Thesis (Ph. D.)--University of New South Wales, 2002. / Also available online.

Thesis (M.S.)--Ohio University, June, 1992. / Title from PDF t.p.

Quantitative chemical and scanning electron microscopical techniques have been employed to investigate the deoxidation kinetics and changes in oxidation product morphology in low carbon steel melts. The techniques have been used to study the deoxidation processes associated with aluminium, titanium, silicon, zirconium and a calcium-aluminium alloy. After the addition of the deoxidant, the total oxygen concentrations of all melts rapidly decreased corresponding with a decrease in the size and number of inclusions observed. This continued to a plateau level of total oxygen concentration and mean inclusion diameter. Samples removed from the melts prior to deoxidation were found to contain globular MnO-FeO inclusions. It was discovered that the morphological sequence for single element deoxidants involved a progressive evolution from liquid globular to solid spherical inclusions followed by polyhedral, dendritic and coralline morphologies. Finally, sintered agglomerates were formed when inclusion clusters collapsed. The extent to which the oxidation products went down the sequence depended on: the dissolution characteristics of the deoxidant; the thermodynamic affinity of the deoxidant for oxygen in the melt; the inclusion/melt interfacial energy characteristics; the refractoriness of the oxidation products and intermediate compounds; and the degree of turbulence experienced by the melt. Explanations have been postulated which elucidate the behaviour of the different deoxidants, as not all displayed the whole morphological sequence. Silicon deoxidation produced spherical silicates, whereas the zirconia inclusions were either spherical or dendritic and the titanium oxidation products had spherical or polyhedral morphologies. Aluminium exhibited all morphologies in the sequence. Deoxidation with the calcium-aluminium alloy was found to have preceded by a two stage process. The initial stage was dominated by the formation of aluminium rich solid oxides followed by the progressive reduction by calcium, resulting in an adhesive liquid calcium-aluminate surface coating. The role of refractory crucible as a collecting surface for the capture and removal of deoxidation products from the melt was investigated, which confirmed that the inclusions were generally incorporated into the low melting point matrix phases. Turbulence also increased the probability that emergence would take place at these capture sites.

The goal of this thesis is to probe the functionality of 2-mercaptobenzimidazole (MBI) as corrosion inhibitor of carbon-steel in both strong and weak aqueous acidic solutions (HCl and H2CO3). To achieve this target electrochemical techniques have been employed, in combination with substrate analysis. Concerning aqueous HCl media, results demonstrate that MBI is an effective corrosion inhibitor, functioning essentially equally well in 1 M, 0.1 M, and 0.01 M HCl concentrations. X-ray photoelectron spectra suggest that MBI is typically bound to the surface in two tautomeric forms (thione and thiol). Furthermore, these data indicate that substrate termination varies as a function of both HCl and MBI concentration, with the interface consisting of MBI bound to film-free carbon-steel on highly inhibited substrates. In further work, the impact of dissolved oxygen, solution temperature, and immersion time on MBI performance in HCl solutions has been assessed. The latter two parameters have considerable influence on MBI inhibition efficiency. More specifically, it was found that MBI decreases dramatically its inhibition efficiency between 60°C and 70°C in 1 M HCl, and also apparently work less well as substrate immersion time increases. As regards MBI performance in deaerated CO2-saturated NaCl (0.62 M) solution, results demonstrate that MBI effectively inhibits corrosion within the parameter space explored i.e. solution temperatures of 30°C and 55°C and total applied pressures (p(H2O) + p(CO2)) of 1 bar and 20 bar. The performance of MBI does not vary greatly for different combinations of these temperatures and pressures. Post immersion substrate characterisation with XRD and SEM indicate that no significant surface scaling occurs under these conditions.

