[Objective]To improve painting efficiency and cut costs,while meeting the higherrequirements for dry film thickness of waterborne epoxy coatings in a single application within the steelstructure coating industry.[Methods] Through the screening of waterborne epoxy curing agents, waterborne epoxy emulsions,and rheological additives,a high-build waterborne epoxy mica iron oxide(MIO) intermediate coating was developed. The study focused on the evaluation of the coating's sagging resistance,neutral salt spray test,pull-off adhesion,and continuous condensation test. Additionally,the water evaporation rate under different temperatures and wet film thicknesses wasmeasured via the mass loss method to determine the optimal application conditions.[Results]The optimized coating demonstrates exceptional application properties:sagging resistance of 425 μm(wet film,one coat),2 280 h neutral salt spray test,7 MPa pull-off adhesion,and 504 h continuous condensation test,meeting industrial requirements for heavy-duty corrosion protection.[Conclusion] The composite coating system met all requirements for atmospheric corrosion category C4(H) as specified in the Chinese industrial standard HG/T 5176—2017(Water-based anticorrosive coatings for steel structures). This work provides a reliable solution for industrial applications of high-performance waterborne epoxy intermediate coatings.