JOAO VICTOR DE SOUSA ARAUJO

JOAO VICTOR DE SOUSA ARAUJO

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Corrosion behaviour of the 2098-T351 Al–Cu–Li alloy after different surface treatments
2022 - BARBOZA, WANESSA das G.; MILAGRE, MARIANA X.; DONATUS, UYIME; MACHADO, CARULINE de S.C.; RAMIREZ, OSCAR M.P.; ARAUJO, JOAO V. de S.; SILVA, REJANE M.P. da; COSTA, ISOLDA
The effect of different surface treatments on the corrosion resistance of the AA2098 Al–Cu–Li alloy has been investigated. Surface characterization was performed using 3D optical profilometry, energy dispersive X-ray spectroscopy and scanning electron microscopy. The corrosion resistance of the 2098 alloy after the surface treatments was investigated in 0.1 mol L−1 NaCl solution by electrochemical techniques and microscopy. Corrosion results showed that the untreated and the chemically etched surfaces were more active than the mechanically abraded and mechanically polished surfaces owing to differences in the nature of the native oxides formed after the surface treatments. Corrosion rate and mode were also affected by how close the exposed surface was to the mid-thickness region of the AA2098-T351 plate relative to the actual top surface (before polishing). This is associated with the variation in the volume fraction and distribution of the T1 phase as the mid-thickness region of the AA2098-T351 plate is approached.
TSA anodising voltage effects on the near-surface coarse intermetallic particles in the AA2024-T3 and AA2198-T8 alloys
2022 - ARAUJO, JOAO V. de S.; MILAGRE, MARIANA X.; KLUMPP, RAFAEL E.; AYUSSO, VICTOR H.; DONATUS, UYIME; COSTA, ISOLDA
In this study, the behaviour of the micrometric particles of the AA2198-T8 alloy during anodising at various voltages and the effect of anodising voltage on the anodised surface morphology have been investigated in a tartaric-sulfuric acid anodising solution. The results were compared with that of the AA2024-T3 alloy. For the AA2198-T8 alloy, partial dissolution of these particles occurred at 0, 3 and 4 V. Besides, for potentials above 5 V, there is a preferential dissolution of the intermetallic particles. For the AA2024-T3 alloy, the results indicated a total dissolution of the micrometric particles at 0 V and a partial dissolution at 3 V, whereas above 4 V total dissolution occurred. Between 1 and 2 V, no dissolution was observed for both alloys. The preferential dissolution of the micrometric particles resulted in defects in the anodic film and cavities on the anodised surfaces.
Influence of chloride ions concentration on the development of severe localised corrosion and its effects on the electrochemical response of the 2198-T8 alloy
2021 - MACHADO, CARULINE de S.C.; SILVA, REJANE M.P. da; ARAUJO, JOAO V. de S.; MILAGRE, MARIANA X.; DONATUS, UYIME; VIVEIROS, BARBARA V.G. de; KLUMPP, RAFAEL E.; COSTA, ISOLDA
The development of severe localised corrosion (SLC) on the 2198-T8 alloy was investigated in solutions of various NaCl concentrations (0.001, 0.005 and 0.01 mol L−1). Immersion tests, optical profilometry, conventional and local electrochemical analyses were performed to evaluate the corrosion behaviour of the alloy. Immersion tests showed that the alloy is susceptible to SLC in all conditions, although the pits sizes were dependent on the solution concentration. The largest anodic areas, corresponding to SLC sites, were observed for the sample immersed in 0.001 mol L−1 NaCl, whereas pits with similar sizes were observed for the samples immersed in solutions with 0.005 and 0.01 mol L−1 of NaCl. Moreover, the maximum depth of attack was observed for the sample immersed in 0.001 mol L−1 NaCl. These results were in agreement with the scanning ionselective electrode technique (SIET) maps which showed stronger acidification on the sample exposed to 0.001 mol L−1 NaCl solution.
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.
The effect of manufacturing process induced near-surface deformed layer on the corrosion behaviour of AA2198-T851 Al–Cu–Li alloy
2019 - DONATUS, UYIME; ARAUJO, JOAO V. de S.; MACHADO, CARULINE de S.C.; MOGILI, NAGA V.V.; ANTUNES, RENATO A.; COSTA, ISOLDA
The effect of the near-surface deformed layer on the corrosion behaviour of AA2198-T851 Al–Cu–Li alloy has been investigated using microscopy and electrochemical techniques. This shows that a deformed layer developed by rolling was more active but only exhibited superficial attack compared to a mechanically polished surface, which produced severe localised corrosion associated with the presence of hexagonal T1 particles. The rolled surface became increasingly corrosion resistant with time, but when coupled, galvanically enhanced severe localised corrosion sites developed on the surface over time.
Comparison of the corrosion resistance of an Al–Cu alloy and an Al–Cu–Li alloy
2019 - MILAGRE, MARIANA X.; DONATUS, UYIME; MACHADO, CARULINE S.C.; ARAUJO, JOAO V.S.; SILVA, REJANE M.P. da; VIVEIROS, BARBARA V.G. de; ASTARITA, ANTONELLO; COSTA, ISOLDA
In this study, the corrosion mechanisms of the AA2024-T3 and the AA2098-T351 were investigated and compared using various electrochemical techniques in 0.005 mol L−1 NaCl solution. The severe type of corrosion in the AA2098-T351 was intragranular attack (IGA) although trenching and pitting related to the constituent particles were seen. On the other hand, the AA2024-T3 exhibited severe localised corrosion associated with micrometric constituent particles, and its propagation was via grain boundaries leading to intergranular corrosion (IGC). Electrochemical techniques showed that the corrosion reaction in both alloys was controlled by diffusion. The non-uniform current distribution in both alloys showed that EIS was not a proper technique for comparing the corrosion resistance of the alloys. However, local electrochemical techniques were useful for the evaluation of the corrosion resistance of the alloys.