Changes of a Corroded Glass Surface on Storage at Room Temperature

A 20Na2O, 80SiO2 glass was corroded at 30° and 50°C for different lengths of time with leach solutions buffered at pH values 0, 10 and 12. The corroded glass surfaces were examined with optical microscopy, and in some cases with Electron Microprobe Analysis. The surfaces were examined just after removal from the leach solution and after storage for 16 hours in a desiccator at room temperature. The glass surface after corrosion showed extensive pitting, cracking, crystal formation; the nature and degree of which varied with changing pH value and temperature of the leach solution and time of corrosion. The morphology of the corroded glass surface changed significantly during storage in a desiccator. At pH 10 and 12 (where the buffered leach solution contained K+) part of Na+ (glass) was found to be exchanged for K+ (solution), the concentration of K+ within the leached layer increased with increasing activity of potassium ion in the leach solution.