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McGeachie, M. T., University of Western Sydney, College of Law and Business e of Construction Property and Planning School. "Characterisation of the Sydney region in relation to corrosion, timber decay risk factors and the corrosion of nails in timber in covered conditions". THESIS_CLAB_CPP_McGeachie_M.xml, 2001. http://handle.uws.edu.au:8081/1959.7/491.
Testo completoAbstract (sommario):
The aim of the study was to characterise the environment in the Sydney region in respect of atmospheric corrosivity, timber decay risk factors and the corrosion of nails in timber in covered conditions. The study reviewed contemporary research in this field, particularly in Australia, developing an understanding of the durability failure mechanisms for timber and nails in timber. The study looked at the effects of climatic aspects, pollutants, corrosion on timber decay risk factors. The study found that the levels of risk in terms of timber degradation, corrosion and nail corrosion were greatest adjacent to the coast and at marine sites.Doctor of Philosophy (PhD)
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Wenk, Christine. "Household scale arsenic removal from drinking water with zero-valent iron corrosion products and performance of Kanchan-type iron nail filters with different synthetic groundwaters /". Zürich : ETHZ, Swiss Federal Institute of Technology Zürich, Department of Environmental Sciences, 2008. http://e-collection.ethbib.ethz.ch/show?type=dipl&nr=421.
Testo completo
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Sampaio, Nilo Antonio de Souza [UNESP]. "Estudo da corrosão das ligas Ni-Cr-Mo para próteses dentárias fixas em solução aquosa de NaF 0,05% , NaCl 0,05% e em colutórios comerciais". Universidade Estadual Paulista (UNESP), 2011. http://hdl.handle.net/11449/103736.
Testo completoAbstract (sommario):
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sampaio_nas_dr_guara.pdf: 3261856 bytes, checksum: 1cec5dd1be792fc77fe196fcf0103c70 (MD5)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
As ligas Ni-Cr-Mo têm sido usadas como próteses dentárias por possuírem boa resistência mecânica, elevada resistência à corrosão e também por serem economicamente viáveis. A proteção contra a corrosão destas ligas em soluções salinas típicas de meios fisiológicos é devida ao fenômeno de passivação com a formação de uma camada superficial de óxidos, principalmente óxidos de cromo. Este filme protetor submetido a esforços mecânicos num ambiente corrosivo pode se romper parcialmente liberando íons que apresentam efeitos deletérios no corpo humano. Íons fluoreto existentes em produtos de higiene modificam o ambiente bucal e sua presença pode possibilitar o início de um processo corrosivo localizado. O objetivo deste trabalho foi estudar a resistência à corrosão de três ligas de Ni-Cr-Mo, de diferentes composições: SC (73% Ni; 14%Cr; 8,5%Mo; 1,8% Be; 1,8%Al), SB (61%Ni; 25%Cr; 10,5%Mo; 1,5%Si) e W (65%Ni; 22,5%Cr; 9,5%Mo; 1,0% Nb; 1,0% Si; 0,5%Fe) em meios contendo fluoretos que simulam as soluções de enxágue bucal. O estudo foi realizado em solução de NaF 0,05 %, NaCl 0,05 % e colutórios comerciais em pH 6,0 a 37ºC, utilizando análise metalográfica, técnica de imersão e ensaios eletroquímicos, . A liga SC, com o maior teor de níquel e o menor teor de cromo não se passiva nos meios estudados apresentando um aumento contínuo na densidade de corrente em função do aumento do potencial, enquanto que as outras ligas apresentam intervalo de passivação de 600 mV e densidade de corrente passiva 10-6 A / cm2. De um modo geral, considerando os ensaios de corrosão por imersão e eletroquímicos, conclui-se que o pior desempenho foi atribuído à liga SC, enquanto que, W e SB apresentaram os melhores desempenhos e comportamentos bastante similares.
Ni-Cr-Mo alloys have been used as dental prostheses due their properties such as good mechanical strength, high corrosion resistance and also because they are economically viable. These alloys corrosion protection in salt solutions which are typical of physiological media, is due to the phenomenon called passivation with an oxide superficial layer formation, particularly chromium oxides. This protective film, subjected to mechanical stress in a corrosive environment,can be broken partially releasing ions that have deleterious effects in a human body. Fluoride ions, existent in hygiene products, change the oral environment and their presence may enable the beginning of a localized corrosion process. The objectics this work is to evaluate the corrosion resistance of three Ni-Cr-Mo alloys, of different compositions: SC (73% Ni, 14% Cr, 8.5% Mo, 1.8% Be, 1.8% Al) SB (61% Ni, 25% Cr, 10.5% Mo, 1.5% Si) and W (65% Ni, 22.5% Cr, 9.5% Mo, 1.0% Nb, 1.0% Si, 0.5% Fe) in media containing fluoride which simulate oral rinse solutions. This study has been in solution of 0.05% NaF, NaCl 0.05% and commercial mouthwashes on pH 6.0 at 37 ° C using metallography analyses, immersion techniques, and electrochemical tests, impedance tests and analysis. SC, with the highest nickel and the lowest chromium content, does not passivate in the studied means showing a continuous increase in current density due to increasing potential, while the other alloys exhibit passivation range of 600 mV and passive current density 10-6 A / cm2. In general, considering the immersion and electrochemical corrosion tests, it is concluded that the worst performance has been attributed to the alloy SC, while W and SB have shown the best performance and very similar behaviors.
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Sampaio, Nilo Antonio de Souza. "Estudo da corrosão das ligas Ni-Cr-Mo para próteses dentárias fixas em solução aquosa de NaF 0,05% , NaCl 0,05% e em colutórios comerciais /". Guaratinguetá : [s.n.], 2011. http://hdl.handle.net/11449/103736.
Testo completoAbstract (sommario):
Resumo: As ligas Ni-Cr-Mo têm sido usadas como próteses dentárias por possuírem boa resistência mecânica, elevada resistência à corrosão e também por serem economicamente viáveis. A proteção contra a corrosão destas ligas em soluções salinas típicas de meios fisiológicos é devida ao fenômeno de passivação com a formação de uma camada superficial de óxidos, principalmente óxidos de cromo. Este filme protetor submetido a esforços mecânicos num ambiente corrosivo pode se romper parcialmente liberando íons que apresentam efeitos deletérios no corpo humano. Íons fluoreto existentes em produtos de higiene modificam o ambiente bucal e sua presença pode possibilitar o início de um processo corrosivo localizado. O objetivo deste trabalho foi estudar a resistência à corrosão de três ligas de Ni-Cr-Mo, de diferentes composições: SC (73% Ni; 14%Cr; 8,5%Mo; 1,8% Be; 1,8%Al), SB (61%Ni; 25%Cr; 10,5%Mo; 1,5%Si) e W (65%Ni; 22,5%Cr; 9,5%Mo; 1,0% Nb; 1,0% Si; 0,5%Fe) em meios contendo fluoretos que simulam as soluções de enxágue bucal. O estudo foi realizado em solução de NaF 0,05 %, NaCl 0,05 % e colutórios comerciais em pH 6,0 a 37ºC, utilizando análise metalográfica, técnica de imersão e ensaios eletroquímicos, . A liga SC, com o maior teor de níquel e o menor teor de cromo não se passiva nos meios estudados apresentando um aumento contínuo na densidade de corrente em função do aumento do potencial, enquanto que as outras ligas apresentam intervalo de passivação de 600 mV e densidade de corrente passiva 10-6 A / cm2. De um modo geral, considerando os ensaios de corrosão por imersão e eletroquímicos, conclui-se que o pior desempenho foi atribuído à liga SC, enquanto que, W e SB apresentaram os melhores desempenhos e comportamentos bastante similares.Abstract: Ni-Cr-Mo alloys have been used as dental prostheses due their properties such as good mechanical strength, high corrosion resistance and also because they are economically viable. These alloys corrosion protection in salt solutions which are typical of physiological media, is due to the phenomenon called passivation with an oxide superficial layer formation, particularly chromium oxides. This protective film, subjected to mechanical stress in a corrosive environment,can be broken partially releasing ions that have deleterious effects in a human body. Fluoride ions, existent in hygiene products, change the oral environment and their presence may enable the beginning of a localized corrosion process. The objectics this work is to evaluate the corrosion resistance of three Ni-Cr-Mo alloys, of different compositions: SC (73% Ni, 14% Cr, 8.5% Mo, 1.8% Be, 1.8% Al) SB (61% Ni, 25% Cr, 10.5% Mo, 1.5% Si) and W (65% Ni, 22.5% Cr, 9.5% Mo, 1.0% Nb, 1.0% Si, 0.5% Fe) in media containing fluoride which simulate oral rinse solutions. This study has been in solution of 0.05% NaF, NaCl 0.05% and commercial mouthwashes on pH 6.0 at 37 ° C using metallography analyses, immersion techniques, and electrochemical tests, impedance tests and analysis. SC, with the highest nickel and the lowest chromium content, does not passivate in the studied means showing a continuous increase in current density due to increasing potential, while the other alloys exhibit passivation range of 600 mV and passive current density 10-6 A / cm2. In general, considering the immersion and electrochemical corrosion tests, it is concluded that the worst performance has been attributed to the alloy SC, while W and SB have shown the best performance and very similar behaviors.
Orientador: Eduardo Norberto Codaro
Coorientador: Heloisa A. Acciari
Banca: Ana Paula Rosifini Alves
Banca: Gilmar Clemente Silva
Banca: Alain Laurent Marie Robin
Banca: Roberto Zenhei Nakazato
Doutor
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Cerra, Florez Mauro Andrés. "Estudo comparativo da resistência à corrosão entre aços alto manganês e o aço 9% níquel em soluções aquosas de H2SO4 e NaCl". reponame:Repositório Institucional da UFC, 2017. http://www.repositorio.ufc.br/handle/riufc/25624.
Testo completoAbstract (sommario):
CERRA FLOREZ, M. A. Estudo comparativo da resistência à corrosão entre aços alto manganês e o aço 9% níquel em soluções aquosas de H2SO4 e NaCl. 2017. 108 f. Dissertação (Mestrado em Ciência de Materiais)–Centro de Tecnologia, Universidade Federal do Ceará, Fortaleza, 2017.Submitted by Marlene Sousa (mmarlene@ufc.br) on 2017-09-13T13:08:35Z No. of bitstreams: 1 2017_dis_macerraflorez.pdf: 7059370 bytes, checksum: 037d39ae844a1b60cbe1183a10902438 (MD5)
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Liquefied natural gas volumes which at present have to be stored and/or transported require that the materials engineering constantly develop materials that adapt to the mechanical, chemical and economic needs of the industry. Aluminum alloys, 9% nickel steel alloys and austenitic stainless steels are currently used for cryogenic applications, however, all these materials have disadvantages, such as high cost of production, welding difficulties, corrosion resistance, among others. High manganese steels offer an attractive alternative because manganese and carbon replace nickel as austenite stabilizer; this change also represents a significant decrease in steel fabrication costs. The present study aims to establish a comparative degree of corrosion resistance in two aqueous solutions between four high manganese steels with a content of 28% Mn, 26% Mn, 22% Mn, 20% Mn in relation to the 9% Nickel that is widely used in petrochemical industry. Mass fraction diagrams were performed in Thermo-Calc® software. The steels were characterized using the techniques: Optical Microscopy, Scanning Electron Microscopy (SEM), Electron Backscatter Diffraction Analysis (EBSD), Energy Dispersive X-ray Spectroscopy (EDS), Optical Emission Spectroscopy, X-ray Fluorescence. The mechanical properties were evaluated by hardness and microhardness measurements. The corrosion resistance was evaluated in aqueous solutions of NaCl and H 2 SO 4 by Open Circuit Potential (OCP), Linear Polarization Curves and Electrochemical Impedance Spectroscopy. The results obtained in the thermodynamic study helped to predict the phases present in these steels as well as the heat treatment temperature. The microstructural study revealed the influence of the phases on the mechanical properties, showing that the 9% nickel steel presents higher hardness values than the high manganese steels. The corrosion tests showed that the high manganese steels have less corrosion resistance than 9% nickel steel, due to the formation of unstable and poorly compacted oxides that do not provide protection against corrosion; In contrast, the oxides formed by the 9% nickel steel gave it a better protection as observed in the curves that were found.
