To address the problem of insufficient durability of concrete in ammonium sulfate environments in coastal areas, this study systematically evaluated the durability of concrete under ammonium sulfate infiltration using different water-cement ratios (w/b) and surface coating treatments. The concrete specimens were coated with colloidal silicate, silane/nanocomposite, and vinyl ester/nanocomposite coatings, and the mass change, and microstructural evolution were tested under baseline infiltration and composite infiltration (freeze-thaw cycle and dry-wet cycle) condition. The results show that composite infiltration caused more serious damage to concrete than baseline infiltration. After reducing the water-cement ratio from 0.6 to 0.4, the cumulative mass loss of the concrete specimens coated with pure vinyl ester is reduced by about 55% compared with the uncoated specimens. Reducing the water-cement ratio densifies the microstructure of concrete and reduces permeability. Although the colloidal silicate surface treatment improved the initial fluid resistance, it failes to effectively protect the concrete due to its hydrophilicity and the shrinkage microcracks of the coating. When the water-cement ratio is 0.6, the cumulative mass loss of the concrete specimen with the silane/nanocomposite coating can be reduced by up to 56% compared with the specimen coated with pure silane due to its hydrophobicity and the enhancement effect of the nanomaterial.When the water-cement ratio is 0.4, the cumulative mass loss of the concrete specimens coated with vinyl ester/nanocomposite can be reduced by up to 65% relative to the specimens coated with pure vinyl ester due to the strong bond and chemical stability of the polymer film. Both silane and vinyl ester nanocomposites show good results in the protection of concrete from ammonium sulfate corrosion in coastal areas, providing effective protective measures for the design and maintenance of concrete structures in coastal areas, which can significantly extend the service life of concrete structures in ammonium sulfate environments and reduce maintenance and replacement costs.