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Ueli Angst - One of the best experts on this subject based on the ideXlab platform.
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the effect of the steel concrete interface on chloride induced Corrosion Initiation in concrete a critical review by rilem tc 262 sci
Materials and Structures, 2019Co-Authors: Ueli Angst, Rob B. Polder, Bernhard Elsener, Mette R. Geiker, Maria Cruz Alonso, Alexander Michel, Karla Hornbostel, Burkan Isgor, H S Wong, Christoph GehlenAbstract:The steel–concrete interface (SCI) is known to influence Corrosion of steel in concrete. However, due to the numerous factors affecting the SCI—including steel properties, concrete properties, execution, and exposure conditions—it remains unclear which factors have the most dominant impact on the susceptibility of reinforced concrete to Corrosion. In this literature review, prepared by members of RILEM technical committee 262-SCI, an attempt is made to elucidate the effect of numerous SCI characteristics on chloride-induced Corrosion Initiation of steel in concrete. We use a method to quantify and normalize the effect of individual SCI characteristics based on different literature results, which allows comparing them in a comprehensive context. It is found that the different SCI characteristics have received highly unbalanced research attention. Parameters such as w/b ratio and cement type have been studied most extensively. Interestingly, however, literature consistently indicates that those parameters have merely a moderate effect on the Corrosion susceptibility of steel in concrete. Considerably more pronounced effects were identified for (1) steel properties, including metallurgy, presence of mill scale or rust layers, and surface roughness, and (2) the moisture state. Unfortunately, however, these aspects have received comparatively little research attention. Due to their apparently strong influence, future Corrosion studies as well as developments towards predicting Corrosion Initiation in concrete would benefit from considering those aspects. Particularly the working mechanisms related to the moisture conditions in microscopic and macroscopic voids at the SCI is complex and presents major opportunities for further research in Corrosion of steel in concrete.
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Predicting the time to Corrosion Initiation in reinforced concrete structures exposed to chlorides
Cement and Concrete Research, 2019Co-Authors: Ueli AngstAbstract:Abstract Reliable predictions of the time to onset of Corrosion in reinforced concrete are essential for service life modelling, to ensure sufficient durability, and for holistic sustainability assessments of new materials. All existing models are based on the same concept, that is, predicting the development over time of the chloride content at the level of the steel and comparing this numerical result with the critical chloride content for Corrosion Initiation, Ccrit. This paper presents example calculations utilizing input data derived from both laboratory specimens and from structures, illustrating the poor predictive power of state-of-the-art models. While it is generally assumed that improving chloride ingress models will improve the prediction of the time-to-Corrosion, this paper shows that the bottle neck to more reliable predictions are rather i) the lack of fundamental understanding of Corrosion Initiation, ii) the use of non-representative laboratory results, and iii) ignoring the size-effect in localized Corrosion.
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Towards understanding Corrosion Initiation in concrete – Influence of local electrochemical properties of reinforcing steel
MATEC Web of Conferences, 2018Co-Authors: Lucas Michel, Ueli AngstAbstract:The ageing of reinforced concrete (RC) structures in the industrialized countries increases the probability of durability issues. The mechanism of chloride-induced Corrosion, the most common deterioration process in RC structures, is still not well understood. Improvement in the understanding of localized Corrosion Initiation is crucially required to allow for cost efficient and durable maintenance of the existing infrastructures and for service life design of new structures. This study reports results from localized electrochemical characterization of reinforcing steel surfaces taken with a local sensor positioned at different locations on the rebars. This permitted “mapping” the local Open Circuit Potentials for different rebars with different surface conditions. Moreover, local cyclic voltammetries on selected spots were also carried out. Subsequently, the samples were exposed to a chloride solution to provoke Corrosion Initiation. The Corrosion Initiation sites from visual inspection were correlated with the local electrochemical characterization. Results show a clear difference depending on the surface condition. Furthermore, for non-rusted surfaces, a spatial distribution of the local electrochemical behaviors seems to follow a pattern depending on the geometry of the steel bar and influencing the location of Corrosion Initiation.
Amin Imani - One of the best experts on this subject based on the ideXlab platform.
