Effect of nitrogen ion implantation on the localized corrosion behavior oftitanium modified type 316L stainless steer in simulated body fluid

Nitrogen ion implantation on titanium-modified type 316L stainless steel (S S) at the energy of 70 keV was carried out at different doses ranging from 1 x 10(15) to 2.5 x 10(17) ions/cm(2). These samples were subjected to open circuit potential (OCP)-time measurement, cyclic polarization, and acceler ated leaching studies-in order to discover the optimum dose that can provid e good localized corrosion resistance in a simulated body fluid condition. The results showed that the localized corrosion resistance improved with an increase in doses up to 1 x 10(17) ions/cm(-2). beyond which it started to deteriorate. The results of the accelerated leaching studies showed that t he leaching of the major alloying elements was arrested upon nitrogen ion i mplantation. Gracing incidence x-ray diffraction studies shelved the format ion of chromium nitrides at a dose of 2.5 x 10(17) ions/cm(2). X-ray. photo electron spectroscopy. studies revealed the presence of these chromium nitr ides in the passive film, which aas attributed to the decreased corrosion r esistance at a higher dose. Secondary ion mass spectroscopy studies on the passive film showed the,variation in the depth profile upon nitrogen ion im plantation Thus, nitrogen ion implantation can be effectively used as a met hod to improve the corrosion resistance of the orthopedic implant devices m ade of titanium-modified type 316L SS. The nature of the passive film and i ts influence on corrosion resistance are discussed in this article.