In general, the Internet represents an unsecured medium of data transfer. Besides the rising popularity of the Internet, the matters of safety are getting to the foreground of importance. Anybody would be able to gain access to the computer network or to other valuable information if no algorithm of verifying the genuineness of identity were used. It is necessary to secure not only the access to the documents but also the content itself, which could be modified during the transfer through an unsecured medium. Last but not least, without the discretion provided by cryptography, the information may become literally public. To provide security and protection for the communicating participants the problems mentioned above are solved with the help of cryptographic techniques. The verification of the identity and the integrity of messages, the credibility of document’s ownership and safe data transfer through an unsecured medium are all the aspects, which the field of communication security on the Internet, thus the public key infrastructure, deals with. The electronic signature, as a part of the security area, is one of many advertised themes nowadays in Czech Republic. The aim of this master’s thesis is to acquaint the reader with the necessary technological procedures of digital signature, such as cryptographic techniques, public key infrastructure and timestamp. The practical part of this thesis consists of a suggested implementation of a web application in the programming language ASP.NET, which forms a certification authority with an opportunity of claiming a timestamp to authorize timestamps. After the problematic of cryptography was explained in the first chapter, the term of electronic signature has been introduced in the second chapter. Very important information, as far as the electronic signature of documents is concerned, is the time of the document’s creation and the subsequent signature verification by an appropriate authority. So the following part of the thesis is dedicated to the timestamp and to the authority of its verification. The fourth section deals with the large scale of public key infrastructure. The fifth part focuses on the description of the support for the whole problem mentioned so far using Microsoft’s programming language ASP.NET. The final sixth chapter represents the practical part of the thesis, namely the web application itself, where the individual modules of the application with its functions are described.

The diploma thesis is focused on the preparation of test samples of paint-filled micronized mica and analysis of electrical properties of insulating material values in different environmental conditions. For this purpose, it was created five sets of composite paint primers with different ratio of mica. Samples were gradually exposed to the environment relative humidity of 0%, 33%, 55%, 65% and 75%. For each environment with a defined moisture characteristics were observed in samples exposed to the temperature of 20 to 50 ° C. The diploma paper analyzed the influence of the mass implementation of mica in each set of samples and placed on the surface structure of samples.

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2015-05-22T11:12:34Z No. of bitstreams: 2 Dissertação - Lucilla Ribeiro Àvila - 2012.pdf: 1507401 bytes, checksum: bf2c2e095da09a43d8131413a5b45a44 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2015-05-22T11:14:19Z (GMT) No. of bitstreams: 2 Dissertação - Lucilla Ribeiro Àvila - 2012.pdf: 1507401 bytes, checksum: bf2c2e095da09a43d8131413a5b45a44 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2015-05-22T11:14:19Z (GMT). No. of bitstreams: 2 Dissertação - Lucilla Ribeiro Àvila - 2012.pdf: 1507401 bytes, checksum: bf2c2e095da09a43d8131413a5b45a44 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2012-02-17 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Introduction: Leishmania (Viannia) braziliensis is the most common etiologic agent of cutaneous leishmaniasis in Brazil. About 1 to 10% of patients infected with this species of parasite develop the mucosal leishmaniasis, whose lesions are progressive, destructive and are characterized by a strong specific immune response. The mechanisms for the development of mucosal leishmaniasis are poorly known, but it is possible that proteins associated with virulence of the parasite, such as META2 LRR17 and/or related with the induction of a strong immune response, such as STI and TSA, participate in the pathogenesis disease, causing the appearance of metastases in the mucosa. Objective: To evaluate the expression of proteins META2, LRR17, STI1 and TSA in promastigotes and amastigotes of Leishmania (Viannia) braziliensis derived from cutaneous or mucosal lesions. Methods: It was used three isolates from cutaneous lesions of patients (JCJ8c, and RPL5c SMB7c) and three isolates from mucosal lesions (ASL9m, and JBC8m PPS6m). Amastigotes of the isolates were obtained after inoculation of biopsies in mice knockout in interferon gamma and promastigotes in logarithmic or stationary