Os volumes de gás natural liquefeito que na atualidade precisam ser armazenados e/ou transportados requerem que a engenharia de materiais desenvolva constantemente materiais que se adaptem às necessidades mecânicas, químicas e econômicas da indústria. As ligas de alumínio, aço 9% níquel e aços inoxidáveis são utilizadas para aplicações criogênicas, mas todos estes materiais têm desvantagens, como altos custos de produção, dificuldades para a soldagem, entre outras. Os aços alto manganês oferecem uma alternativa – devido ao manganês e o carbono substituírem o níquel como estabilizador da austenita no aço, este câmbio também representa uma diminuição apreciável nos custos de fabricação do aço. O presente estudo visa estabelecer um grau comparativo da resistência à corrosão em duas soluções aquosas entre quatro aços alto manganês com conteúdo de 28%Mn, 26%Mn, 22%Mn, 20%Mn em relação ao aço 9% níquel que é amplamente utilizado na indústria petroquímica. Foram realizados diagramas de fração em massa no software Thermo-Calc ® ; os aços foram caracterizados utilizando as técnicas: Microscopia Óptica, MEV, EBSD, EDS, Espectroscopia de Emissão Ótica e Fluorescência de Raios X; as propriedades mecânicas foram avaliadas por medidas de dureza e microdureza. A resistência à corrosão foi avaliada em soluções aquosas de NaCl e de H 2 SO 4 utilizando as técnicas de monitoramento do Potencial de Circuito Aberto (OCP), as Curvas de Polarização Linear e a Espectroscopia de Impedância Eletroquímica. Os resultados obtidos no estudo termodinâmico ajudaram a prever as fases presentes nestes aços, assim como a temperatura de tratamento térmico. O estudo microestrutural revelou a influência das fases nas propriedades mecânicas, mostrando que o aço 9% níquel apresenta maiores valores de dureza que os aços alto manganês. E os ensaios de corrosão mostraram que os aços alto manganês apresentam menor resistência à corrosão do que o aço 9% níquel, devido à formação de óxidos instáveis e pouco compactos que não provêm proteção contra a corrosão; em contraste com os óxidos formados pelo aço 9% níquel, outorgaram-lhe uma melhor proteção como foi observado nas curvas encontradas.
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Oliveira, Mariana Cristina de. "Efeito da deformação plástica na corrosão do aço API 5L X65 em solução ácida de NaCl". Universidade Estadual Paulista (UNESP), 2018. http://hdl.handle.net/11449/155949.
Testo completoAbstract (sommario):
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
O objetivo deste trabalho foi investigar a influência da deformação plástica no comportamento corrosivo de oleodutos em ambiente ácido contendo cloreto de sódio. As tubulações trabalham em ambiente altamente corrosivo e estão sujeitas à deformação plástica, o que altera as propriedades mecânicas do aço. Com isso é necessário avaliar a integridade da tubulação em serviço. Para tanto retirou-se amostras de uma tubulação do aço de baixo carbono API 5L X65, um dos mais utilizados pela indústria do petróleo e gás para fabricação de tubulações de transporte. As amostras foram deformadas plasticamente em 0,5%; 1,0%; 1,5%; 2,0% e 2,5% por meio de um ensaio de tração. A microestrutura das amostras deformadas foi caracterizada, através da microscopia óptica e eletrônica de varredura, apresentando uma matriz de ferrita – perlita fina. Uma nova análise microestrutural foi realizada após os ensaios de corrosão, indicando que o aço sofre um processo de corrosão generalizada. Para avaliar o comportamento corrosivo foram realizados testes laboratoriais de imersão e eletroquímicos para caracterizar o processo corrosivo em solução ácida contendo 3% de cloreto de sódio. O teste de imersão teve a finalidade de comparar a perda de massa de uma amostra sem deformação plástica e outra com deformação plástica de 2,5%. Os resultados indicaram que não há diferença significativa entre as amostras. Utilizou se as técnicas eletroquímicas de OCP, polarização de Tafel, EIS e Permeação de hidrogênio, em todas as técnicas verificou-se que o processo de corrosão é uniforme. O processo de corrosão não apresentou variação significativa devido à deformação plástica, porém indicou que a deformação plástica aumenta a suscetibilidade à permeação de hidrogênio no aço.
This work aims to investigate the influence of plastic deformation on the corrosive behavior of pipelines in acidic environment containing sodium chloride. The pipelines work in a highly corrosive environment and are subject to plastic deformation, which alters the steel’s mechanical properties. Therefore, integrity assessment of a pipeline in service is necessary. For this purpose, samples were taken from a pipeline of API 5L X65 low carbon steel, one of the most used by the oil and gas industry to manufacture transport pipelines. The samples were plastically deformed in 0.5%; 1.0%; 1.5%; 2.0% and 2.5% by a tensile test. The microstructure of deformed samples was characterized by optical and scanning electronic microscopy, presenting a fine ferrite and pearlite matrix. A new microstructural analysis was performed after the corrosion tests, indicating that the corrosion process is uniform. The corrosive behavior was assessed by laboratory immersion and electrochemical tests to characterize the corrosive process in acid solution containing sodium chloride 3%. The immersion test was used to compare the mass loss between a sample without plastic deformation and another 2,5% plastic deformed. The results indicated that there was no significant difference between the samples. It was used the OCP, polarization of Tafel, EIS and Hydrogen Permeation electrochemical techniques, all techniques showed a uniform corrosion process. The corrosion process did not present significant variation due to the plastic deformation, however it indicated that the plastic deformation increases the susceptibility to the hydrogen permeation in the steel.
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Jesus, Antonio Carlos Neto de. "Estudo dos parâmetros: teor de NaCl e acabamento superficial, na resistência à corrosão localizada e generalizada em tubos de cobre". Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/85/85134/tde-07102011-140611/.
Testo completoAbstract (sommario):
Tubos de cobre fabricados com o material ASTM C12200 (99,9%Cu-0,015-0,040%P) são utilizados mundialmente no transporte de água potável. A maior causa de vazamentos nestas tubulações é a corrosão por pite, que usualmente estão relacionadas com a qualidade da água. Estudos recentes mostraram que vazamentos em tubos de cobre usados para transporte de água de rede pública ocorreram em decorrência da corrosão por pite, o que se deu em virtude da presença do íon cloreto originado do tratamento para a desinfecção da água. Outro parâmetro que pode influenciar a corrosão por pite é a condição de acabamento interno dos tubos. Os óleos lubrificantes usados no processo de fabricação de tubos de cobre contêm carbono e este forma um filme deletério após o recozimento destes tubos. Este filme cria condições na superfície interna para a formação de pilhas de ação local. O objetivo deste trabalho é investigar se o teor de cloreto de sódio no meio aquoso, e o acabamento superficial da superfície interna de tubos de cobre utilizados comercialmente para transporte de água (ABNT/NBR-13206), têm influência na resistência à corrosão destes tubos. A resistência à corrosão foi investigada por meio de ensaios eletroquímicos em soluções naturalmente aeradas com várias concentrações de cloreto de sódio, a 25 oC. A superfície interna dos tubos foi observada, antes e após os ensaios eletroquímicos, por microscopia eletrônica de varredura (MEV). Os tipos de acabamentos superficiais estudados foram: desengraxamento, jateamento e acabamento do processo final de fabricação (sem tratamento). Foi também construído um circuito fechado para estudar o efeito do acabamento superficial na resistência à corrosão sob condições mais próximas das encontradas na prática. O efeito do tratamento de recozimento do tubo em atmosfera inerte, que causa a recristalização da microestrutura e eliminação dos resíduos de óleo lubrificante, também foi avaliado. Os resultados indicaram que o mecanismo de corrosão em soluções com teores de cloreto entre 0,06 mol L-1 e 0,12 mol L-1 correspondeu ao de ataque localizado, enquanto que para a concentração de 0,6 mol L-1 prevaleceu o ataque generalizado. Os resultados do estudo do efeito do acabamento superficial indicaram que os tratamentos que reduzem o teor de carbono na superfície são benéficos à resistência à corrosão, mas este não é o único fator que afeta a resistência à corrosão. Outras características superficiais resultantes do tratamento da superfície também devem ser consideradas. Por exemplo, embora o jateamento cause a diminuição do teor de carbono na superfície dos tubos, o aumento de rugosidade produzido por este acabamento pode resultar em uma menor resistência à corrosão. Os tratamentos superficiais que produziram superfície com maiores resistências à corrosão foram aqueles que também produziram superfícies com menores teores de carbono, a saber, desengraxe e recozimento.Copper tubes manufactured with C12200 ASTM (99.9% Cu-0015-0040% P) are used worldwide for potable water transport. The largest number of leakages in these tubes is due to pitting, usually related to the water quality, associated to the presence of chloride ions originated from water disinfecting treatment. The literature on the effect of chloride on the corrosion of copper pipelines is controversial. The finishing of the copper tubes inner might also influence pitting corrosion. The lubricating oils used in the manufacture of copper tubes contain carbon and a deleterious film might form during annealing. The objective of this study is to investigate the effect of sodium chloride content and the inner surface finishing of copper tubes used for water transport (ABNT/NBR-13206) on their corrosion resistance. The study was carried out by electrochemical tests in naturally aerated sodium chloride solutions at various concentrations, at 25 °C. The tubes inner surface was observed previous to and after the electrochemical tests by scanning electron microscopy (SEM). The effects of the following surface finishing were investigated: degrease, sand blasting, annealing and the surface without treatment. A loop was built to simulate the operational conditions of the tubes. Results indicated that the corrosion mechanism in chloride solutions with concentrations between 0.06 mol L-1 and 0.12 mol L-1 was localized attack, whereas in the 0.6 mol L-1 solution, generalized attack was the predominant mechanism. The results the surface finishing investigation indicated that the treatments that leads to carbon content reduction are beneficial to corrosion resistance. However, other features must also be considered. For instance, although sand blasting reduces the carbon content on the tubes surface, the increase in roughness due to this treatment decreases the corrosion resistance. The surface treatments that resulted in increased corrosion resistance were those that also resulted in lower carbon levels at the surface, namely degreasing and annealing.
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Strandheim, Espen Oldeide. "AC Induced Corrosion of Carbon Steel in 3.5wt% NaCl Electrolyte". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-19589.
Testo completoAbstract (sommario):
This paper deals with alternating current (AC) corrosion of low alloy carbon steel in 3.5 wt% NaCl electrolyte. Accelerated corrosion rates have been reported when exposed to AC and the corrosion mechanism is not well understood. Electrical heating of subsea pipelines, applied to avoid hydrate formation and waxing of multiphase hydrocarbon well streams has made this topic increasingly relevant in recent years. To study the effect of AC on corrosion rates, weight loss experiments under a wide range of experimental conditions were performed. Results show that AC strongly influence corrosion kinetics of the system studied. Once AC is applied, a drop in corrosion potential and the formation of a passive iron oxide surface layer is observed. This layer is porous and believed to be the result of a rapid surface alkalization. Pitting corrosion is observed for all applied AC densities at open circuit. Weight loss- and LPR measurements conform well and the use of this technique in the presence of AC is on this basis considered valid. Corrosion rates increase as applied level of AC is increased and an approximately linear relationship has been established between iAC and icorr.
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Lin, Huang. "Atmospheric Corrosion of Ag and Cu with Ozone, UV and NaCl". The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1357309228.
Testo completo
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Petit, Luc. "Etude de la corrosion d'alliages de fer et de nickel par les mélanges Na2SO4, Na2CO3, NaCl et Na2CO3, Na2S, Na2SO4, NaCl entre 300oC et 900oC : application aux chaudières de récupération (procédé KRAFT)". Grenoble INPG, 1986. http://www.theses.fr/1986INPG0119.
Testo completoAbstract (sommario):
Etude de la corrosion en milieu de sels fondus (melanges na::(2)so::(4), na::(2)co::(3), nacl et na::(2)co::(3), na::(2)s, na::(2)so::(4), nacl) pour des temperatures comprises entre 300**(o)c et 900**(o)c d'alliages de nickel (in800, in600. . . ) et d'aciers inoxydables (z6cn1810, z12cn25-20. . . ). Mesure des variations de masse et examen des produits formes. Influence d'un traitement de surface. Influence de la composition de l'alliage. Mecanisme de corrosion
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Berthier, Fabienne. "Spectroscopie d'impédance et vitesse de corrosion : application au cas de la corrosion du zinc en milieu NaCl 3%". Grenoble INPG, 1989. http://www.theses.fr/1989INPG0009.
Testo completo
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Onye, Jermain Eze. "Atmospheric Corrosion of Zn by NaCl, SO2, NH3, O3, and UV Light". The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1408822401.
Testo completo
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McGeachie, Mark Thomas. "Characterisation of the Sydney region in relation to corrosion, timber decay risk factors and the corrosion of nails in timber in covered conditions /". View thesis View thesis, 2001. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20030326.082457/index.html.
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NETO, de JESUS ANTONIO C. "Estudo dos parâmetros: teor de NaCl e acabamento superficial, na resistência à corrosão por PITE em tubos de cobre". reponame:Repositório Institucional do IPEN, 2008. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11614.
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Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
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Figuet, Dewis. "Relations entre structures, comportements à la corrosion et propriétés tribologiques des revêtements de NiW". Thesis, La Rochelle, 2020. http://www.theses.fr/2020LAROS026.
