A construção civil vem se deparando com uma dualidade que envolve avanços dos métodos de cálculo e tecnologia dos materiais contraposto ao incremento das patologias das construções. Inúmeros levantamentos estatísticos, realizados nos últimos anos, vem demonstrando a grande incidência e repercussão dos processos patológicos atuantes sobre as estruturas de concreto. Vários estudos comprovam que a corrosão de armaduras no concreto é de grande incidência nas construções e, na maioria dos casos, aquele que gera os maiores problemas, tanto em termos de custo como de segurança. Isto explica porque técnicas de medição de resistência à corrosão vêm sendo intensamente estudadas. Todavia, dada a complexidade do assunto e a falta de normalização específica, observa-se a existência de uma grande diversidade de métodos de ensaio, aliada à ausência de uma padronização dos tipos e condições de ensaio. A maioria dos pesquisadores adapta ensaios anteriormente realizados, sem realizar estudos específicos sobre a eficiência e reprodutibilidade dos mesmos. O presente trabalho descreve um estudo realizado com o intuito de avaliar qual os efeitos das variações das condições de ensaio, como tempo de exposição e diferença de potencial induzida, no comportamento de corpos-de-prova de diversas relações água/cimento testados pela metodologia CAIM, um tipo de ensaio acelerado comparativo de corrosão por imersão em solução salina, que já foi empregado em várias pesquisas no LEME. O objetivo é entender como o ensaio reage a variações de método, verificando sua sensibilidade a estas e definindo quais as condições padrão mais adequadas. / The construction community is facing a dualistic reality, where advances in design methods and materials technology are opposed by the increase in pathological problems registered in our structures. Several recent surveys have pointed out that several and important deterioration processes occur in concrete structures. Many studies indicate that reinforcement corrosion is one of the most prevalent and costly between these. That explains why there are so much interest in studying methods to evaluate the corrosion resistance of construction materials. However, given the complexity of the theme and the lack of standardization, a great diversity of methods have evolved, without a proper definition and parameterization of testing conditions. A great number of researches simply adapt methods used by others, not paying enough attention to the evaluation of the efficiency and reproducibility of the test method. This prevents the comparison of results and creates obstacles to sharing data and articulate research efforts. The present work describes a study aimed at evaluating the influence of variations in test conditions, such as exposure time and induce voltage, in the performance of mortar samples with different w/c relations subjected to the CAIM test. This comparative accelerated method, in which mortar samples are immersed on a saline solution and connected to a constant voltage source, has already been used in several studies at LEME. The study analyses how the method respond to variations in test conditions and will help establish the more efficient standard conditions for the test considering the whole range of concrete strengths.

A construção civil vem se deparando com uma dualidade que envolve avanços dos métodos de cálculo e tecnologia dos materiais contraposto ao incremento das patologias das construções. Inúmeros levantamentos estatísticos, realizados nos últimos anos, vem demonstrando a grande incidência e repercussão dos processos patológicos atuantes sobre as estruturas de concreto. Vários estudos comprovam que a corrosão de armaduras no concreto é de grande incidência nas construções e, na maioria dos casos, aquele que gera os maiores problemas, tanto em termos de custo como de segurança. Isto explica porque técnicas de medição de resistência à corrosão vêm sendo intensamente estudadas. Todavia, dada a complexidade do assunto e a falta de normalização específica, observa-se a existência de uma grande diversidade de métodos de ensaio, aliada à ausência de uma padronização dos tipos e condições de ensaio. A maioria dos pesquisadores adapta ensaios anteriormente realizados, sem realizar estudos específicos sobre a eficiência e reprodutibilidade dos mesmos. O presente trabalho descreve um estudo realizado com o intuito de avaliar qual os efeitos das variações das condições de ensaio, como tempo de exposição e diferença de potencial induzida, no comportamento de corpos-de-prova de diversas relações água/cimento testados pela metodologia CAIM, um tipo de ensaio acelerado comparativo de corrosão por imersão em solução salina, que já foi empregado em várias pesquisas no LEME. O objetivo é entender como o ensaio reage a variações de método, verificando sua sensibilidade a estas e definindo quais as condições padrão mais adequadas. / The construction community is facing a dualistic reality, where advances in design methods and materials technology are opposed by the increase in pathological problems registered in our structures. Several recent surveys have pointed out that several and important deterioration processes occur in concrete structures. Many studies indicate that reinforcement corrosion is one of the most prevalent and costly between these. That explains why there are so much interest in studying methods to evaluate the corrosion resistance of construction materials. However, given the complexity of the theme and the lack of standardization, a great diversity of methods have evolved, without a proper definition and parameterization of testing conditions. A great number of researches simply adapt methods used by others, not paying enough attention to the evaluation of the efficiency and reproducibility of the test method. This prevents the comparison of results and creates obstacles to sharing data and articulate research efforts. The present work describes a study aimed at evaluating the influence of variations in test conditions, such as exposure time and induce voltage, in the performance of mortar samples with different w/c relations subjected to the CAIM test. This comparative accelerated method, in which mortar samples are immersed on a saline solution and connected to a constant voltage source, has already been used in several studies at LEME. The study analyses how the method respond to variations in test conditions and will help establish the more efficient standard conditions for the test considering the whole range of concrete strengths.