phase obtained in culture in Grace's medium. The kinetics of growth in culture of isolates was performed by counting daily over ten days in the flow cytometer. The expression of proteins of each isolate was assessed by immunoblotting technique and by flow cytometry, the latter being used only to evaluate the expression of proteins whose expression was significant difference between isolates from cutaneous or mucosal lesions. Results: Promastigotes in stationary phase of the isolates SMB7c and JBC8m were the most expressed the protein META2. The greatest expression of this protein in parasites coincided with more severe lesions, since despite of isolated SMB7c being of cutaneous origin, the patient also presented mucosal lesion, and in the isolated JBC8m the patient presented return of lesions. Proteins LRR17 and STI1 were not expressed in significant amount in both promastigotes and amastigotes of different isolates. TSA protein was expressed at higher levels in promastigotes stationary phase and amastigotes of the xi isolates from patients with mucosal lesions, and this difference was also observed in flow cytometric analysis. Conclusion: The results suggest an association of META2 protein, which is related to the virulence of the parasite, with the generation of more severe lesions in the mucosal, since the highest expression of the protein was isolate from patients with mucocutaneous lesions and patients whose treatment was not effective. TSA, which is associated with antigenicity and virulence of the parasite was also expressed in greater amount in isolates from patients with mucosal lesions. The hypothesis is that, despite TSA protein to induce a protective immune response could be conferring protection in the Leishmania after entering the phagolysosomes by being an antioxidant protein. This protection favored the persistence of parasites and later generation of mucosal lesions. / Introdução: A Leishmania (Viannia) braziliensis é o agente etiológico mais frequente da leishmaniose tegumentar no Brasil. Cerca de 1 a 10% dos pacientes infectados com essa espécie de parasito desenvolvem a leishmaniose mucosa, cujas lesões são progressivas, destrutivas e caracteriza-se por uma forte resposta imune específica. Os mecanismos para o desenvolvimento da leishmaniose mucosa são pouco conhecidos, porém é possível que proteínas associadas à virulência do parasito, como a META2 e o LRR17 e /ou relacionadas com a indução de uma forte resposta imune, como a STI e a TSA, participem da patogênese da doença, ocasionando o aparecimento de metástase na mucosa. Objetivo: Avaliar a expressão das proteínas META2, LRR17, STI1 e TSA em formas promastigotas e amastigotas de Leishmania (Viannia) braziliensis oriundas de lesões cutâneas ou mucosas. Métodos: Foram utilizados três isolados oriundos de lesões cutâneas de pacientes (JCJ8c, RPL5c e SMB7c) e três isolados oriundos de lesões mucosas (ASL9m, JBC8m e PPS6m). Formas amastigotas dos isolados foram obtidas após o inóculo das biópsias em camundongos deficientes em interferon gama e as formas promastigotas em fase estacionária ou logarítmicas obtidas em cultura em meio de Grace. A cinética do crescimento dos isolados em cultura foi realizada através de contagem diária durante dez dias em citômetro de fluxo. A expressão das proteínas de cada isolado foi avaliada através da técnica de immunoblotting e por citometria de fluxo, sendo esta última utilizada somente para avaliar a expressão de proteínas cuja diferença na expressão foi significante entre os isolados de lesões cutâneas ou mucosas. Resultados: Promastigotas em fase estacionária dos isolados SMB7c e JBC8m foram as que mais expressaram a proteína META2. A maior expressão desta proteína nos parasitos coincidiu com lesões mais graves, visto que o isolado SMB7c apesar de ser de origem cutânea, o paciente apresentou também lesão na mucosa e no isolado JBC8m o paciente teve o retorno das lesões. As proteínas LRR17 e STI1 não foram expressas em quantidades significativamente diferentes tanto em promastigotas quanto em amastigotas dos diferentes isolados. A proteína TSA foi expressa em maior quantidade nas formas promastigotas em fase estacionária e em amastigotas dos isolados oriundos de pacientes com lesão mucosa, sendo que essa diferença também foi observada na análise citométrica. Conclusão: Os resultados sugerem uma associação da proteína META2, que está relacionada com a virulência do parasito, com a geração de lesões mais graves nas mucosas, visto que a maior expressão da proteína foi em isolados de pacientes com lesão mucocutânea e de pacientes que o tratamento não foi eficaz. A TSA, que está associada à antigenicidade e também virulência do parasito foi mais expressa em isolados oriundos de pacientes com lesão mucosa. A hipótese é que, a proteína TSA apesar de induzir uma resposta imune protetora, estaria conferindo proteção da leishmânia após a entrada no fagolisossomo por ser uma proteína antioxidante. Esta proteção favorecia a persistência dos parasitos e mais tarde a geração de lesões na mucosa.

