［Objective］To address the long-term corrosion protection requirements for Q235 steelstructures in coastal environments with high salinity and humidity，a comparative study was conducted on the protective performance evolution of two coating systems—bare steel with a primer/intermediate/topcoat system and galvanized steel with another primer/intermediate/topcoat system—under accelerated neutral salt spray and ultraviolet aging conditions. The differences in corrosion resistance behavior and failure mechanisms between the two systems were systematically evaluated，providing an experimental basis for the rational selection of coating systems for steelstructures in coastal regions.［Methods］Through surface analysis，chemical structure changes，and electrochemical tests，the failure mechanism of the two coating systems under accelerated corrosion testconditions were elucidated.［Results］The results showed that the bare steel coating system exhibited superior corrosion resistance and stability compared to the galvanized steel coating system under bothneutral salt spray and UV aging tests. The failure of the bare steel coating system was mainly attributedto chloride ion penetration and photo-oxidation，whereas the failure of the galvanized steel coatingsystem was closely associated with insufficient interfacial stability and localized reactions between thegalvanized layer and penetrating species from the coating.［Conclusion］Considering the performance and failure mechanism of the two coating systems，the bare steel with primer/intermediate/topcoatsystem was recommended for coastal and other highly corrosive environments to improve protectiveperformance，reduce maintenance costs，and ensure the long-term stable operation of coastal infrastructure.