Dissolution behaviour of mixed ferrites and chromites in aqueous solutions containing chelating agents

Corrosion product oxide spinels that play host for the radioactive nuclides are formed in the coolant circuits of nuclear reactors at high temperatures. In the present study, model corrosion products were prepared by solid state methods using a-Fe2O3 as starting material and at high temperatures. The dissolution experiments of the mixed ferrites were carried out in aqueous solution containing 2,6-pyridinedicarboxylic acid and other complexing agents. Special attention was given for the study of the dissolution behaviour of zinc ferrite and zinc chromite which are normally formed in systems that have adopted zinc ion passivation. The role of Fe(II) complex in aiding the dissolution of zinc ferrite has been investigated. The effect of citric acid on the dissolution of magnetite powder in various chelating media was studied. The dissolution studies carried out using magnetite coated carbon steel in citric acid an EDTA indicated that the dissolution behaviour of the magnetite film differs very much from that of magnetite powder. The difference in dissolution kinetics observed between light and heavy water medium is also outlined