Deposition, Characterization, and Corrosion Resistance of Nanocrystalline Bioactive Hydroxyapatite Ceramic Coating on New Ti-20Nb-10Zr-5Ta Alloy

A new Ti-20Nb-10Zr-5Ta bioalloy with low Young's modulus (59 GPa) was coated with nanocrystalline hydroxyapatite (HA) ceramic layer by chemical method of soaking in a slightly supersaturated calcium and phosphate ions solution. The formation of HA was demonstrated using XRD, Raman microscopy and energy-dispersive X-ray spectroscopy; the coating morphology and microstructure were determined using SEM. The coating protective capacity and its long-term (2000 h) stability in simulated biofluids were revealed by the improvement of the all electrochemical parameters; also, HA ceramic coating reduced the alloy corrosion and ion release rates. After 2000 immersion hours in biofluids no compositional change occurs in the HA ceramic coating, only depositions from solution take place that change the coating morphology. Also, the in time increase of the coating stability and thickness (as a result of the new deposition from physiological solutions) indicates bioactivity.