Enhancing the corrosion protection of Ti-6Al-4V alloy through reactive sputtering niobium oxide thin films

Here, a set of polycrystalline niobium oxide thin films were produced by using reactive sputtering technique on the Ti-6Al-4V alloy surfaces and characterized by OM, SEM/EDX, AFM, DRX/Rietveld refinement, and XPS techniques. CPDP and SVET tests were performed on the coated and uncoated material considering an aggressive medium (NaF and Hank's solution). The results demonstrated the technique used in the present survey was advantageous to produce thin films on the Ti-6Al-4V surfaces. XPS analysis demonstrated that the niobium oxide thin films were composed by Nb2O5/NbO2. Measured and Rietveld refined X-ray diffraction patterns for the Nb-oxide thin film demonstrated the presence of the Nb2O5, NbO2, and NbO crystalline phases. The thin film acts as a barrier layer, suggesting a better corrosion performance when compared to the bare alloy (E-corr = -111 mV(SCE) vs -290 mV(SCE)). The CPDP results demonstrated the current density of the coated Ti-6Al-4V specimen, at the same potential, was lower when compared to the bare alloy. SVET results revealed the coated material displayed low values of current density (similar to 100 mu A/cm(2) for 15 h of immersion time), whilst the bare material (in the range 700-2200 mu A/cm(2) for 1 h of immersion time), suggesting the niobium oxide thin films act as an effective protective barrier against corrosion process evolution over time.