The accelerated wet-dry cyclic corrosion tests at different chloride content have been carried out on 09CuPCrNi. The morphology and composition of the rust products have been investigated. The rust layers were composed of the dense inner layer and the loose outer layer. The rust layers were mainly composed of magnetite (Fe3O4) and maghemite (γ-Fe2O3). The rust phase of -Fe2O3 was detected in higher amounts in the rust layers of 1% wt NaCl which resulted in the rust layers much denser. The alloying elements of copper, chromium and phosphorus enriched in the rust layers are helpful to the formation of γ-Fe2O3. The protective denser rust layers play an important role in corrosion resistance of the steel.