<p> This thesis investigates the characteristics of noise generation in the gas wiping process, including the effects of the various parameters manipulated in the process and countermeasures used to reduce noise levels. The process of gas wiping is used in many industrial applications such as drying of pulp and paper, photograph production and some high performance cooling applications. One of the most important industrial applications of gas wiping is the production of hot-dipped galvanized sheet steel. Gas wiping is a very efficient and reliable process to control coating thickness and uniformity of galvanized steel products, and can be used for very high line speeds and production rates. Changing the various process parameters such as the jet to strip distance (z), the jet slot width (h), plenum pressure (P) and jet inclination angle (α) allows manufacturers to control the coating thickness and quality of the finished product.</p> <p> The gas wiping process is also responsible for the generation of very high levels of noise, which can be a factor in limiting the overall production rates and indirectly increase production costs for manufacturers. To maintain a constant coating thickness as the line speed and production rate is increased, the plenum pressure supplied to the jets and thus the incident jet velocity must be increased, or the jet-to-strip distance must be decreased. Noise production in the gas wiping process is acknowledged to be proportional to the incident jet velocity and inversely proportional to the jet-to-strip distance. Thus, for a given coating thickness, as the production rates increase, the noise generated by the process must also increase. Ergonomic restrictions in the workplace, which limit the exposure to high sound pressure levels and audible acoustic tones, may indirectly limit the maximum line speed for a steel sheet with a given coating thickness. This limitation is particularly relevant to the production of high quality automotive sheet steels, which often have very thin coating thicknesses and have higher than normal coating uniformity tolerances, which necessitate the use of high plenum pressures and small jet-to-strip distances.</p> <p> At present, the state of knowledge for noise generation in the gas wiping process is very limited. Only two previous investigations have been devoted to this problem, and the experiments for these studies have only modeled specific individual cases, with no attempt at a comprehensive modeling of noise in this process. For the current study, measurements have been performed in both an actual manufacturing environment and on a scaled galvanizing simulator in a laboratory environment. A comprehensive set of experiments over a wide range of gas wiping parameters was performed in order to provide a broad overview of noise generation in the gas wiping process and allow for process optimization to reduce noise and allow higher production rates and efficiency. The creation of noise maps, modeling the overall sound pressure level and tone intensity for gas wiping as function of the various operating parameters of the process, as well as a set of equations and models to determine the frequency of discrete acoustic tones are presented. A full analysis of the frequency response, as well as the acoustic modes generated in various jet impingement regions has also been provided.</p> / Thesis / Master of Applied Science (MASc)

M.S.

In many source waters across the United States (US), chloride levels are increasing and this change could be problematic for galvanized iron pipe (GIP) installed in consumers' homes and buildings. The higher levels of chloride might increase the rate of galvanic corrosion between the sacrificial zinc coating and the underlying iron (steel) pipe. There are also concerns that the iron in GIP can accumulate lead on its surface from upstream lead service lines, occasionally causing high lead in water from GIP during scale sloughing and associated red water events. The role of high chloride and potential mitigation strategies by orthophosphate and alkalinity on galvanic iron-zinc corrosion in GIP were examined by using new iron and zinc wires, and complementary studies with 85-year-old harvested GIP coupons from the Washington Suburban Sanitary Commission (WSSC). Sequential samplings on a constructed pilot-scale test rig with copper – lead – GIP ¬– brass meter configuration were used to evaluate lead source fingerprinting methods (metal co-occurrence, correlating the plumbing configuration to sample profiling data, and evaluation of lead isotope ratios) and role of flow rate. As chloride concentration increased from 2.6 to 554 mg/L, galvanic current and weight loss of sacrificial zinc increased by about an order of magnitude. Iron leaching also increased by 4.4 times as chloride levels increased by a factor of 12 in WSSC modified water to simulate actual road salt runoff events. Increased orthophosphate or alkalinity could at least partly counter the adverse effects of chloride, as the average iron concentration decreased by 43% as orthophosphate level increased from 3.8 to 11.2 mg/L as P, and