Superhydrophobic composite coating with active corrosion resistance for AZ31B magnesium alloy protection

A superhydrophobic, self-healing anti-corrosion coating was prepared by in-situ growth of tungstate corrosion inhibitor intercalated layer double hydroxides (LDHs) conversion film on the AZ31B magnesium alloy and then post-sealing a hydrophobic polymer layer of ureido crosslinked polydimethylsiloxane (U-PDMS) with laurate modified LDHs power (La-LDH) on the surface. The coverage of the dense, water-repellent top layer could suppress the penetration of electrolyte into the bottom LDHs layer and preserve the intercalated tungstate inhibitor from being wasted by ion-exchange at the very beginning of immersion. The anti-corrosion performance provided by the composite film was assessed by multiple methods including, potentiodynamic polarization, open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), immersion test and scanning vibrating electrode technique (SVET). The results indicate that compared to LDHs coating, the superhydrophobic composite coating shows longer term protection and faster self-healing effect, which is of great significance to expand the potential applications of magnesium alloys.