Development of superhydrophobic corrosion resistance coating on mild steel by electrophoretic deposition

A superhydrophobic TiO2 coating was prepared on mild steel to protect/increase life span of the steel by a simple one step electrophoretic deposition (EPD) technique followed by post-deposition treatment with methylhydrogen polysiloxane (trade name KF-99) and heat treatment. Superhydrophobicity was developed at some critical concentration (20 wt% solution) of KF-99. The water contact angle of bare steel, TiO2 coated phosphated steel substrate (PSS) and TiO2 coated PSS post treated with KF-99 (20 wt% solution) were 11 degrees, 41.7 degrees and 160.7 degrees, respectively. The corrosion resistance of the superhydrophobic coating was estimated by Tafel polarization measurement. The potentiodynamic curves clearly demonstrated that the corrosion rate of superhydrophobic coating was an order of magnitude lower than bare mild steel in 3.5 wt% NaCl solution. The E-corr and I-corr values for the superhydrophobic TiO2 PSS coating post treated with KF-99 were - 380 mV and 0.09 mu A respectively, compared to - 930 mV and 120.22 mu A for bare steel and - 820 mV and 20.41 mu A for TiO2 coated (PSS) untreated with KF-99. It clearly shows significant improvement in corrosion resistance properties of the super hydrophobic TiO2 coated PSS. The coating also exhibited very strong adhesion to the surface with a nano indentation hardness value of 0.5 GPa. The superhydrophobic coating with excellent corrosion resistance thus developed is a promising candidate for wide range of industrial applications.