Electrochemical investigations of Ti6Al4V and Ti6Al7Nb alloys used on implants in bone surgery

Purpose: The subject of the research work is an analysis of surface roughness impact and the influence of the steam sterilisation process on physicochemical properties of samples made of Ti-6Al-4V and Ti-6Al-7Nb alloys after their exposure in a solution simulating the osseous environment. Design/methodology/approach: A surface roughness diversification of the samples made of Ti alloys was obtained with the aid of mechanical working – grinding and with the use of mechanical polishing. A corrosion resistance test was performed based on an anodic polarization curves recording. An Electrochemical Impedance Spectroscopy (EIS) method was used as well for assessment of the effects which occur on the surface of the examined alloys. Findings: The potentiodynamic studies showed favourable influence of steam sterilisation process (in an autoclave) on corrosion resistance of Ti alloys, regardless of the applied mechanical treatment. Exposition of the samples in Ringer’ solution caused further increase of corrosion resistance only for Ti-6Al-7Nb alloy. Analysis of impedance spectra showed presence of the capacitive passive layer for all tested variants. Research limitations/implications: Obtained results of potentiodynamic studies showed how a physicochemical condition of the samples surface, exposed to the solution simulating osseous system environment, was changing. In order to determine properties fully and surface structures of the Ti-6Al-4V and Ti-6Al-7Nb alloys after the sterilisation and the 60-day exposure to Ringer’ solution, impedance characteristics, obtained by means of EIS were determined. Differences of parameters describing electrical properties of the layers formed after the exposure to Ringer’ solution, are probably caused by a change of their chemical composition. Originality/value: The potentiodynamic and EIS studies of corrosion resistance in Ringer’ physiological solution allow to predict behaviour of Ti-6Al-4V and Ti-6Al-7Nb implants in osseous system environment.