FERNANDA MARTINS QUEIROZ

FERNANDA MARTINS QUEIROZ

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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.
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.
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.
Investigation of the corrosion behaviour of AA 2024-T3 in low concentrated chloride media
2008 - QUEIROZ, F.M.; MAGNANI, M.; COSTA, I.; MELO, H.G. de
Electrochemical behaviour of electrogalvanized steel with a conversion treatment at room temperature
2012 - TOMACHUK, C.R.; QUEIROZ, F.M.; COSTA, I.