Corrosion behaviour of reactive sputtering deposition niobium oxide based coating on the 2198-T851 aluminium alloy

• Published in: Surface & coatings technology 2022-03, Vol.434, p.128197, Article 128197
• Main Authors: Freitas, L.R., Gelamo, R.V., Marino, C.E.B., Nascimento, J.P.L., Figueiredo, J.M.A., Fernandes, J.C.S., Moreto, J.A.
• Format: Article
• Language: English
• Subjects: 2XXX series Al alloys; Aircraft industry; Aluminum base alloys; Corrosion; Corrosion protection; Niobium oxides; Plasma treatment; Raman spectroscopy; Spectrum analysis; Sputtering; Thin films
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2022.128197

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. [Display omitted] •The reactive sputtering method was able to produce NbxOy film on the 2198-T851.•Coated material has increased the impedance modulus more than one order of magnitude.•A difference of about 210 mV between the corrosion and pitting potentials was obtained..•A higher resistance to localised corrosion was achieved when compared to the untreated alloy.