The Florida Department of Transportation (FDOT) has been using supplementary cementitious materials while constructing steel reinforced concrete marine bridge structures for over three decades. It has been found from previous studies that such additions in concrete mix makes the concrete more durable. This research was conducted to better understand the corrosion propagation stage of steel rebar embedded in high performance concrete exposed to high humidity environment. Reinforced concrete samples that were made with binary mixes, and ternary mixes were considered. None of these concretes had any admixed chloride to start with. An accelerated chloride transport method was used to drive chloride ions into the concrete so that chlorides reached and exceed the chloride threshold at the rebar surface and hence the corrosion process initiated after a short period of time (within few days to few months). Once corrosion has initiated the corrosion propagation can be studied. Electrochemical measurements such as rebar potential measurements, Linear Polarization Resistance (LPR), Electrochemical Impedance Spectroscopy (EIS), and Galvanostatic Pulse (GP) measurements were taken at regular intervals (during and after the electro-migration process) to observe the corrosion propagation in each sample. During the propagation stage, reinforcement eventually reached negative potentials values (i.e., Ecorr≤ –0.200 Vsce) for all the samples. The corrected polarization resistance (Rc) was calculated by subtracting the concrete solution resistance from the apparent polarization resistance measured. The Rc values obtained from LPR and GP measurements were converted to corrosion current (as the corroding area is unknown), and these corrosion current values measured over time were used to obtain the calculated mass loss (using Faraday’s Law). A comparison was made of the calculated corrosion current obtained using the LPR and GP tests. A comparison of mass loss was also obtained from the values measured from LPR and GP tests. From the experimental results, it was observed that the corrosion current values were largely dependent on the length of solution reservoirs. For specimens cast with single rebar as well as three rebars, the most recent corrosion current values (measurements taken between July 2018 to October 2020) in general were larger for the rebars that are embedded in specimens prepared with SL mix, followed by specimens prepared with FA, T1, and T2 mixes respectively. The range of corrosion current values (most recent) were 0.8-33.8 μA for SL samples, 0.5-22.5 μA for FA samples, 0.8-14.8 μA for T1 samples, and 0.7-10.4 μA for T2 samples respectively. It was also found that the calculated mass loss values were larger for rebars that are embedded in specimens (single rebar and three rebars) prepared with SL mix, followed by specimens prepared with FA, T1, and T2 mixes respectively. The range of calculated mass loss values were 0.07-1.13 grams for SL samples, 0.06-0.62 grams for FA samples, 0.12-0.54 grams for T1 samples, and 0.06-0.40 grams for T2 samples respectively. A variety of corrosion related parameters (Ecorr, Rs, Rc, and Icorr) and calculated theoretical mass loss values observed, were due to the changing parameters such as concrete compositions, concrete cover thickness, rebar diameter, total ampere-hour applied, and reservoir size. The specimens showed no visual signs of corrosion such as cracks or corrosion products that reached the concrete surface. The actual size of the corroding sites was unknown as the specimens were not terminated for forensic analysis. The size of the corroding sites could affect how much corrosion products are required to crack the concrete. It is speculated that the corrosion products in liquid form penetrated the pore structure but did not build up enough to cause cracks. No cracks or corrosion bleed outs were observed within the monitored propagation period of approximately 1600 days. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2020. / FAU Electronic Theses and Dissertations Collection

No description available.

