosion and have an estimated annual direct cost of $8.3 billion. Generally, in post-tensioned bridges, ducts filled with poor or incomplete grouting can allow the tendons to come into contact with water, leading to corrosion and fracture. Although new and improved procedures of grouting have been developed to reduce the instances of poor grouting, the problem of how to reliably inspect tendons on existing structures remains. This research aimed to evaluate the feasibility of using currently available local and global corrosion sensing techniques to monitor the performance of concrete structures. This dissertation explores the use of three local corrosion sensors (resistivity sensors, relative humidity sensors, and resistor-inductor- capacity [RLC] sensors). In this research, local sensors (i.e. RH sensors and four-point resistivity sensors) placed at an interval of every three foot were able to detect corrosion conducive environment in PT ducts by measuring the electrical properties and moisture contents of the grout. However, the measured RH was consistently lower in the low point of the specimens compared to the high points for all the specimens. The four-point resistivity sensors were able to detect a clear difference between the grouted ducts with good grout compared to ducts with chloride-rich grout with voids and layered-chloride rich grout without voids. To evaluate destructive testing and monitor the global response, two full-scale prestressed concrete inverted-tee (IT) beams were constructed and instrumented with vibrating wire strain gauges (VWSGs) located in multiple planes along the length. The VWSGs were able to clearly detect the initiation of corrosion in the first prestressing strand in each beam. The local corrosion damage in the first strand resulted in a change in the behavior of the beam, which was detected by the VWSGs (through a change in slope of curvature versus time)

Review and comparison of shearography and active thermography for nondestructive evaluation

postprin

Use of acoustic emission signals through steel reinforcement to detect the onset of corrosion

Corrosion processes produce elastic energy waves in the form of acoustic emission (AE). For corrosion in reinforced concrete structures, AE waves are emitted beginning with the depassivation of oxide layers of reinforcing steel, the initial stage of corrosion processes. This study examines the feasibility of using AE technique to detect corrosion through steel reinforcement, which has relatively lower attenuation than concrete. Comparison of coupling AE sensors on steel and on concrete was made. Accelerated corrosion regime and two-channel multifunctional AE equipment with piezoelectric sensors were employed for laboratory experiments. The detectable distance from corrosion source to sensor was estimated via the calculation of attenuation coefficient and particle surface displacement. The analysis of source location demonstrates that surface wave is the predominant AE wave propagating in rebars with one-inch diameter. Furthermore, an important experiment was performed to compare AE measurement with half-cell potential measurement. As a result, AE was proved to be a promising tool for corrosion detection in reinforced concrete structures.Dept. of Civil and Environmental Engineering. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2005 .C443. Source: Masters Abstracts International, Volume: 44-03, page: 1435. Thesis (M.A.Sc.)--University of Windsor (Canada), 2005

Bridges Structural Health Monitoring and Deterioration Detection Synthesis of Knowledge and Technology

INE/AUTC 10.0