The Oxidation of Hydroxycarbonate Green Rusts

Abstract

Green rusts are elusive Compounds. These hydroxy salts are members of the pyroaurite group. Their structure consists of brucitic layers containing the cations that carry a net positive Charge in alternation with anion plus water containing interlayers. The brucitic layers can contain both iron(II) and iron(III). Their structure and the presence of substantial amounts of iron(II) in them renders the green rusts highly susceptible to rapid oxidation and breakdown. This is probably one of the main factors that has so far prevented their identification in natural systems, should they exist there (e.g. in soils, where their presence has been long suspected). The formation of green rusts as intermediate phases during the corrosion of iron has also been indicated [1,2]. Positive identification of such a phase as a corrosion product has, however, been effected in only one case [3]. It is nevertheless conceivable that green rusts are much more frequently formed in the course of corrosion processes than is hitherto known.