Models for chloride ion diffusion in archaeological iron

The rate at which chloride ions diffuse from archaeological iron into a tre atment solution depends on how the chloride ions are initially distributed int he corrosion layer. This paper compares solutions of the diffusion equa tion for two limiting cases; (1) where the chloride ions are initially spre ad uniformly through the corrosion layer; and (2) where the chloride ions a re initially concentrated at the interface between the iron and the corrosi on layer. Although the first model has been used int he past to describe ch loride ions diffusing from marine iron, the second is more appropriate in c ases where corrosion has drawn chloride ions toward the iron surface. Becau se diffusion processes in archaeological iron are complicated, the limitati ons of both these models are discussed.