Os materiais usados nas indústrias de fabricação de máquinas para o setor de armazenagem e secagem de grãos, devem garantir o desempenho requerido, não gerando nenhum prejuízo ou descontentamento do cliente final. Esta pesquisa tem como objetivo principal, avaliar o desempenho do aço Galvalume® em relação ao aço Galvanizado NBR7008 quando conformados, quanto a resistência a corrosão de ambos os materiais. Para isso foram executados testes em amostras de chapas lisas e conformadas nos aços mencionados. As amostras foram avaliadas quanto à resistência à corrosão a partir de ensaio em câmara de névoa salina (chapas lisas) e ensaio de imersão (chapas conformadas). Além disso, as amostras foram caracterizadas quanto à espessura e morfologia dos revestimentos por MEV e perfilometria em (chapas conformadas). Também foi realizado o ensaio de envelhecimento em campo, que consistiu em avaliar o aspecto visual com ambas as chapas, montadas na tampa de um silo em uso na área rural. A partir dos resultados obtidos nos ensaios, antes e após a conformação mecânica, ficou evidenciada a influencia do processo de conformação sobre a resistência à corrosão do aço Galvanizado NBR7008. Observou-se que as áreas submetidas com as dobras das laterais tiveram a taxa de corrosão aumentada. O mesmo não ocorreu para o aço revestido com Galvalume®, o qual apresentou menor taxa de corrosão do que o aço Galvanizado NBR7008. Os resultados obtidos no ensaio de envelhecimento evidenciaram a grande diferença em relação ao aspecto visual dos painéis, observando-se no aço Galvanizado uma perda excessiva do brilho, com a escurecimento da chapa após 3 anos de exposição em zona rural. Já as chapas de aço Galvalume® mantiveram o brilho após todo esse período de exposição na mesma atmosfera evidenciando a sua superioridade quanto as intempéries. O custo inicial do aço Galvalume® é, em média, 12% mais elevado que o custo do aço galvanizado (NBR7008 ZC/Z275). Contudo é importante salientar que essas características quanto ao aspecto visual são determinantes para a aceitação dos silos pelos clientes. / The most used materials in the industry of manufacture of machines for the storage and grain drying department must ensure the required performance, and should not causing any loss or dissatisfaction to the final customer. This research has as main goal measuring the performance of Galvalume® steel compared to the Galvanized steel NBR7008, when conformed, evaluating the corrosion resistance of both materials. For that, tests were made on samples of plain steel sheet and conformed steel sheet with the mentioned kinds of steel. The samples were evaluated taking into consideration the corrosion resistance in immersion test (shaped plate) and salt spray test (flat sheet). Besides, the samples were described according to thickness and coating morphology by MEV and perfilometry. Also, a test of accelerated aging was made, which consisted in measuring visual aspect in both kinds of steel. They were assembled on the cover of a silo that was working, located in the countryside. From the results reached through the tests, before and after the mechanical conformation, the influence of conformed process on the corrosion resistance of the Galvanized steel NBR7008 was evidenced. It could be noted that the areas submitted with lateral folds had corrosion rates increased. But, with the Galvalume® steel was different, this one showed lower corrosion rate than Galvanized steel NBR7008. The results reached with the accelerated aging test showed the big difference related to visual aspects of the panels, in which an excessive brightness loss on the Galvanized steel, with the darkening of the steel sheet after 3 years of exposure in the countryside was observed. Whereas the Galvalume® steel sheet kept the brightness after all this period of exposure to the same atmosphere, showing its superiority in corrosion resistance. The cost of Galvalume® steel is about 12% higher than cost of Galvanized steel (NBR7008 ZC/Z275). However it is important to point these attributes, regarding to visual aspect, which are determinants for good acceptance of silos by the customers.

