Characterization of thin anodic oxides of Ti-Nb alloys by electrochemical impedance spectroscopy

► passivity of mixed α/β-phase NbTi alloys with 10 or 20 wt% Nb was studied. ► EBSD proved the α/β dual phase structure with complex subgrain crystallography. ► Voltammetry, EIS and Mott-Schottky analysis were performed. ► k, DK and EFlatband are similar, but donor density is doubled. ► Both alloys showed excellent passivity with stable and passive grain boundaries.