Thesis (M. Sc.)(Applied Sciences)--University of Petoria, 2005. / Abstracts in English and Afrikaans. Includes bibliographical references. Available on the Internet via the World Wide Web.

A set of passivated tinplates coated with organic lacquers as used for internal coatings on cans is examined. Adhesion is measured using a butt-joint test and the results of failure load and percent area lacquer removal analysed in order to grade adhesion performance. Fracture behaviour is determined by the surface structure of the tinplates where a defect distribution common to all types is identified by Weibull analysis as responsible for failure initiation. Differences in fracture behaviour seen in the mechanical test results are revealed by examination of the fracture surfaces using optical microscopy, scanning electron microscopy and X-ray photoelectron spectroscopy. The samples with good lacquer adhesion show a positive relationship between failure load and lacquer removal which is not evident in the samples with poor lacquer adhesion. The latter exhibit weak bonding between the passivation layer and tinplate and on examining those areas of fracture surface where tinplate is revealed the fracture is seen to have propagated at this interface whereas those samples with good adhesion had failed near the lacquer-passivation layer interface within the lacquer. Passivation layers are characterised using X-ray photoelectron spectroscopy and transmission electron microscopy. Differences in composition relating to specific tin oxides and chromium oxides are correlated with adhesion performance and models for the structure of passivation layers and failure mechanisms are proposed.

by Chan To = 電鍍錫在銅質底材上晶鬚生長的硏究 / 陳濤. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references. / Text in English; abstracts in English and Chinese. / by Chan To = Dian du xi zai tong zhi di cai shang jing xu sheng chang de yan jiu / Chen Tao. / Abstract --- p.i / 論文摘要 --- p.ii / Acknowledgements --- p.iii / Table of Content --- p.v / Chapter Chapter 1 --- INTRODUCTION / Chapter 1.1 --- Lead-free movement and the problem of whisker --- p.1-1 / Chapter 1.2 --- Properties of tin and tin-copper intermetallics --- p.1-2 / Chapter ´Ø --- Tin --- p.1-2 / Chapter ´Ø --- Tin-copper intermetallics --- p.1-2 / Chapter 1.3 --- Literature Review of Whisker --- p.1-4 / Chapter 1.3.1 --- Feature of the whisker --- p.1-4 / Chapter 1.3.2 --- Conditions prone to whisker growth --- p.1-8 / Chapter 1.3.3 --- Growth mechanism of the whisker --- p.1-10 / Chapter 1.3.4 --- Methods to prevent or remove whisker --- p.1-11 / Chapter 1.4 --- Motivation & Aims of Studies --- p.1-12 / Chapter Chapter 2 --- EXPERIMENTAL & INSTRUMENTATION / Chapter 2.1 --- Sample Preparation --- p.2-1 / Chapter ´Ø --- Electroplating process --- p.2-1 / Chapter 2.2 --- Instrumentation --- p.2-6 / Chapter 2.2.1 --- Scanning Auger Microscope (SAM) analysis --- p.2-6 / Chapter ´Ø --- Experimental conditions --- p.2-9 / Chapter ´Ø --- Sample preparation for Auger analysis --- p.2-10 / Chapter ´Ø --- Depth profile analysis --- p.2-11 / Chapter ´Ø --- Mapping --- p.2-11 / Chapter ´Ø --- Line scan --- p.2-12 / Chapter 2.2.2 --- X-ray diffractometer (XRD) --- p.2-12 / Chapter 2.2.3 --- Scanning Electron Microscope (SEM) --- p.2-13 / Chapter Chapter 3 --- INFLUENCE OF CATHODIC/ANODIC ELECTROCHEMICAL CLEANING ON THE WHISKER GROWTH / Chapter 3.1 --- Introduction --- p.3-1 / Chapter 3.2 --- Theory --- p.3-2 / Chapter ´Ø --- Reactions occurring at the anode/cathode --- p.3-3 / Chapter 3.3 --- Sample description --- p.3-5 / Chapter 3.4 --- Results and discussion --- p.3-5 / Chapter ´Ø --- Surface morphology before electroplating --- p.3-5 / Chapter ´Ø --- Whisker observation --- p.3-7 / Chapter 3.5 --- Summary --- p.3-18 / Chapter Chapter 4 --- INFLUENCE OF COPPER CONCENTRATION IN THE PLATING BATH ON COPPER DIFFUSION AND WHISKER FORMATION / Chapter 4.1 --- Introduction --- p.4-1 / Chapter 4.2 --- Theory and Literature Review --- p.4-2 / Chapter ´Ø --- Diffusion kinetic --- p.4-2 / Chapter ´Ø --- Influence of solute atoms --- p.4-5 / Chapter 4.3 --- Sample description --- p.4-6 / Chapter 4.4 --- Results and discussion --- p.4-6 / Chapter ´Ø --- SEM observations --- p.4-6 / Chapter ´Ø --- Cross-sectional analysis --- p.4-8 / Chapter ´Ø --- Surface and depth profile analysis --- p.4-15 / Chapter ´Ø --- XRD analysis --- p.4-21 / Chapter 4.5 --- Summary --- p.4_24 / Chapter Chapter 5 --- ANNEALING EFFECT ON THE WHISKER GROWTH / Chapter 5.1 --- Introduction --- p.5-1 / Chapter 5.2 --- Theory and Literature Review --- p.5-2 / Chapter 5.3 --- Sample description --- p.5-3 / Chapter 5.4 --- Results and discussion --- p.5-4 / Chapter ´Ø --- SEM whisker observation --- p.5-4 / Chapter ´Ø --- Cross-sectional Auger analysis --- p.5-4 / Chapter ´Ø --- Surface and depth profile analysis --- p.5-16 / Chapter 5.5 --- Summary --- p.5-27 / Chapter Chapter 6 --- FORMATION MECHANISM OF THE STRIATION ON WHISKER / Chapter 6.1 --- Introduction --- p.6-1 / Chapter 6.2 --- Results and discussion --- p.6-2 / Chapter ´Ø --- Texture of the striation --- p.6-2 / Chapter ´Ø --- Time evolution in the surface morphology --- p.6-6 / Chapter ´Ø --- Stage of whisker growth --- p.6-6 / Chapter 6.3 --- Summary --- p.6-12 / Chapter Chapter 7 --- CONCLUSIONS & FUTURE STUDIES / Chapter 7.1 --- Conclusions --- p.7-1 / Chapter 7.2 --- Future studies --- p.7-3 / Reference

Water diffusion is widely believed to be a driving factor in the breakdown of corrosion protection by polymer coatings. However, in the epoxy-phenolic system examined, water absorption into more cured, electrically resistive coatings is shown to increase, contradicting the common perception that hydrophobic coatings yield improvements in corrosion protection. Water uptake into epoxy-phenolic coatings was estimated as a function of time using the dielectric and resistive properties of the coating measured using electrochemical impedance spectroscopy (EIS). Bulk water uptake through the coating surface and the localised nature of corrosive failure was then confirmed using localised electrochemical impedance (LEIS). This technique also allowed comparison of resistance for coatings with different curing degrees. The greater degree of water absorption into highly cured coatings was attributed to diffusion into the polymer free volume, which increases with prolonged crosslinking. Evidence for this mechanism was found in the decreasing density of epoxy-phenolic coatings as a function of cure time. The effect of coating volume was therefore evaluated with respect to the dry coating dielectric properties. Cathodic delamination of the epoxy-phenolic coatings was achieved on tinplated steel substrates, whereas this was not possible from tin-free steel (ECCS). The electrochemical behaviour of these two substrates was examined under the same NaCl concentration, their surfaces were analysed by XPS prior to immersion, and XRD after potentiostatic polarisations. The electrochemical behaviour of the bare substrates was found to be unchanged by heating to the coating cure temperature (within the accuracy of polarisation tests carried out). Nonetheless, the delamination rate of epoxy-phenolic coatings deposited on them was dependent on the coating crosslinking (cure time). The reason coating adhesion selectively failed on tinplate substrates is believed to be the lower concentration of hydroxides on its relatively flat surface, allowing less bonding to take place at the interface with the coating. The impact of the substrate on coating resistivity was further investigated by volume resistivity measurements in the presence and absence of a metallic substrate. The resistivity of free standing films was tested in permeation cells, and showed a direct correlation between the polymer resistivity and the resistivity of the solution in which it was immersed. In comparison, attached films remained highly resistive at all examined concentrations. To conclude, the results presented here demonstrate that water uptake is not as critical to the breakdown in the protection offered by epoxy-phenolics as bonding at the metal-polymer interface. These results suggest that the complex interaction between these two dissimilar materials determines the overall coating electrochemical behaviour.