The presented work deals with preparation of test samples filled microparticles of mica and nanoparticles of silicon dioxide (SiO2). Monitors the impact of climatic conditions and filler on electrical properties of composite materials. Electrical properties of composite materials are measured by dielectric relaxation spectroscopy. Test samples influence of epoxide resin TSA 220S and polyester resin DOLPHON XL 2102. Varnishes are modified with different weight percentage of nanoparticles of silicon dioxide, or micronized mica. The results of this project are frequency dependencies of parts of complex permittivity and their evaluation.

Le virus de la leucémie bovine (BLV) est un rétrovirus B-lymphotrope qui a été identifié comme l’agent étiologique de la leucose bovine enzootique. L’infection par le BLV se caractérise par l’absence de virémie due à la latence du virus dans la majorité des cellules infectées. Cette latence résulte de la répression transcriptionnelle du provirus in vivo; elle favorise très probablement le développement tumoral en permettant aux cellules infectées d’échapper au système immunitaire de l’hôte. Cependant, la transcription du BLV peut être activée de manière rapide et très efficace par la protéine virale TaxBLV. La trans-activation par TaxBLV joue un rôle crucial dans la pathogenèse associée au BLV car elle permet la production de nouvelles particules virales nécessaires à la propagation du virus. Au cours de notre travail de thèse, nous avons étudié différents mécanismes impliqués au cours de ces deux phases clés (latence et trans-activation par TaxBLV) de l’expression du BLV. Le promoteur unique de la transcription du BLV se situe à l’extrémité 5’ du génome proviral, dans la longue répétition terminale 5’ (LTR 5’) composée des régions U3, R et U5. Les mécanismes impliqués dans la trans-activation du LTR 5’ par TaxBLV sont encore mal connus. La trans-activation du LTR 5’ du BLV par TaxBLV requiert la présence de trois répétitions imparfaites de 21pb (TxREs pour Tax Responsive Elements) agissant en cis et situées dans la région U3. Chacune des TxREs possède dans sa partie centrale un motif imparfait de 8 nucléotides correspondant au site de liaison des protéines de la famille CREB/ATF (sites CREs pour cAMP-Responsive Element). Des expériences de retard de migration sur gel ont montré que les protéines CREB, ATF-1 et ATF-2 lient les CREs viraux in vitro. Comme TaxBLV ne semble pas capable de lier directement l’ADN du LTR, il a été suggéré que les facteurs CREB/ATF serviraient de médiateurs de la trans-activation par TaxBLV. De plus, il a également été suggéré au cours de ces dernières années que les facteurs de transcription CREB/ATF jouent aussi un rôle essentiel en l’absence de TaxBLV lors de l’initiation de la transcription virale. CREB/ATF sont connus pour recruter les co-activateurs CBP/p300 qui possèdent une activité histone-acétyltransférase, suggérant qu’à l’instar d’autres rétrovirus tels que HIV-I ou HTLV-I, l’acétylation protéique pourrait jouer un rôle important dans la régulation de la transcription du BLV. Au cours de la première partie de ce travail, nous avons mis en évidence un synergisme transcriptionnel entre TaxBLV et les inhibiteurs de désacétylases TSA et NaBut, indiquant que l’acétylation protéique joue un rôle important dans la trans-activation par TaxBLV. Nous avons ensuite montré que ni TaxBLV, ni son médiateur CREB ne sont acétylés in vivo au niveau d’un résidu lysine interne, mais que la TSA synergise avec TaxBLV via un mécanisme indirect, sensible à l’inhibition de la synthèse protéique. Fonctionnellement, CREB/ATF semblent jouer un rôle crucial dans le synergisme TaxBLV/TSA car la mutation des CREs viraux ou la sur-expression d’un dominant négatif CREB inhibent ce synergisme. Des expériences de gel retard et de ChIP ont démontré, in vitro et in vivo, que les inhibiteurs de désacétylases augmentent la liaison des facteurs CREB/ATF aux TxREs. Nos résultats suggèrent donc que le synergisme TaxBLV/TSA serait dû à une augmentation de la trans-activation par TaxBLV observée suite à l’augmentation, induite par la TSA, du recrutement de CREB/ATF au niveau des TxREs. CREB/ATF appartiennent à la famille des facteurs de transcription CREB/CREM/ATF agissant au niveau des promoteurs contenant des éléments CREs. Cependant, la liaison de CREM aux CREs imparfaits du LTR du BLV n’a jamais été étudiée. Dans la seconde partie de ce travail, nous avons montré que des isoformes du gène CREM sont exprimées dans des PBMCs isolés à partir d’un mouton infecté par le BLV et que ces protéines CREM sont capables de lier in vitro et in vivo le promoteur du BLV, via les motifs CREs présents au centre de chacune des TxREs. Des