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Correlation of surface Volta potential with galvanic Corrosion Initiation sites in solid-state welded Ti-Cu bimetal using AFM-SKPFM
Corrosion Science, 2018Co-Authors: Ehsan Rahimi, Amin Imani, Ali Rafsanjani-abbasi, Saman Hosseinpour, Ali DavoodiAbstract:Abstract This study aims to correlate the microstructure and Volta potential distribution of Ti-Cu welded bimetal to its Corrosion Initiation sites, using AFM-SKPFM, and SEM-EDS. Local melted zones with Ti-Cu intermetallic precipitates in weld interface and in Cu matrix showed different Volta potential values in comparison with those of Ti and Cu regions. SKPFM revealed that Cu region has a higher Volta potential than that of Ti region. AFM and microstructural images after immersion in corrosive media proved the presence of a galvanic cell. Corrosion mainly extends on Cu side due to the increasing growth of Ti passive film.
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the role of constituent phases on Corrosion Initiation of nial bronze in acidic media studied by sem eds afm and skpfm
Corrosion Science, 2014Co-Authors: Davood Nakhaie, Ali Davoodi, Amin ImaniAbstract:Abstract Scanning electron microscopy (SEM), atomic force microscopy (AFM) and scanning Kelvin probe force microscopy (SKPFM) were used to examine the role of constituent phases of a NiAl bronze in Corrosion Initiation in HCl solution. Volta potential revealed anodic character of κ phases with tens of mV higher than copper rich α phase as cathodic matrix. A correlation between SKPFM results and Work function values of constituents was obtained. SEM and AFM images revealed that the iron rich κ phases are the most preferential sites for Corrosion Initiation.
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The role of constituent phases on Corrosion Initiation of NiAl bronze in acidic media studied by SEM–EDS, AFM and SKPFM
Corrosion Science, 2014Co-Authors: Davood Nakhaie, Ali Davoodi, Amin ImaniAbstract:Abstract Scanning electron microscopy (SEM), atomic force microscopy (AFM) and scanning Kelvin probe force microscopy (SKPFM) were used to examine the role of constituent phases of a NiAl bronze in Corrosion Initiation in HCl solution. Volta potential revealed anodic character of κ phases with tens of mV higher than copper rich α phase as cathodic matrix. A correlation between SKPFM results and Work function values of constituents was obtained. SEM and AFM images revealed that the iron rich κ phases are the most preferential sites for Corrosion Initiation.
Ali Davoodi - One of the best experts on this subject based on the ideXlab platform.
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Correlation of surface Volta potential with galvanic Corrosion Initiation sites in solid-state welded Ti-Cu bimetal using AFM-SKPFM
Corrosion Science, 2018Co-Authors: Ehsan Rahimi, Amin Imani, Ali Rafsanjani-abbasi, Saman Hosseinpour, Ali DavoodiAbstract:Abstract This study aims to correlate the microstructure and Volta potential distribution of Ti-Cu welded bimetal to its Corrosion Initiation sites, using AFM-SKPFM, and SEM-EDS. Local melted zones with Ti-Cu intermetallic precipitates in weld interface and in Cu matrix showed different Volta potential values in comparison with those of Ti and Cu regions. SKPFM revealed that Cu region has a higher Volta potential than that of Ti region. AFM and microstructural images after immersion in corrosive media proved the presence of a galvanic cell. Corrosion mainly extends on Cu side due to the increasing growth of Ti passive film.
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Prediction of Corrosion Initiation sites in dissimilar FSW AA5083/AA70232 aluminum alloys joint by quantitative multimodal-Gaussian histogram analysis of AFM-SKPFM microscopy images
2017Co-Authors: Zohreh Esfahani, Ehsan Rahimi, Madjid Sarvghad Moghaddam, Ali DavoodiAbstract:A common way to evaluate the topography and other functional signals (such as Volta potential, magnetic domain) obtained as image by the SPM-based results such as AFM and SKPFM is taking the advantage of line profiles through the data maps. However, in this presentation, it will be shown for the first time that histogram-based data analysis and power spectral density analysis provides more information about the impact of the properties of surface constitutive phases based on desired signal distribution. The de-convolution of data histograms into multimodal Gaussian distributions was performed and the approach has been employed recently to quantitatively analyze the AFM and SKPFM results. Three parameters were acquired from de-convoluted histograms comprising the number of multimodal distribution peaks, the mean value and the standard deviation value. Each parameters were correlated to the various properties of surface constituents of the system as an indication of their chemical composition changes, their heterogeneity in size and micro-galvanic driving forces for Corrosion Initiation. Examples of data analysis and interpretation will be demonstrated on candidate Corrosion systems as the interfacial region in in dissimilar friction stir welded AA5083 to AA7023. The results indicates that quantitative multimodal-Gaussian histogram analysis can be used as tools for prediction of Corrosion Initiation sites. While the AA5083 surface shows lower Volta potential value, it gives less heterogeneity in compare with AA70232 which shows higher Volta potential value but more heterogeneity. Therefore, micro-galvanic Corrosion occurs around intermetallics on AA70232 and also on FSW borderline. PSD analyses of SKPFM images showed that lowest Volta potential in highest spatial frequency is related to AA5083 and also, highest Volta potential in lowest spatial frequency corresponded to intermetallic particles mainly on AA7023 matrix. Immersion test showed that intermetallic particles in two matrixes and especially FSW interface were susceptible to Corrosion attack due to a high driving force between these surface constituents.
