The purpose of this study was to extract galvanized steel wire reinforcement coupons from mechanically stabilized earth (MSE) walls along I-15 and determine the rate of corrosion that has taken place since Phase I, which was conducted by Gerber and Billings (2010). The galvanized steel reinforcement analyzed in this study has been in place for 19 to 20 years at the time of extraction. A total of 85 coupons were extracted and laboratory analysis was performed to determine the thickness of remaining zinc galvanization on each coupon. Soil samples were obtained from each one-stage wall extraction location to determine moisture content for correlation with corrosion. After laboratory testing was performed, the measured zinc coating thickness was compared to that determined in Phase I. An average corrosion rate of approximately 0.032 oz/ft²/year has occurred since Phase I. According to the AASHTO (2017) design corrosion rate of 0.35 oz/ft²/year for the first two years and 0.09 oz/ft²/year until the depletion of the zinc, the zinc coating would have been completely depleted after 16 years. Based on the results of laboratory testing, the initial galvanization coating was likely greater than the specified thickness of 2.0 oz/ft² (86 μm). The zinc galvanization is corroding at a slower rate than the AASHTO design rate. The AASHTO design rate for depletion of zinc coating and subsequent corrosion of the steel reinforcement is conservative for the corrosion conditions present in the MSE wall reinforcement coupons tested. The integrity of the steel reinforcement that is currently in place is not likely to be compromised by corrosion.

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Corrosion-related degradation incurs a significant cost to infrastructure and society. In 2016, the direct corrosion cost was estimated at $276 billion, which is 3.1% of the U.S. gross domestic product. Despite the known consequences of corrosion damage, many unknowns still exist, such as the mechanisms and rates of chloride-induced corrosion initiation and propagation. There is also a lack of high-quality quantitative kinetic data and analysis that can obtain the fundamental micro- and nanostructural mechanisms and initiation of metal corrosion. The corrosion initiation in metals is considered to be governed by dynamic processes that take place at the nanoscale. Thus, the measurement of nanoscale surface structures correlated with electrochemical properties in metals is critical in the understanding of corrosion initiation, and microstructure-corrosion relationship, as well as efforts toward materials design for corrosion mitigation. As a fundamental approach to this study, a systematic review of different surface characterization techniques was initially discussed. This entailed their principles, applications, and perspectives for surface corrosion monitoring, enabling the development of next-generation inhibition technologies, and improving corrosion predictive models. Unprecedented, this research study presented a novel application of a quantitative phase microscopy technique, spectral modulation interferometry (SMI), for in situ nanoscale characterization of corrosion of different alloys in real-time. SMI offers high sensitivity, rapid image acquisition, and speckle-free images; thus, real-time quantification of surface topography evolution during corrosion can be obtained accurately to evaluate the temporally- and spatially-dependent corrosion rates. With an innovative additive-manufactured fluid cell, experiments were performed under flowing solution conditions. Electrochemical tests via stepwise polarization and solution chemistry through collected aliquots of outflow solution were also performed alongside the nanoscale SMI experiment to simultaneously provide corroborating corrosion rate measurements. This innovative approach to measuring dissolution rates of metal at three levels can provide highly quantitative kinetic data of reacting surfaces that are rarely explored in the literature. First, the in situ SMI combined with the stepwise potentiostatic tests and the solution chemistry analysis was used to investigate the nanoscale characterization of corrosion of an AA6111-T4 aluminum alloy in real-time. The corrosion experiment was conducted in a 0.5 wt.% NaCl flowing solution acidified to pH ⁓2.9 by acetic acid. Based on the quantitative 3D height profiles across the corroded surface, pit formation resulting from rapid local corrosion was predominant, which is heterogeneously distributed and was appearing at different times. The computed time-dependent dissolution rates of aluminum also varied as the experiment proceeded, with the combination of linear and nonlinear surface normal distributions. An initial mean linear dissolution rate of (0.40 ± 0.007) μmol m−2 s−1 transitioned to a more rapid mean rate of (1.95 ± 0.035) μmol m−2 s−1, driven by the anodic polarization. Dissolution rates from the three performed methods follow similar trends and there is the visibility of linking the nanoscale in situ SMI data to the electrochemical corrosion measurements and ex situ chemical solution analysis. At the end of the corrosion period, rates of 118, 71, and 2.45 μmol m−2 s−1 were obtained from electrochemical measurements, ex situ solution analyses, and in situ SMI corrosion measurements, respectively. In addition, SMI–electrochemical experiments were performed to evaluate the effect of thermal history on corrosion modes and rates of AA6111. Quantitative estimates of the corrosion initiation and