FERNANDA MARTINS QUEIROZ

FERNANDA MARTINS QUEIROZ

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Investigation on the Effect of a Chromium-Free Sealing Treatment for the Corrosion Resistance of AA2198-T851 after Tartaric Sulphuric Anodizing (TSA)
2023 - QUEIROZ, FERNANDA M.; BUGARIN, ALINE de F.S.; AYUSSO, VICTOR H.; TERADA, MAYSA; COSTA, ISOLDA
The AA 2198-T851 is a third-generation Al-Li alloy developed for use in the aircraft industry. Al-Li alloys are susceptible to localized corrosion due to their complex microstructure resulting from the used thermomechanical treatment. In order to prevent localized corrosion, these alloys are usually protected by anodizing in order to avoid a corrosive environment. Subsequently, for anodizing, a sealing treatment is usually performed for parts. Some sealing treatments use hexavalent-chromiumion-containing solutions. In this investigation, a chromium-free sealing treatment in a solution with cerium ions has been carried out, and the effect on the corrosion resistance of the AA2198-T851 alloy was investigated. Hydrothermally sealed or unsealed samples were also tested for corrosion resistance for comparison reasons. The corrosion resistance of the anodized aluminum alloy, either hydrothermally sealed or in a cerium-ion-containing solution, was evaluated in a sodium chloride solution by electrochemical impedance spectroscopy as a function of immersion time. The samples sealed in a cerium-containing solution increased their corrosion resistance when compared to the hydrothermally sealed. The effectiveness of the sealing process with cerium that was observed in the electrochemical tests indicated that after the corrosive attack of the barrier layer, there was a “sealing” process of the sample surface.
Effect of Cr III passivation on the corrosion resistance of coated electrogalvanized steel
2011 - QUEIROZ, F.M.; ELSNER, C.I.; DI SARLI, A.R.; TOMACHUK, C.R.; COSTA, I.
Effect of trivalent chromium based treatment on the protective properties of steel coated with polymeric film
2012 - QUEIROZ, F.M.; TOMACHUK, C.R.; ZUMELZU, E.; MELO, H.G. de; COSTA, I.
Three main requirements are mandatory in order to achieve optimal quality in canned food: adequate processing of the product, definition of the preserving method, and a correct alloy for the deposit. Lacquer coatings are applied on food cans to enhance corrosion protection and also with decorative purposes. In this investigation, steel coated with a Cr3+ based treatment layer and polyethylene teraphtalate polymeric film (PET), applied by coextrusion, was characterized by electrochemical impedance spectroscopy (EIS) measurements, in NaCl 0.5 M solution, to evaluate the coating corrosion resistance in this environment. The experimental results showed that this new material (tin free) has good corrosion resistance regardless of the porosity found in the polymeric film, indicating that it can be a non-polluting alternative to replace tinplate and hexavalent chromium conversion layer in the food industry, being compatible with the packed product.
Avaliação do sistema Zn-Cr III-revestimento orgânico por espectroscopia de impedância eletroquímica
2013 - QUEIROZ, FERNANDA M.; ELSNER, CECILIA I.; TOMACHUK, CELIA R.; DI SARLI, ALEJANDRO R.; COSTA, ISOLDA
O controle da corrosão de aço eletrogalvanizado empregando soluções à base de sais de Cr VI é amplamente conhecido e estudado. No entanto, pesquisadores vêm buscando alternativas para substituir estes sais já que diretrizes ambientais e industriais exigem que sejam banidos. Os revestimentos de conversão à base de Cr III têm mostrado um desempenho compatível aos baseados em Cr VI. Neste trabalho são utilizadas medidas de espectroscopia de impedância eletroquímica (EIE) em NaCl 0,05 mol/L e em Na2SO4 0,1 mol/L, durante o tempo de imersão, para avaliar a resistência à corrosão de aço eletrogalvanizado revestido com tratamento à base de Cr III e pintado com três diferentes revestimentos orgânicos. Os revestimentos orgânicos sãocaracterizados por sua adesão. Os resultados mostram um comportamento semelhante para os três revestimentos e, apesar de uma segunda constante de tempo ter sido observada nos ajustes de EIE, os valores de R2 indicam uma baixa velocidade de corrosão. O sistema Zn – Cr III – revestimento orgânico é compatível ao sistema Zn – Cr VI – revestimento orgânico, para o período de imersão considerado.
Study of the corrosion behavior of electrogalvanised steel/Cr(III) and Zr conversion layer/paint system by electrochemical and visual methods
2014 - QUEIROZ, F.M.; SERE, P.R.; ELSNER, C.I.; DI SARLI, A.R.; TOMACHUK, C.R.; COSTA, I.
Thermomechanical treatment and corrosion resistance correlation in the AA2198 Al–Cu–Li alloy
2019 - ARAUJO, JOAO V. de S.; BUGARIN, ALINE de F.S.; DONATUS, UYIME; MACHADO, CARULINE de S.C.; QUEIROZ, FERNANDA M.; TERADA, MAYSA; ASTARITA, ANTONELLO; COSTA, ISOLDA
The influence of T3, T8 and T851 thermomechanical treatments on the microstructure and corrosion resistance of the AA2198 was investigated. Differential scanning calorimetry and scanning electron microscopy were used for microstructural characterisation, whereas electrochemical methods were employed to analyse the corrosion behaviour of the alloy. The morphology and composition of constituent particles were similar for the T3 and T8 thermomechanical treatments but varied in the T851. There was an inverse relation between T1 phase density and corrosion resistance. The T3 treatment with the highest corrosion resistance was the one with the lowest density of T1 phase. The mechanisms of corrosion varied with the thermomechanical treatments.
