P-005
Silviu Iulian Drob
sidrob.icf@gmail.com
Romanian Academy, Institute of Physical Chemistry "Ilie Murgulescu", Romania
Doina Margareta Gordin, Thierry Gloriant
Institut National des Sciences Appliquées de Rennes, France
Corrosion bevaviour in simulated physiological solutions of Ti-Ta-Zr
This is a study regarding a comparison between the bare and surface treated versions of a ternary titanium bio-alloy with tantalum and zirconium as non-toxic alloying elements.
Titanium and its non-toxic alloys are widely used as surgical implants due to their low density and modulus and good mechanical properties. However, Ti and its alloys have poor tribological properties. Therefore, an implant’s surface needs to be modified to accomplish these critical demands for long-term stability, durability, affinity to bone, increased osseointegration and biocompatibility.
The bare and N-implantation surface of the Ti-25Ta-25Nb alloy was analyzed by XRD for the hardness using the nano-indentation method and the corrosion behaviour was analyzed in Ringer solutions of different pH values by cyclic and linear polarization and electrochemical impedance spectroscopy.
A new nitrogen-implantation technique was applied to the Ti alloy’s surface (trademark Hardion+) using a source of nitrogen ions, electron cyclotron resonance that assures higher energy and deeper implantation than the conventional techniques.
The XRD pattern of the bare Ti-25Ta-25Nb alloy showed diffraction peaks related to the b phase. The hardness presented a significant increase, about 2 times higher for N-implantation alloy.
The implantation layer was found to have a protective effect, increasing the corrosion and passivation potentials and decreasing the tendency for passivation and passive current density, due to its compactness and reinforcement action. A remarkable decrease of about 10 times of the corrosion current density and rate resulted for the treated alloy in comparison with the bare one, showing that the nitride layer inhibited the tendency of the alloy to corrode, conferring the substrate a high resistance to corrosion.
The polarization resistance for the N-implantation alloy has values twice as high compared with the bare one, indicative of a more resistant layer.
The Nyquist and Bode impedance diagrams exhibited very high values for the impedance, in the order of MX cm2, for the treated alloy in comparison with those for the bare alloy, which were in the order of kX cm2; these increases can only be attributed to the presence of the nitride layer on the alloy’s surface.
Taking into account all the obtained data, the Titanium alloy and its nitrogen-implantation variant are very suitable for implantology applications.