Masters of Science / Nampak packages millions of cans a year and a very small percentage of these cans fail due to many reasons. One of the main reasons that cause 2- piece food cans to fail is split flanges. Split Flanges arises due to a number of reasons which will be discussed in detail.The focus of this thesis was based on the causes of split flanges in 2-piece food cans. A study on manufacturing the steel and can making together with packaging fish in these cans was conducted. Another study on the reasons for split flanges occurring in 2 piece cans was conducted done as well.The purpose of the investigation was to check if hydrogen embrittlement could be the cause for split bodies forming in 2 piece food cans. 2 piece cans are drawn and wall ironed from tinplate; the cans were made up of a top and a shaped body. It was this shaped body that went through a considerable amount of stress during manufacture especially at the top of the can, which gave an explanation to why the cans split at the curved area near the flange of the can.According to previous studies done at Nampak R&D more complaints about split bodies were coming from the Fish canneries on the West Coast than the Vegetable canneries. These canneries used the exact same cans to package their product. The difference between the processes at these canneries was the exhaust boxes at the fish canneries. The exhaust box is a long tunnel filled with steam used to precook the fish; the vegetables are not precooked in exhaust boxes. Non metallic inclusions (NMI) was one of the main reason for these split flanges to occur and a reason of particular interest in this research.NMI’s were distributed throughout the steel of the cans and since the same cans were used for the fish and vegetable canneries, they should be failing at the same rate. Yet only complaints came from the fish canneries. So the primary focus of the research was to check if the additional steam process contributed to the formation of split bodies / flanges. We proposed to investigate if hydrogen atoms collect at grain boundaries, vacancies and non metallic inclusions and also to check if the steam accelerated embrittlement. Hydrogen is believed to penetrate right into the bare steel of the cans that were exposed to steam.Hydrogen atoms are being investigated because of their small size, their ability to diffuse through a metal lattice and form hydrogen molecules within the intermetallic vacancies of the metal. The molecules of hydrogen, once formed within the internal structure of the metal, remain trapped because of their larger size and can generate a significant pressure that can contribute to the formation of split bodies. [1] The first step to prove whether H-embrittlement was present in the cans was to check if hydrogen was present. A spectroscopic method namely, elastic recoil detection analysis (ERDA) was used to check if H could be detected using the Elastic Recoil Detection Analysis technique. Several experiments were designed to make sure the technique was suitable for the detection of H. Even though it is known that all metals are susceptible to corrosion and Hembrittlement, the tinplate metals had to be checked in an environment similar to the exhaust box (suspected area causing hydrogen embrittlement) in the factories.Further characterization was done using X-Ray Diffraction to measure the residual stress and relate it to the effects of H-embrittlement. If the H had penetrated into the metal it would cause some distortion in the atomic distances between the atomic planes in Fe atoms and can be measured using XRD.Another effect of hydrogen embrittlement is to reduce the strength in the metal. Tensile tests were performed to measure the strengths of the metal.