The interaction of the surface of a pure metal or an alloy with the surrounding atmosphere occurs in a highly complex interfacial regime. During atmospheric corrosion this interfacial regime involves the metal surface, often covered by a naturally formed oxide layer of a few nanometers thickness; an aqueous adlayer, typically with a thickness of a few to a few tens of nanometers, and the atmosphere from which airborne particles, oxygen, and gaseous pollutants dissolve into the adlayer and influence the atmospheric corrosion process. This thesis work is mainly concerned with the initial atmospheric corrosion of zinc and brass induced by carboxylic acids (120 parts per billion of formic, acetic, or propionic acid) in laboratory air with 90% relative humidity. This model system has been chosen to mimic indoor corrosion with carboxylic acids as major corrosion stimulators. The study forms part of a broader research program with the ultimate goal to provide a computer model of the early stages of atmospheric corrosion of copper, zinc and copper-zinc alloys, induced by carboxylic acids. Particular emphasis has been given to identify and quantify the corrosion products formed and to determine their lateral distribution over the corroding surface. This has been accomplished through a multi-analytical approach in which two main techniques are infrared reflection absorption spectroscopy (IRAS) which can identify and quantify corrosion products with a relative accuracy of about 10%, and confocal Raman microspectroscopy (CRM) which can identify and resolve corrosion products with a surface lateral resolution of better than one micrometer. The corrosion products identified on pure zinc are zinc oxide (ZnO) and various forms of Zn-carboxylates. On brass, the main corrosion products identified are a cuprite (Cu2O)-like phase and various forms of Zn-carboxylates. For pure zinc and brass the formation rates of corrosion products in presence of the investigated acids depend, among others, on their deposition velocity and acid strength. The interaction of pure zinc and brass with humidified air containing carboxylic acids follows two spatially separated main pathways: a proton-induced dissolution of metal ions followed by the formation of oxides, and a carboxylate-induced dissolution followed by the deposition of metal carboxylates. When applying this multi-analytical approach, it has been possible to distinguish between anodically and cathodically active areas for brass, but not for pure zinc. Galvanic effects have been shown to play a significant role during the initial corrosion of brass.  Further evidence of the selective formation of corrosion products has been found when exploring the more complex heterogeneous surface of Galvalume, a commercial aluminum-zinc alloy coating. This material has been exposed to humidified laboratory air with additions of carbon dioxide (CO2) and sodium chloride (NaCl) and to a marine atmospheric environment. Initiated in the interdendritic zinc-rich areas, a uniform aluminum oxide (Al2O3) layer is formed. This oxide exhibits an inhibiting effect on the subsequent formation of other corrosion products, including aluminum oxyhydroxide (AlOOH), aluminum hydroxide (Al(OH)3), ZnO, zinc hydroxycarbonate and zinc hydroxychloride. / QC 20110607

Os materiais usados nas indústrias de fabricação de máquinas para o setor de armazenagem e secagem de grãos, devem garantir o desempenho requerido, não gerando nenhum prejuízo ou descontentamento do cliente final. Esta pesquisa tem como objetivo principal, avaliar o desempenho do aço Galvalume® em relação ao aço Galvanizado NBR7008 quando conformados, quanto a resistência a corrosão de ambos os materiais. Para isso foram executados testes em amostras de chapas lisas e conformadas nos aços mencionados. As amostras foram avaliadas quanto à resistência à corrosão a partir de ensaio em câmara de névoa salina (chapas lisas) e ensaio de imersão (chapas conformadas). Além disso, as amostras foram caracterizadas quanto à espessura e morfologia dos revestimentos por MEV e perfilometria em (chapas conformadas). Também foi realizado o ensaio de envelhecimento em campo, que consistiu em avaliar o aspecto visual com ambas as chapas, montadas na tampa de um silo em uso na área rural. A partir dos resultados obtidos nos ensaios, antes e após a conformação mecânica, ficou evidenciada a influencia do processo de conformação sobre a resistência à corrosão do aço Galvanizado NBR7008. Observou-se que as áreas submetidas com as dobras das laterais tiveram a taxa de corrosão aumentada. O mesmo não ocorreu para o aço revestido com Galvalume®, o qual apresentou menor taxa de corrosão do que o aço Galvanizado NBR7008. Os resultados obtidos no ensaio de envelhecimento evidenciaram a grande diferença em relação ao aspecto visual