Durable Deep-Cavity Superhydrophobic Coating with Stable Plastron for Long-Term Corrosion Protection of Magnesium Alloy

Abstract

Superhydrophobic coatings hold great promise for corrosion protection, yet their practical application is hindered by the instability of the entrapped air film (plastron). Herein, a durable superhydrophobic coating with deep cavities is prepared via an electrostatic flocking approach using aligned glass fibers and silica nanoparticles, drawing inspiration from the structure of staghorn coral. The optimized coating exhibits a water contact angle of 162.8° and robust plastron stability. A uniform and stable air layer is verified through optical imaging, laser reflection, and thermodynamic analysis. As evidenced by undetectable electrochemical signals, the stable plastron endows the coated Mg alloy with superior corrosion resistance during the initial 60 days of immersion in 3.5 wt % NaCl solution. Even after 140 days of immersion, the coating retains a high protection efficiency of 98.44% for the Mg alloy. The coating exhibits remarkable mechanical-chemical durability, withstanding mechanical abrasion (300 tape peeling, 90 sandpaper abrasion, 10 sand abrasion cycles), high temperature (140 °C), UV irradiation (8 h), and harsh chemical environments (100 min in 1 mol/L HCl, 50 min in 1 mol/L NaOH). The deep-cavity structure enables robust plastron stability, overcoming the inherent limitation of conventional superhydrophobic coatings and offering a durable solution for underwater corrosion protection of metals.