Corrosion-resistant superhydrophobic composite coating with mechanochemical durability

It is important to improve the corrosion resistance of magnesium alloy for expanding its application field. Poor durability seriously restricts the practical application of superhydrophobic anti-corrosion coatings. Here, a durable superhydrophobic anti-corrosion coating was prepared on AZ31 Mg substrate via a facile one-step spraying approach. The microscale glass fibers (GF) and nanoscale hydrophobic SiO2 particles were integrated into the epoxy resin (ER) to construct superhydrophobic composite coating (ER/GF-SiO2). Benefitting from the air cushion and physical barrier effect of superhydrophobic coating, the ER/GF-SiO2 coating exhibits good reinforced protectives properties. Compared with the AZ31, the corrosion current density of superhydrophobic coating decreased by three orders of magnitude and the low-frequency impedance modulus decreased by one order of magnitude. The ER/GF-SiO2 coating still maintained a high protective efficiency (89.44 %) after immersion in 3.5 wt% NaCl solutions for 13 d. The ER/GF-SiO2 coating shown good mechanochemical durability. The superhydrophobicity can be maintained after 40 m of sandpaper abrasion, 30 min of water impact, 20 min of sand impact, and 80 cycles tape-peeling. Furthermore, the high bond strength of the coating-substrate was verified by energetic analysis of molecular dynamics simulation at a microscopic level. The facile and effective preparation process provides an effective strategy for large-scale industrial production of durable superhydrophobic coating.