FERNANDA MARTINS QUEIROZ
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Artigo IPEN-doc 29855 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, ISOLDAThe 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.Resumo IPEN-doc 23667 Microstructural investigation of the anodized (TSA) Al-Li alloys sealed in a cerium solution2016 - 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.