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the role of constituent phases on Corrosion Initiation of nial bronze in acidic media studied by sem eds afm and skpfm
Corrosion Science, 2014Co-Authors: Davood Nakhaie, Ali Davoodi, Amin ImaniAbstract:Abstract Scanning electron microscopy (SEM), atomic force microscopy (AFM) and scanning Kelvin probe force microscopy (SKPFM) were used to examine the role of constituent phases of a NiAl bronze in Corrosion Initiation in HCl solution. Volta potential revealed anodic character of κ phases with tens of mV higher than copper rich α phase as cathodic matrix. A correlation between SKPFM results and Work function values of constituents was obtained. SEM and AFM images revealed that the iron rich κ phases are the most preferential sites for Corrosion Initiation.
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The role of constituent phases on Corrosion Initiation of NiAl bronze in acidic media studied by SEM–EDS, AFM and SKPFM
Corrosion Science, 2014Co-Authors: Davood Nakhaie, Ali Davoodi, Amin ImaniAbstract:Abstract Scanning electron microscopy (SEM), atomic force microscopy (AFM) and scanning Kelvin probe force microscopy (SKPFM) were used to examine the role of constituent phases of a NiAl bronze in Corrosion Initiation in HCl solution. Volta potential revealed anodic character of κ phases with tens of mV higher than copper rich α phase as cathodic matrix. A correlation between SKPFM results and Work function values of constituents was obtained. SEM and AFM images revealed that the iron rich κ phases are the most preferential sites for Corrosion Initiation.
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An insight into the influence of morphological and compositional heterogeneity of an individual intermetallic particle on aluminium alloy Corrosion Initiation
Materials and Corrosion, 2012Co-Authors: Ali Davoodi, Reza Parvizi, Jinshan Pan, Christofer Leygraf, Stefan NorgrenAbstract:In this work, a multi-analytical in situ and ex situ approach was used to provide information needed to identify the role of an individual heterogeneous intermetallic particle (IMP) in localized Corrosion Initiation of aluminium alloys. The heterogeneity of the IMP was studied by combining atomic force microscopy (AFM), scanning electron microscopy and energy dispersive spectroscopy (SEM–EDS) and scanning electrochemical microscopy (SECM). A complex Al–Mn–Fe–Si IMP phase with different chemical composition in its inner and outer parts was characterized by SEM–EDS analysis. AFM results uniquely revealed a brain-like feature of an IMP with 20 nm height variations. Submicron sized galvanic cell induced by morphological and compositional heterogeneity resulted in a localized Corrosion attack inside the individual IMP. Various collected current levels measured by SECM were associated to the morphological and compositional heterogeneity of IMPs.
William H. Hartt - One of the best experts on this subject based on the ideXlab platform.
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Time-to-Corrosion Initiation of Chloride-Exposed Reinforced Concrete Considering Time Dependence of the Diffusion Coefficient
CORROSION, 2013Co-Authors: William H. HarttAbstract:Previous research reported an equation whereby the fraction of electrochemically independent, identically exposed reinforced concrete elements for which Corrosion Initiation has resulted after a gi...
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Quantitative analysis of the effect of coarse aggregate diffusivity on reinforcing steel Corrosion Initiation with a finite element model
Anti-Corrosion Methods and Materials, 2010Co-Authors: William H. HarttAbstract:Purpose – The purpose of this paper is to explore and compare the influence of diverse coarse aggregate (CA) diffusivities on reinforcing steel Corrosion Initiation through a quantitative modeling analysis approach.Design/methodology/approach – Finite element analysis was used to solve two‐dimensional chloride diffusion processes, which follow the Fick's second law within the concrete cover. Two non‐dimensional time‐derating factors were employed to quantify the time‐to‐Corrosion of steel rebar, Ti, for different models.Findings – The finite diffusivity CA exhibits variable effects on Ti, depending upon: diffusivity ratio between the CA and mortar; CA type; reinforcement Corrosion resistance; and cover thickness. The intent of the effects are expressed quantitatively and their implications discussed.Originality/value – The methodology and results presented in this paper provide insights on the variable reinforcement Ti values as a function of CA diffusivity. The approach employed herein provides an effect...