dos painéis, observando-se no aço Galvanizado uma perda excessiva do brilho, com a escurecimento da chapa após 3 anos de exposição em zona rural. Já as chapas de aço Galvalume® mantiveram o brilho após todo esse período de exposição na mesma atmosfera evidenciando a sua superioridade quanto as intempéries. O custo inicial do aço Galvalume® é, em média, 12% mais elevado que o custo do aço galvanizado (NBR7008 ZC/Z275). Contudo é importante salientar que essas características quanto ao aspecto visual são determinantes para a aceitação dos silos pelos clientes. / The most used materials in the industry of manufacture of machines for the storage and grain drying department must ensure the required performance, and should not causing any loss or dissatisfaction to the final customer. This research has as main goal measuring the performance of Galvalume® steel compared to the Galvanized steel NBR7008, when conformed, evaluating the corrosion resistance of both materials. For that, tests were made on samples of plain steel sheet and conformed steel sheet with the mentioned kinds of steel. The samples were evaluated taking into consideration the corrosion resistance in immersion test (shaped plate) and salt spray test (flat sheet). Besides, the samples were described according to thickness and coating morphology by MEV and perfilometry. Also, a test of accelerated aging was made, which consisted in measuring visual aspect in both kinds of steel. They were assembled on the cover of a silo that was working, located in the countryside. From the results reached through the tests, before and after the mechanical conformation, the influence of conformed process on the corrosion resistance of the Galvanized steel NBR7008 was evidenced. It could be noted that the areas submitted with lateral folds had corrosion rates increased. But, with the Galvalume® steel was different, this one showed lower corrosion rate than Galvanized steel NBR7008. The results reached with the accelerated aging test showed the big difference related to visual aspects of the panels, in which an excessive brightness loss on the Galvanized steel, with the darkening of the steel sheet after 3 years of exposure in the countryside was observed. Whereas the Galvalume® steel sheet kept the brightness after all this period of exposure to the same atmosphere, showing its superiority in corrosion resistance. The cost of Galvalume® steel is about 12% higher than cost of Galvanized steel (NBR7008 ZC/Z275). However it is important to point these attributes, regarding to visual aspect, which are determinants for good acceptance of silos by the customers.

Os materiais usados nas indústrias de fabricação de máquinas para o setor de armazenagem e secagem de grãos, devem garantir o desempenho requerido, não gerando nenhum prejuízo ou descontentamento do cliente final. Esta pesquisa tem como objetivo principal, avaliar o desempenho do aço Galvalume® em relação ao aço Galvanizado NBR7008 quando conformados, quanto a resistência a corrosão de ambos os materiais. Para isso foram executados testes em amostras de chapas lisas e conformadas nos aços mencionados. As amostras foram avaliadas quanto à resistência à corrosão a partir de ensaio em câmara de névoa salina (chapas lisas) e ensaio de imersão (chapas conformadas). Além disso, as amostras foram caracterizadas quanto à espessura e morfologia dos revestimentos por MEV e perfilometria em (chapas conformadas). Também foi realizado o ensaio de envelhecimento em campo, que consistiu em avaliar o aspecto visual com ambas as chapas, montadas na tampa de um silo em uso na área rural. A partir dos resultados obtidos nos ensaios, antes e após a conformação mecânica, ficou evidenciada a influencia do processo de conformação sobre a resistência à corrosão do aço Galvanizado NBR7008. Observou-se que as áreas submetidas com as dobras das laterais tiveram a taxa de corrosão aumentada. O mesmo não ocorreu para o aço revestido com Galvalume®, o qual apresentou menor taxa de corrosão do que o aço Galvanizado NBR7008. Os resultados obtidos no ensaio de envelhecimento evidenciaram a grande diferença em relação ao aspecto visual dos painéis, observando-se no aço Galvanizado uma perda excessiva do brilho, com a escurecimento da chapa após 3 anos de exposição em zona rural. Já as chapas de aço Galvalume® mantiveram o brilho após todo esse período de exposição na mesma atmosfera evidenciando a sua superioridade quanto as intempéries. O custo inicial do aço Galvalume® é, em média, 12% mais elevado que o custo do aço galvanizado (NBR7008 ZC/Z275). Contudo é importante salientar que essas características quanto ao aspecto visual são determinantes para a aceitação dos silos pelos clientes. / The most used materials in the industry of manufacture of machines for the storage and grain drying