propagation in the alloy were also assessed. A single coil of AA6111 alloy that was solution heat treated at a temperature above 500°C and quenched with 2 different water quench rates (i.e., slow-quenched at 131ºC/s and fast-quenched at 506ºC/s) with each in T4 and T82 temper condition was investigated in this study. Irrespective of the quenched and/or temper conditions, the electrochemical potential-current (E-i) results showed a similar pattern in the polarization curve and similar current response over the immersed time, and a small difference in their corrosion behavior will be difficult to detect due to the dissolution kinetics that takes place on the nanoscale. As revealed from the SMI topography map, the corrosion modes at the nanoscale were very distinct despite having similar electrochemical responses and chemical compositions. Primarily, heterogeneous dissolution of intergranular corrosion (IGC) and crystallographic pitting was observed in the tested alloy substrates, with the slow-quenched samples susceptible to IGC and the fast-quenched samples susceptible to crystallographic pitting. The nucleation of IGC sites is triggered by the increased coarsening and formation of precipitates in the grain boundary, while the pitting corrosion is attributed to the coarsening of the precipitates in the grain bodies. The quantitative analysis of topography evolution from the SMI data revealed a non-uniform (i.e., heterogenous) surface dissolution, as is typical for aluminum alloys. Notably, the fast-quenched material resisted corrosion initiation for a longer time and showed great resistance even at higher anodic polarization. However, an instant breakdown then occurred after 60mV of polarization and corrosion accelerated faster, relative to the slow-quenched material which initiated sooner (i.e. with less overpotential). In this setup, it is now possible to detect and evaluate these differences quantitatively through a quick corrosion test with the combined electrochemical-SMI technique. Therefore, this work showed that the corrosion susceptibility of AA6111 alloy is influenced by the thermal history, which can be controlled with a proper quench rate and further tempering. Additionally, this research also utilized the novel SMI techniques to investigate in situ chloride-induced corrosion of A615 low-carbon steel at the nanoscale. Along with surface topography monitoring, a potentiostat was connected to simultaneously monitor the bulk electrochemical activity of the carbon steel. Experiments were conducted in chloride-free and chloride-enriched solutions at pH 5 to investigate the role of chloride on topography evolution, dissolution mode, and corrosion kinetics. The 3D topography map acquired from the SMI showed an early formation of localized shallow pits on the surface subjected to the chloride free-solution. A more detrimental form of corrosion was obtained on the samples in chloride-enriched solution, which revealed early-age microcracks or intergranular defective sites associated with the heterogeneous roughening of the sample surface. The presence of chloride ions also influenced the initiation period of corrosion. Indeed, higher grain defects were obtained in samples immersed in 5.0 wt.% NaCl solution than the sample in 1.0 wt.% NaCl solution. The quantitative analysis of the height profile data (acquired from SMI) verified the heterogeneity of the corrosion process of both samples either susceptible to pitting corrosion and/or intergranular corrosion behavior. A faster dissolution rate was acquired on the sample immersed in 5.0 wt.% NaCl solution, with the rate of (3.53 ± 0.103) μmol m−2 s−1 and (5.64 ± 0.0225) μmol m−2 s−1 computed at the initiation and propagation stages, respectively. Likewise, the estimated volume loss followed a similar trend to the 3D surface topography data, but a distinct behavior in the volume loss was observed when compared to the void volume obtained from the electrochemical monitoring. This confirmed that the electrochemical measurement overestimates metal loss and does not present a good representation of material dissolution on the nanoscale. Finally, a different perspective of corrosion mitigation in the metallic alloy was presented. The extensive application of deicing salts has led to significant deterioration in many transportation infrastructures and automobiles due to corrosion. In this regard, the work investigated the corrosion inhibition performance of 2 corn-derived polyols, namely: sorbitol, and mannitol, on reinforced steel rebar. The results demonstrated that the incorporation of polyols in the deicing solution reduced the corrosion initiation while the inhibition rate increased as the polyol content increased from 0% to 5wt.