CORROSION DEGRADATION BEHAVIOR OF ALUMINA CERAMICS IN HOT SULFURIC-ACID

Corrosion behavior of 93 wt% alumina ceramics was investigated. The we ight, the bending strength and the thickness of corroded layer were me asured after exposed in sulfuric acid at temperatures of boiling point and 90-degrees-C. The weight decreased with time, but the weight loss rate became small. On the contrary, the thickness of corroded layer, which was determined by a porous zone depth formed on the surface of s pecimens as a result of dissolution of grain boundary phase, increased linearly with time. The bending strength decreased with an increase i n the corroded layer depth. However, the morphology of fracture was in consistent with the assumption that the corroded layer depth correspon ds to a flaw dimension causing the failure. As large numbers of pore w ere observed on the fracture surface of the specimens, it was suggeste d that a combined flaw of the pore and the corrosion layer governs the strength of corroded alumina.