average iron concentrations decreased by 32% as alkalinity increased from 50 to 90 mg/L as CaCO3. Applying fingerprinting methods on sequential samples has the potential to determine whether premise plumbing contains GIP and/or lead pipe. Specifically, the metal co-occurrence fingerprinting technique was successful in identifying the location of GIP by the detection of low-level cadmium, and the lead isotope ratio fingerprinting technique was fairly successful in identifying lead pipe. Additionally, our study found that GIP was not contaminated by an upstream lead pipe after five months of conditioning; hence, water discoloration (iron level > 400 ppb) does not always indicate lead problems from GIP. However, with longer exposure of GIP to lead pipe, the magnitude of the problem might increase. As flow rate increased from 0.9 to 2.4 GPM, the median particulate iron release increased by 3.3 times, and the median particulate lead release (>83% particulate lead) increased by 4.9 times. / Master of Science / In many source waters across the United States (US), chloride levels are increasing and this change could be problematic for galvanized iron pipe (GIP) installed in consumers' homes and buildings. The higher levels of chloride might increase the rate of galvanic corrosion in GIP. There are also concerns that the iron in GIP can accumulate lead on its surface from upstream lead service lines, occasionally causing high lead in water from GIP during scale sloughing and associated red water events. The role of high chloride and potential mitigation strategies for GIP by adjusting orthophosphate and alkalinity were examined by conducting bench scale testing. Sequential samplings on a constructed pilot-scale test rig with different lead source pipe sections were used to evaluate lead source fingerprinting methods and role of flow rate. Higher chloride in water increased galvanic current and weight loss of zinc coating as chloride concentration increased from 2.6 to 554 mg/L in the fundamental experiments. Iron leaching also increased as chloride levels increased in the GIP coupon testing. Increasing orthophosphate or alkalinity proved to counter the adverse effects of chloride as the average iron concentration decreased. Sampling profiles can be useful in determining whether premise plumbing contains GIP or lead pipe by using fingerprinting methods. Iron and lead leaching from GIP increased as the water flow rate increased.

O processo de soldagem por resistência de chapas galvanizadas automotivas é parte indispensável na concepção de uma carroceria de automóvel. Utilizado na união das chapas metálicas que formam um veículo, a grande importância deste processo deve-se basicamente ao fato de não agregar peso à carroceria, ter um desempenho satisfatório em relação à qualidade e produtividade nas linhas de montagem e ainda não onerar o custo final do produto, visto que seu custo de operação pode ser considerado baixo de modo geral. As variáveis específicas deste processo demandam atenção permanente quanto aos parâmetros dos equipamentos, a limpeza e a manutenção, a refrigeração dos eletrodos, a dressagem e a eliminação da camada de latão formada na superfície de contato entre o eletrodo e a chapa. A durabilidade e o desgaste do eletrodo estão ligados basicamente a estes cuidados, podendo ainda gerar ganhos em produtividade e qualidade do ponto além de reduzir o nível de problemas durante e após a soldagem da chapa. Durante a realização deste trabalho, procurou-se avaliar o comportamento do eletrodo fabricado através da liga Cu-Zr, o desgaste do eletrodo em relação ao número de pontos soldados, sua relação com a dureza e variação de temperatura durante o processo, os cuidados que podem retardar o desgaste e a microestrutura do material ao longo do número de pontos e do desgaste deste eletrodo. / The resistance welding process of automotive galvanized steel is an indispensable part in the design of a body car. Used in the union of the metal plates that form a vehicle, the great importance of this process is basically due to the fact not add weight to the body, have a satisfactory performance in relation to quality and productivity in assembly lines and still does not burden the final cost the product, the operating cost can be considered low in general. The specific variables this process require constant attention regarding the parameters of the equipment, cleaning and maintenance, cooling the electrodes, the dressing and the elimination of the brass layer formed on the contact surface between the electrode and the plate. The durability and the electrode wear are basically related to such care, and may generate gains in productivity and quality of point and reduce the level of problems during and after welding the plate. During this work, we tried to evaluate the electrode manufactured by Cu-Zr alloy, the electrode wear in relation to the number of welding points, their relationship with the hardness and temperature variation during the process, the care can slow the wear and the microstructure of the material during the number of welding points and the wear of this electrode.

