Behavior of yttria-stabilized zirconia in the presence of molten salts: Part 1-Dissolution and recrystallization phenomena

Yttria-stabilized zirconia is supposed to be a promising candidate as anti-corrosion coating on steel tubes in waste-to-energy (WTE) plants. Since the formation of low-melting eutectic salt melts on the surface of those tubes is a common process within WTE plants, the performance of yttria-stabilized zirconia under these conditions was evaluated. Beads of 5 wt.-% Y2O3 stabilized zirconia were embedded in an equimolar mixture of KCl-K2SO4-ZnCl2-ZnSO4. In a temperature range between 600 and 700 degrees C under an atmosphere of N-2-2.55 vol.-% HCl-0.45 vol.-% O-2, a dissolution and recrystallization of the zirconia was observed. The driving force of this process is a changing electromotive force in combination with an increasing basicity of the melt, controlled by reactions between melt and atmosphere. With respect to an application as anti-corrosion coating, the recrystallization process can enable the material to act as a self-healing coating. (C) 2016 Elsevier Ltd. All rights reserved.