Interfacial Barrier Layer Properties of Three Generations of TiO2 Nanotube Arrays

• TiO2 layers were produced by anodizing a Ti substrate in three types of electrolytes.
• EIS is an appropriate method to follow the properties of the barrier oxide layer.
• SECM provides a visual observation of the pitting processes.

Three generations of TiO2 nanotubular arrays (TiNT) were obtained by anodization of titanium foil in three different solutions: Aqueous acid containing fluoride media, organic based containing fluoride media and chloride containing electrolyte.This paper investigates the effect of the electrolyte composition on barrier layer characteristics of TiNT. Correlation between the dimensional aspect of TiNT and the electrochemical properties was investigated. Electrochemical characteristic from Electrochemical Impedance Spectroscopy (EIS) were discussed. EIS is considered to be a highly sensitive technique that allows determining barrier oxide layer characteristics. Semiconducting properties as well as thicknesses are discussed in correlation with anodizing electrolyte. Scanning electrochemical microscopy (SECM) was employed for in situ characterization of surface chemical activity of titanium in chloride containing electrolyte. The SECM has detected corrosion pits as well as the surrounding cathodic reaction. Nucleated pits on titanium takes place on the top of grain most probably with surface orientation (0001).