Abstract Prepainted steel is a new material developed after the year of 1960. It owns mainly advantages accompanied with corrosion resistance, long-life using, beautiful color and shape, easy utilization, and also keep the original strength of the steel. All these characteristics make it appropriate to be used on the wall, roof, and decoration of gym or any big construction and buildings. It can also be seen in the field of vehicles, many electrical appliances, computer shells, etc. Prepainted steel is the downstream product of steel enterprises. It comes manly from Galvanized steel coils, and a little portion of it from cold-rolled steel coils. There are now seven production companies in Taiwan at the annual production of 1.17 million tons. According to statistics, the local consumption of last year is 310,000 tons. It is fortunate that Mainland China has a mass need for it during these years. In 2002, Mainland china imported 1.02 million tons, and in 2003, 1.54 million tons. We need huge export to digest our production. My study case is an medium enterprise with the annual production 300,000 tons of prepainted steel, and without the production line of Galvanized steel with which prepainted steel can be done. This study mainly discusses how an enterprise construct its own competitive advantage and strategy through the outside environment analysis and management ability, then make the best choice of stragtegy which is appropriate to its business model before evaluating the strategy efficiency by theory. The first chapter is about its background and motive of the study, and contents and limits of the study are also included. The second chapter, from the theory basis of documents, try to understand the definition and relative meaning of following issues: vertical integration, strategic alliance, resources leveling and value chains¡Ketc. The third chapter of this study is about the marketing supply and demand situation of prepainted steel local and abroad, and it talks about on what kind of location that prepainted steel enterprise stands. This chapter also goes further introducing these important enterprises in Taiwan which earns prepainted steel, and make an analysis on enterprise environment and five forces analysis. The fourth chapter has an introduction of this study case and its cooperators and opponents. Moreover, a SWOT analysis of this study case is offered. Futher, there has a discussion on its strategy on competitive advantage ¡V strategic alliance, resources leveling,, value chains, vertical integration, business field¡Ketc. And a proof on the basic of the strategy and an evaluation on these strategic efficiency are made. At last, there will be a deep thinking on fast-changing environment and future strategies. We hope the ending can be used for the reference of this enterprise.

Made available in DSpace on 2016-12-08T17:19:21Z (GMT). No. of bitstreams: 1 Ana Paula Domingos Cardoso.pdf: 8690501 bytes, checksum: b120ead6518f05e5ff1cb9d530fa6bfe (MD5) Previous issue date: 2013-12-17 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The present work aims to develop and characterize galvanized steels with chemical post-treatment application, which provides to the metal forming improvement properties. The main reason for this development is related with the fact that the most of zinc coatings problems are related with their sensitivity for abrasion wear during forming process. In view of these difficulties, related with coating steel forming, the Arcelormittal group has been developing Pos-Treatment solutions known as NIT (New Treatment Innorganic) and Pre-phosphate with the main function to promote the improvement of forming properties in deep stamping process through the lubricating properties. The propose solutions was applied over the standard steels known as IF, and galvanized with GI and GA zinc coatings. The forming improvement were evaluated through wear tests by plane friction and pin on disc tribometer, with aim to determine the friction coefficient behaviour for these materials in front of contacts pressure (MPa) application and distance (m). In addition, cracking potential analysis was done through Erichsen and weight loss methods to evaluate the powdering failure possibility. The post-treatment microstructure was evaluated through MEV and FEG-EDS analysis. As a complement study was simulated remobility tests to reproduce one step of the automotive process that can be negative influenced by post treatment application waste on the strip after forming and was evaluated the material corrosion potential in humidity tests cycles / O presente trabalho tem o objetivo de desenvolver e caracterizar aços galvanizados com aplicação de pós-tratamento químico, que visam proporcionar ao metal melhoria de conformabilidade. A justificativa principal deste estudo esta no fato de que o principal problema de revestimentos à base de zinco vêm a ser a sua sensibilidade ao processo de desgaste por abrasão, podendo danificar tanto a peça revestida, como as ferramentas das prensas de estampagem, principalmente no processamento de peças críticas voltados para aplicações da indústria automotiva. Diante destas dificuldades, o grupo ArcelorMittal tem desenvolvido a aplicação de soluções de pós-tratamento do tipo NIT (New Innorganic Treatment) e pré-fosfato , com a função de promover ao aço galvanizado, melhoria de conformabilidade e , através da propriedade de lubrificação, durante processos de estampagem de peças de alta criticidade. As soluções propostas foram aplicadas sobre os aços convencionais do tipo IF, galvanizados com revestimento base Zn denominados GI e GA. Os ganhos de conformação foram avaliados por ensaios de desgaste realizados em tribômetros de fricção planar e pino sobre disco, a fim de avaliar o comportamento do coeficiente de atrito destes materiais diante da aplicação de determinadas pressões de contato (MPa) e distância percorrida (m). Além disto, foram realizados ensaios de avaliação de potencial de fratura do material através de testes em prensa de embutimento Erichsen e Perda de Massa, método este que visa avaliar a possibilidade de ocorrência de fragilizações por Powdering. Com intuito de conhecer a microestrutura dos filmes de póstratamento depositados sobre o aço revestido foram realizadas análises metalográficas via MEV e FEG-EDS. Como complemento ao trabalho foram realizados ensaios de remobilidade dos filmes aplicados, simulações de uma das etapas de processos da indústria automotiva que podem vir a sofrer influência do pós-tratamento após estampagem do material e avaliação do potencial de corrosão em ciclos de câmara úmida.