On the AA2198-T851 alloy microstructure and its correlation with localized corrosion behaviour
2018 - DONATUS, UYIME; TERADA, MAYSA; OSPINA, CARLOS R.; QUEIROZ, FERNANDA M.; BUGARIN, ALINE F.S.; COSTA, ISOLDA
The corrosion behaviour of AA2198-T851 alloy has been investigated using a combination of immersion tests and different microscopy techniques. Results showed that severe localized corrosion initiated within 1 h of corrosion immersion test in 0.01 mol L−1 NaCl solution. The corrosion mechanism in this alloy is intragranular and it propagates crystallographically. The propagation occurs through grain orientation dependent bands and it can be likened to the movement of dislocation through slip planes. Corrosion rings around stable pits result from pH variations. Secondary pits form around primary pits within corrosion rings and are preceded by hydrogen evolution.
On the effects of hydrothermal treatments on the corrosion resistance of the TSA anodized AA7475-T761 alloy
2016 - ALMEIDA, THALLIS L.; QUEIROZ, FERNANDA M.; TERADA, MAYSA; COSTA, ISOLDA; CAPELOSSI, VERA R.
The effect of hydrothermal treatment time on sealing and corrosion resistance of the AA7475-T761 anodized aluminium alloy has been investigated in this study. The hydrothermal treatments tested are environmental compatible without chromium ions involved. Anodizing was carried out by a tartaric-sulphuric anodizing (TSA) process and this was followed by hydrothermal treatments for partial sealing, in various solutions. The effect of propyleneglycol (PRG) and/or cerium ions in the hydrothermal treatment solution was evaluated. Four treatment times were tested, specifically, 2.5, 5.0, 7.5 and 10 min. The corrosion resistance of the anodized and treated samples was evaluated by Electrochemical Impedance Spectroscopy (EIS) and the anodic layers formed were characterized by Scanning Electron Microscopy (SEM). The EIS results showed that the hydrothermal treatments in solutions with cerium ions resulted in similar impedances for periods of treatment from 5 to 10 min whereas in the solutions with PRG the impedance increased with time of treatment from 2.5 to 10 min showing a slower kinetics of anodic layer sealing. However, the fastest kinetics of sealing were associated to the treatments that combined two steps, one in PRG and other in cerium containing solutions with similar impedances obtained from 2.5 to 10 min of treatment. Surface evaluation by SEM showed that the porosities in the anodic layer were not sealed for the periods of hydrothermal treatments corresponding to 2.5 min. The presence of cerium in hydrothermal treatment had a beneficial effect on the stability of the anodic layer formed and provided a healing effect on the corroding sites.
EIS study of the microstructure influence on the corrosion behaviour of AA 2198-T3 compared to AA 2198-T851 alloy
2016 - ARAUJO, J.V. de S.; QUEIROZ, F.M.; TERADA, M.; ASTARITA, A.; COSTA, I.
This paper deals with the study of the influence of the temper state on the electrochemical behavior of an high strength aluminum-lithium alloy. In particular the corrosion resistance of the AA2198 alloy in both T3 and T851 temper condition, has been evaluated by immersion tests as a function of immersion time in NaCl 0.01 mol.L-1. The evolution of the electrochemical behavior was monitored by electrochemical impedance spectroscopy (EIS) and surface observation by optical microscopy and Field Emission Gun- Scanning Electron Microscopy. The results indicated a higher electrochemical activity associated to the T851 treatment comparatively to the T3 one and this was ascribed to the more heterogeneous microstructure related to the first treatment. Severe localized corrosion was seen on the AA2198-T851 alloy after only few hours of exposure to the test medium. This type of corrosion was of the crystallographic type and was related to T1 (Al2LiCu) which is more electrochemically active than the matrix leading to localized attack. Pitting attack was seen on the AA2198-T3 alloy along the surface and it was located at the matrix-precipitates interface. The EIS results supported a faster kinetics and lower impedances associated to the AA2198-T851 comparatively to the AA2198-T3 alloy according to the surface observation along the test period.
Microstructural investigation of the anodized (TSA) Al-Li alloys sealed in a cerium solution
2016 - TERADA, M.; QUEIROZ, F.M.; AYUSSO, V.H.; ASTARITA, A.; COSTA, I.
The AA2198 is a third generation of Al-Li alloy developed for use in the aircraft industry. It is highly susceptible to localized corrosion and it is usually protected by anodizing. Sealing treatments of the anodic layer provide further protection. In this study, samples of the AA2198 alloy were anodized in tartaric sulfuric acid (TSA) solution and subsequently sealed, either in boiling water or in a solution with cerium ions. The surface of the treated samples was investigated by Field Emission Gun-Scanning Electron Microscopy and X-ray energy dispersive analysis. Defects were found in the anodic layer due to the complex microstructure of the AA2198 alloy. The corrosion resistance of the anodized and sealed samples was studied by electrochemical impedance spectroscopy in 0.5 mol.L-1 NaCl solution and compared to that of anodized and unsealed samples. EIS results showed that the sealing treatment in cerium solutions resulted in increase in impedance with time of immersion. Surface observation and EDX analysis showed increase in cerium content with time of test at the defects in the anodic layer sealed in cerium containing solutions and the increasing blockage of the defects in this layer. The EIS results also showed that the impedance associated to this type of samples increased with time whereas it decreased for sealed samples in boiling water. The surface observation and EIS responses indicated a healing process associated to sealing in the cerium solution.