analyses fonctionnelles ont ensuite montré qu’en l’absence de TaxBLV, la surexpression de l’isoforme activatrice CREMt induit la transcription dirigée par le LTR 5’ du BLV. Les résultats que nous avons obtenus suggèrent que CREMt serait capable d’activer la transcription du BLV en réponse à l’activation des cellules B infectées, via la phosphorylation de la sérine 117 de CREMt et via le recrutement par CREMt des co-activateurs CBP/p300. CREMt serait donc impliqué dans les stades précoces de l’initiation de la transcription du BLV. Cependant, nous avons montré que CREMt n’est pas impliqué dans les stades tardifs de l’expression virale puisqu’il ne semble pas capable d’induire la trans-activation par TaxBLV. Au contraire, nous avons montré par des expériences de compétition que CREMt diminue la trans-activation par TaxBLV lorsque celle-ci est induite par CREB, probablement en entrant en compétition avec CREB pour la liaison au niveau des TxREs. L’expression du gène CREM est régulée transcriptionnellement et post-transcriptionnellement et mène à la production de différentes isoformes capables d’agir comme des activateurs ou des répresseurs de la transcription. Des expériences de RT-PCR nous ont permis de mettre en évidence la présence d’isoformes répressives ICER dans les cellules YR2 infectées par le BLV. Par des expériences de transfection transitoire, nous avons montré qu’ICER est capable de réprimer la trans-activation par TaxBLV, suggérant qu’ICER retarderait la trans-activation par TaxBLV afin d’échapper au système immunitaire de l’hôte infecté jusqu’à ce qu’un niveau suffisant du trans-activateur TaxBLV soit produit.

L’étiologie des troubles du spectre autistique (TSA) est multifactorielle mettant en jeu une forte composante génétique ainsi que des facteurs environnementaux. A ce jour, il n’existe aucun biomarqueur facilitant un diagnostic précoce des TSA, ce qui permettrait une meilleure prise en charge des patients. De plus, les mécanismes physiopathologiques sont encore mal connus. La majorité des études sur les TSA ont été réalisées sur des populations occidentales. Ainsi, nous avons voulu étudier un groupe de patients libanais atteints de TSA. Nos objectifs s’articulent autour de trois volets : 1) L’identification de facteurs de risques environnementaux dans le but de mieux comprendre la pathologie. Les résultats de cette étude ont montré que plusieurs facteurs tels que la consanguinité, le stress au cours de la grossesse et la prématurité semblent être des facteurs de risques. 2) L’identification des variations structurales dans le génome des enfants atteints de TSA afin d'évaluer la contribution de CNV par l'approche de CGH array à haute résolution. Cette étude nous a permis d’identifier de nouveaux gènes dans les TSA ainsi de confirmer la présence des régions et des gènes déjà cités dans des études précédentes sur les TSA. 3) L’identification des métabolites urinaires et des voies métaboliques associés afin de proposer des biomarqueurs aidant à un diagnostic précoce et à une meilleure compréhension de la physiopathologie de la maladie. De nouveaux métabolites ont été identifiés, comme nous avons confirmé des variations anomalies déjà citées dans la littérature concernant certains métabolites qui pourraient représenter des marqueurs robustes de la maladie. / The etiology of autism spectrum disorders (ASD) is multifactorial involving a strong genetic component as well as environmental factors. To date, there is no biomarker facilitating early diagnosis of ASD to improve patient management and outcomes. In addition, the physiopathological mechanisms are still poorly understood. Most studies on ASD have been conducted in Western populations. Thus, we wanted to study a group of Lebanese patients with ASD. Our objectives focus around three aspects: 1) The identification of environmental risk factors in order to better understand the pathology. The results of this study showed that several factors such as consanguinity, stress during pregnancy and prematurity appear to be risk factors. 2) The identification of structural variations in the genome of children with ASD in order to evaluate the contribution of CNV by high resolution CGH array approach. This study allowed us to identify new genes in ASD as well as to confirm the presence of regions and genes already cited in previous ASD studies. 3) The identification of metabolites and associated metabolic pathways to provide biomarkers for early diagnosis and to better understanding of the pathophysiology of the disease. New metabolites have been identified and we have confirmed variations already mentioned in the literature concerning certain metabolites that could represent robust markers of the disease.

