The Critical Role of the Solvent Effect on Titanium Anodizing Current

Ti anodization was carried out in five mixed electrolytes containing polyethylene glycol and ethanol of different proportions. We found that in the mixed electrolytes containing a high proportion of ethanol, dense films with uneven surfaces were obtained. In the mixed electrolytes containing low proportion of ethanol, orderly nanotube arrays were obtained and their growth rates were inhibited under smaller anodizing current. We therefore introduce the concept of hydrogen bond and electron mobility to discuss the essential relationship between the solvent effect and the anodizing current; in addition, the ionic and electronic dual–current model and oxygen bubble mold are invoked to explain the microstructures obtained in each electrolyte.