Pre-Curing-Regulated Covalent Interfacial Coupling Enables Robust Anticorrosion and Antifouling Epoxy/PDMS Bilayer Coatings

To address the susceptibility of rigid–flexible bilayer coatings to interfacial peeling in marine anticorrosion and antifouling applications, this study employed a pre-curing-regulated interfacial covalent crosslinking strategy to construct a composite coating consisting of an epoxy primer loaded with 0.1 wt% 2-mercaptobenzothiazole (MBT) and an amino-terminated polydimethylsiloxane (PDMS) topcoat. The results demonstrate that optimal interfacial bonding was achieved with a primer pre-curing time of 10 min, yielding a pull-off strength of ~6.8 MPa. The fracture mode shifted from adhesive failure to cohesive failure within PDMS, indicating significantly enhanced interfacial adhesion. The bilayer coating exhibited excellent anticorrosion performance, with a polarization resistance of 3.5 × 106 Ω·cm2, a corrosion current density of 2.8 × 10−9 A·cm−2, and a corrosion rate of 3.4 × 10−5 mm·a−1. It also demonstrated strong antifouling performance, with anti-adhesion rates against C. closterium, E. coli, and P. pantotrophus reaching ~84%, 87%, and over 90%, respectively. Furthermore, the coating maintained robust interfacial integrity and protective performance under high-speed rotational flushing and ultrasonic cavitation. This study confirms that pre-curing regulation and interfacial covalent crosslinking can effectively improve the interfacial adhesion, anticorrosion, and antifouling properties of epoxy/PDMS bilayer coatings, providing a reliable approach for the multifunctional protection of marine equipment.