Corrosion behaviour of R2O-CaO-SiO2 glasses submitted to accelerated weathering

As far as the results concern, it has been shown that 400 cycles of variable temperature and humidity are capable to develop pits on the glass surface, its shape and intensity depending on the glass composition. When weathering cycles were carried out with 10 ppm SO2 under high humidity conditions, calcium carbonate crystals appeared upon the glass surface, whereas calcium sulphate crystallisation occurred for higher SO2 concentration. The mechanism of chemical damage has been proposed and discussed in terms of the reaction between the Ca2+-ions leached from the glass sample and the environmental SO2. The former whole reaction occurred through an intermediate stage: the calcium carbonate crystallisation. That salt was displaced by sulphate only when the SO2 concentration was high enough.