The objective of this study is to develop a robust portable nano-calorimeter sensor for detection of energetic materials, primarily explosives, combustible materials and propellants. A micro-cantilever sensor array is actuated thermally using bi-morph structure consisting of gold (Au: 400 nm) and silicon nitride (Si3N4: 600 nm) thin film layers of sub-micron thickness. An array of micro-heaters is integrated with the microcantilevers at their base. On electrically activating the micro-heaters at different actuation currents the microcantilevers undergo thermo-mechanical deformation, due to differential coefficient of thermal expansion. This deformation is tracked by monitoring the reflected ray from a laser illuminating the individual microcantilevers (i.e., using the optical lever principle). In the presence of explosive vapors, the change in bending response of microcantilever is affected by the induced thermal stresses arising from temperature changes due to adsorption and combustion reactions (catalyzed by the gold surface). A parametric study was performed for investigating the optimum values by varying the thickness and length in parallel with the heater power since the sensor sensitivity is enhanced by the optimum geometry as well as operating conditions for the sensor (e.g., temperature distribution within the microcantilever, power supply, concentration of the analyte, etc.). Also, for the geometry present in this study the nano-coatings of high thermal conductivity materials (e.g., Carbon Nanotubes: CNTs) over the microcantilever surface enables maximizing the thermally induced stress, which results in the enhancement of sensor sensitivity. For this purpose, CNTs are synthesized by post-growth method over the metal (e.g., Palladium Chloride: PdCl2) catalyst arrays pre-deposited by Dip-Pen Nanolithography (DPN) technique. The threshold current for differential actuation of the microcantilevers is correlated with the catalytic activity of a particular explosive (combustible vapor) over the metal (Au) catalysts and the corresponding vapor pressure. Numerical modeling is also explored to study the variation of temperature, species concentration and deflection of individual microcantilevers as a function of actuation current. Joule-heating in the resistive heating elements was coupled with the gaseous combustion at the heated surface to obtain the temperature profile and therefore the deflection of a microcantilever by calculating the thermally induced stress and strain relationship. The sensitivity of the threshold current of the sensor that is used for the specific detection and identification of individual explosives samples - is predicted to depend on the chemical kinetics and the vapor pressure. The simulation results showed similar trends with the experimental results for monitoring the bending response of the microcantilever sensors to explosive vapors (e.g., Acetone and 2-Propanol) as a function of the actuation current.

本文改良了Shafiee-Topal(2010)所提出之跳躍模型之波動率，並歸納成三種模型:改良跳躍模型、改良平滑跳躍模型以及最佳化跳躍模型，並運用時間序列模型探討樣本期間內黃金價格。第一部份比較三種跳躍模型與Shafiee-Topal模型在訓練集及測試集的預測結果，並預測2012年至2018年之黃金價格走勢。第二部份探討黃金價格、原油價格以及美元加權指數之間的互動關係，建立多變數模型以預測黃金價格之長期趨勢。 首先，本文檢驗黃金價格、原油價格及美元加權指數樣本之恆定性，經由ADF 單根檢定法發現序列具有單根，進而使用TSP(Trend Stationary Process)估計模型參數。其次，黃金價格、原油價格及美元加權指數經共整合檢定發現，各模型變數間均具有共整合關係，即變數間具有長期均衡關係。黃金價格與原油價格呈正向反應，而黃金價格和原油價格與美元加權指數呈負向反應，除了受自身的預測解釋能力外，亦可以做為觀察其他變數的未來走勢方向及影響大小預估。最後，探討黃金價格受波動率的影響情形，本文改良Shafiee-Topal模型之波動率，並比較四種模型對黃金價格趨勢預測之結果，發現改良平滑跳躍模型在實際黃金價格波動率大時，其趨勢預測結果會優於Shafiee-Topal模型。 / This research advanced the volatility component (λ) of the jump and dip model (Shafiee and Topal,2010) on gold prices from 1968 to 2012 and estimated the gold price for the next 6 years. Based on the trend stationary process, we defined the three components and derived three new models: Adjusted Jump and Dip Model, Adjusted Smooth Jump and Dip Model and Optimized Jump and Dip Model. First part of the thesis compared the performance in prediction of the training data and the testing data for three different models and the jump and dip model. Second part of the thesis investigated the relationship among the gold price, crude oil price, and trade weighted U.S. dollar index of the concepts The result illustrated the long term trend of gold price described by a multivariate predictive model. We found evidence that different levels of volatility affect the prediction of gold price, and the adjusted jump and dip Model performs best when the true volatility is relatively high.

