Thesis (M.S. in materials science and engineering)--Washington State University, August 2008. / Title from PDF title page (viewed on Mar. 11, 2009). "School of Mechanical and Materials Engineering." Includes bibliographical references.

Thesis (Ph. D.)--Columbia University, 1940. / Vita.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1956. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 148-150).

Made available in DSpace on 2014-06-11T19:32:50Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-10-22Bitstream added on 2014-06-13T19:06:58Z : No. of bitstreams: 1 dutra_cam_dr_guara.pdf: 4819005 bytes, checksum: 73e78233a4fdf5d98fd8f747070d5fdc (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Os revestimentos de zinco são os mais amplamente utilizados na proteção do aço contra a corrosão. Atualmente, estes vêm sendo substituídos por ligas, como o Zn- Ni, pois têm revelado melhores propriedades mecânicas, maior resistência à corrosão quando comparados aos revestimentos de zinco de mesma espessura, além de poderem ser aplicados em temperaturas mais elevadas. Outros revestimentos de ligas de zinco formados com elementos do grupo VIIIB têm se mostrado promissores por apresentarem propriedades semelhantes e protegerem o aço por ação galvânica. Neste trabalho, eletrodepósitos de Zn, Zn-12%Ni, Zn-0,6%Co e Zn-<3%Fe-0,6%Co obtidos sobre aço SAE 1010, a partir de banhos alcalinos comerciais foram tratados por cromatização e caracterizados quanto às propriedades mecânicas, morfologia, comportamento eletroquímico e resistência à corrosão em solução de NaCl 3,5% e na presença de oxi-ânions do grupo VIB. Os estudos foram realizados através de medidas de microdureza, rugosidade, MEV, EDS, DRX e técnicas eletroquímicas. Dentre os eletrodepósitos estudados, o de Zn-Ni mostrou maior valor de rugosidade, enquanto os demais apresentaram resultados próximos aos do substrato de aço. As ligas Zn-Ni e Zn-Fe-Co apresentaram maior dureza em relação ao Zn. Através de DRX foi verificado que os eletrodepósitos são cristalinos, sendo identificada na liga Zn-Ni a presença das fases g (Ni5Zn21) e d (Ni3Zn22), responsáveis pela sua maior resistência à corrosão. As ligas tratadas por cromatização revelaram maior resistência à corrosão, tanto nos ensaios de salt spray, como nos ensaios eletroquímicos. O principal produto de corrosão encontrado sobre os eletrodepósitos, após os ensaios de salt spray e de imersão em solução de NaCl 3,5 %, foi o Zn5(OH)8Cl2.H2O, não sendo detectados óxidos ou hidróxidos formados... / The zinc coatings are the most widely used in protecting steel against corrosion. Currently, these are being replaced with alloys such as Zn-Ni, for they have shown better mechanical properties, higher corrosion resistance when compared to zinc coatings of equal thickness, and can be applied at higher temperatures. Other zinc alloys coatings formed with elements of group VIIIB were shown to be promising because they have similar properties and protect the steel by galvanic action. In this study, electrodeposited Zn, Zn-12% Ni, Zn-0.6%Co and Zn-<3% Fe-0.6% Co coatings obtained on steel SAE 1010, from alkaline baths have been treated with commercial chromate and characterized by the mechanical properties, morphology, electrochemical behavior and corrosion resistance in NaCl 3.5% and in presence of oxy-anions of group VIB. The studies have been performed by measurements of hardness, roughness, optical microscopy, SEM, EDS, XRD and electrochemical techniques. Among the studied electrodeposits, Zn-Ni showed higher roughness, while others showed results similar to the steel substrate. Ni-Zn and Zn-Fe-Co alloys showed higher hardness in relation to Zn. By XRD it has been observed that electrodeposits are crystalline, being identified in Zn-Ni alloy phases presence of g (Ni5Zn21) and d (Ni3Zn22), responsible for its higher corrosion resistance. Alloys treated by chromate have revealed greater corrosion resistance both in salt spray tests and in electrochemical tests. The main corrosion product found on electrodeposits, after salt spray and immersion in 3.5 % NaCl solution tests, was Zn5(OH)8Cl2.H2O, not being detected oxides or hydroxides formed with metals. All electrodeposits protect steel by galvanic action, for they have presented corrosion potentials more negative than that of steel. Chromate or molybdate addition to the electrolyte further extends the stability range, which shows... (Complete abstract click electronic access below)

The microstructure of high strength steel is susceptible to delayed failure caused by the absorption of hydrogen produced either during cathodic charging or electroplating. When 0.8%C and AISI 4340 steel are subjected to constant load testing, a wide range of failure times is observed. By applying Weibull statistics small changes in experimental parameters such as heat-treatment are detected readily and are explained in the terms of hydrogen trapping at microstructural defects. During the electroplating of steel in a double-cell, quantitative measurements are made of the amount of hydrogen permeated. Current densities are measured in the range 2- 40 mAcm2 and it is shown that, although the lowest current density produces the most mechanically sound plate, it also causes the largest amount of hydrogen absorption. The nickel deposit is found to act as a reservoir for reversibly trapped hydrogen allowing diffusion to continue into the steel after the cessation of plating. Permeation measurements were taken on AISI 4340 steel using an electrochemical probe developed from the Barnacle Electrode. The effects of cathodically charging and electroplating with nickel are compared. Exposure of the steel to the atmosphere is shown to have an important influence on the hydrogen content after a period of time due to a limited occurrence of corrosion. Various post- plating treatments are commonly used to remove a damaging concentration of hydrogen and the quantitative effects of such treatments are described. Finally, a mathematical model is proposed which explains the reason for the wide spread of delayed failure times. It is found that if the stress intensity necessary to initiate a crack is known and, provided either the nominal stress or the crack size is known, it is possible to calculate either the allowable defect size or the allowable stress below which cracking is not expected to occur.

This thesis describes two novel techniques for the metallization of non-electroactive polymer films and thicker sectioned polyethylene and nylon substrates. In the first approach, non-electroactive polymer substrates were impregnated with surface layers of polypyrrole and polyaniline, using electrochemical and chemical methods of polymerization. The relative merits of both these approaches are discussed and compared with other methods in the literature. The resultant composite materials exhibited sufficient conductivity to permit the direct electrodeposition of metal surface coats. Polypyrrole coated substrates were also metallized using chemical methods. Cyclic voltammetry studies and scanning electron microscopy of metal coated polypyrrole, showed that metal deposition occurred mainly at the polymer surface by a mechanism of instantaneous nucleation and growth. Using optimized deposition conditions, both electrochemical and chemical metal deposition methods were used to deposit highly reflecting and coherent metal layers onto conducting polymer coated materials. The second approach of metallizing polymers, was the metallization of non-electroactive polymer films by the electroreduction of silver from non-aqueous based silver plating solutions. The effects of the electrode substrate, the deposition potential, and the concentration of metal ions in solution were investigated to determine suitable metal salt/solvent, and polymer film/solvent combinations. The resultant metallized polymer films were evaluated using optical and scanning electron microscopy, ac impedance, and reflectance measurements. These studies enabled the optimum deposition conditions to be determined, and these were subsequently used for the preparation of high quality, uniform, and reflective metal coated films. The results for the electrodeposition of silver into polymer films using the latter approach are compared with those obtained from alternative electrochemical and chemical methods of metallizing polymer films.

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Thesis (M. Sc.)--University of Hong Kong, 1993.