Corrosion and Elution Behaviors of Al2O3 Ceramics in High-Temperature Demineralized Water
Shoichi Ono, Kiyoshi Suzuki, Mikio Kumagai, Koji Hoashi
Corrosion and dissolution behaviors of Al2O3 ceramics prepared by the pressureless sintering method in demineralized water at 275°C were studied using the small once-through type experimental loop. Experiments were carried out for two specimens with different Al2O3 contents of 92% and 99.5%, respectively. The weight loss of exposed specimen with 92% Al2O3 content was large and reached to 3.48mg/cm2 for 100h exposure. The surface of specimen was corroded deeply, of which corrosion depth was 150μm and changed to porous one. The release levels of the minor constituents of Al2O3 ceramics, Si, Ca, Na and K, were relatively high compared with that of Al, and the level of Al was about one forth of Si. On the other hand, the weight loss of exposed specimen with 99.5% Al2O3 content was very small and was 0.145mg/cm2 including particles released from the corroded layer by ultrasonic cleaning. In addition, γ-AlOOH crystals were formed on corroded surface. These results suggested that the corrosion resistance of Al2O3 ceramics in high temperature water was dependent strongly on Al2O3 content, and then that the corrosion resistance of AO2O3 grain was very high, and on the hand, grain boundary itself was eluted selectively into the solution.