Um dos principais problemas da folha de flandres utilizada no setor de embalagens é a adesão dos revestimentos UV sobre o substrato devido à presença de óxidos na superfície. Dessa forma, o emprego de pré-tratamentos superficiais se faz necessário, e o uso de revestimentos híbridos tem sido proposto para melhorar a aderência e a resistência à corrosão. Contudo, esses revestimentos tendem a serem frágeis e não suportam deformação mecânica. No presente trabalho, os filmes híbridos foram depositados sobre a folha de flandres a fim de avaliar o seu desempenho como revestimento protetor e como pré-tratamento para posterior aplicação do revestimento UV. Visando melhorar o efeito barreira, as folhas de flandres foram revestidas com um filme híbrido obtido a partir de um sol constituído pelos precursores: 3-(trimetoxisililpropil)metacrilato (TMSM) e tetraetoxisilano (TEOS) e Ce(NO3)3 0,01M com adição do plastificante di-isodecil adipato (DIDA) em diferentes concentrações: (0,5, 1, 2 e 4%). Utilizou-se o processo de dip-coating com velocidade de retirada de 10 cm.min-1, com aplicação em monocamada e bicamada, e curados por cura térmica empregando-se duas diferentes temperaturas de cura, 60 °C e 90 °C. Com o objetivo de analisar um pré-tratamento para posterior aplicação do revestimento UV, as folhas de flandres foram revestidas com um filme híbrido obtido a partir de um sol com a mesma formulação citada, substituindo o plastificante DIDA pelo flexibilizante polietilenoglicol (PEG) em diferentes concentrações: (20, 40, 60 e 80 g.L-1). Os filmes foram obtidos e curados conforme descrito anteriormente, além disso, após o pré-tratamento com filme híbrido, a folha de flandres foi submetida ao processo de pintura com tinta uretânica alifática acrilada curada por radiação ultravioleta (UV). Foram empregadas como técnicas para caracterização quanto ao comportamento eletroquímico: monitoramento do potencial de circuito aberto, curvas de polarização potenciodinâmicas, medidas de impedância eletroquímica e svet. O comportamento físico-químico dos filmes foi avaliado por ângulo de contato, termogravimetria, espectroscopia de infravermelho e ressonância magnética nuclear. A resistência ao desgaste foi avaliada pela técnica de esfera sobre plano. Os sistemas de pintura curada por radição ultravioleta foram analisados quanto à adesão, flexibilidade e molhabilidade. Os resultados obtidos, mostraram que a adição de 2% do plastificante di-isodecil adipato melhorou a resistência à corrosão e a cura a 90 °C e com aplicação da bicamada otimizou o efeito barreira do filme. Adição de PEG na concentração de 20 g.L-1 contribuiu para melhorar a flexibilidade do filme retardando a cinética da reação de reticulação e consequentemente evitando a formação de fissuras. Nesta concentração, e curado a 60 °C, o filme melhorou a resistência mecânica para os sistemas com pós-tratamento em tinta UV. / One of the main problems of the tinplate for the packaging sector is the coating adherence of UV coatings on the substrate, due to the presence of oxides on the surface. Thus, it makes necessary the use of surface pretreatments, and the use of hybrid coatings has been proposed to improve the adherence and corrosion resistance. However, these hybrid films tend to be fragile and do not hold on mechanical deformation. In this work, the tinplate was coated with hybrid films aiming to evaluate its performance as protective coating and as pre-treatment for further UV coating application. In order to improve the barrier effect, the tinplate were coated with a hybrid film obtained from a sol constituted by the precursors 3-(trimethoxysilyl)propyl methacrylate (TMSM) and tetraethoxysilane (TEOS), 0.01 mol.L-1 cerium nitrate (Ce(NO3)3) and diisodecyl adipate (DIDA) in different concentrations (0.5, 1, 2 and 4%) as plasticizer. Dip-coating was the process for applying the films with removal rate of 10 cm.min-1. The films were applied in one or two layers and, then, thermally cured at 60 °C or 90 °C. As a pretreatment for further UV coating, the tinplate were coated with a hybrid film with the aforementioned formulation, but replacing the plasticizer DIDA for polyethylene glycol (PEG) in different concentrations (20, 40, 60 e 80 g.L-1). The films were obtained and cured through the same dip-coating process and, after, the samples were painted with aliphatic acrylic urethane coating with ultraviolet radiation curing. The characterization techniques for electrochemical behavior were open circuit potential monitoring, potentiodynamic polarization curves, electrochemical impedance spectroscopy (EIS) and scanning vibrating electrode technique (SVET). The physicochemical behavior of the films was evaluated by contact angle measurement, thermogravimetric analysis, infrared spectroscopy and nuclear magnetic resonance. Wear resistance was evaluated by using a ball-on-plate test. The systems with UV-radiation-cured ink were analyzed regarding adherence, flexibility and wettability. Results showed that adding 2% of DIDA plasticizer improved the corrosion resistance and that curing a bilayer film at 90 °C optimizes the film barrier effect. Adding PEG in a concentration of 20 g.L-1 improved the flexibility of the film, making the cross-linking reaction kinetics slower and, in consequence, avoided cracks. With this concentration and curing at 60 °C, the film had better mechanical resistance for systems post-treated with UV ink.

