Neural networks were applied to the analysis of electrochemical noise data. Electrochemical noise is defined as the fluctuations in either current or potential with time for a metal which is immersed in a conductive solution. This data is of interest because of its relationship to particular corrosion processes. Specifically, a system which is experiencing uniform corrosion will produce a different noise signal than one which is experiencing localized (perforation) corrosion. The economic effects of corrosion are significant and methods which improve the ability to detect, measure and predict corrosion would be extremely valuable.Two series of experiments were conducted. The data for both series were collected from aluminum samples immersed in various aqueous solutions. The series differed from each other in the configuration and programming of the potentiostat which collected the data. The first series only dealt with potential noise while the second series dealt with both potential and current noise. Auxiliary parameters, such as the pH and chloride concentration of the solutions were used in the second series. The first series studied data from only two solutions, while the second series included six solutions.It was possible for neural networks to correctly categorize systems in Series 1 according to the class of corrosion being observed (uniform or perforating). Appropriate data transformation steps were required to effect these classifications and it was also observed that many of these data transformations would lead directly to categorization without the use of a neural network.The additional data collected in Series 2 allowed a more complex analysis. Neural networks were able to simultaneously predict both the propensity towards localized corrosion and the metal dissolution rate. This application demonstrated the power of neural networks.Several types of neural networks and learning algorithms were included in this study. The two systems used most were a backpropagation (multi-layer perceptron) and a radial basis system. Comparisons of the various network systems with regard to speed and accuracy were made. / Department of Mathematical Sciences

Orientador: Rodnei Bertazzoli / Dissertação (mestrado profissional) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica, Faculdade de Engenharia Eletrica e de Computação e Instituto de Quimica / Made available in DSpace on 2018-08-15T03:56:41Z (GMT). No. of bitstreams: 1 Costa_RegisSilvada_M.pdf: 2450991 bytes, checksum: d60e53258406b167bb36e4bd6cce3a71 (MD5) Previous issue date: 2009 / Resumo: A presente dissertação de mestrado tem por objetivo o estudo do fenômeno de corrosão entre dois componentes do motor de combustão interna, ciclo Diesel, caixa de distribuição (liga de alumínio AA A380.0) e bloco de cilindros (ferro fundido cinzento), bem como o estudo de alternativas para minimização desta corrosão. Foram utilizados métodos de medição de diferença de potencial galvânico, caracterização de materiais e medições de perda de massa. A liga de alumínio que atualmente é utilizada na caixa de distribuição apresenta maior diferença de potencial com o bloco de cilindros quando comparada às demais ligas de Al que foram ensaiadas com o bloco de cilindros, com a diferença de potencial em torno de 200 mV. Possui maior susceptibilidade à corrosão galvânica com o bloco de cilindros, agindo como anodo no par galvânico. A liga AA 413 possui menor diferença de potencial (150 mV) no par galvânico com o bloco de cilindros de ferro fundido cinzento, em comparação com a liga AA A380.0, possuindo semelhante resistência mecânica. As ligas AA 410, 5052 e 1100, foram as ligas que apresentaram menor diferença de potencial com o bloco de cilindros, em torno de 45 mV. Com a passivação da liga AA A380.0 em solução polimérica, a diferença de potencial diminuiu para 165 mV. Pelo ensaio de perda de massa da liga A380.0, sem par galvânico, obteve-se a densidade de corrente e taxa de corrosão, e por consequência a perda de massa da caixa de distribuição estimada para 300.000 km que foi de 7 g. O ensaio de perda de massa da liga AA A380.0 com formação de par galvânico com o bloco de cilindros, possibilitou estimar a perda de massa por corrosão para a caixa de distribuição com 300.000 km que ficou em torno de 100 g, evidenciando a severidade da corrosão galvânica na caixa de distribuição no par galvânico com o bloco de cilindros. Para a liga AA A380.0 passivada em solução polimérica a perda de massa estimada para a caixa de distribuição com 300.000 km ficou em torno de 36 g e para a liga AA 413 ficou em torno de 57 g. Para ambas ligas uma melhora significativa na resistência à corrosão, quando comparado à liga AA A380.0 / Abstract: The present investigation has for purpose the study of the corrosion phenomenon between two components of Diesel engine, timing case (aluminum alloy AA A380.0) and crankcase (grey iron casting), and the study of alternatives for the decreasing of this corrosion. Measurement methods of potential galvanic difference, materials characterization and mass loss measurements had been used. The aluminum alloy that is currently used in the timing case presents greater potential difference with the crankcase when compared with the other Al alloys that was tested with the crankcase, with the potential difference around 200 mV. It has greater feasibility to the galvanic corrosion with the crankcase, acting as anode in the galvanic couple. AA 413 alloy presents lower potential difference (150 mV) in the galvanic couple with the crankcase, in comparison with AA A380.0 alloy. AA 410, 5052 and 1100 alloys, had been the alloys that had presented minor potential difference with the crankcase, around 45 mV. With the AA A380.0 protection in polymeric solution, the potential difference decreased to 165 mV. By the mass loss measurements AA A380.0 alloy, without galvanic couple, it was gotten chain density and corrosion rate, and consequently the mass loss of timing case appraised for 300.000 km that was around 7 g. Through the mass loss measurements AA A380.0 alloy, with formation of galvanic couple with crankcase, made possible appraise the corrosion mass loss for the timing case with 300,000 km that was around 100 g, evidencing the severity of the galvanic corrosion in the timing case in the galvanic couple with crankcase. For AA A380.0 alloy passivated in polymeric solution the mass loss appraised for timing case with 300,000 km was around 36 g and for AA 413 alloy it was around 57 g. For both alloys a significant improvement in the corrosion resistance, when compared with AA A380.0 alloy / Mestrado / Materiais e Processos de Fabricação / Mestre em Engenharia Automobilistica

