Mössbauer study of the rust formed on SS-304 exposed to sea water for about 30 d indicates that ferrihydrite and -FeOOH are formed as corrosion products, the cause of corrosion being the presence of chloride ions in sea water. Ferrihydrite is found to exhibit two doublets at 300 K while at 80 K it exhibits a doublet and a sextet. This is contrary to earlier studies in which it was reported that at 80 K ferrihydrite is fully magnetically ordered and exhibits a sextet only.