Surface Coloration and Electrochemical Impedance Spectroscopy Characterization of Oxygen Plasma Implanted Orthopaedic Titanium Alloys

Oxygen plasma immersion ion implantation (O-PIII) is performed at different frequencies to produce stable passive films with different color on titanium alloys. UV-visible reflectance spectra acquired from these films show that the strong reflection region shifts to long wavelength as the implantation frequency or time is increased. X-ray photoelectron spectroscopy indicates that these passive films possess three layers with different thicknesses and chemical compositions. As the frequency is increased, both the outer and intermediate layers become thicker while the thickness of gradient transition layer changes only slightly. EIS spectra and simulated results reveal that the implantation frequency and duration significantly influence the structure, chemical composition, and color of these passive films.