Nous étudions la structuration de dépôts lors du séchage de suspensions colloïdales et de solutions polymères, dans une cellule de Hele-Shaw verticale immergée dans un réservoir (même principe qu'une expérience de dip-coating). La vitesse de la ligne de contact est contrôlée en pompant la solution du réservoir. A faible nombre capillaire un phénomène d'accrochage-décrochage de la ligne triple apparaît lors du séchage des suspensions colloïdales de silice. Nous étudions la longueur d'onde et la morphologie du dépôt en fonction de la vitesse moyenne de la ligne de contact. La variation de force d'accrochage est déduite de l'observation en ligne du mouvement de la ligne de contact. Nous étudions l'influence du pH de la solution et de la taille des particules sur le dépôt. Dans les mêmes conditions, les films obtenus pas séchage de solutions polymères sont presque plats. On observe cependant une structuration à plus haute température. Dans la seconde partie du manuscrit, un modèle 2D a été développé pour décrire l'écoulement dans la cellule de Hele-Shaw induit par la vitesse imposée et le flux d'évaporation non uniforme. Les équations de Stokes et la loi de Fick sont utilisées pour décrire l'écoulement et les transferts. Une troncature est appliquée à la pointe du ménisque pour s'affranchir de la singularité due à la divergence du flux d'évaporation. L'approximation de lubrification et les bilans de masse permettent de définir les conditions aux limites à la troncature. L'épaisseur du dépôt et les propriétés de l'écoulement sont étudiées en fonction des paramètres du processus (vitesse imposée, flux d'évaporation, concentration) ainsi que des propriétés du système

Die Darstellung der Seitenbänder des Hufgelenkes und ihrer Erkrankungen mit Hilfe der Magnetresonanztomographie am stehenden Pferd Mit Einführung des Hallmarq Equine Limb Scanner® wurde es möglich, die distalen Gliedmaßenabschnitte des Pferdes und speziell den Huf einer magnetresonanztomographischen Untersuchung am stehend sedierten Tier zu unterziehen. Die Diagnose der Erkrankung der Kollateralbänder des Hufgelenkes wird damit deutlich einfacher möglich, falls der Niederfeldtomograph hierfür geeignet ist. Zur Bewertung der Eignung des Equine Limb Scanner wurden im Zeitraum von 2005 bis 2009 aus eintausend an der Pferdeklinik Bargteheide mittels des Hallmarq Equine Limb Scanner® 0,27 T-Systems im Stehen untersuchten Pferden diejenigen 69 Patienten ausgewählt, welche ausschließlich eine Erkrankung im Bereich der Kollateralbänder des Hufgelenkes aufwiesen. Die Untersuchung erfolgte damit bei gleichzeitiger physiologischer Zug- und Druckbelastung des zu untersuchenden Gliedmaßenabschnittes. Die Beurteilung der Kollateralbänder und ihrer Erkrankungen wurden anhand eines transversalen und frontalen Fast Spin Echo T2 gewichtet durchgeführt. Um den Ursprungsbereich des Kollateralbandes am Kronbein und den Ansatzbereich am Hufbein zu bewerten wurden zusätzlich Gradientenechos T1 und T2* gewichtet, sowie die STIR Sequenz genutzt. Die Verwendung des Fast Spin Echos T2w mit einer Echozeit von TE=84 ms sowie eine fachgerechte Positionierung des Hufes im Magneten diente zum Ausschluss eines möglichen Magic Angle Effect. Das Kollateralband wurde in