Electrochemical behavior of anodic nano-structured titania synthesized from stirred and unstirred electrolytes

Titanium was anodically oxidized in aqueous electrolyte containing dissolved 1 M Na₂SO₄ and 0.5 wt% NaF. This oxidation was performed for 0.5 and 1 h at 20 and 30 V in unstirred and magnetic pellet stirred baths. Irrespective of the stirring conditions, amorphous, nanotubular oxide was formed at 20 V. Compared to the unstirred condition, the tubular length was increased upon stirring at 20 V. However, flat, anatase layers were produced at 30 V in both stirring conditions. The nanotube network was formed probably in first 5 min and disturbed later, so that the oxidation proceeds laterally and perpendicular to the longitudinal tubular axis. Among the oxides tested, the oxide films obtained by oxidation for 0.5 h at 20 and 30 V under stirring condition (M20, 0.5 and M30, 0.5) have higher impedance and lower corrosion current density in simulated body fluid (SBF). The SBF represents the actual conditions of fluid inside the body. Graphical abstract: [Figure not available: see fulltext.].