Kaolin- and Elastic Adhesive-Reinforced Epoxy Superhydrophobic Anticorrosion Coating for Durable Steel Protection

Epoxy coatings are widely used to protect metals against corrosion. However, their hydrophilic surfaces and limited mechanical durability can accelerate coating degradation in abrasive and corrosive environments. Here, a superhydrophobic anticorrosion coating was constructed on Q235 steel by integrating a kaolin-reinforced epoxy primer, an elastic adhesive interlayer, and a hydrophobic SiO2 nanoparticle top layer. The EP-K/SiO2 coating exhibited a water contact angle (CA) of 157.8° and a sliding angle of 2.1°, indicating the formation of a low-adhesion superhydrophobic surface. The kaolin-filled epoxy underlayer improved the mechanical robustness and barrier performance of the coating. After 19 m of abrasion or 200 cycles of tape peeling, the coating still maintained its superhydrophobic property. The electrochemical analysis in 3.5 wt% NaCl solution revealed that the corrosion current density of the EP-K/SiO2 coating reduced to 7.9 × 10−12 A·cm−2. After immersion for 15 d, the corrosion protection efficiency was still maintained at about 99.33%. During the salt spray test, solution immersion, outdoor exposure, ultraviolet aging, antifouling and self-cleaning tests, the coating preserved its structural integrity and water-repellent property. This triple-layer structure provides a feasible method to produce robust superhydrophobic epoxy coatings for corrosion protection of steel substrates.