Testo completoAbstract (sommario):
Ces travaux de recherche s’inscrivent dans la continuité des travaux menés au LaSIE sur l’élaboration d’alliages de NiW avec pour objectif de comprendre les relations entre paramètres métallurgiques et propriétés fonctionnelles. L’électrodéposition permet d’obtenir des alliages de NiW de composition variant de 0 à 20 at.% constitués d’une solution solide Ni (W). L’addition de W conduit à un affinement notable de la taille de grains mais plusieurs autres caractéristiques microstructurales sont également modifiées. Deux techniques de dépôts sont utilisées afin d’obtenir des alliages à iso-teneur en W et de pouvoir ainsi discuter des paramètres de synthèse en regard des propriétés de surface : usure et résistance à la corrosion en milieu salin. Les analyses structurales des alliages NiW sur substrat acier montrent globalement des états métallurgiques comparables aux revêtements des études précédentes déposés sur substrat nickel. Néanmoins, les revêtements PVD présentent une plus faible contamination en éléments légers. Les essais de tribologie et de micro-rayure ont pu mettre en évidence une corrélation entre la résistance à l’usure et les paramètres métallurgiques. Par exemple, une forte teneur en W (15 at. %) conduit à un faible volume d’usure et peu d’abrasion. Ainsi, le mécanisme d’usure est différent de celui des revêtements de Ni pur de référence. Ce mécanisme est pour partie relié à la taille de grains. Les revêtements élaborés par PVD montrent aussi de la fissuration, qui pourrait affecter l’adhérence. Concernant les essais de corrosion en milieu salin, la dégradation des aciers revêtus est fortement liée à la présence de défauts débouchants. La formation d’oxyde a été détectée sur les revêtements de Ni et de NiW suggérant des contributions anodiques sur ces dépôts. L’augmentation de la teneur en W conduit à une densification du dépôt, probablement corrélée avec leurs états métallurgiques et notamment à la diminution de la taille de grains. L’apport du W entraîne ainsi le passage d’une corrosion localisée au niveau des défauts à une corrosion uniforme du revêtement. Au final, le revêtement NiW 15 at.% est un très bon candidat à l’alternative au chrome dur de par ses bonnes propriétés de résistance à la corrosion et de résistance à l’usureOur research work is a continuation of projects undertaken over the past few years at LaSIE on the development of NiW electrodeposited alloys with the aim of understanding the relationships between metallurgical parameters and functional properties. Electroplating makes possible to obtain NiW alloys with a composition varying from 0 to 20 at. % consisting of a solid Ni (W) solution. The incorporation of W leads to a notable refinement of the grain size but several metallurgical parameters are also modified. Two deposition techniques are used in order to obtain alloys with similar tungsten content and thus to be able to discuss metallurgical parameters comparable to surface properties: wear and corrosion resistance in a saline environment. Metallurgical analyses of NiW alloys on steel substrate show metallurgical states similar to coatings from previous studies deposited on nickel substrate. Nevertheless, the PVD coatings have shown a lower contamination in light elements. Tribology and micro-scratch tests were able to demonstrate a correlation between wear and metallurgical parameters. A high tungsten content (15 at. %) leads to the lowest wear volume and fewer abrasion. Thus, the wear mechanism is not similar to coatings of pure Ni. The latter is much related to the grain size. PVD coatings nevertheless show cracking, which could affect adhesion. Regarding corrosion tests in a saline environment, the degradation of coated steels is strongly linked to the presence of emerging defects. Oxide formation has been detected on Ni and NiW coatings suggesting anodic contributions on the coatings. The increase in the W content leads to a densification of the deposit probably linked to metallurgical parameters and in particular the reduction in grain size. Thus, the addition of tungsten brings about the transition from localized corrosion closed to the defects to uniform corrosion of the coating. Therefore, NiW 15 at. % coating is a very good candidate for the hard chrome alternative due to its good corrosion resistance and wear resistance properties
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Berthaud, Maxime. "Étude du comportement de l'alliage de titane Ti6242S à haute température sous atmosphères complexes : applications aéronautiques". Thesis, Bourgogne Franche-Comté, 2018. http://www.theses.fr/2018UBFCK035/document.
Testo completoAbstract (sommario):
L’utilisation des alliages de titane dans de nombreuses applications (transport, énergie, chimie,...) permet des gains de masse importants en tirant profit du rapport propriétés mécaniques/masse volumique qui est avantageux pour ce type de matériaux. L’utilisation de ces alliages dans des environnements à hautes températures (T>500°C) nécessite de se préoccuper de leur comportement et de comprendre les mécanismes de dégradation dans ces conditions sévères. Certains facteurs peuvent influencer le comportement des alliages de titane en oxydation, comme l’application de cycles de chauffage/refroidissement, la présence de vapeur d’eau ou la présence de sels, selon les conditions d’utilisation.Ce travail de thèse s’est attaché à comprendre les mécanismes d’oxydation d’un alliage de titane utilisé dans l’aéronautique : l’alliage Ti6242S. Il a été étudié à 560°C sous air, sous air humide et en présence de dépôts solides de sel(s) de type NaCl et/ou Na2SO4. Pour cela, des oxydations de longues durées avec et sans dépôts solides de sels ont été réalisées. Les résultats obtenus montrent que la présence de NaCl provoque une dégradation importante du comportement en oxydation des échantillons. La dissolution d’oxygène dans le métal observée sous air ne se produit plus en présence de dépôts de sels. En revanche, une oxydation interne de l’alliage a lieu et des fissures apparaissent dans la profondeur du substrat métallique. La dégradation du matériau est attribuée à la présence de dichlore et à la formation de chlorures métalliques volatiles. Un mécanisme réactionnel a été proposé afin d’expliquer l’effet néfaste des dépôts de NaCl. L’effet d’un dépôt de sels mixte NaCl/Na2SO4 sur l’oxydation de l’alliage Ti6242S est cependant moins marqué.L’évolution des propriétés mécaniques de l’alliage Ti6242S a également été étudiée après oxydation. Une simple oxydation de 100 h sous air provoque une diminution importante de la ductilité du matériau à cause de la zone de dissolution d’oxygène formée pendant l’oxydation. En présence d’un dépôt de NaCl et après 100h d’oxydation à 560°C, la perte de ductilité est encore plus importante et la rupture de l’éprouvette intervient dès la fin du domaine élastique. Dans ces conditions, la pièce perd une partie de sa section porteuse et la limite élastique et le module élastique du matériau restant sont fortement impactés. La présence d’un dépôt mixte NaCl/Na2SO4 pendant l’oxydation a un effet moins marqué sur les propriétés mécaniques du matériau, en accord avec la plus faible réactivité de l’alliage Ti6242S avec ce type de dépôt. Les mécanismes inhérents au changement de propriétés mécaniques sont expliqués dans le travail de thèseThe use of titanium alloys in many applications (transport, energy, chemistry,...) allows significant weight savings in relation to the good mechanical properties/density ratio of these materials. Since titanium alloys are employed at high temperatures (T>500°C), their behavior in such conditions has to be studied in severe conditions in order to understand degradation mechanisms. Moreover, some specific conditions can be met during application, like thermal cycling, water vapour or presence of salts. These parameters are known to influence oxidation behavior of titanium alloys.In this thesis work, oxidation behavior of an aeronautics titanium alloy (Ti6242S) has been studied in air and moist air at 560°C. The effect of solid salt deposits (NaCl and/or Na2SO4) on the oxidation behavior of Ti6242S alloy has also been taken into account. Ti6242S samples were oxidized at 560°C for oxidation times up to 19 000 hours with or without solid salt deposits. NaCl deposit resulted in an important deterioration of Ti6242S alloy behavior at this temperature. Oxygen dissolution in the metal was no longer observed compared to ageing in air, but internal oxidation of the alloy could be evidenced, and cracks were observed deeply into the metallic substrate after oxidation. The corrosion resistance decrease in such conditions was attributed to the presence of chlorine and formation of volatile metallic chlorides due to the presence of NaCl. A degradation mechanism based on active oxidation of Ti6242S alloy exposed to NaCl salt was proposed. The second salt deposit tested consisted in a mixed NaCl/Na2SO4 salt deposit. The harmful effect of this salt deposit on the oxidation behavior of Ti6242S alloy was lower than that of a simple NaCl deposit.Mechanical properties of Ti6242S alloy exposed to solid salt deposits at 560°C were then studied. A simple oxidation in air for 100 hours without salt deposit resulted in an important loss of ductility of the tested samples due to the presence of oxygen solid solution into the metal. The same oxidation time caused an even more important loss of ductility for the samples covered by NaCl deposits. In this case, sample failure occurred at the end of the elastic deformation domain. Elastic modulus and yield strength were also strongly decreased. Mixed NaCl/Na2SO4 deposit exhibited a lower impact on the mechanical properties of the oxidized Ti6242S sample, in accordance with the lower reactivity of Ti6242S alloy with this type of salt deposit. Mechanisms explaining Ti6242S alloy mechanical behavior in such conditions were explained in this thesis work
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Scholant, Camila Monteiro. "Efeito inibidor do tungstato de sódio e da amoxicilina em solução e em filmes de acetato de celulose na corrosão da liga de aço-carbono AISI 1020 em NaCl 0,05 mol/L". Universidade Federal do Pampa, 2014. http://dspace.unipampa.edu.br:8080/xmlui/handle/riu/768.
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Efeito inibidor do tungstato de sódio e da amoxicilina em solução e em filmes de acetato de celulose na corrosão da liga de aço-carbono AISI 1020 em NaCl 0,05 molL.pdf: 3082976 bytes, checksum: 0cd5a0b855088834038b5aff2432de07 (MD5)Approved for entry into archive by Cátia Araújo (catia.araujo@unipampa.edu.br) on 2017-01-25T12:44:16Z (GMT) No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Efeito inibidor do tungstato de sódio e da amoxicilina em solução e em filmes de acetato de celulose na corrosão da liga de aço-carbono AISI 1020 em NaCl 0,05 molL.pdf: 3082976 bytes, checksum: 0cd5a0b855088834038b5aff2432de07 (MD5)
Made available in DSpace on 2017-01-25T12:44:16Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Efeito inibidor do tungstato de sódio e da amoxicilina em solução e em filmes de acetato de celulose na corrosão da liga de aço-carbono AISI 1020 em NaCl 0,05 molL.pdf: 3082976 bytes, checksum: 0cd5a0b855088834038b5aff2432de07 (MD5) Previous issue date: 2014-02-21
Este trabalho teve por objetivo avaliar o tungstato de sódio (Na2WO4) e a amoxicilina como inibidores de corrosão para a liga de aço-carbono AISI 1020 adicionados a um meio contendo 0,05 mol/L de Cloreto de Sódio (NaCl). Além disso, avaliar o efeito desses inibidores quando inseridos em um filme de acetato de celulose. O estudo compreendeu a exposição do metal no meio proposto, na ausência e presença de 0,005, 0,01 e 0,07 mol/L de Na2WO4, e/ou 1000, 2000 e 3000 ppm de amoxicilina inseridos ou não em filmes de 5% e 10% de acetato de celulose. Foram empregadas técnicas eletroquímicas de monitoramento do potencial de circuito aberto (PCA), espectroscopia de impedância eletroquímica (EIE) e polarização anódica. Todos os experimentos foram realizados à temperatura ambiente e em meio aerado. Quanto aos objetivos propostos pode-se concluir que: 1) As medidas de PCA para as diferentes concentrações de Na2WO4, apresentaram deslocamento dos potenciais (E) para valores mais positivos durante os 7 dias de imersão no NaCl, principalmente para 0,07 mo/L de Na2WO4, com E = - 0,407 V no 7º dia, indicando um comportamento inibidor. Para as diferentes concentrações de amoxicilina os valores de potencial não apresentaram variação tão significativa, em 1000 ppm de amoxicilina o E = - 0,560 V no 7º dia. Quando inserida a amoxicilina ao WO4-2, as concentrações melhores foram para 1000, 2000 e 3000 ppm de amoxicilina inserida em 0,07 mol/L Na2WO4, obtendo-se ao 7º dia de imersão valores respectivamente de E = - 0,380 V, E = -0,400 V e E = -,0370 V. Já para os revestimentos a base de acetato de celulose, não apresentaram valores de potencial significativos, ficando entorno de E = -0,645 V ao 7º dia. Quando inserido 2000 ppm amoxicilina e 0,07 mol/L de Na2WO4 ao filme 5 %, continuou estável ao deslocamento do potencial, 2) Por EIE demostrou-se que para 0,07 mol/L de Na2WO4 os valores de resistência aumentaram significativamente do que os demais inibidores, 3) E as curvas de polarização anódica, mostraram que para 0,07 mol/L de Na2WO4 o potencial de rompimento de filme (ERP) possuiu valores mais positivo, ERP = +0,07 V quando comparados com os demais inibidores.
