The metal structure of estuarine ship locks is used to resist upstream saltwater intrusion and the corrosive high-frequency drying-wetting alternating environment caused by frequent water filling and emptying during the operation of ship locks. The corrosion characteristics of the metal structure (gate valve, mooring facilities, etc. ) in this special environment, however, are unknown. Therefore, this paper conducts corrosion tests of steel samples under high-frequency drying-wetting alternation of saltwater and analyzes the change rules of corrosion morphologies and corrosion rates of steel samples under different concentrations of chlorine salt and different drying and wetting regimes. On this basis, it investigates the adaptability of the anti-corrosive coatings of polyurethane, epoxy coal tar pitch, and chlorinated rubber in this special corrosive environment. The results show that the high-frequency wetting-drying alternation of saltwater can considerably accelerate the corrosion rate of steel, and the acceleration degree decreases with the increase in drying time. The corrosion rate of carbon steel in the high-frequency drying-wetting alternating environment of saltwater is about 5. 0 to 6. 0 times that in a freshwater environment and 1. 5 to 2. 0 times that in an ocean tidal environment. According to the measured macro-morphology and adhesion of various anti-corrosive coatings in the above special corrosive environment and the technical and economic analysis, it is suggested that chlorinated rubber coatings should be used as anti-corrosive materials for the metal structure of estuarine ship locks.