The Laboratory of the Musée d'art et d'histoire, Geneva, has been concerned with the problem of conserving excavated iron objects, often very corroded. In the search for a satisfactory method of desalination, the alkaline sulphite treatment developed by North and Pearson for marine objects was studied. Within the framework of a quantitative study of chloride removal, this was compared with five other methods. Further studies were undertaken on the quantitative distribution of chlorides in a corroded iron object, the quantity of chlorides remaining after different treatments, and the chloride concentration threshold at which corrosion starts and becomes dangerous.