Amorphous titanium oxide film on Ti-Ni-Si amorphous alloy ribbons was prepared by anodic polarization process in ten kinds of electrolyte solutions. Addition of NH4F in (NH4)(2)SO4 solution accelerates an increase in current, i.e. formation of soluble Ti-fluoride complexes, resulting in the amorphous titanium oxide layers with nanometer-sized pores. Pore size decreases down to 12 nm with decreasing of applied voltage from 30 to 5 V. However, parallel capacitance Cp, series capacitance Cs, and RCs constant increase with decrease of pore size from 23 to 18 nm and then decrease in pore size region from 18 to 12 nm by formation of penetrating tunnels in the layer. It needs further enhancement of RCs for realization of superior electric storage capacitor. (C) 2015 Elsevier B.V. All rights reserved.