Effect of N2+ ion implantation on the corrosion behavior of pure titanium

N2+ ions were implanted into commercially supplied pure titanium with different doses ranging from 5×1016 to 1×1018 ions/cm2, and the corrosion behavior was investigated in 70% sulphuric acid solution. Anodic polarization curves show that the peak anodic current density, passivation current density, and corrosion potential increase with increase in implantation dose when the dose is less than 1×1017 ions/cm2. When the implanted dose is 5×1017 ions/cm2, the corrosion resistance decreases though it is still larger than no implanted titanium. X-ray diffraction analysis shows the formation of titanium nitride on the implanted surface, i.e., Ti2N is found when the implanted dose is larger than 5×1016 ions/cm2 and both Ti2N and TiN when the implanted dose is 1×1018 ions/cm2. The aging at 673 K after ion implantation largely increases the corrosion resistance, which corresponds to the enhanced precipitation of Ti2N and TiN. AFM observation shows fine particles of titanium nitrides on the implanted surface. It is considered that the precipitation of Ti2N or TiN decreases the effective corrosion area to make the corrosion resistance higher.