Neste trabalho, vários tipos de compostos foram testados com o objetivo de avaliar sua potencialidade para uso como inibidores de corrosão de armadura de aço carbono em concreto armado. Os aditivos testados foram benzoato de sódio, benzotriazol, carbonato de ítrio, polietilenoglicol, e hexametilenotetramina. Inicialmente foram realizados ensaios exploratórios para seleção dos candidatos potenciais entre os compostos testados com base na eficiência de inibição determinada por ensaios eletroquímicos, especificamente ensaios de polarização e espectroscopia de impedância eletroquímica. Os ensaios eletroquímicos foram realizados em uma solução sintética composta por 0,01N de hidróxido de sódio (NaOH) mais 0,05N de hidróxido de potássio (KOH), para simular a composição da solução dentro dos poros no concreto. O aditivo que apresentou melhor potencialidade para uso como inibidor de corrosão foi o benzotriazol (BTA). Após eliminação dos compostos que apresentaram potencial de plicação, e seleção do candidato com maior eficiência de inibição no meio de estudo, o efeito da sua concentração na resistência à corrosão foi avaliado. Soluções de nitrito de sódio foram também usadas nas mesmas oncentrações que as adotadas para as de BTA para efeito de comparação. O nitrito de sódio é um inibidor de corrosão já estabelecido para reforços de aço carbono em concreto, mas este tem sido associado com efeitos tóxicos. O benzotriazol (BTA) foi associado com eficiências de inibição sempre superiores às do nitrito de sódio nas mesmas concentrações. Um filme escuro e aderente foi formado na superfície do aço durante períodos longos de imersão no meio alcalino contendo BTA. Os resultados apontaram para o alto potencial de aplicação do BTA como aditivo inibidor da corrosão do aço em estruturas de concreto armado, podendo vir a substituir o nitrito nestas aplicações. / In this work, various compounds were tested to evaluate their potential capability for their use as corrosion inhibitors of carbon steel reinforcement in concretes. The addit ives tested were sodium benzoate, polyethylene glycol, hexamethylenetetramine, benzot riazole and itrium carbonate. Initially, exploratory tests were carried out to select the ones to be used as corrosion inhibitors, based on the inhibit ion ef f iciency determined from elect rochemical tests, specifically polar ization tests and elect rochemical impedance spect roscopy. These tests were carried out in a solut ion composed of 0.01N sodium hydroxide (NaOH) and 0.05N potassium hydroxide (KOH) to simulate the composition of the solution inside the pores in concretes. The additive that presented the most promising potent ial to be used as cor rosion inhibitor was benzot r iazole (BTA). Af ter the elimination of some compounds and selection of the additive with higher corrosion inhibit ion efficiency in the test medium, the effect of its concent ration on the cor rosion inhibition efficiency was evaluated. Sodium nitrite solutions with the same concentrat ions as those solutions with BTA were tested for compar ison reasons. Sodium nitr ite is a well established corrosion inhibitor for carbon steel reinforcement in concretes but it has been related to toxic effects. The BTA was associated to higher corrosion inhibit ion efficiencies than that of sodium nitrite in similar concentrations. A blackish adherent film was formed on the steel surface exposed to BTA solut ions dur ing long periods of immersion in the alkaline medium. The results suggest that BTA is a potential candidate for subst itution of nit rites as corrosion inhibitor of reinforcements in concrete

