Effect of niobium oxide thin film on the long-term immersion corrosion of the 2198-T851 aluminium alloy

This work aims to study the effect of niobium oxide coating on the long-term immersion corrosion of the 2198T851 aluminium alloy. The niobium oxide thin film was successful obtained on freshly plates of 2198-T851 alloy by reactive sputtering technique. Scanning vibrating electrode tests, electrochemical impedance spectroscopy and immersion tests measurements were used to reveal the insights of global and localised corrosion behaviour of the functionalised material in different concentrations of sodium chloride solution. The electrochemical impedance spectroscopy spectra showed that the coating significantly influenced on the corrosion resistance of the 2198T851 alloy, since the functionalised alloy immersed in 0.6 mol L (-1) NaCl solution during 720 h (30 days) displays the same result as the bare material for 3 h of immersion. The scanning vibrating electrode tests demonstrated the coated material was free of local corrosive attack by the electrolyte in the first 10 h of immersion, whilst the bare alloy exhibited active anodic and cathodic sites over the surface with increasing current density values for longer immersion times. The deposited coating was able to increase the corrosion resistance of the 2198-T851 aluminium alloy used as fuselage skin material by the aeronautical industry as verified by the immersion tests. Finally, experimental results confirm the extraordinary properties of niobium oxide as-deposited coating.