Surface chemistry and the corrosion behavior of magnetron sputtered niobium oxide films in sulfuric acid solution

In this work, magnetron sputtered Nb2O5 films were obtained at two different deposition times. The surface chemistry of the deposited layers was investigated by X-ray photoelectron spectroscopy (XPS). The corrosion behavior was assessed by electrochemical impedance spectroscopy, potentiodynamic polarization and potentiostatic polarization tests in 0.5 M H2SO4 + 2 ppm HF solution at room temperature. The Nb5+/Nb4+ ratio decreased with the deposition time, leading to a higher surface activity for the film obtained at 30 min. This result was confirmed by its lower impedance values and higher current densities when compared to the 15′-film. Surface chemistry played a major role on the corrosion behavior of the sputtered films and can be tailored by the deposition time.