A construção civil vem se deparando com uma dualidade que envolve avanços dos métodos de cálculo e tecnologia dos materiais contraposto ao incremento das patologias das construções. Inúmeros levantamentos estatísticos, realizados nos últimos anos, vem demonstrando a grande incidência e repercussão dos processos patológicos atuantes sobre as estruturas de concreto. Vários estudos comprovam que a corrosão de armaduras no concreto é de grande incidência nas construções e, na maioria dos casos, aquele que gera os maiores problemas, tanto em termos de custo como de segurança. Isto explica porque técnicas de medição de resistência à corrosão vêm sendo intensamente estudadas. Todavia, dada a complexidade do assunto e a falta de normalização específica, observa-se a existência de uma grande diversidade de métodos de ensaio, aliada à ausência de uma padronização dos tipos e condições de ensaio. A maioria dos pesquisadores adapta ensaios anteriormente realizados, sem realizar estudos específicos sobre a eficiência e reprodutibilidade dos mesmos. O presente trabalho descreve um estudo realizado com o intuito de avaliar qual os efeitos das variações das condições de ensaio, como tempo de exposição e diferença de potencial induzida, no comportamento de corpos-de-prova de diversas relações água/cimento testados pela metodologia CAIM, um tipo de ensaio acelerado comparativo de corrosão por imersão em solução salina, que já foi empregado em várias pesquisas no LEME. O objetivo é entender como o ensaio reage a variações de método, verificando sua sensibilidade a estas e definindo quais as condições padrão mais adequadas. / The construction community is facing a dualistic reality, where advances in design methods and materials technology are opposed by the increase in pathological problems registered in our structures. Several recent surveys have pointed out that several and important deterioration processes occur in concrete structures. Many studies indicate that reinforcement corrosion is one of the most prevalent and costly between these. That explains why there are so much interest in studying methods to evaluate the corrosion resistance of construction materials. However, given the complexity of the theme and the lack of standardization, a great diversity of methods have evolved, without a proper definition and parameterization of testing conditions. A great number of researches simply adapt methods used by others, not paying enough attention to the evaluation of the efficiency and reproducibility of the test method. This prevents the comparison of results and creates obstacles to sharing data and articulate research efforts. The present work describes a study aimed at evaluating the influence of variations in test conditions, such as exposure time and induce voltage, in the performance of mortar samples with different w/c relations subjected to the CAIM test. This comparative accelerated method, in which mortar samples are immersed on a saline solution and connected to a constant voltage source, has already been used in several studies at LEME. The study analyses how the method respond to variations in test conditions and will help establish the more efficient standard conditions for the test considering the whole range of concrete strengths.

