Damage-Visualizable Smart Coatings Based on Waterborne Polyurethane: Synergistic Dynamic Monitoring of Surface Damage and Interface Corrosion

Traditional anticorrosion coatings are susceptible to microdefects during service, resulting from mechanical damage or environmental erosion. However, existing technologies are unable to continuously monitor coating conditions. Such microdefects, if not detected and repaired in time, will accelerate the corrosion failure of the metal structure. Herein, we reported environmentally friendly waterborne polyurethane (WPU) smart coatings for the synergistic monitoring of surface damage and interface corrosion. By introducing functional chain extenders into the WPU backbone, dual-mode monitoring of both surface damage and interface corrosion in coating/metal systems was achieved. Specifically, the coatings utilized the clusterization-triggered emission (CTE) characteristics of WPU to visually localize surface damage through fluorescence intensity changes. Simultaneously, by grafting 1,10-phenanthroline-5-amine (NH2–Phen) corrosion probes, the coating triggered color or fluorescence signal changes through chelation with Fe2+/Fe3+ ions released during metal corrosion, enabling real-time tracking of interface corrosion processes. Furthermore, electrochemical tests further demonstrated that the modified coating significantly reduced the corrosion current density from 115 μA/cm2 of pristine WPU to 0.467 μA/cm2, with the corrosion inhibition efficiency of over 90%, confirming that the NH2–Phen probe possesses the dual-functional characteristics of corrosion sensing and metal anticorrosion. This work provides a strategy for developing multifunctional integration of WPU smart coatings, whose smart response properties hold promising potential in diverse areas such as corrosion protection for marine equipment, self-warning coatings for spacecraft, and adhesives for precision electronic packaging.