SURFACE CHARACTERIZATION OF ELECTROCHEMICALLY FORMED PASSIVE FILM ON NITROGEN ION-IMPLANTED TI6AL4V ALLOY

Nitrogen ion implantation was carried out to modify the surface of a T i6Al4V alloy for improving its corrosion resistance in a simulated bod y fluid environment. Ion implantation was carried out at 70 keV energy at the dose of 7x10(20) ions/m(2). The implanted surface was electroc hemically passivated at 1.0 V for 1 h. X-ray photoelectron spectroscop y (XPS) was used to identify the concentration and chemical state of t he elements present in the passivated film. The change in the nature a nd composition of the passive Nm of the implanted-passivated specimen was compared with the unimplanted-passivated and as-implanted specimen s. Open Circuit Potential (OCP)-time measurement and cyclic polarizati on studies were additionally carried out to understand the nature of t he passive film. The results showed that the implanted specimen exhibi ted enhanced corrosion resistance than the unimplanted specimen (one o rder of magnitude) due to the presence of oxynitride along with oxide in the passive film.