Surface characteristics, corrosion behavior, and antibacterial property of Ag-implanted NiTi alloy

NiTi shape memory alloy was modified by Ag ion implantation with different incident doses to improve its antibacterial property. The atomic force microscopy, auger electron spectroscopy, and X-ray photoelectron spectroscopy show that the surface of NiTi alloy is covered by TiO2 nano-film with embedded pure Ag with a peak concentration of 5.0 at% at the incident dose of 1.5 x 10(17) ions center dot cm(-2), and Ni concentration is reduced in the superficial surface layer. The surface roughness reaches the maximum value nearly twice higher than the control sample at the incident dose of 1.5 x 10(17) ions center dot cm(-2). The potentiodynamic anodic polarization curves show that the Ag-implanted NiTi samples possess higher self-corrosion potential (E (corr)) and lower self-corrosion current density (i (corr)) but lower breakdown potential (E (br)). Therefore, the corrosion resistance of the Ag-NiTi is comparable to, if not better than, the untreated NiTi. The antibacterial tests reveal that there is a distinct reduction of the germ numbers on the Ag-NiTi, which is due to the direct contact between Ag and germ, and enhanced by the leaching Ag ions.