Epoxy-coated reinforcement was developed in the 1970s and became the primary corrosion protection technique in North America. Throughout the years, ECR has exhibited mixed results, with some regions and jurisdictions reporting good corrosion protection while others reported poor field performance of ECR. It has been established that epoxy coating can lose its adhesion in a wet environment thus providing poor corrosion protection of reinforcing steel. However, limited research has been done on the influence of concrete pore solution on adhesion of epoxy coating to reinforcing steel. This research investigates the effect of high alkali conditions on performance of ECR bars. Based on the test results, it was found that the rate of disbondment increases as the hydroxyl ion concentration increases and presence of high temperature accelerates the disbondment process.

Epoxy-coated reinforcement was developed in the 1970s and became the primary corrosion protection technique in North America. Throughout the years, ECR has exhibited mixed results, with some regions and jurisdictions reporting good corrosion protection while others reported poor field performance of ECR. It has been established that epoxy coating can lose its adhesion in a wet environment thus providing poor corrosion protection of reinforcing steel. However, limited research has been done on the influence of concrete pore solution on adhesion of epoxy coating to reinforcing steel. This research investigates the effect of high alkali conditions on performance of ECR bars. Based on the test results, it was found that the rate of disbondment increases as the hydroxyl ion concentration increases and presence of high temperature accelerates the disbondment process.

This thesis investigates the application of plasma immersion ion implantation (PIII) to polymers. PIII requires that a high negative potential be applied to the surface of the material while it is immersed in a plasma. This presents a problem for insulating materials such as polymers, since the implanting ions carry charge to the surface, resulting in a charge accumulation that effectively neutralises the applied potential. This causes the plasma sheath at the surface to collapse a short time after the potential is applied. Measurements of the sheath dynamics, including the collapsing sheath, are performed using an electric probe. The results are compared to theoretical models of the plasma sheath based on the Child-Langmuir law for high voltage sheaths. The theoretical model predicts well the sheath dynamics for conductive substrates. For insulating substrates the model can account for the experimental observations if the secondary electron coefficient is modified, justified on the basis of the poly-energetic nature of the implanting ions. If a conductive film is applied to the insulator surface the problem of charge accumulation can be avoided without compromising the effectiveness of PIII. The requirement for the film is that it be conductive, yet transparent to the incident ions. Experimental results are presented which confirm the effectiveness of the method. Theoretical estimates of the surface potential show that a film of the order of 5nm thickness can effectively circumvent the charge accumulation problem. Efforts to produce and characterise such a film form the final two chapters of this thesis. The optimal thickness is determined to be near the percolation threshold, where a marked increase in conductivity occurs. Spectroscopic ellipsometry is shown to be an excellent method to determine the film thickness and percolation threshold non-invasively. Throughout this work cathodic vacuum arcs are used to deposit thin films and as a source of metal plasmas. The design and construction of a pulsed cathodic vacuum arc forms a significant part of this thesis. Investigations of the cathode spots and power supply requirements are presented.

Thesis (Ph. D.)--University of Missouri-Columbia, 1998. / Typescript. Vita. Includes bibliographical references (leaves 240-248). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1998. / Typescript. Vita. Includes bibliographical references (leaves 240-248). Also available on the Internet.