Neste trabalho, vários tipos de compostos foram testados com o objetivo de avaliar sua potencialidade para uso como inibidores de corrosão de armadura de aço carbono em concreto armado. Os aditivos testados foram benzoato de sódio, benzotriazol, carbonato de ítrio, polietilenoglicol, e hexametilenotetramina. Inicialmente foram realizados ensaios exploratórios para seleção dos candidatos potenciais entre os compostos testados com base na eficiência de inibição determinada por ensaios eletroquímicos, especificamente ensaios de polarização e espectroscopia de impedância eletroquímica. Os ensaios eletroquímicos foram realizados em uma solução sintética composta por 0,01N de hidróxido de sódio (NaOH) mais 0,05N de hidróxido de potássio (KOH), para simular a composição da solução dentro dos poros no concreto. O aditivo que apresentou melhor potencialidade para uso como inibidor de corrosão foi o benzotriazol (BTA). Após eliminação dos compostos que apresentaram potencial de plicação, e seleção do candidato com maior eficiência de inibição no meio de estudo, o efeito da sua concentração na resistência à corrosão foi avaliado. Soluções de nitrito de sódio foram também usadas nas mesmas oncentrações que as adotadas para as de BTA para efeito de comparação. O nitrito de sódio é um inibidor de corrosão já estabelecido para reforços de aço carbono em concreto, mas este tem sido associado com efeitos tóxicos. O benzotriazol (BTA) foi associado com eficiências de inibição sempre superiores às do nitrito de sódio nas mesmas concentrações. Um filme escuro e aderente foi formado na superfície do aço durante períodos longos de imersão no meio alcalino contendo BTA. Os resultados apontaram para o alto potencial de aplicação do BTA como aditivo inibidor da corrosão do aço em estruturas de concreto armado, podendo vir a substituir o nitrito nestas aplicações. / In this work, various compounds were tested to evaluate their potential capability for their use as corrosion inhibitors of carbon steel reinforcement in concretes. The addit ives tested were sodium benzoate, polyethylene glycol, hexamethylenetetramine, benzot riazole and itrium carbonate. Initially, exploratory tests were carried out to select the ones to be used as corrosion inhibitors, based on the inhibit ion ef f iciency determined from elect rochemical tests, specifically polar ization tests and elect rochemical impedance spect roscopy. These tests were carried out in a solut ion composed of 0.01N sodium hydroxide (NaOH) and 0.05N potassium hydroxide (KOH) to simulate the composition of the solution inside the pores in concretes. The additive that presented the most promising potent ial to be used as cor rosion inhibitor was benzot r iazole (BTA). Af ter the elimination of some compounds and selection of the additive with higher corrosion inhibit ion efficiency in the test medium, the effect of its concent ration on the cor rosion inhibition efficiency was evaluated. Sodium nitrite solutions with the same concentrat ions as those solutions with BTA were tested for compar ison reasons. Sodium nitr ite is a well established corrosion inhibitor for carbon steel reinforcement in concretes but it has been related to toxic effects. The BTA was associated to higher corrosion inhibit ion efficiencies than that of sodium nitrite in similar concentrations. A blackish adherent film was formed on the steel surface exposed to BTA solut ions dur ing long periods of immersion in the alkaline medium. The results suggest that BTA is a potential candidate for subst itution of nit rites as corrosion inhibitor of reinforcements in concrete

