The low density and high relative strength of Mg alloys means they can offer engineering benefits over steels or Al alloys. However, the susceptibility of Mg alloys to corrosion has limited their exploitation and restricted their use to more benign environments. An Mg-Al intermetallic surface layer is a good candidate for a robust corrosion protection method. This work demonstrates their development by using a novel ionic liquid electroplating process to deposit Al on to Mg substrates that when heat treated diffuses to form discrete intermetallic layers. Examination of three Mg-Al-Zn alloys showed that the amount Mg-Al intermetallic phases in their microstructures was linked to the quantity of Al they contained. Subsequent self-corrosion measurements using electrochemical impedance spectroscopy demonstrated that their performance was connected to the amount of intermetallic present, and in particular the strength of the micro-galvanic couples generated between the anodic and cathodic phases. Measurements of the self-corrosion behaviour of manufactured samples of the Mg-Al intermetallics confirmed that they could provide significant improvements, but it was acknowledged that their noble nature compared to an Mg substrate would encourage galvanic corrosion if a surface layer was damaged. As such the galvanic activity of the Mg-Al-Zn alloys and Mg-Al intermetallics was compared against a pure Mg standard using zero resistance ammetry and the resistance box technique. Galvanic models of alloy self-corrosion and a damaged intermetallic surface layer were also used to assess the potential problem. These measurements demonstrated that the intermetallics could act as strong cathodes, but further discussion on the nature of the behaviour suggested means by which galvanic corrosion might self-limit or self-repair. The galvanic corrosion experiments also revealed how the combination of current flow and a solution saturated with Mg2+ ions could lead to the formation of a highly protective Mg(OH)2 film with promising characteristics.

Analysis of corrosion in marine and acid environments is a complicated task, involving the interaction of thermodynamic, kinetic and geometrical factors. Two mathematical models which predict corrosion behaviour have been implemented for personal computers. The first program uses an assumption of unidirectional current flow to simplify the prediction of potential distributions for systems of essentially cylindrical geometry containing natural seawater-based electrolytes of differing strength. Using experimentally determined electrochemical and flow rig data, experimental and theoretical results were compared. The correlation between the two was shown to be poor, and this is attributed to the unrepresentative nature of the electrochemical data input to the model. The second model involves the synthesis of polarization curves. Several algorithms to model passivating behaviour have been studied, and one was selected and incorporated into the calculation routine. A number of kinetic and thermodynamic parameters are used in algorithms describing such behaviour, along with activation, concentration and solution polarization effects, for a number of redox reactions, which are then combined to produce an overall potential-log current density curve. Experimentally determined data for pure iron and different stainless steels in marine and acid environments of differing dissolved oxygen content and temperature were obtained. Theoretical models were constructed for each system, and compared to experimental data. Excellent correlation between experimental and theoretical data was obtained for potential ranges in excess of 2 V. Trends in parameter values were discussed, and compared to published data. The transition between stable and unstable passivity of stainless steels was shown to be dependent on the oxygen reduction diffusion limited current density and the iron dissolution reaction free corrosion current density, which in turn was linked to the dissolved oxygen content and temperature of the electrolyte. A new model for the behaviour of stainless steels in the transpassive region was proposed.

No description available.

Left hemisphere brain-damaged, right hemisphere brain-damaged and non-brain-damaged controls viewed four videotaped vignettes portraying four different emotions (e.g. neutral, inappropriate happiness, inappropriate anger and sadness). Each of the vignettes was followed by a questionnaire which tested the subjects recall of the emotional, and some non-emotional, content. Additionally all subjects had continuous galvanic skin response recordings taken from the hand ipsilateral to injury during the entire testing session. Left hemisphere brain-damaged subjects and right hemisphere brain-damaged subjects displayed impaired performance on the postvignette questionnaires. Control subjects performance was the highest. Left hemisphere brain-damaged subjects had the greatest increase in GSR from baseline levels for all scenes. The right hemisphere brain-damaged and control subjects remained stable at or around baseline levels.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1957. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 189-196).