Introdução: A formação da memória envolve mudanças na expressão de genes neuronais. Remodelações epigenéticas da cromatina e modificações pós-traducionais reversíveis no DNA ou nas proteínas histonas representam mecanismos centrais na regulação da expressão gênica durante o desenvolvimento do cérebro e a aprendizagem inicial ou recuperação da memória. Desequilíbrios nos níveis de acetilação de histonas estão associados à uma ampla variedade de desordens cerebrais. Histonas deacetilases (HDACs) desempenham um papel fundamental na homeostase da acetilação de histonas e na regulação de atividades celulares fundamentais como a transcrição, tornando-as um foco de estudo. Evidências mostram que a administração de inibidores de histonas deacetilases (HDACis) restauram a memória associada à regulação da expressão gênica e melhora a memória em ratos. Estudos em modelos animais têm mostrado que a formação da memória envolve uma série de alterações bioquímicas em várias áreas do sistema nervoso central, entre as quais se destacam o hipocampo e a amígdala basolateral (BLA). Neste contexto, fármacos experimentais, como a tricostatina A (TSA), que atuam sobre mecanismos epigenéticos, têm sido recentemente propostos como potenciais terapias para o tratamento de disfunção cognitiva e memória associados a doenças neurológicas e psiquiátricas. Objetivo: Neste trabalho objetivamos compreender e elucidar o papel da acetilação de histonas em processos envolvidos na modulação da memória utilizando o fármaco TSA e se baseia na hipótese de que a atividade de HDACs é essencial para a modulação das respostas de aprendizado na tarefa de esquiva inibitória (IA). Métodos: Ratos Wistar foram canulados bilateralmente na amígdala. Os efeitos das micro-infusões intra-amigdalares de TSA foram observados na consolidação e na extinção da memória após o treino na tarefa de esquiva inibitória e nos níveis do fator neurotrófico derivado do cérebro (BDNF) na BLA e no hipocampo referentes à consolidação da memória. Resultados: Os resultados demonstraram que a infusão intra-amigdalar de TSA 1.5 h, 3 h e 6 h após o treino na tarefa de esquiva inibitória resulta na melhora da memória de longa duração (LTM). TSA acelerou a extinção da memória quando infundido imediatamente pós-teste. Além disso, aumentou os níveis de BDNF no hipocampo. Conclusão: Estes resultados indicam que eventos epigenéticos possuem um papel importante no aprendizado e na memória através da atividade de HDACs. / Introduction: Memory formation involves changes in the expression of neuronal genes. Epigenetic remodeling of chromatin and reversible post-translational modifications in the DNA or in the histone proteins represent central mechanisms in the regulation of gene expression during brain development and early learning or memory retrieval. Imbalances in the levels of histone acetylation are associated with a wide variety of brain disorders. Histone deacetylases (HDACs) play a key role in homeostasis of histone acetylation and regulation of fundamental cellular activities, such as transcription, making them a focus of study. Evidences shows that the administration of histone deacetylases inhibitors (HDACis) restore the memory associated with the regulation of gene expression and improves memory in rats. Studies in animal models have shown that memory formation involves a series of biochemical changes in several areas of the central nervous system, which the hippocampus and basolateral amygdala (BLA) are the most highlighted. In this context, experimental drugs, such as trichostatin A (TSA), that act on epigenetic mechanisms, have recently been proposed as potential therapies for the treatment of memory and cognitive dysfunction associated with psychiatric and neurological disorders. Objective: In this work we aimed to understand and elucidate the role of histone acetylation in processes involved in memory modulation using the drug TSA and is based on the hypothesis that HDACs activity is essential for the modulation of learning answers in the inhibitory avoidance (IA) task. Methods: Wistar rats were cannulated bilaterally in the amygdala. The effects of TSA micro-infusions into the BLA were observed in the consolidation and extinction of memory after training in the inhibitory avoidance task and the levels of brain-derived neurotrophic factor (BDNF) in the BLA and hippocampus related to memory consolidation. Results: The results demonstrated that the TSA infusion into BLA 1.5 h , 3 h and 6 h posttraining in the inhibitory avoidance task results in improved long-term memory (LTM). TSA accelerated the extinction of memory when infused immediately post-test. In addition, increased levels of BDNF in the hippocampus. Conclusion: These results indicate that epigenetic events play an important role in learning and memory by HDAC activity.