Um dos principais problemas da folha de flandres utilizada no setor de embalagens é a adesão dos revestimentos UV sobre o substrato devido à presença de óxidos na superfície. Dessa forma, o emprego de pré-tratamentos superficiais se faz necessário, e o uso de revestimentos híbridos tem sido proposto para melhorar a aderência e a resistência à corrosão. Contudo, esses revestimentos tendem a serem frágeis e não suportam deformação mecânica. No presente trabalho, os filmes híbridos foram depositados sobre a folha de flandres a fim de avaliar o seu desempenho como revestimento protetor e como pré-tratamento para posterior aplicação do revestimento UV. Visando melhorar o efeito barreira, as folhas de flandres foram revestidas com um filme híbrido obtido a partir de um sol constituído pelos precursores: 3-(trimetoxisililpropil)metacrilato (TMSM) e tetraetoxisilano (TEOS) e Ce(NO3)3 0,01M com adição do plastificante di-isodecil adipato (DIDA) em diferentes concentrações: (0,5, 1, 2 e 4%). Utilizou-se o processo de dip-coating com velocidade de retirada de 10 cm.min-1, com aplicação em monocamada e bicamada, e curados por cura térmica empregando-se duas diferentes temperaturas de cura, 60 °C e 90 °C. Com o objetivo de analisar um pré-tratamento para posterior aplicação do revestimento UV, as folhas de flandres foram revestidas com um filme híbrido obtido a partir de um sol com a mesma formulação citada, substituindo o plastificante DIDA pelo flexibilizante polietilenoglicol (PEG) em diferentes concentrações: (20, 40, 60 e 80 g.L-1). Os filmes foram obtidos e curados conforme descrito anteriormente, além disso, após o pré-tratamento com filme híbrido, a folha de flandres foi submetida ao processo de pintura com tinta uretânica alifática acrilada curada por radiação ultravioleta (UV). Foram empregadas como técnicas para caracterização quanto ao comportamento eletroquímico: monitoramento do potencial de circuito aberto, curvas de polarização potenciodinâmicas, medidas de impedância eletroquímica e svet. O comportamento físico-químico dos filmes foi avaliado por ângulo de contato, termogravimetria, espectroscopia de infravermelho e ressonância magnética nuclear. A resistência ao desgaste foi avaliada pela técnica de esfera sobre plano. Os sistemas de pintura curada por radição ultravioleta foram analisados quanto à adesão, flexibilidade e molhabilidade. Os resultados obtidos, mostraram que a adição de 2% do plastificante di-isodecil adipato melhorou a resistência à corrosão e a cura a 90 °C e com aplicação da bicamada otimizou o efeito barreira do filme. Adição de PEG na concentração de 20 g.L-1 contribuiu para melhorar a flexibilidade do filme retardando a cinética da reação de reticulação e consequentemente evitando a formação de fissuras. Nesta concentração, e curado a 60 °C, o filme melhorou a resistência mecânica para os sistemas com pós-tratamento em tinta UV. / One of the main problems of the tinplate for the packaging sector is the coating adherence of UV coatings on the substrate, due to the presence of oxides on the surface. Thus, it makes necessary the use of surface pretreatments, and the use of hybrid coatings has been proposed to improve the adherence and corrosion resistance. However, these hybrid films tend to be fragile and do not hold on mechanical deformation. In this work, the tinplate was coated with hybrid films aiming to evaluate its performance as protective coating and as pre-treatment for further UV coating application. In order to improve the barrier effect, the tinplate were coated with a hybrid film obtained from a sol constituted by the precursors 