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

Abstract

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.