drei definierte Zonen (Ursprung, Korpus, Insertion) eingeteilt, um die genaue Lokalisation der Läsion zu beschreiben. Dabei konnte beobachtet werden, dass der Kollateralbandursprung (36%) am häufigsten betroffen ist, gefolgt von Schäden in allen drei Zonen (20%) sowie Ursprung und Korpus (20%), Insertion (16%), und Schäden nur am Korpus (3%) und Korpus und Insertion (3%), Ursprung und Insertion (2%). Bei der klinischen Untersuchung fiel auf, dass bei fast allen Patienten die Lahmheit sowohl auf dem harten als auch auf dem weichen Zirkel jeweils auf der inneren Hand am deutlichsten zu erkennen war. Das Phänomen der schlechten Abgrenzung des Kollateralbandes zu seiner Umgebung (poorly defined borders) wurde im transversalen und frontalen Fast Spin Echo T2w beurteilt. Hierbei konnte festgestellt werden, dass diese Veränderung hauptsächlich im Ursprungsbereich vorkommt. Bei 70% der Patienten mit einem lateralen Kollateralbandschaden im Ursprungsbereich am Kronbein und bei 59% der Patienten mit einem medialen Kollateralbandschaden im Ursprungsbereich am Kronbein konnte dies beobachtet werden. Zur Feststellung einer knöchernen Beteiligung von Kron- und/oder Hufbein wurden zusätzlich Gradientenechos T1 und T2*w sowie die STIR Sequenz hinzugezogen. Dabei zeigte sich, dass eine Beteilung des Knochens vorwiegend im Bereich der medialen Insertion (53%) und weniger lateral (27%) vorkommt. Im Ursprungsbereich ist diese lateral in 16% der Fälle und medial in 3% der Fälle vorzufinden. Die Durchmesser des medialen und lateralen Kollateralbandes im Ursprungs-, Korpus-, und Insertionsbereich wurden im Bild eines transversalen Fast Spin Echo T2w ermittelt. Dazu wurden zusätzlich Referenzwerte von 23 klinisch und magnetresonanztomographisch gesunden Patienten angefertigt. Es wurde festgestellt, dass die Mittelwerte der Flächen der medialen Kollateralbänder in allen drei Zonen bei erkrankten Patienten statistisch signifikant größer waren als bei gesunden Pferden (Ursprung p=0,0297, Korpus p=0,00285 und Insertion p=0,0001603). Die Mittelwerte der Flächen der lateralen Kollateralbänder unterschieden sich bei gesunden und kranken Patienten im Ursprungs-, und Korpusbereich nicht signifikant (Ursprung p=0,4372, Korpus p=0,6258), im Bereich der lateralen Insertion konnte ein deutlicher aber statistisch nicht signifikanter Unterschied (p=0,0753) beobachtet werden bei einer Irrtumswahrscheinlichkeit von α=0,05. Die Ergebnisse dieser Arbeit untermauern die Wichtigkeit moderner bildgebender Verfahren zur Ergänzung und Vervollständigung der klinischen Untersuchung, der Diagnosefindung, der differentialdiagnostischen Abgrenzung, der Therapieplanung und prognostischer Aussagen. Insbesondere im Hufbereich liefert die Magnetresonanztomographie wichtige Informationen zur Erkennung der erkrankten Struktur. Sie bietet eine differenzierte Abgrenzung einer erkrankten Struktur, in diesem Fall der Seitenbänder, die bisher häufig dem Begriff Hufrollensyndrom zugeordnet wurde und mit herkömmlichen bildgebenden Verfahren nicht oder nur teilweise dargestellt werden konnte. Die Untersuchung mit dem Hallmarq Equine Limb Scanner® Niederfeldtomographen am stehend sedierten Pferd ist hierfür nach vorliegenden Ergebnissen hervorragend geeignet.

