Surface characterization, corrosion properties and bioactivity of Ca-doped TiO2 coatings for biomedical applications

Abstract

This paper presents the preparation and characterization of calcium-doped titanium dioxide coatings for biomedical applications. The coatings were produced on the surface of the biomedical alloy M30NW by the sol–gel dip-coating technique using two different titanium alkoxide precursors. The effect of calcium ion doping on the topographical and anticorrosion properties, as well as the bioactivity of TiO2 coating was examined. The phase composition, thickness, morphology, topography and roughness of undoped and Ca-doped TiO2 coatings were investigated using X-ray diffraction (XRD), X-ray reflectivity (XRR), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Corrosion measurements were carried out in PBS solution using electrochemical methods. Anticorrosion properties of TiO2 and Ca/TiO2 coatings were specified based on the determined values for corrosion potential Ecor, polarization resistance Rp, corrosion rate CR, current density in passive range i0.5 and also breakdown Eb and repassivation Erep potentials. The porosity of TiO2-based coatings was determined from the measured polarization resistance. The bioactivity of TiO2 sol–gel coatings was examined with an immersion test in simulated body fluid (SBF) for 4weeks. The sol–gel procedure used in this study allowed the production of anticorrosive TiO2 coatings. As a result of calcium doping thicker, more porous and bioactive coatings were obtained.