A crystalline TiO
2 (c-TiO
2) film was electrochemically deposited onto a 10 cm × 20 cm hot-dip-galvanized (HDG) steel plate at 60 °C from an alkaline
aqueous solution containing 0.1 M titanium potassium oxalate dehydrate and 1 M hydroxylamine. The electrochemical deposition
was carried out by a galvanostatic method. First, a current density of 10 mA cm
−2 was applied for 5 min, which led to the formation of a uniform coating of TiO
2 on a 1 cm × 1 cm small HDG plate. A crystalline layer was observed, however, only in the central area, whereas the upper
and the edge areas were amorphous. Both calculations and experiments confirmed that this was due to the difference of the
local current densities in the vicinities of different areas. Next, three different currents (5 mA cm
−2 (2 min), 10 mA cm
−2 (2 min) and 20 mA cm
−2 (1 min)) were applied continuously so that the local current density for each part of the substrate achieved appropriate
deposition conditions. The film thus obtained was crystalline in all areas and of uniform thickness.
Keywords Crystalline TiO2
- Electrochemical deposition - Finite element calculation - Hot-dip-galvanized steel - Staged pulse deposition - Uniform coating