Electrochemical behavior of different structural states of the alloy Ti60Ni40

Potentiodynamic polarization studies were carried out on nanocrystalline I, nanocrystalline II and nanocrystalline III states having crystallite size 35 ± 5 nm, 18 ± 2 nm and 10 ± 2 nm of the alloy Ti60Ni40 in 1 M H2SO4 aqueous medium. It was observed that the nanocrystalline III state exhibits superior corrosion resistance as compared to the nanocrystalline II and nanocrystalline I states of the alloy Ti60Ni40. XPS studies were also performed after corrosion test and it was observed that nanocrystalline III state contains only Ti2+ and Ti4+ species whereas nanocrystalline I and nanocrystalline II state contains Ti2+, Ti3+and Ti4+ along with some unoxidized metallic Ti0 in the case of nanocrystalline I state. Thus the small crystallite size and the presence of only Ti2+ and Ti4+ species in the form of TiO and TiO2 leads to the formation of a protective oxide film which is adherent, stable and improves the corrosion resistance of the nanocrystalline III state of the alloy Ti60Ni40.