This study aimed to evaluate the sodium tungstate (Na2WO4) and amoxicillin as corrosion inhibitors for carbon steel alloy AISI 1020 added to a medium containing 0.05 mol/L sodium chloride (NaCl). Moreover, to evaluate the effect of these inhibitors when inserted in a film of cellulose acetate. The study consisted of exposing the metal in the proposed environment, in the absence and presence of 0.005, 0.01 and 0.07 mol/L of Na2WO4 and/or 1000, 2000 and 3000 ppm of amoxicillin or not inserted into films 5 % and 10 % cellulose acetate. Electrochemical techniques for monitoring the open circuit potential (PCO), electrochemical impedance spectroscopy (EIS) and anodic polarization were employed. All experiments were performed at room temperature and aerated environment. As for the proposed objectives can be concluded that: 1) PCO measures for the different concentrations of Na2WO4 showed displacement of the potential (E) towards more positive values during the 7 days of immersion in NaCl mainly to 0.07 mol/L Na2WO4 with E = - 0.407 V on day 7, indicating an inhibitory behavior. For different concentrations of amoxicillin potential values showed no significant variation as in 1000 ppm of amoxicillin E = - 0.560 V on the 7th day. When inserted amoxicillin to WO4-2 concentrations were the best for 1000, 2000 and 3000 ppm of amoxicillin inserted in 0.07 mol/L Na2WO4 obtaining the 7th day of immersion values respectively E = - 0.380 V, E = -0.400 V and E = - 0370 V. As for the coatings based on cellulose acetate showed no significant potential values, getting around E = -0.645 V to day 7. When inserted amoxicillin 2000 ppm and 0.07 mol/L of Na2WO4 the film 5 % remained stable potential shift, 2) It is demonstrated that EIS to 0.07 mol/L of Na2WO4 resistance values increased significantly than other inhibitors, 3) and the anodic polarization curves showed that for 0.07 mol/L of the Na2WO4 potential breakup film (ERP) possessed more positive values, ERP = +0.07 V when compared with the other inhibitors.
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Tsaur, Charng-Cheng. "High temperature oxidation and NaCl-induced accelerated corrosion of hot-dip aluminized 9Cr-1Mo and 310 stainless steel". Texas A&M University, 2004. http://hdl.handle.net/1969.1/1375.
Testo completoAbstract (sommario):
The behaviors of high temperature corrosion on hot-dip aluminized on 9Cr-1Mo and 310 stainless steels when catalyzed by NaCl and cyclic heating environment were studied experimentally. The corrosion behavior and morphological development were investigated by weight gain kinetics, metallographs, depths of attack, metal losses, and X-ray analyses. The results of 310SS deposited with salt mixtures show that weight gain kinetics in simple oxidation reveals a steady-state parabolic rate law after 3 hr, while the kinetics with salt deposits display multi-stage growth rates. NaCl is the main corrosive specie in high-temperature corrosion involving mixtures of NaCl/Na2SO4 and is responsible for the formation of internal attack. Uniform internal attack is the typical morphology of NaCl-induced hot corrosion, while the extent of intergranular attack is more pronounced as the content of Na2SO4 in the mixture is increased.
The thermal-cycling test results of 310SS deposited NaCl and coated 7wt%Si/93wt%Al show that the aluminized layers have good corrosion resistance during the first four cycles of testing, while degradation occurs after testing for five cycles. The reason for degradation of aluminized layers is attributed to the formation of interconnecting voids caused by aluminum inward diffusion, chloridation/oxidation cyclic reactions and the penetration of molten NaCl through the voids into the alloy substrate.
The 9Cr-1Mo steels coated with 7wt%Si/93wt%Al oxidized at 750, 850, and 950°C in static air show that oxidation kinetics followed a parabolic rate law at 750 and 850 °C. The cracks propagated through the FexAly layer due to the growth of brittle FeAl2 and Fe2Al5 at 750 and 850°C. The voids condensed in the interface of intermetallics and substrate are attributed to the Kirkendall effect. At 950°C, the fast growing aluminide layer has a different expansion coefficient than oxide scale, leading to scale cracking, oxygen penetration, and internal oxidized, evidenced by a rapid mass gain.
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Chen, Zhuo Yuan. "The role of particles on initial atmospheric corrosion of copper and zinc : lateral distribution, secondary spreading and CO2-/SO2-influence". Doctoral thesis, KTH, Korrosionslära, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-431.
Testo completoAbstract (sommario):
The role of sodium chloride (NaCl) particles and ammonium sulfate ((NH4)2SO4) particles on the initial atmospheric corrosion of copper and zinc was investigated under in situ and ex situ conditions using microgravimetry, FTIR spectroscopy, ion chromatography, scanning electron microscopy with x-ray microanalysis and the scanning Kelvin probe. For the first time, in situ infrared spectra were collected on a micron level during particle induced atmospheric corrosion using a recently developed experimental set-up for in situ FTIR microspectroscopy. Lateral distribution of corrosion and reaction products on copper and zinc surfaces was determined and could be connected with the mechanisms of the initial particle induced corrosion. The recently discovered secondary spreading effect from NaCl electrolyte droplets on metal surfaces was studied under in situ conditions and the effect of CO2 on the spreading process was elaborated. The ambient level of CO2 (350 ppm, 1 ppm = 10-6 volume parts) results in a relatively low secondary spreading effect, whereas the lower level of CO2 (<5 ppm) causes a much faster secondary spreading effect over a large area. At low CO2 concentration alkaline conditions will prevail in the cathodic area, leading to large changes in the surface tension at the oxide/electrolyte interface in the peripherical parts of the droplet. This induces a surface tension driven convective flow of electrolyte from the NaCl droplet. The continuous growth of the secondary spreading area at low CO2 concentration is possible due to the galvanic coupling with the droplet leading to transport of sodium ions to this region and maintenance of the alkaline conditions. At 350 ppm CO2, carbonate formation in the secondary spreading area results in lowering of the pH, increasing the surface tension of the oxide/electrolyte interface and inhibiting the secondary spreading. CO2 strongly affects the NaCl-induced atmospheric corrosion rate of copper. The overall influence of CO2 and NaCl depends on at least three identified mechanisms. At low NaCl particle density, CO2 affects the secondary spreading effect from the electrolyte droplet. This leads to a larger effective cathodic area at low CO2 concentration and a higher corrosion rate. The more alkaline surface electrolyte present at low CO2 concentration also affects the formation of corrosion products and the amount of soluble copper chloride. Whereas the presence of larger amounts of soluble chloride tends to increase the corrosion rate, the formation of CuO results in a more protective surface film which decreases the corrosion rate. This effect was observed at higher NaCl particle densities, where the secondary spreading areas overlapped with adjacent NaCl particle clusters. The formation of CuO leads to lower corrosion rates compared to ambient CO2 concentration in which this phase was not formed. For zinc, the formation of a more protective corrosion product layer was not observed and the corrosion rate is generally higher for low than for ambient CO2 concentration. The presence of NaCl particles on the metal surfaces strongly affects the SO2 interaction with the metal surfaces. The oxidation of S(IV) turned out to be fast at the area of the NaCl-containing electrolyte droplet, both for copper and zinc. On copper surfaces, both sulphate (SO4 2-) and dithionate (S2O6 2-) ions formed which is consistent with a copper catalysed reaction route for sulfite oxidation including the formation of a Cu(II)–sulfito complex as an important step. For zinc, a surface mediated sulfite oxidation process leads to rapid formation of sulphate in the electrolyte droplet area. The presence of SO2 strongly inhibits the secondary spreading due to the decrease in pH induced by absorption of SO2 in the cathodic areas. The presence of gaseous oxidants, such as NO2 and O3, has previously been considered as an important prerequisite for the oxidation of sulfite on copper. The results obtained here suggest that the formation of local electrochemical cells induced by deposited NaCl particles could be another important route for S(IV)- oxidation to sulfate formation. On copper, SO2 was also found to promote the formation of less soluble copper chlorides, such as paratacamite (Cu2(OH)3Cl) and nantokite (CuCl). The electrolyte droplet was dried after 24 hours of exposure due to the formation of less soluble paratacamite (Cu2(OH)3Cl) and nantokite (CuCl) and led to a decrease in the corrosion rate. Thus, SO2 alone promotes the corrosion rate of copper, whereas in the presence of NaCl particles the corrosion rate of copper may slow down due to the formation of insoluble copper chloride compounds. The lateral distribution of corrosion products after exposure of NaCl contaminated copper and zinc surfaces to humid air with gaseous pollutants is a result of the formation of local electrochemical cells at the particles and concomitant differences in chemical composition and pH. For (NH4)2SO4 deposited copper and zinc surfaces the corrosion effects increase with the amount of pre-deposited particles and with the exposure time. On copper, the size of the particles affects the corrosion rate, smaller particles resulting in a higher corrosion rate than larger particles at equal amount of deposition. The formation of Cu2O was the dominant corrosion product after exposure longer than 10 days. (NH4)2SO4 particles result in enhanced Cu2O formation on copper due to a reaction sequence involving catalysis by NH3. The corrosion of copper by (NH4)2SO4 particles was much larger than that induced by NaCl particles. However, for zinc, the (NH4)2SO4 particles lead to smaller corrosion effects than those of NaCl particles. For both particles, significant corrosion attack was observed at relative humidity (RH) lower than the deliquescence point of the salts.QC 20101001
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Reffass, Mohammed. "La corrosion localisée des aciers en milieu NaHCO3/NaCl et son inhibition par les ions HPO42 et NO2 : rôle des composés à base de Fe(II)". La Rochelle, 2006. http://www.theses.fr/2006LAROS164.
Testo completoAbstract (sommario):
L’objet de ce travail est de comprendre les mécanismes de corrosion par piqûres d’un acier faiblement allié (S235) dans une solution aqueuse aérée de NaHCO3/NaCl et d’étudier l’effet de deux inhibiteurs de corrosion (HPO42- et NO2-) sur la résistance à la piqûration de l’acier. La Piqûration de l’acier a été étudiée en couplant des mesures électrochimiques et des analyses spectroscopiques. Un suivi in situ de l’activité électrochimique des piqûres, a été réalisé par imagerie électrochimique à électrode vibrante (SVET). La microspectroscopie Raman a permis d’identifier puis de suivre, in situ, l’évolution des produits de corrosion au cours du temps. En parallèle, une étude chimique de synthèse et d’oxydation des produits de corrosion susceptibles de se former dans les piqûres a été effectuée dans des conditions expérimentales similaires à celles régnant dans les piqûres. La caractérisation, in situ, des produits de corrosion formés dans les piqûres a montré que le premier produit de corrosion formé est un carbonate de fer FeCO3 appelé sidérite. L’action oxydante du dioxygène dissous présent dans la solution conduit à une transformation de la sidérite en rouille verte carbonatée, qui est ensuite elle-même oxydée en goethite. Ces résultats semblent montrer qu’il existe une relation significative entre la nature des produits de corrosion formés et le processus de développement des piqûres. En effet, la formation de sidérite et de rouille verte signe un développement rapide des piqûres, alors que la formation de composées ferriques est associée à un ralentissement du développement des piqûres et à une accélération de leur repassivation. La même démarche a été réutilisée pour l’étude de l’effet des ions HPO42- et NO2- sur le processus de piqûration de l’acier étudié. L’inhibition de la piqûration par l’ion HPO42- se traduit par une diminution de la proportion de la sidérite formée au profit d’un phosphate de fer (la vivianite), produit connu être plutôt protecteur. Pour des concentrations élevées en HPO42-, la formation exclusive de la vivianite conduit à une meilleure protection contre la piqûration. Pour l’ion NO2-, l’effet inhibiteur semble provenir de la formation d’un complexe de Fe(III) [Fe(H2O)6]3+. En effet, la caractérisation des produits de corrosion formés dans les piqûres en présence de l’ion nitrite a donné le complexe [Fe(H2O)6]3+ avec une faible proportion de la sidérite. L’ion NO2-, connu pour son action oxydante, réduit énormément la quantité de sidérite formée dans les piqûres et oxyde rapidement le Fe(II) dissous, conduisant à des complexes de Fe(III) probablement précurseurs des oxydes de Fe(III) constitutifs du film passifThe aim of this work is to understand the pitting mechanisms of S235 carbon steel in aerated aqueous NaHCO3/NaCl solutions and to study the effect of two inhibitors (HPO42- and NO2-) on pitting of steel in the same media. Electrochemical measurements coupled to spectroscopic analysis were used to characterize pitting corrosion. The activity of a given pit has been studied by scanning Vibrating Electrode Technique (SVET). The micro Raman spectroscopy is used to identify and to follow, in situ, the evolution of the corrosion products formed in the pits. In parallel, a chemical study of synthesis and oxidation of the products likely to form in the pit has been done in experimental conditions similar to those found in the pits. The characterization, in situ, of the products of corrosion formed in the pits showed that the first corrosion product formed is an iron carbonate FeCO3 named siderite. The oxidizing action of the dissolved oxygen present in solution, transforms siderite into carbonated green rust, that is then oxidized into goethite. These results seem to show that a meaningful relation exists between the nature of the corrosion products and the process of development of the pits. Indeed, the formation of siderite and green rust signs a fast development of the pit, whereas the formation of ferric compounds is associated to a slowing of the development of the pit and an acceleration of their repassivation. The same methodology has been used for the study of the effect of two corrosion inhibitors (HPO42- and NO2-) on the process of pitting of the studied steel. The inhibition by the HPO42- ions is explained by a reduction of the proportion of siderite formed to the profit of an iron phosphate (vivianite), product known to be rather protective. For elevated concentrations of HPO42-, the exclusive formation of the vivianite gives a better protection against pitting. For the NO2- ion, the inhibiting effect seems to come from the formation of Fe(III) complexes [Fe(H2O)6]3+. Indeed, the characterization of the corrosion products formed in the pits in presence of the nitrite ions gave the complex [Fe(H2O)6]3+ with a weak proportion of siderite. NO2- ions oxidize quickly the dissolved Fe(II), giving a Fe(III) complex probably precursors of the Fe(III) spinel oxides of the passive film
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Sancy, Velasquez Mamie Odette. "Etude de la corrosion du cuivre en milieu 0,1 M NaCl et de la capacité inhibitrice de phtalocyanines tetra-sulphonées". Paris 6, 2006. https://tel.archives-ouvertes.fr/tel-01596357.