This study is mainly aimed at interstital-free and dual-phase steels, analyzing the compositions and distribution of selective surface oxides after annealing and then to know the influence of these oxidation for the formation of FeAl inhibition layer in hot-dip galvanizing. Interstital-free and dual-phase steels were first annealed at 800 oC for 1-200 s in a 10% H2-N2 protected atmosphere of -70 oC and 0 oC dew point respectively and then dipped in zinc bath with Al content 0.12-0.18 wt% for 0-20 s. Using this combined SEM, Auger electron spectroscopy(AES), X-ray photoelectron spectroscopy(XPS) and ICP-AES etc. instruments, it is shown that the MnAl2O4 spinels were the major oxidation on the surface of IF steel after annealing. The average oxidation thickness was about 5-15 nm. Annealing times has little effect on the thickness. On the other hand, MnO were observed on DP steel surface after anneaing. The MnO paticles mainly distributed at the grain boundaries ,and the average oxdaiton thickness increase rapidly from 20 nm(10 s) to 110 nm(200 s) with annealing times. The growth of the FeAl inhibition layer can separate to nucleation in initial stage and diffusion growth later. The Fe2Al5 nucleation times were all about 0.1 s in both steels , and average thicknesses were approximately 20 nm. For IF steels , Al uptake in the zinc bath and steel interface was depleted in nucleation stage with 0.12 wt% Al content, so that delayed the growth of Fe2Al5, and the rate determining step was the diffusion of Al in zinc bath. When Al content raise up to 0.14 wt%, the phenomenon of growth delay was not happened, and the rate determining step of Fe2Al5 growth changed to the solid-state diffusion of Fe in Fe2Al5. For DP steels, when Al content up to 0.14 wt%, the growth mechanism was similar to IF steels, but the rate determining step of Fe2Al5 growth was mainly in the grain boundary diffusion of Fe in Fe2Al5. Moreover, where the MnO paticles was rich could obviously observe the delay of Fe2Al5 growth. It was probably because of consuming a great deal of Al to reduce the MnO oxides.

The master's degree thesis deals with the analysis of the quality management system in a selected organisation. The theoretical part focuses on history and quality management, quality principles and its concept. It describes the quality management system, its implementation and documentation. General standards and standards for hot-dip galvanising are an essential part for an easier orientation in the issues. The practical part describes a company engaged in hot-dip galvanising, the company's goals and the process of hot-dip galvanising. The next part provides a detailed description of the technological process concerning hot-dip galvanising to illustrate practically the quality management system. In order to follow the production process, one contract was selected and was closely observed during every step of the whole process of hot-dip galvanising. The last part of the chapter includes data analysis of the quality management system as well as a description of the Pareto analysis, which represents the only instrument of quality management in the organisation. The conclusion provides some improvement suggestions which should be applied by the company to enhance the quality management system and at the same time to prevent possible complications.

Este trabalho investigou a obtenção de filmes de TiO2 por sol-gel e dipcoating (SGDC) e sua caracterização microestrutural e como fotocatalisador para a produção de hidrogênio a partir da água. Os precursores e reagentes utilizados foram: propóxido de titânio, ácido acético, etanol anidro, acetilacetona, Triton X-100 e polivinilbutiral (PVB). Foram preparadas 2 soluções precursoras, uma com PVB e outra sem. Foram produzidos filmes com 1, 2 e 3 camadas através da técnica de dip-coating. Os filmes foram tratados termicamente a 400, 500 e 600ºC, com uma taxa de 100ºC/h e um patamar de 2 h. O TiO2 sintetizado e os filmes produzidos foram caracterizados por difração de raios X (DRX) quanto à cristalinidade, fases presentes e tamanho de cristalito; microscopia eletrônica de varredura (MEV), adsorção de nitrogênio (método BET), análises termogravimétricas (ATG) e termodiferenciais (ATD), elipsometria espectroscópica, perfilometria óptica, espectroscopia Raman e de reflectância difusa (determinação do band gap). Após o tratamento térmico os filmes apresentaram uma microestrutura bastante irregular e com muitas trincas, com a presença da fase anatase em todas as temperaturas de tratamento térmico, e um teor de 3,7% de rutilo à 600ºC. O band gap dos filmes aumentou com a quantidade de camadas adicionadas, com a elevação da temperatura de tratamento térmico e adição de PVB. As medidas de fotocorrente foram realizadas no escuro e sob iluminação de lâmpada de Xe com 250W (simulador de luz solar de 1,5AM). A maior fotocorrente medida foi de 12 μA a 0,5V. A produção de H2 aumentou linearmente com o tempo de exposição para ambas as amostras com PVB. Foi possível relacionar a adição do PVB com o favorecimento da