Dissolution of chromium-substituted iron oxides in V(II) formulations

Abstract

The dissolution behaviour of Cr-substituted (0-20 at.%) hematites and magnetites is reported with relevance to the removal of corrosion product(s) deposits on iron-based alloys by way of chemical dissolution. The dissolution was carried out using synthetically prepared oxides in V(II) formulations, namely V(II)-picolinate and V(II)-citrate at 353 ± 5 K. The dissolution rate coefficients were determined using a general kinetic equation applicable for polydispersed samples. A comparison has been drawn with the dissolution behaviour reported using organic acid-based formulation, i.e., citric acid-EDTA-ascorbic acid (CEA) mixture. The V(II) formulations are found to be more efficient than CEA. The reductive action of Fe(II)-picolinate or Fe(II)-citrate was not observed even with simple iron oxides such as α-Fe2O3 or Fe3O4. The oxidative pre-treatment of the oxides using reagents such as alkaline permanganate (AP), nitric permanganate (NP) and HMnO4 improved the dissolution and HMnO4 was found to be marginally advantageous. © 2001 Elsevier Science B.V.