Studies have shown that fluorine ions play a significant role in the initiation and growth of TiO2 nanotubes. As fluorine is doped in titanium nanotubes (TiO2 NTs), fluoride gases form during TiO2 NT anodization. The concentration of fluorine in an electrolyte decreases as the anodization period increases. Maintaining a constant concentration of fluorine levels is a challenging task. In this paper, we discuss and calculate the quantity of fluorine reduced in an electrolyte given various electrolyte temperatures, sample sizes, and anodization time effects. According to thermodynamic calculations, F, FO, and FO2 have relatively low vapor pressures but HF, H2F2, H3F3, H4F4, H5F5, H6F6, and H7F7 have relatively high vapor pressures during anodization. The effects of fluorine contained in TiO2 NT (12.2 wt%) and vaporized from the electrolyte can cause the fluorine concentration in the electrolyte to decrease. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3374640] All rights reserved.