3-(trimethoxysilyl)propyl methacrylate (TMSM) and tetraethoxysilane (TEOS), 0.01 mol.L-1 cerium nitrate (Ce(NO3)3) and diisodecyl adipate (DIDA) in different concentrations (0.5, 1, 2 and 4%) as plasticizer. Dip-coating was the process for applying the films with removal rate of 10 cm.min-1. The films were applied in one or two layers and, then, thermally cured at 60 °C or 90 °C. As a pretreatment for further UV coating, the tinplate were coated with a hybrid film with the aforementioned formulation, but replacing the plasticizer DIDA for polyethylene glycol (PEG) in different concentrations (20, 40, 60 e 80 g.L-1). The films were obtained and cured through the same dip-coating process and, after, the samples were painted with aliphatic acrylic urethane coating with ultraviolet radiation curing. The characterization techniques for electrochemical behavior were open circuit potential monitoring, potentiodynamic polarization curves, electrochemical impedance spectroscopy (EIS) and scanning vibrating electrode technique (SVET). The physicochemical behavior of the films was evaluated by contact angle measurement, thermogravimetric analysis, infrared spectroscopy and nuclear magnetic resonance. Wear resistance was evaluated by using a ball-on-plate test. The systems with UV-radiation-cured ink were analyzed regarding adherence, flexibility and wettability. Results showed that adding 2% of DIDA plasticizer improved the corrosion resistance and that curing a bilayer film at 90 °C optimizes the film barrier effect. Adding PEG in a concentration of 20 g.L-1 improved the flexibility of the film, making the cross-linking reaction kinetics slower and, in consequence, avoided cracks. With this concentration and curing at 60 °C, the film had better mechanical resistance for systems post-treated with UV ink.

Um dos principais problemas da folha de flandres utilizada no setor de embalagens é a adesão dos revestimentos UV sobre o substrato devido à presença de óxidos na superfície. Dessa forma, o emprego de pré-tratamentos superficiais se faz necessário, e o uso de revestimentos híbridos tem sido proposto para melhorar a aderência e a resistência à corrosão. Contudo, esses revestimentos tendem a serem frágeis e não suportam deformação mecânica. No presente trabalho, os filmes híbridos foram depositados sobre a folha de flandres a fim de avaliar o seu desempenho como revestimento protetor e como pré-tratamento para posterior aplicação do revestimento UV. Visando melhorar o efeito barreira, as folhas de flandres foram revestidas com um filme híbrido obtido a partir de um sol constituído pelos precursores: 3-(trimetoxisililpropil)metacrilato (TMSM) e tetraetoxisilano (TEOS) e Ce(NO3)3 0,01M com adição do plastificante di-isodecil adipato (DIDA) em diferentes concentrações: (0,5, 1, 2 e 4%). Utilizou-se o processo de dip-coating com velocidade de retirada de 10 cm.min-1, com aplicação em monocamada e bicamada, e curados por cura térmica empregando-se duas diferentes temperaturas de cura, 60 °C e 90 °C. Com o objetivo de analisar um pré-tratamento para posterior aplicação do revestimento UV, as folhas de flandres foram revestidas com um filme híbrido obtido a partir de um sol com a mesma formulação citada, substituindo o plastificante DIDA pelo flexibilizante polietilenoglicol (PEG) em diferentes concentrações: (20, 40, 60 e 80 g.L-1). Os filmes foram obtidos e curados conforme descrito anteriormente, além disso, após o pré-tratamento com filme híbrido, a folha de flandres foi submetida ao processo de pintura com tinta uretânica alifática acrilada curada por radiação ultravioleta (UV). Foram empregadas