Dissolution behavior of synthetic Mg/Zn-ferrite corrosion products in EDTA and NTA based formulations

Dissolution behavior of Mg/Zn-ferrites in citric acid—EDTA/NTA formulations with or without ascorbic acid is reported. This study is relevant to the dissolution of such corrosion product oxides during the chemical decontamination of primary systems of nuclear reactors wherein Zn2+/Mg2+ ion passivation is practiced/proposed. Two sets of oxide systems namely (a) mixed phase system containing (Mg/Zn ferrites + MgO/ZnO + Fe3O4) and (b) single phase system of (MgFe2O4/ZnFe2O4) are investigated. In the absence of ascorbic acid, the dissolution of single phase oxides is hindered significantly unlike the mixed phase system. However, the single phase could be dissolved completely in presence of externally added Fe3O4. The dissolution rate coefficients are determined using two kinetic models. Activation energy for Mg-ferrite dissolution in mixed phase and single-phase is ∼35 kJ mol−1 while in Zn-ferrite case it is ∼57 kJ mol−1.