Graphene nanoplatelet-functionalized polyurea coatings for high strength, corrosion resistance and smart sensing

Structural health monitoring in harsh environments demands scalable sensing coatings with exceptional mechanical robustness, weatherability and stability. We present a polyurea‑based nanocomposite spray sensing coating (PHSC). It integrates hexamethylene diisocyanate trimer-functionalized graphene nanoplatelets (HT‑GNPs) into a two‑component sprayable polyurea matrix. The covalent functionalization facilitates filler dispersion and network formation. The coating exhibits exceptional mechanical performance, achieving a tensile strength of 43.4 MPa and an elongation at break of 707.8% at 0.1 vol% of HT‑GNPs. The optimized formulation (2 vol% HT-GNPs) provides the best balance of properties, delivering robust piezoresistive sensing with gauge factors of 8.4 (0–235% strain) and 16.0 (>235% strain), along with rapid response (88 ms) and recovery (92 ms) times. The coating demonstrates excellent adhesion to diverse substrates (e.g., ceramic, automotive chassis) and maintains stable performance after damp-heat, salt-spray and UV-aging tests. Electrochemical analysis confirms robust corrosion resistance, exhibiting corrosion potentials of 0.23 V (H₂SO₄), 0.12 V (NaOH) and 0.15 V (NaCl). By combining rational molecular design with scalable spray processing, this work delivers a weather-resistant, multifunctional coating with promising potential for structural health monitoring in infrastructure and automotive applications.