como técnicas para caracterização quanto ao comportamento eletroquímico: monitoramento do potencial de circuito aberto, curvas de polarização potenciodinâmicas, medidas de impedância eletroquímica e svet. O comportamento físico-químico dos filmes foi avaliado por ângulo de contato, termogravimetria, espectroscopia de infravermelho e ressonância magnética nuclear. A resistência ao desgaste foi avaliada pela técnica de esfera sobre plano. Os sistemas de pintura curada por radição ultravioleta foram analisados quanto à adesão, flexibilidade e molhabilidade. Os resultados obtidos, mostraram que a adição de 2% do plastificante di-isodecil adipato melhorou a resistência à corrosão e a cura a 90 °C e com aplicação da bicamada otimizou o efeito barreira do filme. Adição de PEG na concentração de 20 g.L-1 contribuiu para melhorar a flexibilidade do filme retardando a cinética da reação de reticulação e consequentemente evitando a formação de fissuras. Nesta concentração, e curado a 60 °C, o filme melhorou a resistência mecânica para os sistemas com pós-tratamento em tinta UV. / One of the main problems of the tinplate for the packaging sector is the coating adherence of UV coatings on the substrate, due to the presence of oxides on the surface. Thus, it makes necessary the use of surface pretreatments, and the use of hybrid coatings has been proposed to improve the adherence and corrosion resistance. However, these hybrid films tend to be fragile and do not hold on mechanical deformation. In this work, the tinplate was coated with hybrid films aiming to evaluate its performance as protective coating and as pre-treatment for further UV coating application. In order to improve the barrier effect, the tinplate were coated with a hybrid film obtained from a sol constituted by the precursors 3-(trimethoxysilyl)propyl methacrylate (TMSM) and tetraethoxysilane (TEOS), 0.01 mol.L-1 cerium nitrate (Ce(NO3)3) and diisodecyl adipate (DIDA) in different concentrations (0.5, 1, 2 and 4%) as plasticizer. Dip-coating was the process for applying the films with removal rate of 10 cm.min-1. The films were applied in one or two layers and, then, thermally cured at 60 °C or 90 °C. As a pretreatment for further UV coating, the tinplate were coated with a hybrid film with the aforementioned formulation, but replacing the plasticizer DIDA for polyethylene glycol (PEG) in different concentrations (20, 40, 60 e 80 g.L-1). The films were obtained and cured through the same dip-coating process and, after, the samples were painted with aliphatic acrylic urethane coating with ultraviolet radiation curing. The characterization techniques for electrochemical behavior were open circuit potential monitoring, potentiodynamic polarization curves, electrochemical impedance spectroscopy (EIS) and scanning vibrating electrode technique (SVET). The physicochemical behavior of the films was evaluated by contact angle measurement, thermogravimetric analysis, infrared spectroscopy and nuclear magnetic resonance. Wear resistance was evaluated by using a ball-on-plate test. The systems with UV-radiation-cured ink were analyzed regarding adherence, flexibility and wettability. Results showed that adding 2% of DIDA plasticizer improved the corrosion resistance and that curing a bilayer film at 90 °C optimizes the film barrier effect. Adding PEG in a concentration of 20 g.L-1 improved the flexibility of the film, making the cross-linking reaction kinetics slower and, in consequence, avoided cracks. With this concentration and curing at 60 °C, the film had better mechanical resistance for systems post-treated with UV ink.

