The thermal decomposition reactions of prepared FeOC1 and natural marine cast iron corrosion products in inert, oxidizing and reducing atmospheres were determined for temperatures up to 1000°C. The results were used to discuss thermal stabilization treatment of marine iron. Pure dry hydrogen was shown to be the best atmosphere to use in thermal stabilization treatments but even in this case, to achieve complete chloride removal would require treatment temperatures above the limit of metallurgical stability.