Corrosion and solid-state properties of Nb2O5 coating deposited on Ti-6Al-4V Alloy via DC reactive sputtering

• The reactive sputtering technique was advantageous for the deposition of Nb 2 O 5 on the Ti-6Al-4 V alloy. • Ti-6Al-4V/Nb 2 O 5 exhibits superior corrosion resistance compared to bare Ti-6Al-4 V alloy. • The Nb 2 O 5 coating deposited on Ti-6Al-4 V alloy surfaces by DC reactive sputtering exhibits n-type semiconducting characteristics. • The modified electrode surface presented a lower Urbach energy. • An evident relationship exists between the solid-state properties of the Nb₂O₅ coating and its ability to enhance the corrosion resistance of the Ti-6Al-4 V alloy. This study investigates the surface modification of Ti-6Al-4V alloy substrates via Nb₂O₅ coatings deposited through reactive sputtering. The solid-state properties and corrosion behaviour of the Nb₂O₅ coatings were analysed using electrochemical techniques and optical ellipsometry. The results demonstrate a significant enhancement in the corrosion resistance of the Ti-6Al-4V/Nb₂O₅ system compared to the uncoated alloy. The Nb₂O₅ thin film exhibits n-type semiconducting behaviour with a donor concentration of approximately 10¹⁶ cm⁻³. Photoelectrochemical studies revealed energy band gaps of 3.39 eV for Ti-6Al-4V and 3.27 eV for Ti-6Al-4V/Nb₂O₅ and a lower Urbach energy (0.44 eV) for the coated system compared to the substrate (0.68 eV), indicating that the coatings produced via reactive sputtering effectively reduced the energy states linked to defects and imperfections, acting as a passivating layer for the Ti-6Al-4V surface and enhancing its corrosion resistance. These findings establish a clear relationship between the solid-state properties of the Nb₂O₅ coating and its ability to enhance the corrosion resistance of the Ti-6Al-4V alloy.