Self-healing, superhydrophobic coating based on mechanized silica nanoparticles for reliable protection of magnesium alloys

A new type of host–guest feedback active coating was constructed on a magnesium alloy surface by incorporation of “guest” mechanized silica nanoparticles (MSNPs) as smart nanocontainers into a host self-assembled nanophase particle (SNAP) barrier coating. MSNPs, consisting of mesoporous silica nanoparticles and supramolecular nanovalves in the form of pseudorotaxanes, are capable of blocking entrapped corrosion inhibitor, 2-hydroxy-4-methoxy-acetophenone (HMAP), in mesopores under neutral solution conditions, and only release this chemical upon alkali or Mg2+ stimuli that corresponds to environmental stimuli occurring on corroding micro-regions of magnesium alloy. The particular alkali/Mg2+ dual stimuli-responsive release property of the MSNPs endows the physical barrier coating with self-healing potential. Taking advantage of the rough micro/nanostructural surface of the feedback active coating, the superhydrophobic surface was subsequently obtained by modification with 1H,1H,2H,2H-perfluorodecyltriethoxysilane, and the self-healing superhydrophobic coating was successfully fabricated. The well-designed coating exhibited excellent anticorrosion performance when compared to a reference SNAP coating, and isolated magnesium alloy from aggressive attack in 0.05 M NaCl for 15 days due to the water-repellent surface as well as active protection deriving from the MSNPs. Furthermore, once the surface was mechanically scratched, the alkali/Mg2+-triggered release of HMAP from MSNPs formed a compact molecular film on the damaged alloy surface, inhibiting corrosion propagation and executing the self-healing function.