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Laboratory investigation of reinforcement Corrosion Initiation and chloride threshold content for self-compacting concrete
Cement and Concrete Research, 2010Co-Authors: Xianming Shi, William H. HarttAbstract:Abstract Time-to-Corrosion (Ti) of reinforcement in concrete and chloride threshold content (Cth) are important service life determinants for reinforced concrete structures in chloride-laden environments. In this study, the two determinants of a series of self-compacting concretes (SCC) and regular concretes were experimentally investigated. A new sampling approach for Cth determination (milling powder from Corrosion active site at the rebar/concrete interface) was adopted to accurately express chloride content resulting in Corrosion occurrence. It is found that the Ti and Cth follow the 3-parameter Weibull distribution. The results indicate that the Corrosion Initiation of rebar in concrete slabs depends upon both cement alkalinity and superplasticizer. Rebar, embedded in high alkalinity cement SCC, exhibits better Corrosion resistance as indicated by the longer Ti, higher Cth and larger Weibull modulus, m. A larger Weibull modulus indicates that anti-Corrosion performance of rebar in slabs is more stable and less scattered. The effects of specific superplasticizer on rebar Corrosion resistance are discussed from the viewpoint of air void amount and size distribution at the rebar/concrete interface.
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Effects of Air Void at the Steel-Concrete Interface on the Corrosion Initiation of Reinforcing Steel in Concrete under Chloride Exposure
Journal of the Korea Concrete Institute, 2005Co-Authors: Jingak Nam, William H. Hartt, Ki-joon KimAbstract:A series of reinforced G109 type specimens was fabricated and pended with a 15 weight percent NaCl solution. Mix design variables included 1) two cement alkalinities (equivalent alkalinities of 0.32 and 1.08), 2) w/c 0.50 and 3) two rebar surface conditions (as-received and wire-brushed). Potential and macro-cell current between top and bottom bars were monitored to determine Corrosion Initiation time. Once Corrosion was initiated, the specimen was ultimately autopsied to perform visual inspection, and the procedure included determination of the number and size of air voids along the top half of the upper steel surface. This size determination was based upon a diameter measurement assuming the air voids to be half spheres or ellipse. The followings were reached based upon the visual inspection of G109 specimens that were autopsied to date. First, voids at the steel-concrete interface facilitated passive film breakdown and onset of localized Corrosion. Based upon this, the Initiation mechanism probably involved a concentration cell with contiguous concrete coated and bare steel serving as cathodes and anodes, respectively. Second, the Corrosion tended to initiate at relatively large voids. Third, specimens with wire-brushed steel had a lower number of voids at the interface for both cement alkalinities, suggesting that air voids preferentially formed on the rough as-received surface compared to the smooth wire brushed one.
Davood Nakhaie - One of the best experts on this subject based on the ideXlab platform.
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the role of constituent phases on Corrosion Initiation of nial bronze in acidic media studied by sem eds afm and skpfm
Corrosion Science, 2014Co-Authors: Davood Nakhaie, Ali Davoodi, Amin ImaniAbstract:Abstract Scanning electron microscopy (SEM), atomic force microscopy (AFM) and scanning Kelvin probe force microscopy (SKPFM) were used to examine the role of constituent phases of a NiAl bronze in Corrosion Initiation in HCl solution. Volta potential revealed anodic character of κ phases with tens of mV higher than copper rich α phase as cathodic matrix. A correlation between SKPFM results and Work function values of constituents was obtained. SEM and AFM images revealed that the iron rich κ phases are the most preferential sites for Corrosion Initiation.
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The role of constituent phases on Corrosion Initiation of NiAl bronze in acidic media studied by SEM–EDS, AFM and SKPFM
Corrosion Science, 2014Co-Authors: Davood Nakhaie, Ali Davoodi, Amin ImaniAbstract:Abstract Scanning electron microscopy (SEM), atomic force microscopy (AFM) and scanning Kelvin probe force microscopy (SKPFM) were used to examine the role of constituent phases of a NiAl bronze in Corrosion Initiation in HCl solution. Volta potential revealed anodic character of κ phases with tens of mV higher than copper rich α phase as cathodic matrix. A correlation between SKPFM results and Work function values of constituents was obtained. SEM and AFM images revealed that the iron rich κ phases are the most preferential sites for Corrosion Initiation.
