Corrosion of the Fe-25Ni-15Cr under the combined effects of marine atmospheric exposure and the subsequent high-temperature oxidation was investigated in the present work. The results indicated that high-temperature oxidation rate of the superalloy after field exposure was significantly accelerated due to the deposited salts and corrosion products. The oxidation kinetic process of the superalloy was clearly divided into two stages, resulting in changes in morphology, structure and composition of the oxide film. And also, the spontaneous passive state of the superalloy was changed to active dissolution by high–temperature oxidation, indicating a substantial deterioration in corrosion resistance. A degradation model for superalloy under the combined effects of electrochemical corrosion and high temperature oxidation was proposed.