Modification of corrosion properties of titanium by N-implantation

Nitrogen implantation in titanium has been carried out at 125 and 100 keV with nominal doses between 4 × 1017 and 8 × 1017 ions cm-2, respectively. Surface characterization by Auger electron spectroscopy has demonstrated the presence of a TiN layer near the surface, which increased the surface hardness from 300 to 1000 HV. From the corrosion viewpoint, N-implantation has little effect in saline solutions, although a slight increase of corrosion resistance could be achieved. In acid solutions, impedance data show that the low frequency impedance of the implanted alloy was higher than that for pure titanium. The capacitance value was similar for all the implanted materials, being somewhat below the value found for unimplanted titanium. These data lead us to conclude that resistance is conferred by the surface formation of titanium nitride, rather than a surface oxide layer. No differences have been found in the corrosion behaviour of samples processed at doses of 4 × 1017 and 8 × 1017 ions cm-2.