As part of the water resources policy of the state of CearÃ, in Northeast Brazil, COGERH, as an operational instrument, has among its tasks the distribution of bulk water for various uses. Among the water systems that COGERH operates are the pumping stations, which are responsible for supplying water for cities, industries, irrigation, etc. It is vital that these structures operate satisfactorily and efficiently. Among the many devices that make up the pumping stations are the semisubmersible floating metal chambers that are located on the water surface of the reservoirs, providing support to the pumps and motors such that they can be set and operated reliably and efficiently. However, these structures are made from steel and therefore are subject to severe corrosion processes, making it necessary for the painting of the submerged areas to ensure the necessary protection to avoid oxidation of them. As painting alone is not a process that ensures 100% efficiency in terms of coating and has a relatively short lifespan, complementary processes are necessary to ensure safe protection against corrosion. Among these processes is the Cathodic Protection, which ensures that, while a difference in electrochemical potential is being generated between the structure to be protected and a sacrificial anode, the structure will not undergo corrosion processes. For this study, it has been designed and installed an Impressed Current Cathodic Protection System with a potential ON of protection of -2.67 Volts (DC) for the Pumping Station known as "EB GaviÃoâ chosen due to its strategic importance within the state infrastructure of water resources, responsible for supplying water for major cities and industries. Keywords : / Dentro da polÃtica dos recursos hÃdricos do estado do CearÃ, no Nordeste do Brasil, a COGERH, como instrumento operacional, tem entre suas atribuiÃÃes a distribuiÃÃo de Ãgua bruta para usos diversos. Dentre os sistemas que a COGERH operacionaliza estÃo as estaÃÃes de bombeamento, as quais sÃo responsÃveis por abastecer cidades, indÃstrias, irrigantes, etc. à fundamental que tais estruturas operem de forma satisfatÃria e eficiente. Dentre os muitos equipamentos que compÃem as estaÃÃes de bombeamento estÃo Ãs cÃmaras metÃlicas flutuantes emisubmersÃveis que se localizam na superfÃcie de Ãgua dos reservatÃrios, dando sustentaÃÃo para que as bombas e motores possam ser fixados e operados de forma confiÃvel e eficiente. No entanto estas estruturas, por serem de aÃo, estÃo sujeitas a processos de corrosÃo severos, fazendo-se necessÃrio que a pintura das Ãreas submersas assegurem a proteÃÃo necessÃria para que nÃo haja oxidaÃÃo das mesmas. Como a pintura nÃo à um processo que garante uma eficiÃncia de 100% e termos de revestimento e tem uma vida Ãtil relativamente curta, fazem-se necessÃrios processos complementares para uma segura proteÃÃo anti-corrosÃo. Dentre esses processos està a ProteÃÃo CatÃdica que assegura que enquanto estiver sendo gerada uma âdiferenÃa de potencial eletroquÃmicoâ entre a estrutura a ser protegida e um anodo de sacrifÃcio a estrutura nÃo sofrerà severos processos de corrosÃo. Neste estudo foi dimensionado e instalado um Sistema de ProteÃÃo CatÃdica por Corrente Impressa assegurando um potencial ON de proteÃÃo de -2,67 Vcc para a estaÃÃo de bombeamento denominada âEB GaviÃoâ pela importÃncia estratÃgica que ocupa dentro da infraestrutura estadual de recursos hÃdricos, fazendo parte de sistema responsÃvel pelo abastecimento de importantes cidades e indÃstrias.

京都大学 / 0048 / 新制・課程博士 / 博士(人間・環境学) / 甲第22859号 / 人博第967号 / 新制||人||229(附属図書館) / 2020||人博||967(吉田南総合図書館) / 京都大学大学院人間・環境学研究科相関環境学専攻 / (主査)教授 内本 喜晴, 教授 吉田 寿雄, 准教授 戸﨑 充男 / 学位規則第4条第1項該当 / Doctor of Human and Environmental Studies / Kyoto University / DFAM

A thin wire Ag/AgCl reference electrode was prepared using 50 μm Ag wire in dilute FeCl3. The wire was embedded beneath the polyurethane topcoat of two sacrificial coating systems to monitor their corrosion potential. This is the first report of a reference electrode embedded between organic coating layers to monitor substrate health. The embedded reference electrode (ERE) successfully monitored the corrosion potential of Mg primer on AA 2024-T3 for 800 days of constant immersion in dilute Harrison’s solution. Zn primer on steel had low accuracy in comparison. This is in part due to short circuiting by Zn oxidation products, which are much more conductive than Mg corrosion products. Data interpretation was improved through statistical analysis. On average, ERE corrosion potentials are 0.1 to 0.2 V and 0.2 to 0.3 V more positive than a saturated calomel electrode (SCE) in solution for AA 2024-T3 and steel coating systems, respectively. Further research may confirm that ERE obtains corrosion potential information not possible by an exterior, conventional reference electrode. The ERE is stable under polarization. AA 2024-T3 was polarized to -0.95 V vs ERE to emulate controlled potential cathodic protection (CPCP) applications. Polarizations of -0.75 V vs ERE are recommended for future experiments to minimize cathodic delamination. The ERE was utilized to analyze coating mixtures of lithium carbonate, magnesium nitrate, and Mg metal on AA2024-T3. Corrosion potential, low frequency impedance by electrochemical impedance spectroscopy (EIS), and noise resistance by electrochemical noise method (ENM) were reported. Coating performance ranking is consistent with standard electrochemical characterization and visual analyses. The results suggest anti-corrosion resistance superior to a standard Mg primer following 1600 hours of B117 salt spray. Both lithium carbonate and magnesium nitrate are necessary to achieve corrosion protection. Unique corrosion protective coatings for aluminum could be designed through continued mixture optimization. The Ag wire ERE has been utilized for the characterization and ranking of experimental coatings on metal substrates. Structural health monitoring and corrosion potential feedback of cathodic protection systems are additional uses. There is some indication that CPCP may be applied by ERE to control the substrate polarization for an organic coating system.

