Superhydrophobic and corrosion-resistant siloxane-modified MgAl-LDHs coatings on Mg alloy prepared under mild conditions

A superhydrophobic and corrosion-resistant LDH-W/PFDTMS composite coating was prepared on the surface of Mg alloy. The LDH-W/PFDTMS composite comprised of a tungstate-intercalated (LDH-W) underlayer that was grown at a low temperature (versus hydrothermal reaction condition) under atmospheric pressure and a polysiloxane outer layer obtained in a solution containing perfluorodecyltrimethoxysilane (PFDTMS) by a simple immersion method. The successful intercalation of tungstate into the LDH phase and the following formation of the polysiloxane layer were confirmed by the X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The corrosion resistance of the LDH-W film before and after PFDTMS modification was evaluated by electrochemical impedance spectroscopy (EIS), Tafel curves, and immersion experiments. Compared with the pure LDH-W film, the LDH-W/PFDTMS coating exhibited significantly enhanced corrosion protection for Mg alloy, with no apparent signs of corrosion after exposure to a 3.5wt% NaCl solution for 15 days. The static contact angle and water repellency tests of the LDH-W/PFDTMS coating demonstrated the superior superhydrophobicity and self-cleaning ability for water and several common beverages in daily life. These results guide the preparation of superhydrophobic and corrosion-resistant LDH-based composite coatings on Mg alloy surfaces under relatively mild reaction conditions.