Multi‐Functional Waterborne Polyurethane Coatings Enabled by the Cooperative Effect of Graphene Oxide and <scp> CeO ₂ </scp> Nanoparticles for Superior Anti‐Corrosion Protection

ABSTRACT Metal materials in engineering structures face severe corrosion challenges. Waterborne polyurethane (WPU) is widely regarded as a sustainable coating alternative and holds potential in corrosion protection; nevertheless, its actual usage is constrained by inadequate mechanical characteristics, limited water resistance, and insufficient corrosion resistance. In this study, graphene oxide (GO) and nano‐cerium oxide (CeO 2 ) were introduced as functional fillers into a WPU matrix via physical blending to prepare three composite materials (WPU‐GO, WPU‐Ce, and WPU‐GO‐Ce). The influence of nanofillers on the characteristics of WPU was comprehensively examined. The findings indicated that the addition of nanofillers substantially improves the overall properties of the composites. Specifically, CeO 2 (at 0.25 wt%) interacts with the hard segments of polyurethane through interfacial hydroxyl groups, increasing the tensile strength of WPU‐Ce to 31.37 MPa. The synergistic effect of GO (at 0.125 wt%) and CeO 2 (at 0.125 wt%) in the WPU‐GO‐Ce system forms a dense physical barrier, achieving an impedance modulus of 8.03 × 10 5 Ω·cm 2 two orders of magnitude higher than WPU, indicating optimal corrosion resistance. Additionally, nanofillers delay corrosive medium diffusion via a “maze effect,” while improving thermal stability (T 50 up to 404.63°C) and UV shielding performance (near‐zero transmittance across the entire UV spectrum). This work reveals that the GO/CeO 2 co‐modification strategy significantly enhances the multifunctional performance of WPU coatings, providing theoretical and technical support for long‐term corrosion protection in complex environments.