by Cho, King-sum. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (leaves 108-110). / Text in English; abstracts in English and Chinese. / by Cho, King-sum. / Abstract --- p.i / 摘要 --- p.iii / Acknowledgment --- p.iv / Contents --- p.v / List of figures --- p.x / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Review of non-destructive techniques --- p.2 / Chapter 1.1.1 --- Liquid penetration technique --- p.2 / Chapter 1.1.2 --- Eddy current inspection --- p.2 / Chapter 1.1.3 --- Ultrasonic testing --- p.3 / Chapter 1.1.4 --- Radiography --- p.3 / Chapter 1.1.5 --- Magnetic testing methods --- p.4 / Chapter 1.2 --- Barkhausen emission --- p.4 / Chapter 1.3 --- The development of Barkhausen Emission --- p.5 / Chapter 1.4 --- The advantages of using Barkhausen emission --- p.6 / Figures for chapter1 --- p.8 / Chapter 2 --- Iron-carbon System --- p.9 / Chapter 2.1 --- Iron-iron carbide phase diagram --- p.9 / Chapter 2.2 --- Invariant reactions in the Fe-Fe3C phase diagram --- p.11 / Chapter 2.3 --- Classification of carbon steels --- p.12 / Chapter 2.4 --- Effect of heat treatment on plain-carbon steels --- p.13 / Chapter 2.4.1 --- Annealing and normalizing --- p.14 / Chapter 2.4.2 --- Slow cooling --- p.15 / Chapter 2.5 --- Process of recovery and recrystallization --- p.15 / Chapter 2.5.1 --- Recovery --- p.16 / Chapter 2.5.2 --- Recrystallization --- p.16 / Chapter 2.5.3 --- Grain growth --- p.17 / Figures for chapter2 --- p.18 / Chapter 3 --- Background Theory --- p.23 / Chapter 3.1 --- Ferromagnetism --- p.23 / Chapter 3.1.1 --- Localized moment theory --- p.24 / Chapter 3.1.2 --- Band theory --- p.25 / Chapter 3.1.3 --- Hysteresis loop --- p.25 / Chapter 3.2 --- Domain theory --- p.26 / Chapter 3.2.1 --- Magnetic domain --- p.26 / Chapter 3.2.2 --- Structure of domain wall --- p.27 / Chapter 3.2.3 --- Domain wall motion --- p.29 / Chapter 3.2.4 --- Magnetostatic energy --- p.30 / Chapter 3.2.5 --- Magnetization process --- p.32 / Chapter 3.3 --- Effect of applied stress --- p.33 / Chapter 3.3.1 --- Stress --- p.33 / Chapter 3.3.2 --- Magnetostriction --- p.34 / Chapter 3.3.3 --- Effect of stress on magnetization --- p.34 / Figures for chapter 3 --- p.37 / Chapter 4 --- Instrumentation --- p.39 / Chapter 4.1 --- Introduction --- p.39 / Chapter 4.2 --- Experimental setup for Barkhausen emission --- p.39 / Chapter 4.2.1 --- Magnetizing unit --- p.40 / Chapter 4.2.2 --- Signal detection unit --- p.41 / Chapter 4.2.3 --- Signal processing unit --- p.42 / Chapter 4.3 --- The typical BE profile --- p.42 / Chapter 4.4 --- Specimen treatment --- p.43 / Chapter 4.4.1 --- Optical microscope --- p.43 / Chapter 4.4.2 --- Vickers´ة hardness tester --- p.44 / Chapter 4.4.3 --- Thermal resistance furnace --- p.45 / Chapter 4.4.4 --- Instron loading machine --- p.45 / Figures for chapter4 --- p.47 / Chapter 5 --- Experiments and Results: Evaluation of Carbon Content in Steel --- p.52 / Chapter 5.1 --- Introduction --- p.52 / Chapter 5.2 --- Experiments and results --- p.52 / Chapter 5.3 --- Discussions --- p.53 / Chapter 5.3.1 --- The magnetization process --- p.53 / Chapter 5.3.2 --- The BE profiles 、 --- p.54 / Chapter 5.3.3 --- Hardness --- p.57 / Chapter 5.4 --- Conclusions --- p.57 / Figures for chapter5 --- p.58 / Chapter 6 --- Experiments and Results: The Effects of annealing on Barkhausen Emission in Mild Steel Bars --- p.64 / Chapter 6.1 --- Introduction --- p.64 / Chapter 6.2 --- Experiments --- p.64 / Chapter 6.3 --- Results and discussions --- p.64 / Chapter 6.3.1 --- The mechanical properties --- p.65 / Chapter 6.3.2 --- Grain size --- p.65 / Chapter 6.3.3 --- BE profiles --- p.66 / Chapter 6.4 --- Conclusions --- p.67 / Figures for chapter6 --- p.68 / Chapter 7 --- Experiments and Results: The Effects of Dynamic and Residual Stresses on Barkhausen Emission in Annealed Mild Steel Bars --- p.76 / Chapter 7.1 --- Introduction --- p.76 / Chapter 7.2 --- Experiments --- p.76 / Chapter 7.2.1 --- Measurement of dynamic loading (with samples of Set A) --- p.77 / Chapter 7.2.2 --- Measurement of residual stress (with samples of Set B) --- p.77 / Chapter 7.2.3 --- Measurement of continuous tensile stress (with samples of Set C) --- p.77 / Chapter 7.3 --- Results and discussions --- p.78 / Chapter 7.3.1 --- Peak ratio of the BE profile --- p.78 / Chapter 7.3.2 --- The initial peak value under the effects of increasing tensile stress --- p.81 / Chapter 7.4 --- Conclusions --- p.82 / Figures for chapter7 --- p.83 / Chapter 8 --- Experiments and Results: The Recovery of Strained Steel Bars by Annealing --- p.94 / Chapter 8.1 --- Introduction --- p.94 / Chapter 8.2 --- Experiments --- p.94 / Chapter 8.2.1 --- Measurement of annealed sample (Set D) --- p.95 / Chapter 8.2.2 --- Results of the Set E samples --- p.95 / Chapter 8.3 --- Results and discussions --- p.95 / Chapter 8.3.1 --- Hardness --- p.96 / Chapter 8.3.2 --- Peak ratio of the BE profile --- p.97 / Chapter 8.3.3 --- BE profile for the samples of Set E --- p.98 / Chapter 8.4 --- Conclusions --- p.99 / Figures for chapter8 --- p.100 / Chapter 9 --- Conclusions and Suggestions for Further Studies --- p.104 / Bibliography --- p.108

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 138-141). Also available via the Internet.