fotoatividade dos filmes de TiO2. / This work has investigated the effect of polyvinyl butyral addition in the synthesis of TiO2 films by sol-gel and dip-coating, their microstructural features and their photoelectrochemical activity for water-splitting hydrogen production. The precursors and reagents used were: titanium propoxide, acetic acid, anhydrous ethanol, acetylacetone, Triton X-100 and polyvinyl butyral (PVB). Two precursor solutions were prepared: one with PVB and another without it. The dip-coating technique was used to produce films with 1, 2 and 3 layers. The films were heat treated at 400, 500 and 600ºC, at a rate of 100°C/h and dwelling time of 2h. Afterwards the synthesized films were characterized by X-ray diffraction (XRD); scanning electron microscopy (SEM), nitrogen adsorption (BET method), thermogravimetric (TGA) and differential thermal analysis (DTA), spectroscopic ellipsometry, optical profilometry, Raman and diffuse reflectance spectroscopy (determination of the band gap). The films after heat treatment showed a very irregular microstructure with many cracks. The anatase phase was presented in all temperatures and a small content of rutile at 600 °C (around 3.7%) was identified. The band gap of the films increased with the number of layers, heat treatment and addition of PVB. The photocurrent measurements were carried out in the dark and under illumination with 250W Xe, using a sunlight simulator (1,5AM). The highest photocurrent was 12A at 0.5V. The H2 production increased linearly with time of exposure for both samples with PVB. Therefore, it was possible to relate the addition of PVB with improvement the photoactivity of TiO2 films.

Este trabalho investigou a obtenção de filmes de TiO2 por sol-gel e dipcoating (SGDC) e sua caracterização microestrutural e como fotocatalisador para a produção de hidrogênio a partir da água. Os precursores e reagentes utilizados foram: propóxido de titânio, ácido acético, etanol anidro, acetilacetona, Triton X-100 e polivinilbutiral (PVB). Foram preparadas 2 soluções precursoras, uma com PVB e outra sem. Foram produzidos filmes com 1, 2 e 3 camadas através da técnica de dip-coating. Os filmes foram tratados termicamente a 400, 500 e 600ºC, com uma taxa de 100ºC/h e um patamar de 2 h. O TiO2 sintetizado e os filmes produzidos foram caracterizados por difração de raios X (DRX) quanto à cristalinidade, fases presentes e tamanho de cristalito; microscopia eletrônica de varredura (MEV), adsorção de nitrogênio (método BET), análises termogravimétricas (ATG) e termodiferenciais (ATD), elipsometria espectroscópica, perfilometria óptica, espectroscopia Raman e de reflectância difusa (determinação do band gap). Após o tratamento térmico os filmes apresentaram uma microestrutura bastante irregular e com muitas trincas, com a presença da fase anatase em todas as temperaturas de tratamento térmico, e um teor de 3,7% de rutilo à 600ºC. O band gap dos filmes aumentou com a quantidade de camadas adicionadas, com a elevação da temperatura de tratamento térmico e adição de PVB. As medidas de fotocorrente foram realizadas no escuro e sob iluminação de lâmpada de Xe com 250W (simulador de luz solar de 1,5AM). A maior fotocorrente medida foi de 12 μA a 0,5V. A produção de H2 aumentou linearmente com o tempo de exposição para ambas as amostras com PVB. Foi possível relacionar a adição do PVB com o favorecimento da fotoatividade dos filmes de TiO2. / This work has investigated the effect of polyvinyl butyral addition in the synthesis of TiO2 films by sol-gel and dip-coating, their microstructural features and their photoelectrochemical activity for water-splitting hydrogen production. The precursors and reagents used were: titanium propoxide, acetic acid, anhydrous ethanol, acetylacetone, Triton X-100 and polyvinyl butyral (PVB). Two precursor solutions were prepared: one with PVB and another without it. The dip-coating technique was used to produce films with 1, 2 and 3 layers. The films were heat treated at 400, 500 and 600ºC, at a rate of 100°C/h and dwelling time of 2h. Afterwards the synthesized films were characterized by X-ray diffraction (XRD); scanning electron microscopy (SEM), nitrogen adsorption (BET method), thermogravimetric (TGA) and differential thermal analysis (DTA), spectroscopic ellipsometry, optical profilometry, Raman and diffuse reflectance spectroscopy (determination of the band gap). The films after heat treatment showed a very irregular microstructure with many cracks. The anatase phase was presented in all temperatures and a small content of rutile at 600 °C (around 3.7%) was identified. The band gap of the films increased with the number of layers, heat treatment and addition of PVB. The photocurrent measurements were carried out in the dark and under illumination with 250W Xe, using a sunlight simulator (1,5AM). The highest photocurrent was 12A at 0.5V. The H2 production increased linearly with time of exposure for both samples with PVB. Therefore, it was possible to relate the addition of PVB with improvement the photoactivity of TiO2 films.

