MOLECULAR MECHANISMS FOR CORROSION OF SILICA AND SILICATE-GLASSES

Dissolution, selective leaching, and stress-corrosion cracking are all processes which can degrade the performance of silica and silicate glasses exposed to aqueous environments. Reactions which corrode glass in water include hydration, hydrolysis and condensation, and ion-exchange processes. Techniques such as solid-state nuclear magnetic resonance, Raman and Fourier transform infrared spectroscopies, pH stat titrations and elemental depth profiling have been used to establish the relative importance of the above reactions on glass degradation as a function of solution pH and composition, temperature and stress level. This paper reviews results obtained for silica, alkali silicate, and alkali boro- and aluminosilicate glasses. For most glasses, the rate at which water enters the glass structure controls the kinetics of the other glass-water reactions, explaining the corrosion characteristics of different glass compositions.