A hierarchically amphiphobic structure enables coating an extraordinary anti-corrosion performance

Abstract

Amphiphobic coatings have great potential in anti-corrosion coatings, oil-water separation, and so on. These are usually achieved by building multistage micron/nanometer roughness or re-entrant curvature surface through low surface energy materials. However, the complexity and mechanical brittleness of amphiphobic coatings derived from surface micro/nano structures have long posed challenges to their practical application. Here, we constructed a hierarchical structure coating with amphiphobic properties using polydopamine/polyethylenimine (PDE) as a connecting layer between the 1H,1H,2H,2H-perfluorodecyltriethoxysilane (PFDTES)-modified epoxy coating (POS-EP) and the carboxylated carbon nanotube (CNTs-COOH) modified epoxy coating (CNTs-EP) via dip-coating technology. CNTs-COOH addition reduces the porosity defects in the epoxy resin and impart hydrophilicity to the coating, demonstrating excellent underwater oleophobicity (OCA = 134.6°), thereby preventing the POS-EP coating from being eroded by oily organic substances in aqueous environments. PFDTES is employed to enhance the hydrophobicity of the epoxy resin, improving the coating's impermeability and corrosion resistance, with a water contact angle of 127.2° on its smooth surface. Surface morphology and elemental analysis confirm the seamless connection of the hydrophobic and hydrophilic layers facilitated by the PDE transition layer. Consequently, the amphiphobic coating with the hierarchical structure exhibits outstanding anti-corrosion performance. Compared to the epoxy resin coatings, the amphiphobic coating's resistance (R_c) and low-frequency modulus (|Z|_0.01Hz) are improved by 2 to 4 orders of magnitude after 60 days of immersion testing in 3.5 wt% NaCl and 18 days of neutral salt spray tests. Even the coating suffered the local damages, the synergistic effects between the amphiphobic interface can still hinder the attacks of corrosion media, and thus continues to supply good anti-corrosion properties. Given its low cost, scalability, and durability, this novel coating is expected to pave new avenues for the construction of various amphiphobic coatings.