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

We have developed a superhydrophobic and corrosion-resistant LDH-W/PFDTMS composite coating on the surface of Mg alloy. This composite comprised a tungstate-intercalated (LDH-W) underlayer that was grown at low temperature (relative to hydrothermal reaction conditions) under atmospheric pressure and an outer polysiloxane layer created from a solution containing perfluorodecyltrimethoxysilane (PFDTMS) using a simple immersion method. The successful intercalation of tungstate into the LDH phase and the following formation of the polysiloxane layer were confirmed through X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The corrosion resistance of the LDH-W film, both before and after the PFDTMS modification, was evaluated using electrochemical impedance spectroscopy (EIS), Tafel curves, and immersion experiments. The results showed that Mg coated with LDH-W/PFDTMS exhibited significantly enhanced corrosion protection compared to the unmodified LDH-W film, with no apparent signs of corrosion after exposure to 3.5wt% NaCl solution for 15 d. Furthermore, the LDH-W/PFDTMS coating demonstrated superior superhydrophobicity and self-cleaning properties against water and several common beverages, as confirmed by static contact angle and water-repellency tests. These results offer valuable insights into preparing superhydrophobic and corrosion-resistant LDH-based composite coatings on Mg alloy surfaces under relatively mild reaction conditions.