CORROSION OF ZIRCONIUM IN HALOGENIDE MELTS

摘要

We propose a method for the evaluation of stability of the corrosion products of zirconium in melts of different compositions. The method is based on the analysis of the dependence of the equilibrium potential of zirconium electrode on the initial concentration of its compounds in the oxidation state 4+. It is discovered that zirconium compounds in the oxidation state 2+ are in equilibrium with the metal in all investigated systems and their stability depends on the composition of the melt and decreases in the following order: (NaBr-KBr) > KBr >= KCl > (LiCl-KCl). It is also established that, parallel with zirconium compounds in the oxidation state 2+, the investigated systems contain its compounds in the other oxidation states. The stability of these compounds in bromide melts decreases in the following order: Zr(II) (NaBr-KBr) > Zr(IV) (NaBr-KBr) > Zr(II) (KBr) > Zr(IV) (KBr). In chloride melts, the observed sequence has a somewhat different form: Zr(II) (KCl) > Zr(IV) (KCl) > Zr(II) (LiCl-KCl). Lithium is present among the corrosion products in LiCl-KCl melts. We also determined the thermodynamic characteristics (Delta H and Delta S) of equilibria of the corrosion products of zirconium with the investigated melts.