Abstract
This work aims to improve the corrosion properties of the 2198-T851 aluminium alloy by coating with a set of niobium oxide thin films, using the reactive sputtering technique. The structural and morphological properties of the niobium oxide thin films were characterized by using SEM/EDX, AFM, FTIR and Raman spectroscopy. Global electrochemical tests (OCP, PPc, CV, and EIS) were performed in 0.6 mol L−1 NaCl solution. The results demonstrated that the reactive sputtering technique was advantageous for producing thin films on the 2198-T851 aluminium surface. Raman spectroscopy results revealed a band near 650 cm−1 related to NbO single bonds, whilst the band centred at 868 cm−1 may be attributed to NbO double bonds. The PPc results indicated that the niobium oxide acts as a protective barrier, since a difference of about 210 mV was observed between Epitting and Ecorr. The coated specimens displayed a superior breakdown potential when compared to the base material (−0.387 vs − 0.505 V/SCE). The impedance modulus has increased more than one order of magnitude and the phase angle is closer to - 90°, demonstrating a capacitive thin film was deposited on the 2198-T851 aluminium alloy surface.
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