Made available in DSpace on 2016-12-08T17:19:24Z (GMT). No. of bitstreams: 1 Resumo - Alessandro.pdf: 35986 bytes, checksum: 64527c70f5220aac3e4860e883de96f7 (MD5) Previous issue date: 2014-08-08 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Carbon steel is among the most widely used materials in manufacturing metallic structures in the world, due to its low cost and good physical and mechanical properties. However, steel is the metal that suffers the greatest corrosive impact among building materials. Carbon steel corrosion is one of the biggest factors of structural degradation in the world. One of the applications for carbon steel is manufacturing bus bodies, whereas steel is used in making the frame and body components. Steel has always attracted interest in its use, but this material has always been susceptible to corrosive degradation compromising its properties. In many studies, researchers have presented alternatives to slow down the corrosion process and thus extend the life of metal components. The purpose of this work has been to study the corrosion of unpainted and painting galvanized steel plates, similar to components used in bus bodies, thus seeking to analyze the influence of painting on the corrosion resistance in galvanized steel. The test specimens were prepared using the 1020 steel ZAR230 specimens in the Albrecht Equipamentos Industriais Company from specimens donated by ArcelorMittal Vega do Sul. The specimens were prepared and painted with galvanic corrosion primer paint at the Gabivel Honda dealership purchased from the WEG tintas Company. The specimens were cleaned and sorted into three types, without painting, one coat of paint, and two coats of paint. The specimens were then weighed and measured, and the coats of paint were analyzed for thickness and adhesion. Then the specimens were placed in a laboratory machine donated by Schultz S / A. They salt sprayed for accelerated testing and cyclic corrosion and subjected to testing for 480 hours. We also conducted accelerated corrosion tests by immersion in saline solution for 1032 hours. Throughout the tests, the specimens were visually examined and upon completion these specimens underwent cleaning and weighing, for visual analysis and mass loss. The corrosion in the specimens caused corrosive pitting and corrosive scaling. The painted specimens displayed a higher corrosion resistance compared to unpainted specimens. The red oxidation and mass loss were higher in unpainted specimens. / Dentre os materiais mais utilizados na confecção de estruturas pelo mundo, o aço carbono se destaca pelo seu baixo custo e boas propriedades físicas e mecânicas. Contudo, o aço é o metal que mais sofre com a corrosão dentre os materiais de construção. A corrosão do aço carbono é um dos maiores fatores de degradação das estruturas no mundo. Uma das aplicações do aço carbono é na fabricação de carrocerias de ônibus, onde o aço é utilizado na confecção da estrutura e dos componentes da carroceria. O aço sempre despertou interesse em sua utilização, porém este material sempre foi susceptível a degradação pela corrosão o que acaba por comprometer suas propriedades. Em muitos trabalhos, os pesquisadores vêm apresentando alternativas para retardar o processo corrosivo e assim prolongar a vida útil de componentes metálicos. O presente trabalho teve por objetivo estudar a corrosão de chapas de aço galvanizado sem pintura e com pintura anticorrosiva, similares aos componentes utilizados em carrocerias de ônibus, buscando assim analisar a influência da pintura na resistência à corrosão do aço galvanizado. Os corpos de prova foram confeccionados na empresa Albrecht Equipamentos Industriais, a partir de amostras doadas pela ArcelorMittal Vega do Sul, sendo estas amostras de aço 1020 tipo ZAR230. Os corpos de prova foram preparados e pintados na Concessionária Honda Gabivel com a tinta primer anticorrosiva galvânica adquirida na empresa WEG tintas. As amostras foram limpas e separadas em três tipos, sem pintura, com uma camada de pintura e com duas camadas de pintura. Os corpos de prova foram então pesados e dimensionados, e suas camadas de pintura analisadas quanto à espessura e aderência. Em seguida as amostras foram posicionadas em máquina de ensaio acelerado e cíclico de corrosão acelerada por névoa salina, no laboratório cedido pela Schultz S/A, e submetidos ao ensaio por 480 horas. Foram realizados ainda, ensaios acelerados de corrosão por imersão em solução salina por 1032 horas. Ao longo dos ensaios, os corpos de prova foram analisados visualmente e após a finalização destes foram submetidos à limpeza e pesagem, para análise visual e de perda de massa. A corrosão presente nas amostras foi do tipo corrosão por pite e corrosão por placas. As amostras, com pintura, apresentaram uma maior resistência à corrosão em relação ás amostras sem pintura. A oxidação vermelha e a perda de massa foram maiores nos corpos de prova sem pintura.