With the reliability requirements of automobile microelectronics pushing towards near 0 ppb levels of failure control, halide induced corrosion issues in wire bonded devices have to be tightly controlled to achieve such a high reliability goal. With real-time corrosion monitoring, for the first time we demonstrated that the explosive H2 evolution coupled with the oxygen reduction reaction, occurring at the critical Al/Cu interfaces, is the key driving force for the observed aggressive corrosion. Several types of passivation coating on Cu wire surfaces to effectively block the cathodic H2 evolution were explored with an aim to disrupt this explosive corrosion cycle. The properties of the protective coating were evaluated using various analytical techniques. The surface coating exhibited high thermal stability up to 260 °C (evaluated using TGA analysis). A uniform, highly hydrophobic coating (surface contact angle of >130° with water), was achieved by carefully controlling CVD parameters such as time of deposition, surface control of Cu metal, amount of inhibitor compound loading, temperature of coating process etc. FTIR spectroscopy combined with corrosion screening was used to optimize the CVD passivated coating with strong chemisorption. SEM and EDX, XPS were carried out on various coated surfaces to understand the composition and selectivity of the film formed through this surface treatment. The surface selective nature of this coating (towards Cu) proved helpful in preventing potential delamination issues during epoxy molding process. The corrosion testing was carried out via HAST testing at 130°C, 2 atm pressure and 100% RH for 48 hours. Delamination analysis and continuity test showed that the inhibitor compound was able to effectively prevent the corrosion even after exposure to harsh HAST conditions.

No description available.

Made available in DSpace on 2014-12-17T14:09:16Z (GMT). No. of bitstreams: 1 JardelDC_TESE_Parcial.pdf: 1739659 bytes, checksum: 19974b9395e0d9fcb23b07c3997dab2f (MD5) Previous issue date: 2012-07-30 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The resistance of aluminum and their alloys, to the corrosion phenomenon, in aqueous solutions, is a result of the oxide layer formed. However, the corrosion process in the aluminum alloy is associated with the presence a second phase of particles or the presence of chloride ions which promote the disruption of the oxide layer located producing the corrosion process. On the other hand, the term water produced is used to describe the water after the separation of the oil and gas in API separators. The volumes of produced water arrive around 5 more times to the volume of oil produced. The greatest feature of the water is the presence of numerous pollutants. Due to the increased volume of waste around the world in the current decade, the outcome and the effect of the discharge of produced water on the environment has recently become an important issue of environmental concern where numerous treatments are aimed at reducing these contaminants before disposal. Then, this study aims to investigate the electrochemical corrosion behavior of aluminum alloy 6060 in presence of water produced and the influence of organic components as well as chloride ions, by using the electrochemical techniques of linear polarization. The modification of the passive layer and the likely breakpoints were observed by atomic force microscopy (AFM). In the pit formation potential around -0.4 to -0.8 V/EAg/AgCl was observed that the diffusion of chloride ions occurs via the layer formed with the probable formation of pits. Whereas, at temperatures above 65 ?C, it was observed that the range of potential for thepit formation was -0.4 to -0.5 V/EAg/AgCl. In all reactions, the concentration of Al(OH)3 in the form of a gel was observed / A resistencia do aluminio e suas ligas a corros?o em meio aquoso ? resultado da camada de oxido formada. Entretanto, o processo corrosivo nas ligas de alum?nio esta associado a presen?a de part?culas de segunda fase ou a presen?a de ions cloreto que promovem a ruptura da camada de ?xido produzindo o processo corrosivo localizado. Por outro lado, o termo ?gua produzida ? usado para descrever a ?gua ap?s a sua separa??o do ?leo e g?s nos separadores API. Os volumes de ?gua produzida chegam em m?dia de 5 vezes o volume do ?leo produzido. A maior caracter?stica dessa ?gua ? a presen?a de in?meros contaminantes. Devido ao aumento do volume dos res?duos em todo o mundo na d?cada atual, o desfecho e do efeito da descarga de ?gua produzida sobre o meio ambiente tem recentemente tornar-se uma quest?o importante de preocupa??o ambiental onde in?meros tratamentos s?o destinados a redu??o destes contaminantes antes do descarte. Ent?o, o presente estudo visa investigar o comportamento eletroquimico de corros?o da liga de aluminio 6060 em presen?a de ?gua produzida e a influencia dos componentes organicos assim como dos ions cloreto, atrav?s do uso das tecnicas eletroqu?micas de polariza??o linear. A modifica??o da camada passiva e os prov?veis pontos de ruptura foram observados por microscopia de for?a atomica (AFM). No potencial de forma??o de pit de -0,4 a -0,8 V/EAg/AgCl observa-se que ocorre a difus?o dos ?ons cloreto pela camada formada com prov?vel forma??o de pites. Entretanto, em temperaturas superiores a 65?C observou-se que a faixa de potencial de forma??o de pit foi de -0,4 a -0,5V/ EAg/AgCl. Em todas as rea??es observou-se o aumento na concentra??o de Al(OH)3 sob a forma de um gel / 2020-01-01