Testo completo
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Oliveira, Mariana Cristina de 1991. "Efeito da deformação plástica na corrosão do aço API 5L X65 em solução ácida de NaCl /". Guaratinguetá, 2018. http://hdl.handle.net/11449/155949.
Testo completoAbstract (sommario):
Orientador: Eduardo Norberto CodaroCoorientadora: Heloisa Andréa Acciari
Banca: Roberto Zenhei Nakazato
Banca: Rosinei Batista Ribeiro
Resumo: O objetivo deste trabalho foi investigar a influência da deformação plástica no comportamento corrosivo de oleodutos em ambiente ácido contendo cloreto de sódio. As tubulações trabalham em ambiente altamente corrosivo e estão sujeitas à deformação plástica, o que altera as propriedades mecânicas do aço. Com isso é necessário avaliar a integridade da tubulação em serviço. Para tanto retirou-se amostras de uma tubulação do aço de baixo carbono API 5L X65, um dos mais utilizados pela indústria do petróleo e gás para fabricação de tubulações de transporte. As amostras foram deformadas plasticamente em 0,5%; 1,0%; 1,5%; 2,0% e 2,5% por meio de um ensaio de tração. A microestrutura das amostras deformadas foi caracterizada, através da microscopia óptica e eletrônica de varredura, apresentando uma matriz de ferrita - perlita fina. Uma nova análise microestrutural foi realizada após os ensaios de corrosão, indicando que o aço sofre um processo de corrosão generalizada. Para avaliar o comportamento corrosivo foram realizados testes laboratoriais de imersão e eletroquímicos para caracterizar o processo corrosivo em solução ácida contendo 3% de cloreto de sódio. O teste de imersão teve a finalidade de comparar a perda de massa de uma amostra sem deformação plástica e outra com deformação plástica de 2,5%. Os resultados indicaram que não há diferença significativa entre as amostras. Utilizou se as técnicas eletroquímicas de OCP, polarização de Tafel, EIS e Permeação de hidrogênio, em tod... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: This work aims to investigate the influence of plastic deformation on the corrosive behavior of pipelines in acidic environment containing sodium chloride. The pipelines work in a highly corrosive environment and are subject to plastic deformation, which alters the steel's mechanical properties. Therefore, integrity assessment of a pipeline in service is necessary. For this purpose, samples were taken from a pipeline of API 5L X65 low carbon steel, one of the most used by the oil and gas industry to manufacture transport pipelines. The samples were plastically deformed in 0.5%; 1.0%; 1.5%; 2.0% and 2.5% by a tensile test. The microstructure of deformed samples was characterized by optical and scanning electronic microscopy, presenting a fine ferrite and pearlite matrix. A new microstructural analysis was performed after the corrosion tests, indicating that the corrosion process is uniform. The corrosive behavior was assessed by laboratory immersion and electrochemical tests to characterize the corrosive process in acid solution containing sodium chloride 3%. The immersion test was used to compare the mass loss between a sample without plastic deformation and another 2,5% plastic deformed. The results indicated that there was no significant difference between the samples. It was used the OCP, polarization of Tafel, EIS and Hydrogen Permeation electrochemical techniques, all techniques showed a uniform corrosion process. The corrosion process did not present significant variati... (Complete abstract click electronic access below)
Mestre
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Liang, Dong. "Environmental and Alloying Effects on Corrosion of Metals and Alloys". The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1243995273.
Testo completo
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Villagran, Olivera Víctor Andrés Eduardo. "Estudio de la corrosión de acero al carbono en soluciones salinas de Nacl y el efecto de la hidrodinámica". Tesis, Universidad de Chile, 2012. http://www.repositorio.uchile.cl/handle/2250/112046.
Testo completoAbstract (sommario):
Ingeniero Civil QuímicoEste estudio consistió en determinar el efecto de la hidrodinámica en la corrosión de acero al carbono en soluciones con concentraciones de NaCl en el rango 0,01-0,1 M. Para esto se fabricó una celda en acrílico en la cual se colocó una placa de acero rectangular. La forma triangular del canal de la celda permite tener un gradiente de velocidades sobre la placa de acero. Se realizó un estudio cualitativo fotografiando las placas rectangulares de acero antes y después de ser corroídas. Se utilizó SEM-EDS para el análisis de la superficie del acero sin corroer y después de ser corroído, lo que permitió observar y contar los picados y las inclusiones compuestas de Mn, Al, Ca, S, O y Fe. Para comparar cuantitativamente la velocidad de corrosión entre las placas se contó el número de núcleos de corrosión a simple vista y el número de picados utilizando las microfotografías tomadas por una cámara digital conectada a un microscopio óptico. A partir de las mediciones se determinó que el número de picados disminuye con el aumento de la velocidad del fluido y que hay, además, una velocidad crítica sobre la cual la formación de picaduras se inhibe completamente. Se determinó que la velocidad crítica se encuentra en el rango 1-2,5 [m/s], sin embargo no se observó una dependencia clara de esta velocidad crítica en función de la concentración de NaCl. Esta velocidad crítica es similar a la medida en otros metales, lo que lleva a concluir que la inhibición o disminución de la corrosión se debe a la rápida repasivación producto de la alta transferencia de masa entre la superficie y la solución de los reactantes (oxígeno) y productos de corrosión.
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Petit, Luc. "Etude de la corrosion d'alliages de fer et de nickel par les mélanges NaSO,NaCO,NaCl et NaCO,NaS,NaSO,NaCl entre 300 °C et 900 ° application aux chaudières de récupération (procédé KRAFT) /". Grenoble 2 : ANRT, 1988. http://catalogue.bnf.fr/ark:/12148/cb37619457t.
Testo completo
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Mathias, Cathy. "Examination of interactions between ferrous metals and the archaeological burial environment at a seventeenth-century plantation site". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape10/PQDD_0025/MQ42481.pdf.
Testo completo
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Najjar, Denis. "Compétition entre les mécanismes de dissolution anodique et de fragilisation par l'hydrogène dans le processus de fissuration par corrosion sous contrainte de l'alliage Al-Zn-Mg-Cu 7150 sollicité en traction lente en milieu chlorure (NaCl 3)". Lille 1, 1994. http://www.theses.fr/1994LIL10098.
Testo completoAbstract (sommario):
Les alliages d'aluminium alznmg(cu) de la serie 7000 utilises dans l'industrie aeronautique ont fait l'objet de nombreuses etudes en corrosion sous contrainte (csc). Neanmoins, le mecanisme de fissuration est toujours sujet a controverses: dissolution anodique et fragilisation par l'hydrogene sont souvent proposes de maniere mutuellement exclusive. Le principal objectif de ce travail est de faire la part des choses entre ces deux grandes familles de mecanismes lors de la fissuration par csc de l'alliage 7150 sollicite en traction lente en milieu chlorure (nacl 3%). En couplant des essais mecaniques discriminatoires a des observations en microscopie electronique a balayage, nous montrons que dissolution anodique et fragilisation par l'hydrogene operent conjointement. L'influence relative de ces deux mecanismes depend des principaux parametres qui gouvernent la fissuration: l'etat microstructural, le potentiel electrochimique et la vitesse de deformation. En consequence, seule une modelisation qui considere cette influence relative semble appropriee pour rendre compte des resultats experimentaux. Jusqu'a presente, seule la phase de propagation avait fait l'objet d'etudes approfondies et nous proposons d'introduire la notion de defaut critique pour decrire la phase d'amorcage.
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Kravetz, André Silvestre. "Estudo da curva de polarização cíclica da liga de níquel Inconel 625 em solução de NaCl". Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/3/3133/tde-17072018-134630/.
Testo completoAbstract (sommario):
As curvas de polarização potenciodinâmicas cíclicas da liga de níquel Inconel 625, em solução de NaCl 3,56 %, pH 7,5, desaerada e a temperatura ambiente, obtidas com base na metodologia descrita na norma ASTM G61, foram estudadas com o objetivo de interpretá-las, especialmente no trecho após a reversão da polarização. Para esse estudo, foram realizadas análises complementares por MEV/EDS e por espctroscopia Raman da superfície do eletrodo de trabalho e determinação qualitativa por EDS da composição do eletrólito coletado nas vizinhas do eletrodo de trabalho. Medidas de pH e determinação do teor de O2 do eletrólito junto ao eletrodo de trabalho também foram feitas. Os resultados obtidos mostraram que, entre o potencial de circuito aberto até potencial de quebra (Eb), da ordem de 0,600 V (ECS), a curva de polarização apresenta um comportamento passivo com tendência a atingir a densidade de corrente da ordem de 10-6 A/cm². Nessa região, ocorre o espessamento da camada devido à formação principalmente de Cr2O3. Após Eb, ocorre a mudança na inclinação da curva, devido à ocorrência da reação de oxidação da água, comprovada pela acidificação do eletrólito. No potencial de 0,750 V (ECS) ocorre uma inflexão na curva, causando a diminuição discreta da corrente, atribuída à formação de MoO42- (gel) que evita a incorporação de ânions como Cl- ou OH-, dificultando, porém não evitando, a oxidação/dissolução da camada passiva, comprovada pela presença de íons de Cr e de Ni no eletrólito, caracterizando uma região transpassiva. Após a reversão da polarização no potencial de 1,130 V (ECS), a curva apresenta uma histerese positiva, com valores de densidades de correntes menores em relação ao mesmo potencial aplicado durante a polarização direta, indicando a ocorrência de repassivação devido principalmente à formação de uma camada rica em Mo sobre a liga, cuja formação pode ser atribuída à transformação do molibdato para o óxido MoO3 decorrente da forte acidificação do eletrólito verificado nesse trecho da curva. Ainda, após a inversão da polarização, ocorre a transição da corrente anódica para catódica em um potencial próximo de 0,720 V (ECS). Do potencial de 0,600 V (ECS) até 0,200 V (ECS), observa-se uma região de passivação secundária, atribuída à formação do MoO3 de maneira mais significativa. Ao final a densidade de corrente volta a aumentar, indicando o início da oxidação/dissolução do MoO3 para Mo3+.Cyclic potentiodynamic polarization curves of the nickel alloy Inconel 625 in 3.56 % NaCl solution, pH 7.5, deaerated and at ambient temperature, obtained according to the ASTM G61, were studied in order to interpret them, especially after the reversion of the scanning direction. For this study, complementary analyzes by MEV/EDS and by Raman spectroscopy of the working electrode surfaces as well as EDS analyses of the electrolyte collected near the working electrode were carried out. The pH values and O2 content of the electrolyte near the working electrode were also obtained. From the open circuit potential (OPC) up to breakdown potential (Eb), at about 0,600 V (ECS), the polarization curve presents a passive behavior with a tendency to reach the current density of 10-6 A/cm². In this region, the thickening of the passive film takes place mainly due to the formation of Cr2O3. After Eb, a change of the curve slope occurs due to the oxygen evolution reaction which is confirmed by the acidification of the electrolyte. At the 0,750 V (ECS) potential, an inflection of the curve is observed causing a discrete decrease in the current which was attributed to the formation of MoO42- (gel) which, in turn, avoids the incorporation of anions as Cl- or OH- in the passive film. This fact makes the oxidation/dissolution of the passive film difficult but does not avoid it since Cr and Ni ions were detected in the electrolyte after the inflection, characterizing a transpassive region. After the reversion of the scanning direction at the potential 1,130 V (ECS), the curve shows a positive hysteresis with lower current densities than the values obtained at the same potential applied during the direct polarization. This indicates the occurrence of repassivation mainly due to the formation of a Mo rich layer on the alloy whose formation can be attributed to the transformation of the molybdate to the MoO3 because of the strong acidification of the electrolyte. After the reversion of the polarization, a transition from the anodic current to cathodic occurs at a potential close to 0,720 V (ECS). From the potential of 0,600 V (ECS) up to 0,200 V (ECS), a secondary passivation region is observed which was attributed to the significant formation of MoO3. At the end of the reverse polarization, the current increases again, indicating the initiation of the oxidation/dissolution of MoO3 to Mo3+.
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Trachli, Bouchra. "Étude sur la corrosion du cuivre en milieu NaCl 0,5M et sa protection par des inhibiteurs organiques et des films polymères obtenus par électropolymérisation". Paris 6, 2001. http://www.theses.fr/2001PA066484.
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Aguiar, Aloysio de. "A influencia do teor de silicio na corrosão localizada das ligas AL-Si em solução de NaCl 3,0%". [s.n.], 1988. http://repositorio.unicamp.br/jspui/handle/REPOSIP/267179.