%. The outcome of this study contributed to the search for mitigation strategies to minimize the impact of deicing chemicals on steel infrastructures. Overall, it is evident that corrosion is a huge durability problem and requires significant consideration when designing metals or alloys that are usually exposed to hostile environments. Understanding the nanostructural and kinetics of corrosion at both the initiation and propagation periods, as well as its thermodynamics, is important for designing a suitable protection strategy. This dissertation is expected to present the application of the surface technique to directly quantify the dynamic evolution of site-specific local corrosion of metals during early initiation stages at the nanoscale. / Doctor of Philosophy / Corrosion-related degradation incurs a significant cost to infrastructure and society. In 2016, the direct corrosion cost was estimated at $276 billion, which is 3.1% of the U.S. gross domestic product. Despite the known consequences of corrosion damage, many unknowns still exist, such as the mechanisms and rates of chloride-induced corrosion initiation and propagation. There is also a lack of high-quality quantitative kinetic data and analysis that can obtain the fundamental micro- and nanostructural mechanisms and initiation of metal corrosion. The corrosion initiation in metals is considered to be governed by dynamic processes that take place at the nanoscale. Thus, the measurement of nanoscale surface structures correlated with electrochemical properties in metals is critical in the understanding of corrosion initiation, and microstructure-corrosion relationship, as well as efforts toward materials design for corrosion mitigation. As a fundamental approach to this study, a systematic review of different surface characterization techniques was initially discussed. This entailed their principles, applications, and perspectives for surface corrosion monitoring, enabling the development of next-generation inhibition technologies, and improving corrosion predictive models. Unprecedented, this research study presented a novel application of a quantitative phase microscopy technique, spectral modulation interferometry (SMI), for in situ nanoscale characterization of corrosion of different alloys in real-time. SMI offers high sensitivity, rapid image acquisition, and speckle-free images; thus, real-time quantification of surface topography evolution during corrosion can be obtained accurately to evaluate the temporally- and spatially-dependent corrosion rates. With an innovative additive-manufactured fluid cell, experiments were performed under flowing solution conditions. Electrochemical tests via stepwise polarization and solution chemistry through collected aliquots of outflow solution were also performed simultaneously with the nanoscale SMI experiment to provide corroborating corrosion rate measurements. This innovative approach to measuring dissolution rates of metal at three levels simultaneously can now provide highly quantitative kinetic data of reacting surfaces that are not explored in the literature.

To meet the requirements of precise temperature monitoring at high temperatures in extremely corrosive environments, such as in coal gasifiers, a new sensor technology has been developed. This optical, ultra high temperature measurement system utilizes single crystal sapphire as a sensing element. A series of experiments was performed to determine the corrosion resistance of single crystal sapphire and single crystal fully stabilized cubic zirconia at high temperatures in coal slag and soda lime glass. The amount of corrosion of sapphire and zirconia in corrosive slags was measured at 1200°C, 1300°C, and 1400°C for different exposure times. The microstructural features at the interface of sapphire and zirconia were investigated using SEM and EDX analysis. The experimental measurements as well as SEM micrographs show very little or no degradation of sapphire and zirconia samples in corrosive slags. An interesting phenomenon was observed in the EDX scans of sapphire in the coal slag: the iron from the slag appears to have completely separated from the silicon and deposited at the sapphire surface. This interesting observation can be further explored to study whether this iron layer can be used to control the corrosion of sapphire. / Master of Science

Yes / Limited information related to the application of nano silica in recycled aggregate concretes has been available in the literature. However, investigations on the effect of nano silica on the bond performance of reinforcement embedment length in recycled aggregate concrete have not been conducted yet. Therefore, the present study aimed at investigating the bond strength for recycled aggregate concretes incorporating nano silica under different levels of corrosive environments. The experimental work consisted of testing 180 pull-out specimens prepared from different mixtures. The main parameters studied were the amount of recycled aggregate (i.e. 0%, 25%, 50% and 100%), nano silica (1.5% and 3%), embedment length (5 and 13Ø) as well as reinforcement diameter (12 and 20mm). Different levels of corrosion were electrochemically induced by applying impressed voltage technique for 2, 5, 10 and 15 days. Finally, the experimental results were compared with the existing models. Experimental results showed that the bond performance between un-corroded steel and RCA concrete slightly reduced, while a significant degradation was observed after being exposed to corrosive conditions, in comparison to normal concrete. On the other hand, the use of a small quantity of NS (1.5%) showed between 8 and 21% bond enhancement with both normal and RCA concretes under normal conditions. However, much better influence was observed with the increase of corrosion periods, reflecting the improvement in corrosion resistance. NS particles showed a more effective role with RCA concretes rather than conventional concretes in terms of enhancing bond and corrosion resistance. Therefore, it was superbly effective in recovering the poor performance in bond for RCA concretes. By doubling the content of NS (3%), the bond resistance slightly enhanced for non-corroded samples, while its influence becomes more pronounced with increasing RCA content as well as exposure time to corrosion.