The extent to which dissolved Li2CO3 can inhibit corrosion of lightweight Mg alloy sheet metal in contact with aqueous NaCl solutions was determined. Two Mg alloy sheet metal alloys were studied, which include: AZ31B (3% Al, 1% Zn, 0.5% Mn, balance Mg) and ZEK100 (1.3% Zn, 0.2% Nd, 0.25% Zr, balance Mg). Corrosion inhibition was first determined for each alloy separately when immersed in 0.1 M NaCl (aq), with and without dissolved Li2CO3 added. The addition of 100 mM Li2CO3 (aq) reduces the corrosion rate of AZ31B by a factor of ~10 and ZEK100 by a factor of ~12. Inhibition involves a reduction in both global anodic dissolution and cathode (H2 gas evolution) kinetics. It also involves suppression of localized filament-like corrosion and associated anode/cathode activation. Site specific cross-sectional analysis of the surface film formed during forced anode activation (polarization) revealed the formation of a Li-doped MgO film, akin to what forms, and provides protection to, Mg alloys with Li added as an alloying element. Such film formation was used to explain all corrosion inhibition aspects. Corrosion inhibition was then determined for ZEK100 when immersed in 0.1 M NaCl (aq) with and without a spray-deposited Li2CO3 surface coatings added. A commercial hexafluoro-titanate/zirconate-polymer conversion coating (Bonderite® MNT 5200) also served as the comparative basis. The Li2CO3-coated surface exhibits the lowest relative corrosion, whereas the conversion-coated surface exhibits the highest. Improved corrosion control is attributed to the formation of a compact coating (physical contribution) and the ability of dissolved Li2CO3 to inhibit both the anode and cathode kinetics (electrochemical) contribution. The findings are of interest to automotive industry as a possible means to effectively control corrosion of Mg alloy sheet metal using Li2CO3 as a surface pre-treatment or the inclusion of Li2CO3 to a polymer as an inhibitor additive. / Thesis / Doctor of Philosophy (PhD) / The objective of this research was to determine the extent to which dissolved lithium carbonate (Li2CO3) can inhibit corrosion of lightweight magnesium (Mg) alloy sheet metal in contact with aqueous NaCl solutions. Corrosion inhibition by dissolved Li2CO3 in 0.1 M NaCl (aq) was demonstrated for two Mg alloy sheet metal alloys: AZ31B (3% Al, 1% Zn, 0.5% Mn, balance Mg) and ZEK100 (1.3% Zn, 0.2% Nd, 0.25% Zr, balance Mg). As a next step towards the development of a protective coating scheme, corrosion inhibition of ZEK100 by Li2CO3, as a surface coating applied, is achieved through a reduction of both the anodic dissolution and the cathode (H2 gas evolution) kinetics in large part by the formation of a Li-doped MgO film at anodic dissolution sites.

This thesis is devoted to the investigation of ion generation and fluxes from cathodic arc spots for a better understanding of energetic deposition of thin film. The ion generation is related to the arc spot properties, and ion fluxes influence the film deposition. Significantly, the cathodic arc has the explosion characteristic for the ignition process, which is the generation process of ions. Thus, it is not easy to observe the spot characteristics, and some fundamental questions related to cathodic arc spot motion are still open. The multiply charged ions produced from the arc spot ignition process have a higher ion potential energy than ions of other deposition techniques; therefore, consideration of the effect of ion potential energy on film growth is required for the cathodic arc technique. The first part of this thesis deals with fundamental arc spot characteristics, especially the trend of spot motion in a magnetically steered arc source placed in vacuum or in a reactive gas atmosphere. This is investigated with a streak camera having high spatial and temporal resolutions. To answer the fundamental question of whether the spots have characteristic times, such as a 'periodic spot lifetime' or a 'the periodic characteristic time between spot ignitions”, the streak images were analyzed by fast Fourier transformation (FFT). It was found that the power spectrum of the arc spot fluctuations does not show any specific frequencies, which means the arc spot ignition process can be described by a fractal model, and the spectral slope in the log-log power-frequency diagram has a tendency to be reduced in the presence of a compound (for example oxide or nitride) layer on the cathode surface. Through the fractal analysis and measurements of optical emission spectroscopy, the fundamental limitation of the temporal resolution for the optical emission method is determined and considered. The second part of this thesis considers cathodic arc’s application aspects: the energetic deposition of thin films and coatings. Most studies related to energetic deposition have previously investigated the effects of ion kinetic energy on film deposition; however, this thesis focuses on the effects of ion potential energy on film growth. To investigate the effect of ion potential energy on film growth, plasma diagnostic by energy-resolved mass spectrometry and deposited film characterization by XRD, XRR, AFM, profilometry and SEM were carried out. The ion potential energy influences the preferential direction of film growth or a polycrystalline growth in the case of aluminum deposition. This result could be a starting point for further research into the effect of ion potential energy on film deposition.