SURFACE CHARACTERIZATION OF NITROGEN ION IMPLANTED TITANIUM AND ITS ELECTRO-CHEMICALLY FORMED PASSIVE FILM IN SIMULATED BODY FLUID CONDITION

摘要

Surface modification of titanium CP (Commercially Pure) was attempted through nitrogen ion implantation to increase its corrosion resistance in the simulated body fluid. Nitrogen ion of 70 keV energy was implanted at the dose of 7 X 10~(20) and 2.5 X 10~(21) ions/m~2. Grazing Incidence X-ray Diffraction (GIXD) studies have been carried out on the modified surface to identify the compounds formed during implantation. Open Circuit Potential (OCP)-time measurements and cyclic polarization studies have been carried out to evaluate the corrosion resistance of the modified material. Specimens implanted at 7 X 10~(20) ions/m~2 showed optimum corrosion resistance and a decrease in the corrosion resistance was noticed at the dose of 2.5 X 10~(21) ions/m~2, The specimen implanted at 7 X 10~(20) ions/m~2 was electrochemically passivated at 1.0 V for an hour. X-ray photoelectron spectroscopy (XPS) was employed on the implanted-passivated specimen to understand the role played by nitrogen on the corrosion resistance and the chemical state of other alloying elements present in the passive film. The changes in the nature and composition of the passive film of the implanted-passivated specimen was compared with that of the unimplanted-passivated and as-implanted specimens. The results of the investigation showed that the nitrogen ion implanted specimen exhibited enhanced corrosion resistance, and this was attributed to the formation of oxynitride along with oxides in the passive film.