Robust, scalable and fluorine-free superhydrophobic anti-corrosion coating with shielding functions in marine submerged and atmospheric zones

Abstract

Biomimetic superhydrophobicity endows various substrates with amazing multi-functional properties. However, fragile hierarchical structures, fluorine-containing chemicals usage, and strict requirements for substrate scopes remain thorny challenges. Herein, we constructed a mechanical robust superhydrophobic ZnO@STA@PDMS coating with fluorine-free reagents through wide-applicable and substrate-independent spray-coating method. Field-emission scanning electron microscopy (FE-SEM), energy-dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and contact angle meter were used to assess the surface micro-nano structures, chemical compositions, thermal stability and wettability variations. The corrosion resistance of the developed superhydrophobic ZnO@STA@PDMS coating was evaluated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements. The corrosion current density (Icorr) of the substrate reduces by two orders of magnitude after being spray-coated with superhydrophobic ZnO@STA@PDMS coating, indicating excellent corrosion resistance in marine submerged zone. In simulated marine atmospheric conditions with high relative humidity, the salt-deliquesce behaviors of single and double NaCl particles on bare and coated Q235 carbon steel surfaces were recorded. In a high humidity atmospheric environment, the instantaneous salt-deliquesce self-coalescence phenomena provides a new type of anti-corrosion mechanism. Furthermore, the prepared superhydrophobic coating can withstand more than 30 tape-peeling cycles and 400 cm abrasion distance, demonstrating good mechanical stability in prospective real-world applications.