Este trabalho investigou a obtenção de filmes de TiO2 por sol-gel e dipcoating (SGDC) e sua caracterização microestrutural e como fotocatalisador para a produção de hidrogênio a partir da água. Os precursores e reagentes utilizados foram: propóxido de titânio, ácido acético, etanol anidro, acetilacetona, Triton X-100 e polivinilbutiral (PVB). Foram preparadas 2 soluções precursoras, uma com PVB e outra sem. Foram produzidos filmes com 1, 2 e 3 camadas através da técnica de dip-coating. Os filmes foram tratados termicamente a 400, 500 e 600ºC, com uma taxa de 100ºC/h e um patamar de 2 h. O TiO2 sintetizado e os filmes produzidos foram caracterizados por difração de raios X (DRX) quanto à cristalinidade, fases presentes e tamanho de cristalito; microscopia eletrônica de varredura (MEV), adsorção de nitrogênio (método BET), análises termogravimétricas (ATG) e termodiferenciais (ATD), elipsometria espectroscópica, perfilometria óptica, espectroscopia Raman e de reflectância difusa (determinação do band gap). Após o tratamento térmico os filmes apresentaram uma microestrutura bastante irregular e com muitas trincas, com a presença da fase anatase em todas as temperaturas de tratamento térmico, e um teor de 3,7% de rutilo à 600ºC. O band gap dos filmes aumentou com a quantidade de camadas adicionadas, com a elevação da temperatura de tratamento térmico e adição de PVB. As medidas de fotocorrente foram realizadas no escuro e sob iluminação de lâmpada de Xe com 250W (simulador de luz solar de 1,5AM). A maior fotocorrente medida foi de 12 μA a 0,5V. A produção de H2 aumentou linearmente com o tempo de exposição para ambas as amostras com PVB. Foi possível relacionar a adição do PVB com o favorecimento da fotoatividade dos filmes de TiO2. / This work has investigated the effect of polyvinyl butyral addition in the synthesis of TiO2 films by sol-gel and dip-coating, their microstructural features and their photoelectrochemical activity for water-splitting hydrogen production. The precursors and reagents used were: titanium propoxide, acetic acid, anhydrous ethanol, acetylacetone, Triton X-100 and polyvinyl butyral (PVB). Two precursor solutions were prepared: one with PVB and another without it. The dip-coating technique was used to produce films with 1, 2 and 3 layers. The films were heat treated at 400, 500 and 600ºC, at a rate of 100°C/h and dwelling time of 2h. Afterwards the synthesized films were characterized by X-ray diffraction (XRD); scanning electron microscopy (SEM), nitrogen adsorption (BET method), thermogravimetric (TGA) and differential thermal analysis (DTA), spectroscopic ellipsometry, optical profilometry, Raman and diffuse reflectance spectroscopy (determination of the band gap). The films after heat treatment showed a very irregular microstructure with many cracks. The anatase phase was presented in all temperatures and a small content of rutile at 600 °C (around 3.7%) was identified. The band gap of the films increased with the number of layers, heat treatment and addition of PVB. The photocurrent measurements were carried out in the dark and under illumination with 250W Xe, using a sunlight simulator (1,5AM). The highest photocurrent was 12A at 0.5V. The H2 production increased linearly with time of exposure for both samples with PVB. Therefore, it was possible to relate the addition of PVB with improvement the photoactivity of TiO2 films.

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.