Electrochemical Corrosion Performance of Anodic TiO₂ Nanotubes Synthesized from Glycerol–NH₄F Stirred Electrolytes

Titanium oxide (TiO₂) nanotubes produced on titanium (Ti) alloys by electrochemical anodic synthesis are used in biomedical and energy applications. Synthesis of these nanotubes involves fluoride ions, which travel in the electrolyte and reach the anodic Ti. Stirring of the electrolyte pushes the fluoride ions to move toward the anode and participate in oxidation. In this research work, anodic TiO₂ was produced on Ti using 0.5 wt.% NH₄F containing glycerol electrolyte (100 ml) for 20 and 30 V with the electrolyte being stirred by a magnetic pellet. Oxidation was done for 0.5 and 1 h at 20 V and 30 V using stirred and unstirred electrolyte conditions. The oxides produced from this method were amorphous (as synthesized) in all these conditions and became crystalline after the annealing process. This research showed that the nanotube length (minimum 600 and maximum 2300 nm) increased with electrolyte stirring, applied voltage, and oxidation time. The electrolyte stirring retained the tubular structure and provided rib-structured nanotubes for both the potential conditions. This study showed that oxidation for 1 h at 30 V in the unstirred condition produced nanotubes with excellent corrosion resistance in simulated body fluid (SBF).