Alumínio Pulverizado Termicamente (TSA) é amplamente utilizado em instalações offshore como revestimento de ânodo de sacrifício em tubulações de aço carbono. O transporte e a instalação desses componentes podem levar a pequenos danos no revestimento, o que pode expor a superfície do aço à água do mar. Sabe-se que o depósito calcário é formado na superfície do aço polarizado catodicamente. Assim, esta pesquisa avaliou o TSA aplicado por sistema de pulverização de arco duplo (TWAS) no aço ao carbono S355J2 + N quando ocorrem danos (holidays) para estudar a formação de depósitos calcários no aço e adquirir dados sobre o desempenho do TSA sob altas temperaturas. A aplicação de diferentes condições também foi considerada: presença de selantes; liga do revestimento (99,5% de Al e Al-5% de Mg) e condições enterradas/não enterradas. Dois tipos de experimentos foram realizados: i) testes em potencial livre sob temperaturas constantes (30, 60 e 90°C) e diferentes tamanhos de holidays (expondo 5, 10 e 20% da superfície do aço) e ii) testes sob gradient térmico onde óleo a ~125°C foi adicionado em uma torre polimérica e água externa a ~10°C ficou em contato com a superfície das amostras (tanto potencial livre como polarização de -950 mVAg/AgCl foram aplicados). Análises incluíram inspeção visual, microscópio eletrônico de varredura e difração de Raio-X. A partir dos testes em temperaturas constante, o TSA atingiu um bom potencial de proteção (-800 a -900 mVAg/AgCl) e pouca diferença nos resultados devido à diferença na composição doTSA e no tamanho do holiday foi observada. As taxas de corrosão foram mantidas entre 0,02 e 0,01 mm/ano. No ensaio sob gradiente térmico e potencial livre, a perda de revestimento e as taxas de corrosão foram de 0,4 a 0,002 mm/ano. Além disso, o potencial alcançado foi de uma faixa menor do que a obtida anteriormente (-745 a -835 mVAg/AgCl). No entanto, quando o TSA foi combinado com proteção catódica externa e gradiente térmico, a espessura do TSA foi satisfatório e as taxas de corrosão obtidas foram inferiores a 0,076 mm/ano. O depósito calcário formado no holiday protegeu o aço contra a corrosão e seu mecanismo de crescimento baseado nesta pesquisa foi construído. / Thermally Sprayed Aluminium (TSA) is widely used in offshore facilities as sacrificial anode coating for carbon-steel risers and pipelines. Transportation and installation of those components can lead to small damages in the coating, which can expose the steel surface to the seawater. It is known that calcareous deposit is formed on the cathodically polarised steel surface. Thus, this research evaluated the TSA applied by twin wire arc spray system (TWAS) on S355J2+N carbon-steel when damage (holidays) is present in order to study the calcareous deposit formation on steel and acquire data regarding the TSA performance at high temperatures. Application of different conditions was also considered: presence of sealing; coating alloy (99.5%Al and Al-5%Mg) and buried/unburied conditions. Generally, two types of experiment were conducted – i) tests at free potential at steady temperatures (30, 60 and 90°C) and different holiday sizes (exposing 5, 10 and 20% of the steel surface) and ii) tests under thermal gradient where oil at ~125°C was added in polymeric tower and external water at ~10°C was in contact with the samples surface (both free potential and polarisation of -950 mVAg/AgCl were applied). Methodology of analyses included visual inspection, scanning electron microscope and X-ray Diffraction. From the tests at steady temperatures, the TSA reached a very good protective potential (-800 to -900 mVAg/AgCl) and little difference in results due to difference in TSA composition and holiday size was observed. Corrosion rates were kept between 0.02 and 0.01 mm/year. From the thermal gradient test under free potential, the coating loss and corrosion rates were 0.4 to 0.002 mm/year. Also, the potential achieved was in a lower range than previously obtained (-745 to -835 mVAg/AgCl). However, when TSA was combined with external cathodic protection and thermal gradient, the thickness of the TSA was satisfactory and corrosion rates obtained were below 0.076 mm/year. The calcareous deposit formed within the holiday protected the steel substrate against corrosion and its growth mechanism based in this research was built.

