Electrochemical behaviour of the nanostructured surface of Ti‐35Nb‐2Zr alloy for biomedical applications

Abstract

Titanium β‐alloys are perspective material for orthopaedic implants. Their bioactivity could be increased by surface nanostructuring. The nanotubular surface on the Ti‐35Nb‐2Zr alloy was prepared by anodic oxidation. The surfaces were characterised by electron microscopy and photoelectron spectroscopy. The electrochemical behaviour was determined by impedance spectroscopy and Mott–Schottky measurement. The surface analysis indicates enrichment of the oxidic layer by niobium. Nanotubular oxide layer behaviour in phosphate‐buffered solution was compared with native passive oxides surface and with thick oxide layer. The results of impedance measurement on the nanotubes were strongly affected by oxygen in the test solution. The corrosion resistance of the nanostructure was higher than that of the native passive layer. In the terms of the corrosion behaviour, the nanostructuring seems to be a promising surface treatment for medical applications.

Corrosion behaviour of the titanium beta alloy nanotubular surface in the presence of fluoride ions

“…Same results were stated by Kim et al in the case of nanotubes prepared on Ti-xZr alloys [24]. However, increased corrosion currents could be caused by differences in geometrical and real surface [25]. Application of titanium and its alloys in dental implantology represent a specific problem, because of they get in contact with fluoride ions coming from dental treatment products.…”

“…According to the potentiodynamic curves in physiological solution without fluoride ions (an environment without acceleration of corrosion processes), the real exposed area of the nanostructured surface caused an order increase in the passive current density which in this case corresponds predominantly to electrolyte reactions ( Fig. 4) [25]. This trend is not so obvious in physiological solution with 1000 ppm F -.…”

“…In the physiological solution, both the polished and nanostructured surfaces reached high total resistance values. The lower resistance of the nanostructured surface was caused by higher real surface than the relative geometrical [25]. The resistance of the pore solution (R1) was lower for the nanostructured surface.…”

“…This behaviour results from the surface state -the polished surface consists of a native passive layer which is relatively thin and contains also non-stoichiometric oxides, while the nanostructure is formed by the thick oxide layer containing single elements of the alloy in their highest oxidation state. Detailed analysis of the nanostructure was described in our previous study [25].…”

“…Their applications are mainly in orthopaedics and dental implantology due to their low density, high fatigue strength, excellent corrosion resistance, biocompatibility and osseointegration ability [1][2][3]. However, these materials may exhibit the considerable degree of biomechanical incompatibility because of the relatively high modulus of elasticity, approximately 110 GPa, compared to the compact bone (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25) [4]. This incompatibility may cause the "stress shielding effect".…”