The electrochemical behaviour of titanium based biomaterials in HNO<inf>3</inf>and hank oxidant solutions. II. Electrochemical impedance spectroscopy

Abstract

The most advantageous titanium alloys for implantology are T-6Al-4V and Ti-5Al-2.5Fe. The second alloy has very good corrosion resistance, no toxicity and high mechanical properties. In soft tissues, aluminium and iron show a reaction of "sequestration", namely the formation of connective tissue membrane around the implant. Also, the implant is integrated in bone, the phenomenon of "osseointegration". However, the titanium and its alloys behaviour in physiological environment, in special conditions of surgery, temperature, inflammations or infection is not enough known. The implanted material response must be favourable, otherwise it is affected the implant performance and implicitly can be dangerous for the life of the patient. This paper proposes to study, by the electrochemical impedance spectroscopy method, the titanium and its alloy Ti-5Al-2.5Fe behaviour in Hank and 1N HNO3 solutions, which try to reproduce the physiological environment in normal and infectious conditions, respectively. Nyquist diagrams obtained at more positive electrode potentials and different polarisation times show the increase and compactness of passive layer This anticorrosion resistance increases with the shift of the potential to more electropositive values and with the immersion time, being better in the case of Ti-5Al-2,5Fe alloy than of Ti.