This study investigates the effects of various additives and aging treatments on the properties of marine engineering protective coatings. An organic-inorganic composite protective coating was prepared using kaolin as the primary raw material, combined with ethylene-vinyl acetate copolymer emulsion. The corrosion resistance of the coating was evaluated by accelerated aging treatments such as thermal aging, ultraviolet aging, and alkali soaking. The results showed that alkali immersion had the most adverse impact on the corrosion resistance of the coating, significantly increasing the self-corrosion current density and decreasing the polarization impedance markedly. Additionally, the effects of various admixture coatings on weather resistance were discussed, as measured by the mass loss rate, water absorption rate, water contact angle, and tensile properties. The results showed that the three admixtures improved the weatherability of the coating, and the addition of the coupling agent significantly improved its performance in various environments. It was found that the organic-inorganic composite protective coating exhibited excellent corrosion resistance and durability in harsh marine environments, providing a crucial theoretical basis for designing and selecting marine engineering protective coatings.