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A new Ti-20 Nb-10 Zr-5 Ta 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. [ABSTRACT FROM AUTHOR]

A new Ti-15Zr-5Nb alloy with suitable microstructure and mechanical properties was processed by galvanostatic anodization in 0.3 M H3P04 solution and a continuous nanostructured layer of protective Ti02 oxide was electrodeposited. The obtained anatase oxide layer has a nanotubes-like porosity (SEM observations) and contains significant amount of phosphorus in phosphotitanate compound embedded in the oxide lattice (Raman, FT-IR, SEM, and EDX analysis). This layer composition can stimulate the formation of the bone and its porosity can offer a good scaffold for bone cell adhesion. The electrochemical behaviour, corrosion stability, and variations of the open circuit potentials, Eoc, and corresponding open circuit potential gradients, ▵ Eoc for 1500 soaking hours in Ringer solutions of 3.21, 7.58, and 8.91 pH values were studied. The anodized layer was more resistant, stable (from EIS spectra), and was formed from an inner barrier insulating layer that assures the very good alloy corrosion resistance and an outer porous layer that provides the good conditions for cell development. The nanostructured alloy has higher corrosion stability, namely, a more reduced quantity of ions released and a lower toxicity than that of the bare one. The monitoring of Eoc and ▵Eoc showed the enhancement and stabilizing of the long-term passive state of the anodized alloy and, respectively, no possibility at galvanic corrosion. [ABSTRACT FROM AUTHOR]