Superhydrophobic copper stearate/copper oxide thin films by a simple one-step electrochemical process and their corrosion resistance properties

Superhydrophobic films were coated on an aluminum alloy surface via a one-step electrochemical modification process in an ethanolic stearic acid (SA) solution containing copper nitrite (Cu(NO3)2) under a DC voltage. Various morphologies were obtained when different molar ratios of Cu/SA were used in the solution. The electrochemically modified films were characterized using X-ray diffraction and infrared (IR) spectroscopy; the films consisted of low surface energy copper stearate. This chemical component and the hierarchical rose petal-like micro-nano structure together provided a maximum contact angle of 162°and a minimum contact angle hysteresis of 1.52° with water roll-off properties. Furthermore, the polarization resistance was calculated from the Tafel curve of the superhydrophobic surface obtained from a Cu/SA solution with molar ratio of 0.5, which was 66 times greater than that of a chemically cleaned aluminum alloy substrate. Electrochemical impedance spectroscopy (EIS) revealed an increase in the charge transfer resistance of the chemically cleaned aluminum alloy substrate from 1.56 kΩ cm2 to 1130 kΩ cm2 for the superhydrophobic surface. Accordingly, the corrosion resistance of the superhydrophobic aluminum alloy surface produced by the one-step electrochemical process was superior to that of the chemically cleaned aluminum substrate