Long Term Stability of a New Implant Alloy in Biological Environment

Abstract

This paper studies the long term (3000 exposure hours) behaviour of a new titanium base Ti-6Al-4V-1Zr alloy un-covered and covered with hydroxyapatite (HA) or bovine serum albumin/hydroxyapatite (BSA/HA) in Ringer solution of different pH values for to reproduce the complex conditions from the human body. Electrochemical cyclic voltammetry and linear polarization methods were used. Also, open circuit potentials and gradients were monitored for 3000 immersion hours in Ringer solution of different pH values. Bare Ti-6Al-4V-1Zr alloy presented more electropositive corrosion potentials, lower values of the tendency to passivation and passive current densities indicating an easier passivation and a very resistant passive film than of Ti. Covered BSA/HA/Ti-6Al-4V-1Zr alloy exhibited lower values of the tendency to passivation and lower passive current densities than the covered HA/Ti-6Al-4V-1Zr alloy and bare alloy due to the more stable coating. The corrosion rates have lower values for bare Ti-6Al-4V-1Zr alloy than Ti. Comparing with the un-covered alloy, lower corrosion rates were obtained for covered alloy, proving the very good protective properties both of HA and BSA/HA coating.