A bi-layer superhydrophobic coating with long-term anti-corrosion enabled by functionalized hexagonal boron nitride and PDMS-based polyurethane on Mg alloy

Two-dimensional (2D) nanocomposite coatings and superhydrophobic coatings are applied to retarding corrosion of Magnesium (Mg) and its alloys. However, stability of the delicate micro/nanostructure and corrosion durability are still intractable issues. In this work, a bi-layer superhydrophobic coating with excellent corrosion resistance has been successfully constructed on Mg alloy via a facile spray/spin assisted self-assembly technique. The polyurethane (PU) coating containing well-dispersed hydroxylated hexagonal boron nitride (OH-BN) nanoparticles acts as the barrier layer and “adhesive”, while the superhydrophobic modified h-BN (f-BN) nanoparticles serve as the water-repellent surface. In addition, the modifying agents containing dynamic disulfide bonds provide covalent bonding effect to construct a stable superhydrophobic surface. Hence, the obtained coating presents extreme non-wettability with an impressive static water contact angle (WCA) of 155° as well as possesses outstanding anti-water adhesion, anti-fouling and self-cleaning performance. Meanwhile, the designed coating shows excellent corrosion durability, which the value of |Z| f = 0.01 Hz retains at 9.5 × 10 9  Ω cm 2 , higher than PU coating of two orders of magnitude. The developed coating shows promising potentials as a durable protective material for Mg alloy and other metals and alloys, shedding new lights on developing high-performance corrosion resistance technologies.