The corrosion damage of carbon steel due to the breakdown of the coating becomes a major problem in causing the failure of the structure. Therefore, immediate and effective coating repair agents are particularly important. Cerium-based inorganic salts have been well-studied as corrosion-protective inhibitors but are less effective for carbon steels. To solve this problem, organic–inorganic hybrid methods can be applied. In this study, a rare earth element solvent extraction method was used to prepare a repair agent containing organic cerium phosphate complex (organo-cerium) in one step. A corrosion-protective hydrophobic film was formed after dropping it on the exposed substrate after scratch. The morphology, composition, and corrosion resistance of the formed film were investigated by scanning electron microscopy (SEM), Raman spectroscopy, and electrochemical impedance spectroscopy (EIS). The EIS results showed that the formed film has excellent corrosion protection for damaged coating. The quick repair agent prepared in this study has great application value in protecting the exposed steel substrate due to the coating damage in the marine environment.