Initial stages of glass corrosion in water

Abstract

Soda-lime-silica glass samples with fresh fracture surfaces were treated in H2O, D2O, H2-18O, and D2-18O for 15, 30, 60, and 120 min at 60 and 85 °C. The leached layers were analyzed by NPB-SIMS, a technique which avoids surface charging by using neutral primary particles. A distinct isotopic effect occurred neither with respect to the hydrogen isotopes nor with respect to the oxygen isotopes. From these and Corbach's results it is concluded that in the initial stage, every alkali ion exchanges with exactly one hydronium ion, but with increasing time, a growing number of unhydrated protons may participate in the exchange process. The reaction of calcium strongly depends on temperature. At 85 °C calcium ions were found to be leached from the outer region of the hydrated layer and to be enriched in a certain depth beneath the surface. On the other hand, at 60 °C calcium does not react in a measurable degree. When the glass is subjected to irreversible deformation occurring in the "plastic zone" around the crack tip, a surface layer with a modified structure is created. The influence of this deformed layer on the leaching kinetics was taken into account by a simple mathematical model.