The present study investigates the effect of fluorine species during anodizing of aluminium and AA2024-T3 alloy in sulphuric acid and tartaric-sulphuric acid (TSA) electrolytes. The investigation comprises four main parts; (i) Effects of fluoride on barrier film formation on aluminium. (ii) Effects of fluoride and fluorozirconic acid (FZ) on porous film growth on aluminium in sulphuric acid. (iii) Effects of FZ on porous film growth on aluminium and AA 2024-T3 alloy in sulphuric acid and TSA. (iv) Effects on anodizing of other fluoroacids (fluoroboric (FB), fluorosilicic (FS) and fluorotitanic acid (FT)). The anodic films were examined by analytical scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, Rutherford backscattering spectroscopy, nuclear reaction analysis and glow discharge optical emission spectroscopy. The behaviour of fluoride ions during the growth of barrier-type films on aluminium was investigated in ammonium pentaborate solution with added sodium fluoride. Additions of up to 3.5 x 10-3 M sodium fluoride had a negligible influence on the film growth. In contrast, 3.5 x 10-2 M sodium fluoride reduced the efficiency to 60% as fluoride ions promoted field-assisted ejection of Al3+ ions from the film. Incorporated fluoride ions migrated inwards at a rate about twice that of O2- ions, forming a fluoride-rich layer at the film base. The study of the influence of FZ on formation of porous anodic films in sulphuric acid and TSA employed a range of anodizing voltages, electrolyte temperatures and anodizing times. Fluoroacid increased the growth rate, with a reducing influence as the temperature increased. The films contained fluoride and sulphate ions, zirconium was not detected. The fluoride concentration decreased with increasing temperature, whereas the sulphate concentration was unaffected. Anodizing aluminium and AA 2024-T3 alloy in other fluoroacids resulted in similar influences on the anodizing behaviour as FZ. The differences in growth rate, film composition and film morphology were comparatively small and did not show a systematic dependence on the type of fluoroacid employed. Boron, silicon and titanium were not detected in the films.

Aluminium alloys are widely used in the aerospace industry due to their lightweight and high specific strength. However, these alloys are particularly sensitive to localized corrosion in chloride environments and need to be protected by a robust system. One of the protection methodologies consists in anodizing. The produced layer increases the corrosion resistance and also serves as anchoring site for organic coatings application. Chromium-based anodizing has been usually employed, nevertheless, as chromate compounds are toxic for health and the environment, chromium-based surface treatments will be prohibited in the aerospace industry in a near future. Tartaric-sulphuric acid (TSA) anodizing is a promising environment compliant alternative, which is already being used at industrial level with appropriate corrosion protection and paint adhesion properties. This study aims at proposing a hybrid sol-gel treatment after TSA anodizing of AA2524 specimens in order to improve the corrosion resistance of the anodized layer while maintaining its compatibility with organic coatings. For this, anodic aluminium oxides (AAO) were produced at different anodizing voltages and protected by dip-coating with a hybrid sol-gel layer obtained from a tetraethoxysilane (TEOS) and 3-glycidoxypropyltrimethoxysilane (GPTMS) hydrolysis solution with high water content. Corrosion resistance evaluation was carried out by means of electrochemical impedance spectroscopy (EIS) in NaCl 0.1 mol L-1 and salt-spray chamber exposure (ASTM B117-11 standard). The morphology of the anodic porous layer was investigated by means of FE-SEM, whereas glow discharge optical emission spectroscopy (GDOES) was employed to evaluate the distribution of the sol-gel layer within the porous AAO. FE-SEM characterization confirmed that the layer properties (pore distribution, porosity and thickness) were strongly dependent on the anodizing conditions, whereas GDOES depth profile showed penetration of the hybrid coating within the pores of the anodized layer. The two characterization techniques showed inefficient surface sol-gel coverage for the samples anodized at higher voltage, likely due to insufficient sol-gel deposition. The results of the EIS characterization tests up to 1008 h (42 days) showed that, irrespectively to the anodizing voltage, the hybrid sol-gel protected AAO was stable with only slight evolution of the diagrams with immersion time. Moreover, the hybrid coating protected samples presented higher low frequency impedance modulus than hydrothermally sealed (HTSed) reference TSA anodized samples, which was confirmed by electrical equivalent circuit (EEC) fitting of the EIS data. EEC fitting also revealed that the resistance of the pores to