Made available in DSpace on 2016-12-08T17:19:37Z (GMT). No. of bitstreams: 1 Parte 1.pdf: 175711 bytes, checksum: 4c45110c54dab616ccb4e24cf3e91d86 (MD5) Previous issue date: 2011-02-28 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / In coastal and in industrial region the atmosphere is considered aggressive due to the high relative humidity, and also due to the presence of chloride ions (Cl&#1470;) and sulphate (SO4 -²)ions, accelerating the corrosion process to accelerate. This onerous on electric distribution companies due to direct costs, because even the galvanized metal components must be replaced often, and indirect costs such as disruption of electricity supply for maintenance. Thus, the aim of this work, together with CELESC SA (Electric Centrals of Santa Catarina), was to study the atmospheric corrosion of the galvanized steel used in electric distribution networks in the south coast of Santa Catarina. For this it was installed 10 different locations, monitoring stations of atmospheric parameters to measure the rate of sulfate, chloride and sedimentary particles in a period of six months. The zinc layer applied to the SAE 1010 steel plates used in corrosion tests were characterized by optical and electron microscopy. The corrosion products formed on the surface of galvanized steel in corrosion tests were characterized by X-ray diffraction and scanning electron microscopy. The results indicated that most of the locations had a high rate of corrosion, classified according to ISO 9223 as C5. The variations in the chloride content per month were attributed to the wind direction. The Simonkolleite (Zn5(OH)8Cl2.H2O) was the main corrosion product formed on the galvanized steel, due to the presence of chloride in the air at all monitoring stations. This product was also observed in salt spray corrosion tests. / Em regiões litorâneas e industriais a atmosfera é considerada agressiva devido à umidade relativa ser elevada, e também devido à presença de íons de cloreto (Cl&#1470;) e de sulfato (SO4 -²), fazendo com que o processo de corrosão seja acelerado. Isso onera as empresas de distribuição de energia elétrica devido aos custos diretos, pois freqüentemente componentes metálicos mesmo galvanizados devem ser substituídos, e custos indiretos como interrupções do fornecimento de energia elétrica para manutenção. Sendo assim, o objetivo principal deste trabalho, vinculado a CELESC S.A. (Centrais Elétricas de Santa Catarina) foi estudar a corrosão atmosférica em aço galvanizado empregado em redes de distribuição de energia elétrica no litoral sul de Santa Catarina. Para isto foram instaladas em 10 locais diferentes, estações de monitoramento de parâmetros atmosféricos, tais como, taxa de sulfatação, teor de cloretos e partículas sedimentáveis em um período de seis meses. A camada de zinco aplicada nas placas de aço SAE 1010 utilizadas nos ensaios de corrosão foi caracterizada por meio de microscopia óptica e eletrônica. Os produtos de corrosão formados na superfície do aço galvanizado nos ensaios de corrosão foram caracterizados por difração de raios-X e microscopia eletrônica de varredura. Os resultados indicaram que a maioria dos locais apresentou alto índice de corrosividade, classificado segundo a norma ISO 9223 como C5. As variações nos valores de teor de cloretos mensais foram atribuídas à direção dos ventos. O Simonkolleite (Zn5(OH)8Cl2.H2O) foi o principal produto de corrosão formado sobre o aço galvanizado, devido à presença de cloretos no ar em todas as estações de monitoramento. Esse produto também foi encontrado nos ensaios de corrosão em névoa salina.

