Corrosion Study of Ti5Al4V and Ti6Al4V in Different Simulated Body Fluids

Abstract

The (α + β) Ti6Al4V alloy is widely used in different industrial applications and in medicine. The decrease in the content of the α-strengthening element Al in Ti5Al4V as opposed to conventional Ti6Al4V alloy reduces the hardness as Al is a solid solution hardener but simultaneously, the alloy is expected to have lower cytotoxicity, improved plasticity and low precipitation hardening ability at precipitation temperature. The role of the alloying elements and the influence of heat treatment on corrosion resistance of Ti5Al4V and Ti6Al4V alloys have been studied after a short and long-term immersion in Ringer (RS), phosphate buffer saline (PBS) with and without the addition of H2O2, and 5 M HCl at 37 ± 0.1 °C. It has been found out that lower pH and higher Cl− concentration in RS make the surface of the alloys more prone to pitting corrosion and showing nobler corrosion potentials at the same time, in contrast to PBS where salt films of insoluble products are formed on some pits. The potentiodynamic polarisation measurements show higher anodic reaction rate after a 30-days’ period of immersion in PBS and H2O2 for both alloys. The dissolution of Ti, Al, and V and oxidation in 5 M HCl are the highest for solution treated Ti6Al4V and Ti5Al4V alloys, while the corrosion rate for the 10-days’ period in the acid was the lowest for the as-received Ti5Al4V.