Duplex stainless steel (DSS) that developed in the 1930’s is a type of steel that consists of bothaustenite and ferrite phases in an almost equal proportion. It inherits properties of both ferriticand austenitic stainless steel and so it has good mechanical and corrosion resistance propertiesthat makes it suitable material in different industries with aggressive environment. There aredifferent approaches that used to evaluate the susceptibility of stainless steels to pitting corrosionlike Pitting Resistance Equivalent Number (PREN) and electrochemical methodologies. In thisstudy, focus is on the potentiodynamic (AL 101 5170) and potentiostatic (ASTM G150) testmethods as laboratory evaluations in which standard DSS (2205) is exposed to the differentchloride concentrations 0.1 M and 1 M respectively. In these methods parameters like PittingPotential (Ep) and Critical Pitting Temperature (CPT) can be measured respectively and used topredict the susceptibility of DSS to pitting corrosion. DSS owes its good corrosion resistance tothe oxide film that protects the metal from corrosion. Pitting can be initiated as a result of anyheterogeneities on the metal surface which act as a passive film defect like non-metallicinclusions and intermetallic precipitations such as sigma phase when metal is exposed toaggressive environment and high temperature. The aim of the present work is to make acomparison between two electrochemical methods besides finding how inclusions andmicrostructure can have impact on their results and on pitting corrosion. The results of theexperiment shows that there is a positive linear relation only in longitudinal direction betweenCPT and Ep. Also, among two test methods only ASTM G150 can detect sigma phase existence(<3%). Based on investigations in this experiment, inclusion characteristics such as numberdensity and composition has compatible results in both methods so that samples with big sizeinclusions (>8 μm) have negative effect on corrosion resistance and in terms of composition,samples with nitride inclusions has lower CPT and Ep compared with those with only oxide oroxide/sulfide inclusions. It is also discovered that phase arrangement is not the same in allspecimens that produced by different production methods and samples with finer phases havehigher CPT values in both longitudinal and transvers directions. However, this shape ofmicrostructure only affect the Ep in longitudinal directions but not transvers.

Pour les structures aéronautiques, les zones sensibles à la corrosion sont principalement celles où le plan de protection de la structure peut être mis en défaut, comme à l’intérieur des joints de recouvrement (dénommé «lap joint» en anglais). Les assemblages de tôles métalliques réalisés par recouvrement en utilisant, par exemple le rivetage, peuvent présenter des défauts de contact et donc il peut exister un interstice entre les deux parties de l’assemblage. En général cet interstice est isolé de l’environnement extérieur par un mastic. Mais il y a un risque de piégeage d’humidité plus ou moins concentrée en ions agressifs qui peut provoquer des endommagements ou aggraver ceux initiés sur des défauts des revêtements. Le premier objectif de cette thèse est de développer une méthodologie permettant de reproduire, de manière contrôlée et de façon la plus représentative de cas réels, la corrosion d’un alliage d’aluminium 2024-T3 constituant un joint de recouvrement afin d’effectuer des observations complétées par des mesures chimiques et électrochimiques. Le deuxième objectif est de tester l’application de modèles de transport réactif (en milieu confiné) pour voir s’il est possible de simuler les réponses (chimiques ou électrochimiques) mesurées expérimentalement et donc de prédire sur le long terme l’évolution d’un assemblage. / For aircraft structures, corrosion sensitive areas are mainly those where the protection of the structure may suffer local breakdowns, as encountered inside lap joints. The assemblies of metal plates by overlapping (riveting) may present some defects in contact and consequently a gap can exist between the two parts of the assembly. Typically this gap is isolated from the outside environment by a sealant. But there is a risk of trapping of moisture more or less concentrated in aggressive ions which can induce corrosion or increase the damages initiated on coating defects. The first objective of this thesis is to develop a methodology to reproduce in a controlled manner and in the most representative way regarding actual cases, the corrosion of a lap joint made of aluminum alloy 2024- T3 plates, to perform not only observations but also chemical and electrochemical measurements. The second objective is to test the application of reactive transport models (in confined media) to check if it is possible to simulate the chemical or electrochemical changes recorded during experiments and thus to predict the long-term evolution of lap-joint in humid environment.

This thesis refers to Fe-based biodegradable materials and their potencial aplications in medicine, especially as temporary bone implants. This work generaly summaries aplications of biomaterial in medicine with more interest kept on biodegradable materials and their in-vivo corrosion. The experimental part refers to conduction of porous Fe-based materials with silica addition. The structure of prepared specimens is identified by EDX and XRD analysis. The imersion test and electrochemical studies were conducted to observe corrosion behaviour with respect to different concentration of silica. Potenciodynamic curves were obtained to determine corrosion potencial and corrosion current density of prepared samples.