Corrosion of Sintered High-Purity Mullite in Molten KF Salt

Abstract

Corrosion behaviors of sintered mullite bodies (99% in RD) with spherical and columnar shapes fabricated from high-purity mullite powders synthesized using a sol-gel processing have been investigated at 900°C, 950°C and 1000°C for 5-180min in KF melt. For both shapes, the reaction of the sintered mullite bodies with KF melt proceeded from the entire surface bodies towards the inner part uniformly at the interface. The thickness of corrosion layer formed at the interface increased relatively uniformly with increases in dipping temperature and time, and it was revealed that the corrosion proceeds parabolically. The corrosion layer acted as a protective layer against the corrosion reaction and suppressed the subsequent corrosion reaction. Using a geometrical shape-parameter depending on the initial sample shape, the process of corrosion progress could be expressed in terms of the diffusion controlled reaction rate equation based on the unreacted core model through the reaction layer.