Effect of N⁺ ion implantation on the corrosion behaviour of Ti—6Al—7Nb and Ti—5Al—2Nb—1Ta orthopaedic alloys in Hanks solution

Abstract

Ti—6Al—7Nb and Ti—5Al—2Nb—1Ta alloys were implanted with N⁺ ions with an ion energy of 75 keV at a dose rate of 1 × 10¹⁷ and 1 × 10¹⁸ ions cm⁻². Open circuit potential (OCP) and potentiodynamic cyclic polarization measurements were carried out on the titanium alloys in Hanks solution to assess their corrosion resistance. The tendency for repassivation is higher in the case of implanted alloys than in untreated alloys owing to the formation of stable passive films. The impedance data showed a decrease in the double layer capacitance and an increase in the charge transfer resistance of the treated alloys. Nitrogen ion implanted Ti—6Al—7Nb was found to be more corrosion resistant than implanted Ti—5Al—2Nb—1Ta alloy.