XPS characterization of corrosion films formed on the crystalline, amorphous and nanocrystalline states of the alloy Ti60Ni40

X-ray photoelectron spectroscopy investigations were carried out on the crystalline, amorphous and nanocrystalline states of the alloy Ti60Ni40 after corrosion test in 1 M HNO3 aqueous medium using potentiodynamic polarization method. Polarization plots revealed that the nanocrystalline state is more corrosion resistant than the amorphous and crystalline states of the alloy Ti60Ni40. The XPS characterization of the oxide film formed after corrosion tests revealed that a multiple phase oxide film is formed on the crystalline and amorphous specimens of the alloy Ti60Ni40 consisting of Ti2+, Ti3+ and Ti4+ species along with some unoxidized Ti in metallic form (Ti0) in the case of crystalline specimen whereas the oxide film formed on nanocrystalline specimen consists of only Ti2+ and Ti4+ species. The high corrosion resistance of nanocrystalline state is attributed to the presence of fewer oxide species in the oxide film than that of the amorphous and crystalline states of the alloy Ti60Ni40.