Corrosion of silicon nitride materials in acidic and basic solutions and under hydrothermal conditions

The corrosion behavior of gas pressure sintered Si nitride ceramics with different amts. and compns. of the grain boundary phases was analyzed in acids, bases and under hydrothermal conditions. The studies show, that the corrosion is strongly affected by the SiO2 content in the grain boundary phase and the amt. of the additives. The differences in the corrosion kinetics are correlated with the structure of the formed corrosion layer. Some correlations between compn. and corrosion stability in the different media are given.