No description available.

An extensive investigation with parallel field andlaboratory exposures has been conducted to elucidateatmospheric corrosion and metal runoff processes on copper andzinc used for roofing applications. Detailed studies have beenperformed to disclose the effect of various parameters on therunoff rate including: surface inclination and orientation,natural patination (age), patina composition, rain duration andvolume, rain pH, and length of dry periods inbetween rainevents. Annual and average corrosion rates and runoff rateshave been determined consecutively during urban field exposuresin Stockholm on naturally patinated copper and zinc of varyingage and patina composition. The corrosion rate was found todecrease with time, amounting to 6.7 g Cu/(m2.y) and 5.0 gZn/(m2.y) after 48 weeks of exposure, whereas the runoff ratewas relatively constant with time on a yearly basis, being 1.3g/(m2.y) and 3.1 g/(m2.y) for copper and zinc, respectively.The annual runoff rate was found to be significantly lower thanthe corresponding corrosion rate for both copper and zinc.Somewhat higher runoff rates of copper were determined fromnaturally green-patinated copper (&gt;40 years old, 2.0g/(m2.y)) compared to brown-patinated copper (1 year old). Themain reasons are specific environmental conditions combinedwith characteristics of the patina layer, which increase themagnitude of dissolved species flushed from the surface duringthe first flush volume of a rain event. No intrinsic effect ofpanel age on the runoff rate was seen for naturally patinatedzinc. However, differences in prevailing environmentalconditions during the initial exposure period and, hence,differences in formation rate and surface coverage of thecorrosion patina, resulted in variations in runoff rate. Thisinitial difference remained also during prolonged exposureperiods and was referred to as a memory effect. Model roof investigations and laboratory studies showedsurface orientation and inclination to have a detrimentaleffect on the runoff rate with high runoff rates from surfacesof low inclination from horizon and surfaces exposed towardsthe wind direction. Based on fieldexposures and literature data, a correlationwas established between the runoff rate and the prevailingSO2-concentration. The runoff rate increases with increasingSO2 level for exposure sites of similar annual precipitationquantities (500-1000 mm/y). A rain device, using artificialrain, was shown to successfully simulate outdoor rain events ofvarying intensity and pH and result in realistic runoff ratesof both copper and zinc. The device was used to monitor changesin metal concentration and quantity of runoff water duringindividual rain events. High metal concentrations are found inthe initial rain volume flushing the surface (first flush),which decreased to rather constant metal concentrations duringthe subsequent rain volume (steady-state). The magnitude offirst flush depends primarily on environmental conditions priorto a rain event and the characteristics of the corrosionpatina. The metal concentration in runoff water increases withrain acidity, decreases with rain intensity and increases withlength of the dry period preceding a rain event. A comparison between instantaneous corrosion rates,monitored by electrochemical impedance spectroscopy using a2-electrode set-up, and runoff rates during a continuous rainevent was performed for naturally patinated copper panels.Corrosion rates were found to be approximately 10 (brownishpatina) and 25 times (greenish patina) lower than correspondinginstantaneous runoff rates. A schematic description of the first flush and steady-stateregion of the runoff process was established. The magnitude ofthe concentration during first flush is primarily affected byprevailing environmental conditions prior to a rain event,while rain pH and intensity primarily affect the concentrationduring steady-state. <b>Key words:</b>atmospheric corrosion, corrosion rate, runoffrate, copper, zinc, field study, laboratory study, roof, firstflush, rain quantity, rain intensity, rain pH, dry and wetdeposition, corrosion and runoff process.

