TOWARDS A CONSISTENT RATE LAW: GLASS CORROSION KINETICS NEAR SATURATION

Abstract

Although glass corrosion resistance has been tested with laboratory methods for decades, investigators are now just beginning to understand the reaction phenomena at or close to saturation with respect to the rate-limiting phase(s). Near saturation, the phenomena that govern element release rates include alkali-hydrogen (species) exchange, differential reactivity of phase-separated glass, and accelerated corrosion rates due to precipitation of key secondary phases. These phenomena were not anticipated by early models of glass dissolution and are incompletely quantified in current rate representations. This review discusses the two over-arching models for glass reactivity, diffusion and surface reaction control, and demonstrates the importance of glass reactivity in terms of glass composition and micro-heterogeneity of the glass. Our conclusion is that surface reaction control best describes the release of elements to solution, but that models based on current interpretations of transition state theory (TST) must be modified to account for reported anomalies in behaviour near saturation.