Corrosion and fire-induced strength degradation are primary drivers of severe economic losses and catastrophic failures in metallic structures. Polymer coatings serve as critical safeguards against corrosion; however, their flammability presents a fire risk, undermining the overall safety of the protected structure. Polyvinyl chloride (PVC) exhibits excellent inherent barrier properties and flame retardancy, but its poor film-forming ability has limited its practical application in high-performance coatings. To address this limitation, a core–shell nanostructure hybrid latex was successfully synthesized via seed emulsion polymerization, combining PVC with polyurethane (PU) and polybutyl acrylate (PBA). The resulting coating exhibits exceptional anti-corrosion performance, demonstrated by a low-frequency impedance modulus (|Z|0.01Hz) exceeding 4 × 1011 Ω cm2 after 30 days of immersion in a 3.5 wt% NaCl solution, confirming its robust and durable protective capability. Furthermore, the cone calorimeter test (CCT) revealed a 7.3% reduction in the peak heat release rate (PHRR) and an increased fire performance index (FPI) of 0.079 m2 s kW−1 for the PVC–PU–PBA film. This work presents a feasible and scalable strategy for fabricating multifunctional waterborne coatings with integrated corrosion resistance and flame retardancy, offering a promising solution for advanced steel protection.