<p>An extensive investigation with parallel field andlaboratory exposures has been conducted to elucidateatmospheric corrosion and metal runoff processes on copper andzinc used for roofing applications. Detailed studies have beenperformed to disclose the effect of various parameters on therunoff rate including: surface inclination and orientation,natural patination (age), patina composition, rain duration andvolume, rain pH, and length of dry periods inbetween rainevents. Annual and average corrosion rates and runoff rateshave been determined consecutively during urban field exposuresin Stockholm on naturally patinated copper and zinc of varyingage and patina composition. The corrosion rate was found todecrease with time, amounting to 6.7 g Cu/(m2.y) and 5.0 gZn/(m2.y) after 48 weeks of exposure, whereas the runoff ratewas relatively constant with time on a yearly basis, being 1.3g/(m2.y) and 3.1 g/(m2.y) for copper and zinc, respectively.The annual runoff rate was found to be significantly lower thanthe corresponding corrosion rate for both copper and zinc.Somewhat higher runoff rates of copper were determined fromnaturally green-patinated copper (>40 years old, 2.0g/(m2.y)) compared to brown-patinated copper (1 year old). Themain reasons are specific environmental conditions combinedwith characteristics of the patina layer, which increase themagnitude of dissolved species flushed from the surface duringthe first flush volume of a rain event. No intrinsic effect ofpanel age on the runoff rate was seen for naturally patinatedzinc. However, differences in prevailing environmentalconditions during the initial exposure period and, hence,differences in formation rate and surface coverage of thecorrosion patina, resulted in variations in runoff rate. Thisinitial difference remained also during prolonged exposureperiods and was referred to as a memory effect.</p><p>Model roof investigations and laboratory studies showedsurface orientation and inclination to have a detrimentaleffect on the runoff rate with high runoff rates from surfacesof low inclination from horizon and surfaces exposed towardsthe wind direction.</p><p>Based on fieldexposures and literature data, a correlationwas established between the runoff rate and the prevailingSO2-concentration. The runoff rate increases with increasingSO2 level for exposure sites of similar annual precipitationquantities (500-1000 mm/y). A rain device, using artificialrain, was shown to successfully simulate outdoor rain events ofvarying intensity and pH and result in realistic runoff ratesof both copper and zinc. The device was used to monitor changesin metal concentration and quantity of runoff water duringindividual rain events. High metal concentrations are found inthe initial rain volume flushing the surface (first flush),which decreased to rather constant metal concentrations duringthe subsequent rain volume (steady-state). The magnitude offirst flush depends primarily on environmental conditions priorto a rain event and the characteristics of the corrosionpatina. The metal concentration in runoff water increases withrain acidity, decreases with rain intensity and increases withlength of the dry period preceding a rain event.</p><p>A comparison between instantaneous corrosion rates,monitored by electrochemical impedance spectroscopy using a2-electrode set-up, and runoff rates during a continuous rainevent was performed for naturally patinated copper panels.Corrosion rates were found to be approximately 10 (brownishpatina) and 25 times (greenish patina) lower than correspondinginstantaneous runoff rates.</p><p>A schematic description of the first flush and steady-stateregion of the runoff process was established. The magnitude ofthe concentration during first flush is primarily affected byprevailing environmental conditions prior to a rain event,while rain pH and intensity primarily affect the concentrationduring steady-state.</p><p><b>Key words:</b>atmospheric corrosion, corrosion rate, runoffrate, copper, zinc, field study, laboratory study, roof, firstflush, rain quantity, rain intensity, rain pH, dry and wetdeposition, corrosion and runoff process.</p>

No description available.

No description available.