Achieving lasting corrosion protection for superhydrophobic epoxy coatings with photothermal conversion property via constructing functionalized graphene nanoplatelet

Conferring versatility to the epoxy (EP) coating is highly desirable to achieve long-term corrosion resistance. In this work, a simple and effective strategy is reported to integrate corrosion protection, superhydrophobicity, and photothermal conversion into EP coating. Specifically, a functional filler based on graphene nanoplatelet is fabricated by the anchoring of polytannic acid and the grafting reaction of octadecylamine. The good interface compatibility, excellent adhesive strength (4.8 MPa), and stable superhydrophobicity (water contact angle of 152.4° and water sliding angle of 7.4°) provide a reinforced barrier effect (low water absorption and low permeability of oxygen and chloride ions), resulting in the impedance modulus of the composite coating being nearly three orders of magnitude higher than that of the pure EP coating after 28 days of immersion in 3.5 wt% NaCl solution. Furthermore, the surface temperature rises rapidly to 78.4 °C within 2 min under the sunlight of 200 mW/cm2, demonstrating the efficient photothermal conversion capability of the composite coating and accelerating the evaporation of water from the coating surface. Gratifying, the superhydrophobic property of the composite coating can be restored even after the salt spray test, which is attributed to the migration of long-chain alkyl under sunlight irradiation. Therefore, the prepared composite coating with photothermal conversion and superhydrophobic performance is expected to be a promising candidate for long-lasting corrosion protection under harsh application environments.