department must ensure the required performance, and should not causing any loss or dissatisfaction to the final customer. This research has as main goal measuring the performance of Galvalume® steel compared to the Galvanized steel NBR7008, when conformed, evaluating the corrosion resistance of both materials. For that, tests were made on samples of plain steel sheet and conformed steel sheet with the mentioned kinds of steel. The samples were evaluated taking into consideration the corrosion resistance in immersion test (shaped plate) and salt spray test (flat sheet). Besides, the samples were described according to thickness and coating morphology by MEV and perfilometry. Also, a test of accelerated aging was made, which consisted in measuring visual aspect in both kinds of steel. They were assembled on the cover of a silo that was working, located in the countryside. From the results reached through the tests, before and after the mechanical conformation, the influence of conformed process on the corrosion resistance of the Galvanized steel NBR7008 was evidenced. It could be noted that the areas submitted with lateral folds had corrosion rates increased. But, with the Galvalume® steel was different, this one showed lower corrosion rate than Galvanized steel NBR7008. The results reached with the accelerated aging test showed the big difference related to visual aspects of the panels, in which an excessive brightness loss on the Galvanized steel, with the darkening of the steel sheet after 3 years of exposure in the countryside was observed. Whereas the Galvalume® steel sheet kept the brightness after all this period of exposure to the same atmosphere, showing its superiority in corrosion resistance. The cost of Galvalume® steel is about 12% higher than cost of Galvanized steel (NBR7008 ZC/Z275). However it is important to point these attributes, regarding to visual aspect, which are determinants for good acceptance of silos by the customers.

Orientador: Celia Marina de A. Freire / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-07-29T00:11:40Z (GMT). No. of bitstreams: 1 Beserra_AntonioAdelmoFreire_D.pdf: 6476925 bytes, checksum: 51577bdfab4d41fd0bb2c35bf250bfc2 (MD5) Previous issue date: 2001 / Resumo: O revestimento de Al55-Zn apresenta uma resistência à corrosão atmosférica em média doze vezes superior à do revestimento galvanizado. Entretanto, após deformação mecânica, o revestimento de Al55-Zn apresenta microtrincas que comprometem a sua resistência à corrosão. Neste trabalho estudou-se a variação na resistência à corrosão do revestimento de Al55-Zn após deformação sob tração ou dobramento e a influência de tratamentos térmicos a '200 GRAUS' e a '360 GRAUS' durante 16h na resistência à corrosão do revestimento antes e depois das deformações. Para isso, um grupo de amostras do material foi deformado sob tensão de tração até 10% ou 15% de seu comprimento inicial e outro grupo foi dobrado até '90 GRAUS' ou '180 GRAUS'. A variação na resistência à corrosão do revestimento foi analisada através das técnicas de extrapolação de Tafel e de espectroscopia de impedância eletroquímica. Como resultado, observou-se que tanto a deformação axial quanto o dobramento do material reduzem a sua resistência à corrosão. Após o tratamento térmico a '360 GRAUS' as amostras deformadas até 10% ou 15% recuperaram a sua resistência à corrosão, entretanto, as amostras dobradas até '90 GRAUS' ou '180 GRAUS' apresentaram apenas uma recuperação parcial na sua resistência à corrosão após os tratamentos térmicos / Abstract: The atmospheric corrosion resistance of 55%Al-Zn alloy coating on average is twelve times that of an equal thickness of galvanized coating. However, it has been shown that microcracks were observed at all levels of strain under simple uniaxial tension. Our research has been focused on determining the degree of corrosion experienced by these coatings after deformation under simple tension or bending and how much the heat treatment at '200 DEGREES' or '360 DEGREES' for 16h can influence the corrosion resistance of the coating. The coated sheet samples were strained to 10% or 15% engineering strain while another group of samples was bent to bend angles of '90 DEGREES' or '180 DEGREES'. The corrosion resistance of the samples was evaluated trhough Tafel extrapolation and electrochemical impedance spectroscopy methods. As a result, it was observed that both the straining and the bending of the coating reduces its corrosion resistance. After the heat treatment at '360 DEGREES' the samples strained to 10% or 15% recover their corrosion resistance, but the specimens bended to '90 DEGREES' or '180 DEGREES' recuperate only partially the corrosion resistance after the heat treatments / Doutorado / Materiais e Processos de Fabricação / Doutor em Engenharia Mecânica