Made available in DSpace on 2014-06-11T19:32:22Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-10-31Bitstream added on 2014-06-13T19:02:56Z : No. of bitstreams: 1 delbianco_gab_dr_rcla.pdf: 1713652 bytes, checksum: 5e32e8b54d395b31da88b469da16ea58 (MD5) / O encapsulamento de resíduos em massas cerâmicas tem sido uma solução extremamente interessante porque permite a imobilização de resíduos tóxicos. O objetivo deste trabalho é estudar a aplicação de rejeitos de galvanoplastia às massas cerâmicas, sem o comprometimento das propriedades físico-químicas do produto final, possibilitando assim o desenvolvimento de uma cerâmica rústica, com variação de cores e boas propriedades tecnológicas. Os ensaios de caracterização das matérias primas foram a Fluorescência de Raios X, Iodometria e Difração de Raios X. Corpos de prova foram preparados por via seca, em formulações de massa variando o tipo de argila, a concentração do resíduo e o tipo de processo, foram realizados ensaios para controle das propriedades físico-químicas e para classificação de uso, de acordo com a NBR 13818/97. A análise petrográfica permitiu observar o comportamento do resíduo nos diferentes processos de preparação e os ensaios de eflorescência, lixiviação e solubilização comprovaram a inertização do resíduo. A utilização dos resíduos como aditivo apresentaram resultados bastante satisfatórios e indicam a viabilidade comercial da cerâmica rústica, pois a presença de CuO e NiO possibilitaram o aumento da vitrificação das massas cerâmicas e permitiu utilizar a argila considerada “rejeito” pelos ceramistas do Pólo de Santa Gertrudes-SP. / The encapsulating of residues in ceramic masses has been an extremely interesting solution because it allows the immobilization of toxic residues. The objective of this paper is to study the application of wastes of galvanoplasty to the ceramic masses, without compromising the physicist-chemistries properties of the final product, thus making possible the development of rustic ceramics, with variation of colors and good technological properties. The assays of characterization of the raw materials were the X Rays Fluorescence, Iodometry and X Ray Diffraction. Samples were prepared by dry process method, in mass formularizations varying the type of clay, the concentration of the residue and the type of process, assays were carried out to know the control of physicist-chemistries properties and classification of use, according to NBR 13818/97. The petrographic analysis allowed to observe the behavior of the residue in different processes of preparation and the assays of efflorescence, leaching and solubilization had proven the inertness of the residue. The use of the residues as additive presented sufficiently satisfactory results and indicates the commercial viability of rustic ceramics; therefore the presence of CuO and NiO makes possible the increase of the vitrification of the ceramic masses and allowed to use the considered clay “waste” for the ceramists of the pole of Santa Gertrudes-SP.

Scanning electrochemical microscopy is a method that incorporates an ultramicroelectrode capable of facilitating electrochemical reactions paired with an XYZ positioning system capable of micron-level movements. This study investigates the corrosion behavior of structural transition joint clad material that contains steel, pure aluminum, and an aluminum alloy blast welded into a single joint. This study will characterize the corrosion response of the structural transition joint and identify the galvanic activity measured between its layers. High-temperature coatings in this study are designed to be used effectively up to 1400?F. In this study, we characterized several commercial high-temperature coatings exposed to different levels of heat. General trends of decreasing barrier performance were observed with the exception when these coatings are exposed to their rated temperature limit of 1400?F, at which the barrier increased slightly, indicated by their low-frequency impedance modulus. The cause is a combination of sintering and oxide formation.

