Abstract: This study aims to investigate the compatibility between intumescent fireproof coatings for steel structures and epoxy micaceous iron oxide intermediate paint systems, to establish an evaluation method for their compatibility, and to provide technical support for material selection in related protective engineering applications. Polarization curve testing, neutral salt spray testing, large-scale panel combustion testing, Scanning Electron Microscopy (SEM), interfacial gap measurement, and water resistance testing were employed to evaluate the individual properties and compatibility of three epoxy micaceous iron oxide intermediate paints (B1~B3) and three intumescent fireproof coatings for steel structures (C1~C3). The results indicate that the B3 intermediate paint exhibited the best corrosion resistance, with a corrosion current density of 1.52 × 10⁻6 A/cm2, while after 20 min of fire exposure, the expanded char layers of the C1 and C2 fireproof coatings remained intact. The coating systems B1C1, B2C2, B3C1, and B3C2 demonstrated good compatibility and water resistance, among which the acrylic-based C2 fireproof coating showed the best compatibility and interfacial adhesion with the epoxy micaceous iron oxide intermediate paints. Methods including microscopic interfacial bonding observation, interfacial gap width measurement, and adhesion testing were proven to be effective approaches for evaluating the compatibility and matching performance between epoxy intermediate paints and fireproof coatings, and can provide technical support for material selection and coating system optimization in corrosion protection and fireproofing engineering applications for steel structures, such as high-speed railway stations and industrial plants.

Key words: flame resistant coatings, intermediate paints, compatibility, interface, SEM