Anodic TiO₂ from stirred Na₂SO₄/NaF electrolytes: Effect of applied voltage and stirring

TiO₂ was anodically formed on titanium from electrolyte containing 1M Na₂SO₄ and 0.5 wt.% NaF. Oxidation was carried out for 1 h at potentiostatic 20, 30 and 40 V from unstirred as well as stirred baths. At 20 V amorphous and nanotubular oxide is produced irrespective of the stirring conditions. Stirring increased the tubular length compared to the unstirred condition at 20 V. Oxidations at 30 and 40 V produced flat, crystalline anatase under both the bath conditions. A nanotubular network may be formed in the first 5 min and then anodic oxidation may occur laterally, perpendicular to the long-axis of the nanotubes.