Peroxidase enzymes are of critical importance within the scientific community for their applications in biosensing assays. In a living system, natural peroxidases function as catalysts in the oxidation of peroxide (e.g., H2O2) - a harmful byproduct of aerobic processes and convert them into harmless compounds. Such an ability allows peroxidases to serve as labels in biosensing assays, where they are conjugated to antibodies and accurately produce a detection signal by catalyzing substrates. However, due to intrinsic limitations, namely instability, Peroxidase made of proteins substantially inhibit broader applications. Alternatively, nanoparticles produced from noble metals have been found to exhibit peroxidase-like abilities and, therefore, can be used as synthetic enzymes with the potential to replace their natural counterparts. Given that the stability of most peroxidase mimics is already much better than their natural counterparts, in this field, the principal challenge has been creating substantial improvements to the catalytic efficiency of the mimics. This study sought to create a cage-like nanostructure ( denoted as nanocages) consisting of two platinum group metals. This experiment uses Galvanic replacement as a mechanism to hollow all Nanocages formed. Galvanic replacement has been primarily demonstrated using coinage metals ( Ex. Ag and Au). This experiment seeks to show that this process is viable for other Nobel metals, as well. In particular, palladium cubes were used as scaffolds or sacrificed templates to induce the reaction with a precursor containing a secondary Nobel metal (Platinum, Rhodium, or Ruthenium). Once viable samples where produced and checked via TEM ( Transmission Electron microscope), the peroxidase-like activity was compared to the activity of a non-hollowed nanostructure of the same material composition using TMB colorimetric assay.

Chloride levels are increasing in some water supplies around the country due to use of road salts and seawater intrusion, which can increase the chloride-to-sulfate mass ratio (CSMR) and trigger serious water lead contamination from galvanic lead solder: copper pipe corrosion. Previous attempts to control this problem through simple water chemistry modifications were unsuccessful, but in this work a combination of zinc orthophosphate and moderate alkalinity mitigated lead release in testing at two utilities. Either zinc alone or phosphate alone were irrelatively ineffective, but the combination of zinc orthophosphate reduced lead leaching by 54-99% (compared to the control without inhibitors) if alkalinity was above about 55 mg/L as CaCO3. These results may help mitigate future lead in water contamination events. / MS

Lead corrosion in premise plumbing systems from materials, such as lead pipes, soldered joints, and brass, can cause elevated lead in drinking water. This work examined mechanisms by which galvanic corrosion of lead solder:copper joints is accelerated by high chloride, low sulfate, and high nitrate in the water. Galvanic corrosion studies conducted using simulated copper plumbing joints showed lowered pH and concentrated anions at the lead solder surface. A combination of low pH and high chloride can prevent passivation of the solder surface, indefinitely sustaining high corrosion rates and lead contamination of potable water supplies. The mass of lead leached to water correlated with predictions based on Faraday's law, although a portion of the oxidized lead remained attached to solder in a scale layer. When the level of sulfate in water increased relative to chloride, galvanic currents and associated lead contamination could be greatly reduced. The impact of chloride-to-sulfate mass ratio (CSMR) on lead leaching from 50:50 lead:tin solder galvanically coupled to copper was examined at the bench scale.The CSMR can be affected by coagulant changeover, use of desalinated water, anion exchange, brine leaks, and other treatment changes. Consistent with prior experiences, increasing the CSMR in the range of 0.1 to 1.0 produced dramatic increases in lead leaching from this source. Above this range, while lead leaching was generally very high, there was little correlation between lead release and CSMR. The impact of nitrate was tested at the bench scale using synthesized water. Results consistently showed that increasing nitrate in the range of 0 to 10 mg/L NO??N, could dramatically increase lead leaching from simulated soldered pipe joints. Although higher nitrate slightly increased the galvanic current, the main factor affecting lead release appears to be initiation of non-uniform corrosion, with small pieces of solder detaching into the water. Under some circumstances, the decay of chloramine after it leaves the treatment plant, and formation of nitrate via nitrification, can markedly increase corrosivity of distributed water to lead solder. The bench scale experiments conducted in this work illuminated many issues related to accelerated lead corrosion of solder. However, future research is necessary to further elucidate the mechanisms behind nitrate-accelerated corrosion, as well as methods for inhibition of corrosion due to chloride and nitrate. / Master of Science