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 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.
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.
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 the sealing and corrosion resistance of the anodized AA7475-T761 aluminium alloy has been investigated in this study. The treatments tested are environmental compatible and has not chromium ions involved. Anodizing was carried out by tartaric-sulphuric anodizing (TSA) and this was followed by hydrothermal treatments for partial sealing, either with or without propyleneglycol (PRG) and/or cerium ions. Four different treatment times were tested, specifically, 2.5, 5.0, 7.5 and 10 min. The corrosion resistance of the treated samples was evaluated by Electrochemical Impedance Spectroscopy (EIS) and the anodic layers formed by anodizing and hydrothermal treatments were characterized by Scanning Electron Microscopy (SEM). The EIS results indicated that the best corrosion resistance was related to the treatments that combined hydrothermal treatments in boiling water with PRG for 10 minutes or boiling water with PRG and cerium ions for 5 min. The SEM images for the samples showed the formation of a homogeneous anodic layer and the thickness is approximately 3 m. It was noticed that the porosities were not completed sealed by the treatments tested and this was on purpose in order to allow coating adhesion to the anodic layer.
Avaliação da resistência a corrosão intergranular da liga AA2198-T8
2016 - ARAUJO, J.V.; MACHADO, C.S.C.; MILAGRE, M.X.; QUEIROZ, F.M.; COSTA, I.
The intergranular corrosion is a form of corrosion which can result in loss of mechanical properties and might lead to rupture of the material. These properties are of fundamental importance for the materials used in aircraft for security reasons. It is important to characterize the intergranular corrosion resistance of materials used in aeronautical applications. This study investigated the intergranular corrosion resistance of the AA2198-T8 alloy that presents copper and lithium as the main alloying elements. The results showed that this alloys is susceptible to this form of corrosion.
Monitoramento da corrosão em ligas de alumínio dissimilares unidas por processo de soldagem por fricção e mistura (FSW) utilizadas no setor aeronáutico
2016 - BUGARIN, A.F.S.; QUEIROZ, F.M.; TERADA, M.; MELO, H.G. de; COSTA, I.
The corrosion behavior of the aluminum alloys ( AA2024 -T3 and AA7475 - T761 ) joined by the friction and mixing welding process (FSW) was monitored by immersion test in 10 mM NaCl solution as a function of exposure time to the test solution. The corrosion resistance was also evaluated by a gel test (agar- agar) by means of which the galvanic coupling between the two alloys was observed. The AA2024 alloy acted as the cathode and the AA7475 as the anode of the galvanically coupled pair. The immersion tests showed galvanic coupling in the mixed region (ZM) or nugget. The zone most affected by corrosion was the thermomechanically affected zone (ZTMA) at the interface with the thermally affected one (ZTA) on the side of the AA7475 alloy. At this interface, intergranular corrosion was seen from the first two hours of immersion.
Comparação do comportamento de corrosão da liga convencional AA2024-T351 e da liga Al-Li 2098-T351
2016 - MILAGRE, M.X.; ARAUJO, J.V.; QUEIROZ, F.M.; MACHADO, C.S.C.; COSTA, I.
In this work, the localized corrosion behavior of an Al-Li alloy (AA2098-T351) was compared with that of the AA2024-T351 conventional alloy by immersion test in 0.01 mol L-1 NaCl solution. The evolution of localized corrosion in both alloys was monitored by optical microscopy and scanning electron microscopy after several test periods from 2h to 24h. The results showed high susceptibility of the two alloys to pitting from the early hours of immersion. The corrosion mechanism in the two alloys, however, was different. Localized corrosion in the AA2024 alloy was associated with the microcells generation between micrometric precipitates and the matrix leading to superficial attack homogeneously distributed throughout the surface exposed to the corrosive environment. In the AA2098 alloy, however, a severe localized corrosion ascribed in the literature to the presence of phase T1 was also observed besides the localized corrosion type similar to that observed in the AA2024 alloy.
EIS behavior of anodized and primer coated AA2198–T851 compared to AA2024–T3 exposed to salt spray CASS test
2016 - QUEIROZ, F.M.; BUGARIN, A.F.S.; HAMMEL, N.P.; CAPELOSSI, V.R.; TERADA, M.; COSTA, I.
In this investigation, the corrosion behavior of AA2198–T851 was compared to AA2024–T3 by electrochemical impedance spectroscopy and the surface of both alloys was analyzed by Field Emission Gun (FEG) scanning electron microscopy (SEM) and Xray energy dispersive analysis (EDX). Electrochemical impedance spectroscopy (EIS) results for the uncoated surface of both alloys showed higher pitting susceptibility associated to the AA2198–T851 alloy comparatively to the AA2024–T3. In order to improve the corrosion resistance of both alloys, tartaric sulphuric acid anodising (TSA) was carried out with both alloys followed by primer application. The corrosion resistance of the anodized and primer coated samples was also evaluated by CASS salt spray test followed by EIS tests at increasing periods of exposure to the CASS test. The results showed larger amounts of corrosion products associated to the primer coated AA2198–T851 alloy comparatively to the AA2024–T3 alloy. Diffusionwas only indicated in the EIS results of the AA2198–T851 samples likely because of large amounts of porous corrosion products on the exposed surface of this alloy to the corrosive environment.
Avaliação da proteção contra corrosão de aço eletrogalvanizado, passivado com cromo trivalente e pintado: sistema eletrogalvanizado - cromo III - pintura
2011 - QUEIROZ, FERNANDA M.; ELSNER, CECILIA I.; SARLI, ALEJANDRO R. di; TOMACHUK, CELIA R.; COSTA, ISOLDA
Electrochemical, chemical and morphological characterization of galvannealed steel coating
2007 - QUEIROZ, F.M.; COSTA, I.