Reinforced concrete structures require continuous monitoring and maintenance to prevent corrosion of the carbon steel reinforcement. In this work, concrete columns with carbon and stainless steel ...reinforcements were exposed to a real marine environment. In order to monitor the corrosion processes, two types of corrosion probes were embedded in these columns at different height levels. The results from the monitoring of the probes were compared to the actual corrosion damage in the different exposure zones. Electrical resistance (ER) probes and coupled multi-electrodes (CMEs) were shown to be promising methods for long-term corrosion monitoring in concrete. Correlations between the different exposure zones and the corrosion processes of the steel in the concrete were found. Macrocell corrosion properties and the distribution of the separated anodic/cathodic places on the steel in chloride-contaminated concrete were addressed as two of the key issues for understanding the corrosion mechanisms in such environments. The specific advantages and limitations of the tested measuring techniques for long-term corrosion monitoring were also indicated. The results of the measurements and the corrosion damage evaluation clearly confirmed that the tested stainless steels (AISI 304 and AISI 304L) in a chloride-contaminated environment behave significantly better than ordinary carbon steel, with corrosion rates from 110× to 9500× lower in the most severe (tidal) exposure conditions.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
In this study, the influence of voids on corrosion process at the steel-concrete interface was investigated, as the exact influence of these features on corrosion processes under various ...environmental conditions is not entirely understood. Coupled multi electrode arrays and electrical resistance probes were implemented to monitor the evolution of corrosion under cyclic exposure to chlorides and carbonation. MicroCT was used to determine the location and volume of corrosion damage. It was found that, in most cases, corrosion damage initiated outside the voids. During initiation and the early propagation phase, the steel beneath the voids rarely participated in the redox reaction. In following phases, various kinds of corrosion evolution were observed. Specific corrosion mechanisms were proposed and discussed to explain these corrosion processes.
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•Processes of corrosion around voids at the steel-concrete interface were studied.•Complementary monitoring techniques were implemented to characterize the corrosion.•Voids rarely participated in corrosion current exchange during corrosion initiation.•Corrosion mechanisms were proposed to explain evolution of anodic / cathodic sites.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Supplementary cementitious materials can affect the porosity of concrete, pore solution pH and chloride binding, all of which influence the type and magnitude of corrosion damage. Advanced corrosion ...monitoring techniques are needed to follow the development of corrosion on steel embedded in concrete across space and over time. In this study, coupled multi-electrode arrays (CMEAs) were used to characterise corrosion processes in OPC and three blended cements. Cyclic wetting with chlorides was undertaken to initiate corrosion. The results showed three distinct types of corrosion: localised corrosion (CEM I), localised corrosion that expanded over time (CEM II), and a combination of localised and general corrosion (CEM III and CEM IV). Cathodic locations were also monitored successfully, and the corrosion behaviour was related to total porosity and pH of the pore solution. MicroCT was used to quantify the volume of corroded material, which agreed well with results calculated from the CMEA measurements.
•Corrosion of steel in blended cements was studied using coupled multi-electrode arrays.•Three distinct corrosion types were monitored across space and over time.•The most localised corrosion behaviour occurred in CEM I.•Porosity and pH were identified as potential factors contributing to the development of corrosion.•MicroCT damage evaluation correlated well with the damage calculated by CMEA.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This work focuses in monitoring the corrosion processes on copper in a slightly saline environment under oxic conditions, which simulated the first part of high-radioactive waste disposal in ...bentonite. Besides coupled multi-electrode arrays (CMEA), also electrochemical impedance spectroscopy measurements were implemented. It was expected that this combination of methods would define the general corrosion rate, as well as the spatio-temporal evolution of anodic and cathodic processes. Anodic currents measured by CMEA showed that the corrosion rates decreased with time. Since maximum anodic activity switched between the electrodes, this situation was not individually valid for all the electrodes. At the end of exposure, different spectroscopic techniques were applied in order to identify the modes of corrosion and types of corrosion products. Uneven general corrosion without evident pits was indicated.
This paper is part of a supplement on the 6th International Workshop on Long-Term Prediction of Corrosion Damage in Nuclear Waste Systems.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The inhibition of under deposit corrosion (UDC) of steel X-60 (UNS K03006) was studied under field-collected sludge deposits in a simulated sour environment by means of linear polarization resistance ...(LPR), coupled multi-electrode array system (CMAS). and weight-loss coupons. X-ray diffraction (XRD) and energy-dispersive x-ray spectroscopy (EDS) techniques were employed to identify the deposit composition. The adsorption of two corrosion inhibitors, fatty acid imidazoline and benzyl alkyl pyridinyl quaternary ammonium chloride (benzyl chloride quaternary), designed for steel corrosion protection in sour environments, and their inhibition activities under sludge deposits were investigated. The significance of determining the adsorption affinity of the inhibitors to field-sludge deposit in the selection of corrosion inhibitors was also demonstrated. The XRD analysis indicated that the field-sludge deposit consisted mainly of calcite phase. Fatty acid imidazoline inhibitor was found to exhibit higher affinity to the sludge deposit than did benzyl chloride quaternary. As a consequence, benzyl chloride quaternary inhibitor was more effective in inhibiting general and localized corrosion of carbon steel in the presence of sludge deposit in a simulated sour environment. The corrosion rate is increased by the deposit even in the absence of inhibition. Thus, the field-sludge deposit decreased the performance of inhibitors, as compared with inhibiting steel samples that contained no sludge deposits. A clear understanding of the inhibitor's interaction with field-sludge deposits is necessary to predict its inhibition performance under field-sludge deposits.
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