Effect of bending on anodized Ti6Al4V alloy: II. Behavior in vitro

Purpose: Evaluation of the influence of plastic deformation and characterization of the electrochemical behaviour of anodized implant rods made of the titanium alloy Ti6Al4V after immersion in air-saturated Ringer’s solution was presented in the paper. Design/methodology/approach: The specimens (dia 6 mm) were anodized and deformed by bending at angle 20o. The comparative characteristics of two zones: the max tensile (I) and the max. compressive stress (II) was based on the determination of electrochemical properties. Impedance spectra (EIS) and corrosion potential measurements were performed on 1, 6, 10 and 16th day after immersion in Ringer`s solution. Findings: Although bending caused an apparent decrease of the protective properties of the anodic layer, the characteristic two-layer anodic film and the values of corrosion potentials were restored due to immersion in Ringer’s solution. The regions of the compressive stresses show the much stronger tendency to restore. Research limitations/implications: The electrochemical tests in Ringer’s solution were performed only in static conditions. Fatigue tests in SBF are in progress. Practical implications: The explanation of the observed phenomena is proposed. Results of the work are of great importance for surgical practice in the pre-operative stage of spinal surgery procedures. Originality/value: Various stress zones formed on implant alloy during bending were described. The results of studies presented in the paper evidenced that changes noticed in the electrochemical behaviour in vitro in Ringer’s solution are advantageous with regard to the protective properties of the investigated alloy.