A functionalized duplex coating on CP-titanium for biomedical applications

Abstract

An oxygen diffusion layer (ODL) was produced on a commercially pure titanium (CP-Ti) using atmospheric thermal oxidation at a temperature of 850 °C for 36 h. The ODL was then electrochemically anodized in a 1 M sulfuric acid solution at various voltages of 100, 150 and 175 V. SEM images showed a non-uniform anodized titanium oxide layer due to insufficient potential driving force under a voltage of 100 V. A uniform porous layer containing anatase and rutile phases was formed at an anodizing voltage of 150 V, however, rutile was the only constituent of the layer formed under a higher voltage of 175 V. A hardness of 330–430 HV was obtained for the anodized layers compared with 200 and 1200 HV for CP-Ti and the ODL, respectively. However, the cell viability assay and cell adhesion results indicated an improved biocompatibility of the anodized top layer compared with the ODL and CP-Ti. Furthermore, polarization curves obtained in the PBS solution showed that the top anodized layer led to a lower corrosion current density by more than one order of magnitude compared with the ODL and CP-Ti. In addition, tribocorrosion experiments were conducted in PBS solution under a normal load of 1.5 N under various sliding distances of 25–300 m. The results showed a remarkable improvement of tribocorrosion resistance for the ODL and anodized layers compared with CP-Ti.