Enhanced Long-Term Barrier and Corrosion Protection of Epoxy Coatings Modified With Silica Nano-Oil

In marine environments, epoxy coatings suffer from the penetration of corrosive species through microstructural defects and interfacial discontinuities, causing a rapid degradation in barrier performance during service. Nano-oil can alleviate the aggregation and poor interfacial compatibility of conventional nano filler in epoxy. Here, we synthesized the SiO₂ nano-oil by γ-Glycidoxypropyltrimethoxysilane functionalization and ring-opening grafting with bis(3-aminopropyl)-terminated polydimethylsiloxane and then incorporated it into epoxy coatings. SiO₂-K@PDMS exhibited liquid-like characteristics such as shear-thinning behavior and low surface tension. Electrochemical impedance spectroscopy results showed that the 4 wt% SiO₂-K@PDMS/EP system achieved an initial |Z| at 0.01 Hz of 1.73 × 10¹⁰ Ω·cm², 436 times that of pure EP. After immersion in 3.5 wt% NaCl solution for 30 d, its |Z| at 0.01 Hz remained at 3.07 × 10⁹ Ω·cm², about 3.88 × 10⁴ times that of pure EP. Scratched salt spray and fracture surface SEM results showed that SiO₂-K@PDMS mitigated corrosion propagation at defect sites and reduced filler aggregation and interfacial voids, which is consistent with its superior long-term impedance retention. In addition, this filler increased the surface hydrophobicity of the coating and reduced the initial adhesion of E. coli. SiO₂ nano-oil shows great potential for enhancing long-term protection performance of anticorrosion coatings.