Investigation of the formation mechanism of titanium oxide nanotubes and its electrochemical evaluation

Abstract

The electrochemical synthesis of titanium dioxide nanotubes (TNTs) on titanium alloys depends on the electrolyte composition and process parameters. To gain insight of titanium oxidation on commercially pure titanium grade 2 (cpTi-2), the effects of individual electrolyte species have been investigated by cyclic voltammetry. At constant 60 V potential, different nanotubular structures were obtained by varying time. Under synergistic action of anionic species and electric field with increase in anodizing time, the field enhanced dissolution become dominant as validated from the increase in the inner tubes diameter and decrease in wall thickness. On the other hand, the dissolution of inter-tubular region was also observed which resulted in the separation of nanotubes at higher anodizing time. The electrochemical performance of anodized samples has been evaluated in 1 wt% NaCl. The lower corrosion current density and passive current density registered by 30 min anodized sample corresponded to the limited ingress of ionic species at the Ti/TNTs interface compared to 60, 90, 120 and 150 min samples which contained large inter-tubular spacing. The electrochemical impedance spectroscopy (EIS) analysis was in support to potentiodynamic results confirming the diffusion-controlled reactions at the Ti/TNTs interface.