Orientador: Célia Marina de Alvarenga Freire / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-21T02:18:10Z (GMT). No. of bitstreams: 1 Pelici_BiancadeOliveira_M.pdf: 3905161 bytes, checksum: 85a5220db551a3df1468acd995cba296 (MD5) Previous issue date: 2012 / Resumo: As latas em folha-de-flandres representam a maior parte das embalagens metálicas para conservas alimentícias. Como não são inertes, durante o período de estocagem, ocorre interação com o produto e alguma dissolução de metais pode acontecer, principalmente quando se acondiciona alimentos ácidos. Para minimizar essa interação faz-se uso de revestimentos orgânicos, sendo a resina epóxi-fenólica a mais utilizada. Uma vez que os alimentos são sistemas bioquímicos complexos, na maioria dos estudos relacionados à interação produto/embalagem utiliza-se simulantes, que são substâncias orgânicas com propriedades difusivas análogas aos de um alimento e que apresentam composição química mais simples. Essas substâncias são utilizadas nos ensaios em substituição ao alimento, visando facilitar, agilizar e reduzir custos de procedimentos analíticos. A escolha do simulante é feita de acordo com as características físicoquímicas do alimento, que segue a classificação determinada pela legislação. No caso de alimentos aquosos ácidos o simulante proposto é o ácido acético 3% (m/v). Este trabalho teve por objetivo avaliar soluções simulantes alternativas ao ácido acético, realizando análises quanto ao desempenho de latas com camada nominal de estanho 2,0 g/m2 revestidas com verniz do tipo epóxi-fenólico (dupla camada interna) quando em contato com estas soluções. A técnica de espectroscopia de impedância eletroquímica foi utilizada para monitorar a degradação do revestimento orgânico e para caracterizar suas propriedades de barreira ao longo do tempo quanto a resistência à corrosão; a polarização foi aplicada para determinar a taxa de corrosão e a susceptibilidade do material metálico à corrosão. Também foram obtidas imagens da superfície das amostras através da Microscopia Eletrônica de Varredura e da Espectroscopia de Energia Dispersiva (MEV/EDS) após os ensaios eletroquímicos para complementar a caracterização do filme / Abstract: Tin-plate cans represent most of the cans for canned food. Since they are not inert, during the storage period, interaction occurs with the product and metal dissolution can occur, especially when it is acid food. To minimize this interaction it is used organic coatings, and epoxy-phenolic resin is the the most used. As the foods are complex biochemical systems, in most of the studies related to the interaction product / package simulants are used, that are organic substances that are analogous to the diffusive properties of food and have simpler composition. These substances are used in the tests to replace the food, to facilitate, speed up and reduce costs in analytical procedures. The choice of simulating is made according to the physico-chemical properties of the food, which follows the classification determined by the legislation. For acidic aqueous food the proposed simulant is acetic acid 3% (w / v). This work aimed to evaluate alternative solutions to acetic acid simulating, analyzing the performance in cans with nominal layer of tin 2.0 g/m2 coated with lacquer-type epoxy phenolic (double inner layer) when in contact with these solutions . The technique of electrochemical impedance spectroscopy was used to monitor the degradation of organic coating and to characterize their barrier properties over time as corrosion resistance; polarization was applied to determine the corrosion rate and susceptibility to corrosion of metallic material. Also images were also obtained of the sample surfaces by Scanning Electron Microscopy and Energy Dispersive Spectroscopy (SEM / EDS) after the electrochemical tests to complement the characterization of the film / Mestrado / Materiais e Processos de Fabricação / Mestra em Engenharia Mecânica

Chromium passivation treatment on tinplate is important in stabilising the active tin surface in terms of oxidation resistance, sulphide stain resistance and ensuring good lacquer adhesion properties. Through this research, the reason was explored why dip passivation treatment, in sodium dichromate, provides superior lacquer adhesion properties on tinplate compared to electrolytic sodium dichromate (CDC) treatments. A critical assessment of the current knowledge of chromium passivation treatments on tinplate formed the basis of the experimental work. Through electrochemical and surface analytical techniques (X-Ray Photoelectron Spectroscopy and Auger Electron Spectroscopy) both dip and CDC treated tinplate surfaces were characterised in terms of surface species. It was shown through XPS, using angle resolved techniques, that no metallic chromium forms on the tinplate surface during CDC treatments. Furthermore, a difference in chromium surface species was established for the dip and CDC processes showing additional SnO and Cr(OH)3.nH2O species for the latter. Complementary to these findings, it was verified that the formation of additional chromium hydroxide species is a function of pH, governed by the applied cathodic current during the CDC process itself. The inferior adhesion properties of CDC treated tinplate were shown to be related to the difference in the respective surface species formed during dip and CDC applications. Copyright 2004, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. Please cite as follows: Biermann, MC 2004, A critical assessment of the current understanding of chromium passivation treatments in tinplate, MSc dissertation, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-04172007-123305 / > / Dissertation (MSc(Applied Sciences))--University of Pretoria, 2007. / Materials Science and Metallurgical Engineering / unrestricted