electrolyte penetration was increased by the application of the sol-gel coating when compared to the resistance of the HTSed reference samples and indicated better anticorrosion performance for the sample anodized at 16 V. These results were confirmed by the salt-spray tests. Investigation on the ageing of the hybrid sol-gel hydrolysis solution showed that its viscosity hardly changed up to two weeks of test and that hybrid coatings applied from these solutions were stable and afforded good corrosion protection to the TSA anodized substrate, an improvement of the anticorrosion properties of the hybrid coating was verified for an ageing time of 168 h. Preliminary tests performed with a solvent-free organic coating (epoxy) indicated good compatibility with the hybrid TEOS-GPTMS coating characterized by very high impedance and good stability upon exposure to the salt-spray chamber. / Ligas de alumínio são muito utilizadas na indústria aeronáutica por serem materiais leves e altamente resistentes. Porém, essas ligas são particularmente sensíveis à corrosão localizada em meios que contêm cloretos, e precisam de sistemas robustos de proteção. Uma das metodologias de proteção consiste em anodização. A camada produzida aumenta a resistência à corrosão e também serve como sítio de ancoragem para aplicação de revestimentos orgânicos. A anodização crômica tem sido usualmente empregada na indústria aeronáutica. No entanto, como compostos contendo íons cromato são tóxicos para a saúde e para o meio-ambiente, tratamentos de superfície à base de cromo serão proibidos na indústria espacial em um futuro próximo. Anodização em banho de ácido sulfúrico-tartárico (TSA) é uma alternativa promissora e ambientalmente compatível, a qual já está sendo usada industrialmente com apropriada proteção à corrosão e adesão para pintura. Este estudo tem como objetivo propor um tratamento utilizando um revestimento híbrido sol-gel para melhorar a resistência à corrosão da liga AA2524 anodizada em TSA e que mantenha sua compatibilidade com revestimentos orgânicos. Para isso, camadas anodizadas de alumínio (CAA) foram produzidas em diferentes voltagens e protegidas por camada de híbrido sol-gel obtida pela hidrólise de tetraetilortosilano (TEOS) e glicidóxipropiltrimetóxisilano (GPTMS) em solução com alto teor de água e aplicada pela técnica de dip-coating. A avaliação da resistência à corrosão foi realizada através de espectroscopia de impedância eletroquímica (EIS) em NaCl 0,1 mol.L-1 e por exposição à câmara de névoa salina (norma ASTM B117-11). A morfologia da camada porosa foi investigada por MEV e a espectroscopia de emissão óptica por descarga luminescente (GDOES) foi empregada para avaliar a distribuição do híbrido sol-gel no interior dos poros da camada porosa. As caracterizações por MEV confirmaram que as propriedades da camada (distribuição dos poros, porosidade e espessura) são fortemente dependentes das condições de anodização, e a composição em profundidade obtida por GDOES mostrou que o revestimento híbrido penetrou nos poros da camada anodizada. As duas técnicas de caracterização mostraram uma cobertura ineficiente da camada sol-gel para as amostras anodizadas nas voltagens mais elevadas, provavelmente devido à deposição insuficiente do híbrido. Os testes de EIS com duração de até 1008 h (42 dias) mostraram que, independentemente da voltagem de anodização empregada, a camada anódica coberta com sol-gel ficou estável ocorrendo apenas pequenas evoluções dos diagramas com o tempo de imersão. Além do mais, as amostras protegidas com o revestimento híbrido apresentaram maiores valores de módulo de impedância em baixa frequência do que as amostras anodizadas em TSA e hidrotermicamente seladas (HTsed) usadas como referências. Essa tendência foi confirmada pelo ajuste com circuitos elétricos equivalentes (EEC) dos resultados de EIS que também mostrou que a aplicação do sol-gel híbrido torna mais difícil a penetração do eletrólito agressivo nos poros da camada anodizada quando comparada com as amostras HTSed, e indicou melhor desempenho anticorrosivo para a amostra anodizada em 16 V. Esses resultados foram confirmados pelos testes de névoa salina. A investigação do envelhecimento da solução de sol-gel mostrou pouca mudança na viscosidade da solução de hidrólise em duas semanas de testes e que os revestimentos híbridos aplicados a partir dessas soluções foram estáveis e promoveram boa proteção à corrosão para as amostras anodizadas em TSA, com melhora das propriedades anticorrosivas após 168 h de envelhecimento. Testes preliminares realizados com revestimento orgânico livre de solvente (epóxi) indicaram boa compatibilidade deste com o revestimento híbrido TEOS-GPTMS. O revestimento epóxi propiciou valores de módulo de impedância elevados e estáveis e também boa estabilidade após exposição à câmara de névoa salina quando aplicado sobre o revestimento híbrido aplicado sobre a liga 2524.