O processo de soldagem por resistência de chapas galvanizadas automotivas é parte indispensável na concepção de uma carroceria de automóvel. Utilizado na união das chapas metálicas que formam um veículo, a grande importância deste processo deve-se basicamente ao fato de não agregar peso à carroceria, ter um desempenho satisfatório em relação à qualidade e produtividade nas linhas de montagem e ainda não onerar o custo final do produto, visto que seu custo de operação pode ser considerado baixo de modo geral. As variáveis específicas deste processo demandam atenção permanente quanto aos parâmetros dos equipamentos, a limpeza e a manutenção, a refrigeração dos eletrodos, a dressagem e a eliminação da camada de latão formada na superfície de contato entre o eletrodo e a chapa. A durabilidade e o desgaste do eletrodo estão ligados basicamente a estes cuidados, podendo ainda gerar ganhos em produtividade e qualidade do ponto além de reduzir o nível de problemas durante e após a soldagem da chapa. Durante a realização deste trabalho, procurou-se avaliar o comportamento do eletrodo fabricado através da liga Cu-Zr, o desgaste do eletrodo em relação ao número de pontos soldados, sua relação com a dureza e variação de temperatura durante o processo, os cuidados que podem retardar o desgaste e a microestrutura do material ao longo do número de pontos e do desgaste deste eletrodo. / The resistance welding process of automotive galvanized steel is an indispensable part in the design of a body car. Used in the union of the metal plates that form a vehicle, the great importance of this process is basically due to the fact not add weight to the body, have a satisfactory performance in relation to quality and productivity in assembly lines and still does not burden the final cost the product, the operating cost can be considered low in general. The specific variables this process require constant attention regarding the parameters of the equipment, cleaning and maintenance, cooling the electrodes, the dressing and the elimination of the brass layer formed on the contact surface between the electrode and the plate. The durability and the electrode wear are basically related to such care, and may generate gains in productivity and quality of point and reduce the level of problems during and after welding the plate. During this work, we tried to evaluate the electrode manufactured by Cu-Zr alloy, the electrode wear in relation to the number of welding points, their relationship with the hardness and temperature variation during the process, the care can slow the wear and the microstructure of the material during the number of welding points and the wear of this electrode.

Made available in DSpace on 2016-04-18T21:36:00Z (GMT). No. of bitstreams: 4 Danieli Cristina Pedroso1.pdf: 893786 bytes, checksum: 0b49df9c67021da69e5f47f5170c5703 (MD5) Danieli Cristina Pedroso2.pdf: 3031650 bytes, checksum: bbf4b2dc04de906b1c5596adb5c76bb8 (MD5) Danieli Cristina Pedroso3.pdf: 2597659 bytes, checksum: 1a3e7d52a670d6eb3f003b1583e76702 (MD5) Danieli Cristina Pedroso4.pdf: 198943 bytes, checksum: 16b69ef67e7c298a9fc35b695825e236 (MD5) Previous issue date: 2009-08-17 / In this work the causes of rejection of lots of artifacts from the company Produto para Linhas Preformados, PLP, were analyzed which are made of steel SAE 1010 and SAE 1020 and zinc coated by hot-dip galvanizing. Lots of samples from different manufacturers were selected, with different chemical composition and geometry, but belonging to rejected lots and approved lots in accordance with usual market standards. The rejections are due to problems related to the adhesion of the layer of zinc. The samples were submitted to optical microscopy test, scanning electron microscopy and X-ray diffractions for comparative checking of between the structures of zinc formed layers by hot -dip galvanizing. To verify the corrosion in coating failure, corrosion tests were performed in three different environments: urban environment considered to be low-polluted; environment simulating sea water, salt spray. There is no failure evidence between the zinc coating and the substrate structure; irregular coatings and not very well defined phases were found in the rejected parts. In regions with failures, the results show a behavior similar to the literature with the rapid formation of rust at the beginning of the exposure followed by a show oxidation. / Neste trabalho foram analisadas as causas da rejeição de lotes de artefatos da empresa Produto para Linhas Preformados, PLP, fabricados com aços SAE 1010 e SAE 1020 e zincados por imersão a quente. Foram selecionadas amostras de lotes de fabricantes diferentes, com composição química e geometrias distintas, pertencentes a lotes rejeitados e a lotes aprovados de acordo com normas usuais de mercado. As rejeições se devem a problemas relacionados a aderência da camada de zinco. As amostras foram submetidas a exames por microscopia óptica, microscopia de varredura e análises por difração de raio-X para verificação comparativa entre as estruturas das camadas de zinco formadas no processo zincagem por imersão a quente. Para verificar a corrosão nas falhas de revestimento de zinco, foram realizados ensaios de corrosão em três ambientes diferentes: ambiente considerado urbano de baixa poluição; ambiente simulando água do mar; câmara de névoa salina. Não há indício de relação entre a falha nos revestimentos de zinco e a estrutura do substrato; revestimentos irregulares e com fases não muito bem definidas foram encontrados nas peças rejeitadas. Nas regiões com falha, os resultados evidenciam um comportamento semelhante ao da literatura, com formação rápida de ferrugem no início da exposição das peças seguida por uma oxidação lenta.