Testo completoAbstract (sommario):
Orientador: Ettore Bresciane FilhoDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Campinas
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Resumo: No presente trabalho foi estudada a influência do teor de silício na corrosão das ligas alumínio-silícíc em soluções de NaCl 3,01. As ligas, com concentrações de silício dc 4,8%, 11,3% e 22,0%, foram obtidas com alumínio e silício com graus de pureza 99, 75% e 99,52%, respectivamente, em condições controladas de solidificação. A resistência â corrosão em NaCl 3,0% foi analisada através de curvas de polarização anódicas e catódicas e de ensaios de imersão total em soluções estagnadas. A morfologia do ataque foi caracterizada através de microscopia eletrônica de varredura, microssonda e microscopia óptica na secção transversal. A partir dos resultados experimentais foi proposto um mecanismo da ação do silício na corrosão localizada das ligas alumínio-silício
Abstract: The influence of the silicon grade in the corrosion resistance of the aluminum-silicon alloys has been investigated in a aqueous solution of sodium chloride 3,0%. Alloys, with silicon grades of 4,8%, 11,3% and 22,0% has been obtained with aluminum 99,75% and silicon 99,52% pure in controled conditions of solidification. The corrosion resistance in sodium cloride 3,0% has been evaluated by anodic and cathodic polarization curves and total immersion tests in stagnated solutions. The morphology of the attack has been evaluated by scanning eletronic microscope, microprobe and optic microscope in the transvertial section. Finally, from the experimental results, a mechanism of the silicon action in the localized corrosion of the aluminum-silicon alloys was proposed
Mestrado
Mestre em Engenharia Química
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Xavier, Marco Antonio Kresko. "Revestimentos de polianilina e polianilina/melamina sobre aço inox 304: eletrossíntese em meio aquoso neutro e avaliação da proteção contra corrosão em meio NaCl 0,5 mol/l". Universidade Tecnológica Federal do Paraná, 2013. http://repositorio.utfpr.edu.br/jspui/handle/1/876.
Testo completoAbstract (sommario):
A polianilina é dos polímeros condutores mais estudados e com diversas aplicações, dentre elas o uso no recobrimento de aços para proteção à corrosão. Este trabalho objetivou encontrar as condições de eletrossíntese de polianilinas em meio aquoso neutro e a avaliação de proteção à corrosão, tendo como substrato o aço inox 304. As polianilinas eletrossintetizadas foram uma forma pura (PAni) e outra modificada com a adição de melamina (PAni/MM). Dentre as justificativas deste trabalho está a necessidade de aprofundar os escassos estudos em eletrossínteses em meio aquoso neutro. Neste trabalho, são apresentados as condições de eletrossíntese das polianilinas, a caracterização preliminar das polianilinas por UV-visível, FTIR e MEV, ensaios de polarização potenciodinâmica e impedância eletroquímica do aço inox 304 sem e com filmes das polianilinas para avaliar a resistência à corrosão em meio aquoso de NaCl 0,5 mol/L. O trabalho mostrou que a eletrossíntese das polianilinas em meio aquoso neutro é viável. Além disso, foi verificada a seguinte ordem do potencial de corrosão, do menor para o maior: aço inox 304 puro, aço inox 304 com PAni e aço inox 304 com PAni/MM.Polyaniline is one of the most studied conducting polymers and with various applications, including use on steels for corrosion protection. This work aimed to find the conditions for electrosynthesis of polyanilines in neutral aqueous media and to evaluated the corrosion protection of 304 stainless steel. The electrosynthesizeds polyanilines were one pure form (PAni) and one with the addition of melamine (PAni/MM). One of the justifications of this work is the need to deepen the scarce studies in electrosynthesis in neutral aqueous media. In this work, we will see the conditions for electrosynthesis of polyanilines, the UV-visible, FTIR and SEM polyanilines preliminary characterization, the potentiodynamic polarization experiments and impedance spectroscopy of 304 stainless steel without and with films from polyanilines for evaluate the corrosion resistance in NaCl 0,5 mol/L aqueous media. This work showed that electrosynthesis of polyanilines is feasible in neutral aqueous media. In addition, it was verified the following order of corrosion potencial, from lowest to highest: pure 304 stainless steel, 304 stainless steel with PAni and 304 stainless with PAni/MM.
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Candido, Luiz Claudio. "Comportamento do aco inoxidavel ABNT 304 a corrosao-sob-tensao em solucoes aquosas neutras de nacl a temperatura de ebulicao utilizando a tecnica de carga constante". reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 1987. http://hdl.handle.net/10183/2418.
Testo completoAbstract (sommario):
Estudou-se o comportamento do aço inoxidável ABNT 304 à corrosão-sob-tensão (C.S.T.) em soluções aquosas com 0,1%, 3,5% e 20% de NaCl, na temperatura de 103°C, através de ensaios de carga constante. Com auxílio das técnicas e conceitos de Mecânica de Fratura Linear Elástica e das análises eletroquímicas procurou-se encontrar as condições em que ocorre C.S.T. no sistema aço inoxidável austenítico/solução aquosa de NaCl a 103°C. Utilizou-se o corpo-de-prova do tipo dupla viga em balanço (T-notch double cantilever beam: TN-DCB), com intuito de observar a influência do fator de intensidade de tensão, concentração da solução e potencial eletroquímico. Estimou-se o valor do fator de intensidade de tensão limite (KICST) e a velocidade de propagação das trincas; também foram analisadas outras importantes características em termos mecanísticos. Definiu-se faixas de potenciais e valores de intensidade de tensão a partir dos quais ocorre o surgimento de trincas por C.S.T.. Fêz-se análises metalográficas dos corpos-de-prova onde se pode constatar trincas transgranulares bem típicas do fenômeno de C.S.T.. Foram feitos alguns testes em solução aquosa saturada de MgCl2, em ebulição, para se comparar as diferentes soluções quanto ao fenômeno de C.S.T.. Alterou-se as dimensões do corpo-de-prova para avaliar a orientação da propagação das trincas por C.S.T..Stress-corrosion cracking behavior of ABNT 304 stainless steel in 0,1%, 3,5%, and 20% NaCl solutions at 103°C was analised through the constant charge method. With the help of the thedniques and concepts of fracture mechanics linear elastic and electrochemical methods the conditions in wich the SCC appeared in the system austenitic stainless steel/NaCl - aqueous solution (103°C) were determined. T-notch double cantilever beam (TN-DCB) specimen was used to observ the influence of the charge intensity, solution concentration and electrochemical potential. Values for KISCC and the velocity of crack propagation were estimated. Values of KI and potential ranges in wich SCC appears were defined. Typical transgranular fractures were observed. Some tests were made in saturated boiling MaCl2 solutions. Dimensions of TN-DCB specimens were modified to evaluated their influence on the direction of crack propagation.
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Dutra, Conceição Aparecida Matsumoto [UNESP]. "Estudo do comportamento eletroquímico e da resistência à corrosão de eletrodepósitos de zinco e ligas de zinco em solução de NaCL e na presença de oxi-ânions do grupo VIB". Universidade Estadual Paulista (UNESP), 2010. http://hdl.handle.net/11449/103755.
Testo completoAbstract (sommario):
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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)
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Picaud, Thierry. "Application des mesures d'impédance électrochimique à l'étude des performances vis-à-vis de la corrosion en milieu NaCl 3% de tôles d'acier, prétraitées ou non, peintes". Toulouse, INPT, 1986. http://www.theses.fr/1986INPT032G.
Testo completoAbstract (sommario):
Etude par des mesures electrochimiques d'impedance de l'influence des traitements de surface (phosphatation) et des revetements de peinture sur la resistance a la corrosion de toles d'acier en milieu salin. Determination d'une hierarchie de tenue a la corrosion en fonction du type de phosphatation (zinc ou fer)
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Picaud, Thierry. "Application des mesures d'impédance électrochimique à l'étude des performances vis-à-vis de la corrosion en mileu NaCl 3% de tôles d'acier, prétraitées ou non, peintes". Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb37608827j.
Testo completo
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Dutra, Conceição Aparecida Matsumoto. "Estudo do comportamento eletroquímico e da resistência à corrosão de eletrodepósitos de zinco e ligas de zinco em solução de NaCL e na presença de oxi-ânions do grupo VIB /". Guaratinguetá : [s.n.], 2010. http://hdl.handle.net/11449/103755.
Testo completoAbstract (sommario):
Resumo: 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... (Resumo completo, clicar acesso eletrônico abaixo)Abstract: 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)
Orientador: Roberto Zenhei Nakazato
Coorientador: Luis Rogerio de Oliveira Hein
Banca: Marcelo dos Santos Pereira
Banca: Alain Laurent Marie Robin
Banca: Cecílio Sadao Fugivara
Doutor
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Klok, Simone Maria. "Avaliação da supersaturação na formação da camada de FeCO3 no processo corrosivo do aço carbono em meio de NaCl saturado com CO2". reponame:Repositório Institucional da UFPR, 2017. http://hdl.handle.net/1884/53496.
Testo completoAbstract (sommario):
Orientador: Prof. Dr. Haroldo de Araújo PonteTese (doutorado) - Universidade Federal do Paraná, Setor de Tecnologia, Programa de Pós-Graduação em Engenharia e Ciência dos Materiais - PIPE. Defesa: Curitiba, 18/09/2017
Inclui referências : f. 122-126
Área de concentração: Engenharia e ciência de materiais
Resumo: O aço carbono é amplamente empregado na exploração, produção e escoamento de gás e petróleo. Porém, é suscetível à corrosão por dióxido de carbono. Sob condições específicas, pode ocorrer a formação e o depósito de um produto de corrosão, o carbonato de ferro (FeCO3), que reduz significativamente a taxa de corrosão do aço carbono. A formação deste filme protetor é fortemente dependente de várias condições do meio em que o aço carbono se encontra. Nesse estudo limitou-se: ao efeito da rugosidade superficial, do pH do meio e da supersaturação de íons [Fe2+]. Sabe-se que em condições de pH ácido é termodinamicamente pouco favorável a formação da camada protetora de carbonato de ferro. Nesse contexto, este trabalho visa comprovar que a supersaturação de íons ferro disponíveis em solução é uma variável importante. Sua concentração altera a morfologia do filme de carbonato formado sobre o aço carbono, alterando assim sua capacidade protetora. Neste estudo empregou-se medidas eletroquímicas de Resistência a Polarização Linear e analíticas para verificar-se a dificuldade na formação do filme protetor em ambientes ácidos. Observou-se que em meios neutros (pH 7,0), o estabelecimento de uma camada protetora de FeCO3 e o controle da corrosão. Em meios ácidos (pH 3,5), as taxas de corrosão foram elevadas devido ao mecanismo de corrosão por frestas e consequente evolução para pites, caracterizando um ataque localizado com severos danos à superfície metálica. Entretanto, mesmo em condições pouco favoráveis, obteve-se um filme de carbonato de ferro - FeCO3 sobre a superfície do aço carbono, em meio ácido, quando atingido a valor teórico da concentração de íons [Fe2+] e excedido o limite de solubilidade do carbonato - kps, evidenciando o efeito da supersaturação na estabilização do filme em um ambiente termodinamicamente pouco favorável. Palavras-chave: corrosão, aço carbono, dióxido de carbono, pH ácido e supersaturação
Abstract:Carbon steel make up an important category of metallic materials, widely used in the exploration, production and distribution of gas and oil. However, corrosion is likely carbon dioxide. Under specific conditions, may form and deposit a corrosion product, iron carbonate (FeCO3), which significantly reduces the carbon steel corrosion rate. The formation of this protective film is strongly dependent on various conditions of the environment in which the carbon steel is in. Since this study was limited to: the effect of surface roughness, the medium pH and ion supersaturation of [Fe2+]. It is known that under conditions of acid pH is not thermodynamically favorable the formation of the protective layer of iron carbonate. In this study we used electrochemical measurements of Resistance to Linear Polarization and analytical to verify the difficulty in the formation of the protective film in acidic environments. In this context, this paper aims to prove that the supersaturation of iron ions available in solution is an important variable. Your concentration changes the carbonate film morphology formed on carbon steel, thereby altering its protective capacity. In this study we used electrochemical and analytical steps to verify the difficulty in forming the protective film in acidic environments. It was observed that in neutral media (pH 7,0), the establishment of a protective layer of FeCO3, and corrosion control. In acidic conditions (pH 3,5), corrosion rates were high due to the corrosion mechanism by cracks and consequent evolution to pits, featuring a localized attack with severe damage to the metal surface. However, even in non favoráreis conditions, there was obtained an iron carbonate film - FeCO3 on the surface of carbon steel in acid medium, when reached the theoretical value of the ion concentration [Fe2+] and exceeded carbonate solubility limit - kps. Showing the effect of supersaturation in stabilizing the film in a thermodynamically unfavorable environment. Keywords: corrosion, carbon steel, carbon dioxide, pH acid and supersaturation
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Silva, Fernando Nunes da. "Desgaste corrosivo-cavitativo-erosivo de um a?o-carbono em meio aquoso com fra??es de sal (NaCl), CO2 e particulados s?lidos (SiO2)". Universidade Federal do Rio Grande do Norte, 2012. http://repositorio.ufrn.br:8080/jspui/handle/123456789/15699.
