EIS tests of electrochemical behaviour of Ti6Al4V and Ti6Al7Nb alloys

Purpose: This study has been undertaken in order to establish the influence of parameters of the electrochemical treatment of Ti-alloys on their electrochemical behaviour in Tyrod solution. Design/methodology/approach: Surface of the Ti-alloys: Ti6Al4V and Ti6Al7Nb in the form of a rod submitted to grounding, electropolishing and anodic passivation. Electrochemical investigations were carried out by means of the electrochemical impedance spectroscopy method. Scope of this paper includes analysis of the impedance spectra based on Bode plot. Findings: Prolongation time of anodic passivation to 60 minutes caused formation of a two - layer model consisting of an inner layer which is compact and the barrier type, and outer layer which is porous. Research limitations/implications: Obtained results are the basis for the optimization of anodic passivation parameters of the Ti alloys as a metallic biomaterial. The future research should be focused on selected more suitable parameters of the electrochemical impedance spectroscopy test to better describe process on the solid/liquid interface. Practical implications: It has been found that a good resistance to corrosion and homogeneous oxide layer on the Ti6Al4V and Ti6Al7Nb alloys surface can be achieved due to the application of electrolytic polishing of these alloys in a special bath and anodic passivation in sulphuric acid (VI), phosphoric acid (V) and inorganic salts. Originality/value: Results of the experiments presents the influence of various conditions of anodic passivation of the surface of the Ti6Al4V and Ti6Al7Nb alloy. In this cases, when the surface roughness plays important role, this method can be applied in treatment of the material intended for medical applications especially.