Natural tannic acid-based intumescent coating towards efficient fire resistance and thermal performance for steel structure

Developing fire protection coatings that reconcile outstanding fire safety with environmental sustainability remains a critical challenge in materials engineering. In this study, a new biomass-based intumescent coating was constructed from biomass-derived tannic acid, ammonium polyphosphate, melamine, zinc carbonate, and basalt scales. The resulting coating demonstrated excellent fire resistance performance, maintaining backside temperature of steel below 150 °C during 1200 s butane torch exposure, while the control steel with neat epoxy coating reaching structural failure threshold of 450 °C within 160 s. Cone calorimeter test indicated the rapid char formation behavior of the coating, achieving 88 % reduction in peak heat release rate, 49 % decrease in total heat release, and 83 % suppression in fire growth rate index compared to control coating. SEM-EDS, FTIR, XRD, Raman, and XPS techniques were employed to elucidate the fire protection mechanism of the coating, and it was proven that zinc carbonate and basalt scales participated in the carbonization process of the coating. The hierarchical structure combining chemical cross-linking and physical reinforcement resulted in the improvement in the integrity, cohesion, and morphology of char layer, thereby inhibiting heat and mass transfer during burning. Furthermore, the increase in surface roughness resulting from the introduction of basalt scales enhanced the hydrophobicity of the coating and allowed it to maintain strong adhesion and mechanical stability. In summary, this study not only demonstrates high fire resistance in biomass-based intumescent coatings but also offers insights for the sustainable design and functional optimization of fire protection coatings for steel structures.