Testo completoAbstract (sommario):
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Previous issue date: 2012-08-27Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico
A batch of eighty-four coupons of low carbon steel were investigated at laboratory conditions under a corrosive, cavitative-corrosive (CO2) and corrosive-erosive (SiO2 + CO2) in an aqueous salt solution and two levels of temperature. The following measurements were made on Vickers (HV0,05, HV0,10, HV0,20) Microhardness tests at three levels of subsurface layer. A turbulent flow collided on the cylindrical sample, with and without mechanical stirring and gas bubbling, with and without fluid contamination by solid particles of SiO2, at two temperatures. Surface Roughness and Waviness, under two conditions "as received, after machining" and "after worn out", as well as gravimetric and electrochemical parameter were measured on the two opposite generatrices of each cylindrical sample, on the flow upstream (0?) and downstream (180?) by Profilometry, Mass Variation and Linear Polarization Resistance (LPR). The results of the Microhardness and Surface Texture of all coupons were subjected to statistical comparison, using the software Statgraphics? Centurion XVI, 95% statistical certainty, and significant differences were observed in some arrays of measurements. The corrosive wear rate measured by LPR and mass variation shown to be sensitive to the presence of bubbles and hydrodynamic fluctuations inside the cell, considering the temperature and contamination of corrosive fluid by solid particles. The main results of visual inspection relative to some topologies of the surface damages involving different mechanisms that were seen to give explanation for some fluctuations in wear rates of the steel experimentally investigated
Um lote de oitenta e quatro corpos-de-prova (CP) de a?o AISI 1018 foi investigado em laborat?rio sob solicita??es corrosivas, cavitativo-corrosivas (CO2) e erosivocorrosivas (SiO2+CO2) em meio aquoso salino e a duas temperaturas. Foram realizados ensaios de microdureza Vickers a tr?s n?veis de subsuperf?cie (HV0,05, HV0,10, HV0,20). Um fluxo agitado colidiu contra os CPs, em todas as condi??es de ensaio, sem e com agita??o mec?nica e borbulhamento de g?s, sem e com contamina??o do fluido por part?culas s?lidas de SiO2, nas duas temperaturas estudadas. A rugosidade e ondula??o superficial, nas condi??es como recebidos, ap?s usinagem e ap?s desgastados , bem como medi??es gravim?tricas e eletroqu?micas foram realizadas em duas geratrizes opostas de cada corpo-deprova, a montante (0?) e a jusante (180?), atrav?s das t?cnicas de perfilometria, varia??o m?ssica e resist?ncia de polariza??o linear (RPL). Os resultados da microdureza e da textura superficial em todos CPs foram submetidos ? compara??o estat?stica, utilizando-se o software Statgraphics? Centurion XVI e, com 95% de certeza estat?stica, diferen?as significativas foram observadas em alguns grupos de medidas. As medidas das taxas de desgaste corrosivo, por RPL e por varia??o m?ssica, demonstraram serem sens?veis ? presen?a de bolhas e ?s flutua??es hidrodin?micas no interior da c?lula, consideradas a temperatura e a contamina??o do fluido corrosivo por part?culas s?lidas. Apresentam-se, tamb?m, os principais resultados da inspe??o visual em que se evidenciam algumas topologias do dano superficial nas geratrizes a 0? e a 180?, involvendo diferentes mecanismos que foram presenciados, para justificar algumas flutua??es nas taxas de desgaste do a?o em estudo
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ZAID, BACHIR. "Obtention de films de polypyrrole en milieu aqueux ou organique par oxydation electrochimique du pyrrole sur des surfaces de zinc modifiees et evaluation de leurs proprietes anti-corrosion au milieu nacl". Paris 7, 1994. http://www.theses.fr/1994PA077333.
Testo completoAbstract (sommario):
La reaction d'electropolymerisation du pyrrole sur electrode de zinc a ete realisee en milieux aqueux et organiques: soit en traitant le metal (par le sulfure de sodium ou par des heteropolyanions), soit en incorporant dans le milieu reactionnel un sel capable de passiver partiellement le metal sans inhiber la reaction d'electropolymerisation. Le traitement par les heteropolyanions s'est revele efficace pour l'electropolymerisation du pyrrole dans le milieu propylene carbonate + tetraethyleammonium-paratoluene-sulfonate, mais inefficace en milieu aqueux. Le traitement par le sulfure de sodium est apparu le mieux approprie pour l'obtention des films de polypyrrole, que ce soit en milieu organique ou aqueux. Cette etape de traitement a par ailleurs pu etre supprimee en introduisant directement le sulfure de sodium dans le milieu reactionnel contenant le pyrrole en presence d'oxalate de sodium. La structure, la morphologie et la qualite des films de polypyrrole obtenus a fait l'objet d'etudes spectroscopiques xps, raman, meb et ir, qui ont confirme la similarite de ces films a ceux obtenus habituellement sur les metaux nobles (pt). L'evolution de differentes plaques de zinc nues et recouvertes de ppy (selon les differents procedes) a ete suivie par impedancemetrie au cours de leur immersion dans une solution de nacl 0. 03m. Les premiers resultats indiquent que les systemes zn/ppy presentent une tenue a la corrosion tout a fait acceptable et parfois meilleure que celle observee avec des plaques d'acier zingue chromatees ou phosphatees
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Clark, Tad Dee. "An Analysis of Microstructure and Corrosion Resistance in Underwater Friction Stir Welded 304L Stainless Steel". Diss., BYU ScholarsArchive, 2005. http://contentdm.lib.byu.edu/ETD/image/etd872.pdf.
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Nery, Macclarck Pessoa. "Efeito da tensão média e frequência na resistência a fadiga e corrosão-fadiga de parafusos prisioneiros de aço inoxidável AISI 304". Pós-Graduação em Ciência e Engenharia de Materiais, 2018. http://ri.ufs.br/jspui/handle/riufs/7284.
Testo completoAbstract (sommario):
The use of bolts as an element of union has a great importance in industrial situations that need frequent assembling and disassembly. In the present study, the effect of the mean stress and frequency on the fatigue of screw bolts made from cold-formed threaded bars was evaluated. The bolts was made with austenitic stainless steel, AISI 304, and it were tested in two different environments, air and 35g/L NaCl aqueous solution. Initially, tensile testing, chemical analysis, microstructural analysis, x-ray diffraction and hardness were did by the metallurgical characterization. The fatigue tests occurred with mean stress equal to 40% and 60% of yield strength. After the tests, the appearance of the fracture surface was observed. It has been found that the fatigue limit remains unchanged with respect to the mean stress in the air tests at a higher frequency. However, air tests at low frequencies and under corrosion fatigue follow Goodman's prediction. Already, in the tests under corrosion, the higher mean stress tends to decrease the value of the stress amplitude resistant to corrosion fatigue under the conditions applied in the present study. The results were compared with the theoretical models of life expectancy in fatigue and with the results of Burguete and Patterson (1995).A utilização de parafusos como elementos de união tem grande importância em situações industriais com montagens e desmontagens frequentes. No presente estudo, avaliou-se o efeito da tensão média e frequência de solicitação na fadiga de parafusos prisioneiros confeccionados a partir de barras roscadas conformadas a frio. Fabricados em aço inoxidável austenítico, AISI 304. Os parafusos foram caracterizados através de ensaio de tração, análise química, análise microestrutural, difração de raios x e dureza. Esses parafusos foram testados em dois diferentes ambientes, ao ar e em solução aquosa a 35g/L de NaCl. Os ensaios de fadiga ocorreram com carregamento médio a 40% e 60% da tensão de escoamento. Após os ensaios, o aspecto da superfície de fratura foi observado. A amplitude de tensão de fadiga se mantém inalterada em relação à tensão média nos ensaios ao ar com frequência elevada. No entanto, ensaios ao ar em baixas frequências e corrosão fadiga seguem a previsão de Goodman. Estes ensaios mostraram que a maior tensão média tende a diminuir o valor da tensão alternante resistente à corrosão-fadiga nas condições aplicadas no presente estudo. Os resultados foram comparados com os modelos teóricos de previsão da vida em fadiga e com os resultados de Burguete e Patterson (1995).
São Cristóvão, SE
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Al, Bacha Serge. "Générateur d’Hydrogène « vert » pour mobilité légère ou de courte distance Hydrogen generation via hydrolysis of ball milled WE43 magnesium waste Hydrogen generation from ball milled Mg alloy waste by hydrolysis reaction Effect of ball milling strategy (milling device for scaling-up) on the hydrolysis performance of Mg alloy waste Effect of ball milling in presence of additives (Graphite, AlCl3, MgCl2 and NaCl) on the hydrolysis performances of Mg17Al12 Corrosion of pure and milled Mg17Al12 in “model” seawater solution Mechanism of hydrogen formation during the corrosion of Mg17Al12 Hydrolysis properties, corrosion behavior and microhardness of AZ91 "model" alloys SECM investigation of galvanic coupling between Mg and Mg17Al12 in AZ alloys Valorization of AZ91 by the hydrolysis reaction for hydrogen production (Electrochemical approach) Clean hydrogen production by the hydrolysis of Magnesium-based material: effect of the hydrolysis solution". Thesis, Bordeaux, 2020. http://www.theses.fr/2020BORD0312.
Testo completoAbstract (sommario):
L’hydrolyse des déchets d’alliages de magnésium dans l’eau de mer (i.e. solution aqueuse à 3,5% en masse de NaCl) est une nouvelle approche qui permet à la fois la production de l’hydrogène in-situ et la valorisation de déchets a priori non recyclables. L’objectif de ce travail de thèse est d’optimiser la réactivité de ces déchets par broyage mécanique en présence d’additif(s). Nous avons donc investigué les principaux paramètres de broyage (e.g. atmosphère de broyage, vitesse de broyage, ordre d’ajout des additifs) sur la réactivité d’un alliage WE43 et des déchets d’alliages Mg–Al. Un « scale-up » du procédé de traitement des matériaux a été mené pour explorer la possibilité d’industrialisation du procédé. En outre, nous avons montré que le broyage sous argon est plus avantageux que celui sous hydrogène.Les alliages Mg–Al (plus précisément AZ91) sont les plus utilisés. Dans ces alliages, l’aluminium forme avec le magnésium l’intermétallique Mg17Al12. Pour comprendre le mécanisme de production d’hydrogène à partir d’alliages Mg–Al biphasés (i.e. Mg + Mg17Al12), l’évaluation du comportement de chacun de leurs constituants et de leurs interactions est primordiale. A cet égard, les aspects chimique (i.e. hydrolyse) et électrochimique (i.e. corrosion) de la réaction de Mg17Al12 avec une solution similaire à l’eau de mer et l’effet du broyage en présence d’additifs (e.g. graphite, NaCl, MgCl2 et AlCl3) ont été étudiés. L’évolution de la chimie de surface lors des tests de polarisation a prouvé expérimentalement (par spectroscopie Raman), pour la première fois, la formation d’intermédiaires réactionnels et nous a permis de proposer un mécanisme de formation de H2.L’interaction entre Mg et Mg17Al12 a été explorée en comparant les propriétés de matériaux modèles « AZ91 » (Mg + Mg17Al12). Grâce à la microscopie électrochimique à balayage, l’effet du couplage galvanique est étudié à l’interface des deux composants du matériau. La contribution de Mg17Al12 dans la corrosion des alliages AZ91 a ainsi été clarifiée. L’intermétallique est résistant à la corrosion et accélère la corrosion de Mg en raison du couplage galvanique. Les diverses stratégies de broyage adoptées dans ce travail ont été comparées en les appliquant sur un alliage commercial AZ91. Le matériau traité mécaniquement en présence de graphite et d’AlCl3 présente les meilleures performances en hydrolyse.Finalement, nous avons évalué semi-quantitativement la pureté de H2 (la composition du mélange gazeux et son humidité) produit. L’incidence de certaines conditions expérimentales (e.g. composition de la solution, température, rapport de la masse de poudre au volume de la solution) est reportée. Il a ainsi été montré qu’un réacteur d’hydrolyse de Mg opérant à température ambiante avec l’eau de mer produit de l’hydrogène « propre » in-situ et peut être considéré comme un générateur d’hydrogène « vert » à la demandeThe hydrolysis of magnesium alloys wastes in seawater (i.e. 3.5 wt.% of NaCl aqueous solution) is a new approach which allows both in-situ hydrogen production and the valorization of a priori non-recyclable wastes. The objective of this research work is to optimize the reactivity of magnesium-based wastes by ball milling with additives. Therefore, we investigated the effects of the main milling parameters (e.g. milling atmosphere, milling rotation speed, order of the addition of additives) on the reactivity of WE43 alloys and Mg – Al alloys wastes. A « scale-up » of the materials treatment process was conducted to explore the possibility of industrializing the process. In addition, we have shown that milling under argon is more advantageous than under hydrogen.Mg – Al alloys (more precisely AZ91) are the most widely used. In these alloys, Al forms with Mg the intermetallic Mg17Al12. To better understand the mechanism of hydrogen production from these binary Mg – Al alloys (Mg + Mg17Al12), evaluating the behavior of each of their constituents and their interactions is essential. In this regard, the chemical (i.e. hydrolysis) and electrochemical (i.e. corrosion) aspects of the reaction of Mg17Al12 with the model seawater solution and the effect of milling in the presence of additives (e.g. graphite, NaCl, MgCl2 and AlCl3) were studied. The evolution of the surface chemistry during polarization tests has proven experimentally (by Raman spectroscopy), for the first time, the formation of reaction intermediate and has allowed us to propose a mechanism of H2 formation.The interaction between Mg and Mg17Al12 was explored by comparing the properties of model materials of « AZ91 » (Mg + Mg17Al12). Using scanning electrochemical microscopy, the effect of galvanic coupling was studied at the interface of the two components of the material. In view of these studies, the contribution of Mg17Al12 in the corrosion of AZ91 alloys was clarified. The intermetallic is corrosion resistant and accelerates the corrosion of Mg due to galvanic coupling. The various milling strategies adopted in this work were compared by applying them to a commercial AZ91 alloy. Mechanical treated materials with graphite and AlCl3 showed the highest hydrolysis performances.Finally, we semi-quantitatively evaluated the purity of H2 (the composition of the gas mixture and its humidity) produced. The impact of few experimental conditions (e.g. composition of the solution, temperature, ratio of the mass of powder to the volume of solution) is reported. Thus, it has been shown that an Mg hydrolysis reactor operating at room temperature with seawater produces « clean » hydrogen in-situ and can be considered as a « green » hydrogen on demand generator
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Valencia, Violeta. "Electrochemical Characterization Of Zinc-Rich Epoxy Primer-Cnt Nanocoating / Steel Interface In Co2 Saturated Under Different Flow Conditions". University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1431108599.
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Yan, Ting-Syuan, e 顏婷萱. "Evaluation of Heat-treated Wood on the Performances of Nail Corrosion, Adhesion, and Coating". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/58392614431548455076.
Testo completoAbstract (sommario):
碩士國立宜蘭大學
森林暨自然資源學系碩士班
101
The first part of this study was to investigate the corrosion properties of five kinds metal nail connected with heat-treated Japanese cedar, southern yellow pine, and Douglas fir during 37 weeks of outdoor exposure test. The heat treatments were carried out at temperature levels of 170, 190, 210, and 230℃, respectively. The other part was to investigate the difference of surface and strength properties between heat-treated and untreated hoop pine, Douglas fir, American ash, and red meranti wood. The performance of adhesion was evaluated using urea-foraldehyde resin (UF), melamine-formaldehyde resin (MF), resorcinol- formaldehyde resin (RF), and styrene butadiene rubber resin (SBR) on those four heat-treated wood species, and those for finishing properties by using lacquer NC and polyurethane coating. The results showed mass loss of both high carbon content and low carbon stainless steel nails connected with test specimens were the lowest after exposure test. Both have well corrosion resistance against weathering. There was not significant relationship between mass loss of nails and pH values of heat-treated wood. After heat reatment, the hardness of wood was decreased; the wood surface will become more smooth than untreat wood with respect to testing of surface roughness. Most comtact angle between liquid and wood specimen will be increased after heat treatment, but the MF and SBR on Araucaria and UF on Douglas fir will be decreased. Some species of heat treatment wood may improve glued performance. According to non-destructive vibration test, the dynamic modulus of elasticity (DMOE) of heat treated Araucaria and plywood will be slightly decreased. On bending test and adhesive shear experiment results showed the strength of heat-treated wood will be significantly decreased. The delamination test showed the adhesive performance of RF and SBR were 100% qualified rate, while the UF was 0%. We suggest using RF and SBR resins as binder between heat-treated wood and plywood because of better glue strength and water resistant property. Heat treatment wood has a significant color change after coating. When heat-treatedwood used for floor metarials, we should pay more attention on this phenomenon. Pencil hardness test results showed that heat treatment wood had lower hardness characteristic. It is recommended that before coating, heat treatment wood surfaces should pretreatment, such as wood surface densification process. The performance of coating film peeled of PU on test specimens was better than that of NC. We suggest that PU paint is a better choice on wood coating.
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McGeachie, M. T. "Characterisation of the Sydney region in relation to corrosion, timber decay risk factors and the corrosion of nails in timber in covered conditions". Thesis, 2001. http://handle.uws.edu.au:8081/1959.7/491.
Testo completoAbstract (sommario):
The aim of the study was to characterise the environment in the Sydney region in respect of atmospheric corrosivity, timber decay risk factors and the corrosion of nails in timber in covered conditions. The study reviewed contemporary research in this field, particularly in Australia, developing an understanding of the durability failure mechanisms for timber and nails in timber. The study looked at the effects of climatic aspects, pollutants, corrosion on timber decay risk factors. The study found that the levels of risk in terms of timber degradation, corrosion and nail corrosion were greatest adjacent to the coast and at marine sites.
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Ma, hsi-chang, e 馬錫章. "The 3.5%NaCl Aqueous Corrosion of Fe-based Alloys After Hot Corrosion with pre-coating NaCl/Na2SO4 Mixtures". Thesis, 2000. http://ndltd.ncl.edu.tw/handle/77005925651458949779.
Testo completoAbstract (sommario):
碩士國立臺灣科技大學
工程技術研究所材料科技學程
88
The room-temperature corrosion behavior of three Fe-Cr alloys(containing SB450 and STPA24, and STPA26) was studied in 3.5% NaCl aqueous electrolyte after hot corrosion with 2mg/cm2 NaCl/Na2SO4 deposit at 750℃ and 850℃. The aqueous-corrosion mechanism was evaluated in terms of scale morphology by OM and SEM, XRD, and dynamic polarization curve measurements. The results showed that the higher the Cr content the lower icorr and the higher Ecorr values of the alloy which tends to be more noble. STPA 26 has the best corrosion-resistant ability among the alloys studied, having the lower icorr values and forming a passive zone. The main reason to affect the Ecorr after hot corrosion is sort of electrodes, in which the higher valence of oxides the higher Ecorr values and the more noble of noble alloy. In addition, the main reason to the icorr and the repeatability of cyclic polarization curve is strongly dependent on the scale morphology, in which particle-like or loose scale are much easier to induce crevice corrosion. The higher the icorr values, the worse the repeatability of cyclic polarization curve present. In addition, electrolyte may also contact with lower valence oxides or substrate, which decrease Ecorr values, thereby resulting in a more active state for the alloy. Because the oxychloridation taken place when hot corrosion with NaCl deposits, scales become more porous and easy to corrode, leading to an increase of icorr value by a factor of 2 as compared to the alloy. Thus, the repeatability of cyclic polarization curve gets worse, and decreases Ecorr values. On the other hand, the scales are more dense in pure oxidation, so that crevice corrosion is more difficult to occur. As a result, icorr will be close to that of the raw alloy, and the repeatability of cyclic polarization curve is second to that alloy, in which the corrosion resistance of scales is much improved. The hot-corrosion atmosphere tend to transfer to air-oxidation or complete Na2SO4-deposit environments as increase temperature and exposure duration. As a result, the overall reaction is favorable to form dense oxide-scales, which reduces the icorr but increases the Ecorr values. However, the high-defective Fe1-XO scale retained on the alloy cause a significant increase in the icorr values as compare to that without Fe1-XO.
47
孫稟厚. "Corrosion behavior of Al-Sc alloys in 3.5wt% NaCl solution". Thesis, 2007. http://ndltd.ncl.edu.tw/handle/64238258490963313139.
Testo completoAbstract (sommario):
碩士中華大學
機械與航太工程研究所
95
AbstractThe corrosion behavior of aluminum alloys alloyed with Sc after different heat treatment has been reported in a 3.5% NaCl aqueous solution by using electrochemical method. The surface morphology of the corroded samples was investigated by a scanning electron microscope. Experimental results showed that micro harduess of the Al-Sc alloy was 206.8Hv after a precipitation heat treatment (homogenized at 480℃ for 24h and aged at 100℃ for 24h), due to the presence of Al3Sc precipitates. The precipitates are also affect the corrosion behavior of the alloy. Electrochemical measurement results indicated that the Al-Sc alloy after precipitation heat treatment possesses the most noble corrosion potential. However, the Al-Sc alloy after homogenization possess uniform chemical compositions in the matrix and manifest the lowest corrosion rate.
48
Rong-SinLin e 林榮信. "Corrosion behavior of copper-containing carbon steels in NaCl solution". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/29067094217870965790.
Testo completoAbstract (sommario):
碩士國立成功大學
材料科學及工程學系碩博士班
101
The corrosion behavior of Cu-containing carbon steels in various acidity 3.5 wt% NaCl solution was investigated. By immersion test to calculated the weight loss. The properties of electrochemical corrosion behavior were obtained from potentiodynamic polarization curves and electrochemical impedance spectroscopy. The corrosion products’ crystal structure and chemical bonding energy after potentiostat testing obtained from the X-ray diffraction and X-ray photoelectron spectroscope. The immersion test showed that the weight loss of SS400 steel was higher than that of Cu-containing carbon steels in acidic solution. The weight loss of the Cu-containing carbon steels is decreased with increasing Cu content of the carbon steel. Furthermore, the weight loss of SS400 steel was still higher than that of Cu-containing carbon steels in neutral or basic solution. Potentiodynamic polarization curves showed that the corrosion potential (Ecorr) of Cu-containing carbon steels did not change greatly by adding various Cu content in carbon steel. However, the corrosion potential of Cu-containing carbon steels decreased as the pH value of solution increased. In case of anodic region, the anodic current density of Cu-containing carbon steels was lower than that of SS400 steel. There was a passivation region could be observed in the anodic curves with the pH value of solution was more than 10. The electrochemical impedance spectroscopy (EIS) results indicated that the polarization resistance (Rp) of Cu-containing carbon steel varied from 130 ohm-cm2 to 958 ohm-cm2, depending on the Cu content, in acidic solution (pH = 2). On the other hand, the results also shows that the Rp was increased as the solution pH increased. A significant increase in Rp (3166 ohm-cm2) could be obtained for 4.5 wt% Cu in carbon steel, in basic solution (pH = 12). After potentiostatic test at -0.7 VSCE for 30 minutes, iron oxide, Cu oxide and Cu could be formed on the Cu-containing carbon steels, as confirmed by X-ray photoelectron spectroscopy (XPS) analysis According to the results, the corrosion resistance could be improved by adding Cu element for carbon steels in 3.5 wt% NaCl solution, especially under acidic solution.
49
Lin, Chien Shing, e 林建勝. "Hot Corrosion of Fe-Ni-Cr Alloys Caused by NaCl Deposits". Thesis, 1996. http://ndltd.ncl.edu.tw/handle/84080028990499032508.
Testo completoAbstract (sommario):
碩士國立臺灣科技大學
機械工程研究所
84
The purpose of this study is to investigate the NaCl-induced hot corrosion performances and mechanism of the Fe-Ni-Cr alloys which were studied by means of T.G.A, metal loss and internal penetration methods. The results show that NaCl-induced hot corrosion of Fe-Ni-Cr alloys were influenced by reaction temperature and the chromium- and nickel-contents. Chloridation was the major reaction when the reaction temperature was above the melting point of NaCl. On the other hand, oxidation predominated the corrosion mechanism when the temperature was below melting point of NaCl. The volatile chlorides which were produc ed by chloridation reaction diffused outward through pores in the oxide scale to the regions of higher oxygen potential, where they were then reoxidized into oxides and formed a porous bi- layered oxide scale, consisting of an outer layer of iron oxide and an inner layer of chlominum oxide. At the same time, chlorides attacked alloy''s matrix and generated an internal attacked pore-structure on the high nickel-content alloys.
50
fu-fu, peng, e 彭富福. "The High Temperature Corrosion of 2205 Duplex Stainless Steel with NaCl Deposit". Thesis, 2004. http://ndltd.ncl.edu.tw/handle/83618937000182316392.
Testo completoAbstract (sommario):
碩士國立臺灣科技大學
機械工程系
92
Abstract The objective of this study is to figure out the hot corrosion behavior of 2205 duplex stainless steel (2205 DSS) within the temperature range from 550 to 850℃ in the static air condition with 2mg/cm2 NaCl deposit , and in the air atmospheres condition with a constant flow rate of 500vppm NaCl(g) respectively. Experimental results show that the hot corrosion kinetics met the parabolic rate law and the corrosion rate increased constantly with increasing temperature. The scales formed included Fe2O3/Fe3O4/Cr2O3 and FeCr2O4 from outer layer to inner layer. The sequence of formation is independent of the environment temperature, but the SiO2 and NiO can be found in the substrate of 850℃specimen. Experimental results also show that the corrosion sequence in two phase structure of 2205 DSS was too much conformity and without distinction in the 2mg/cm2 NaCl deposit and in the air atmospheres condition with a constant flow rate of 500vppm NaCl(g). For the case of constant flow rate of 500vppm NaCl(g) condition, the corrosion rate in the γ phase was greater than that in the α phase.