On the effect of glass composition in the dissolution of glasses by water

The dissolution rate in aqueous solution has been measured for three families of glasses of technological interest (borosilicates, aluminosilicates and lead-silicates). Borosilicates have been altered at a slightly basic pH (8–9), whereas the aluminosilicates and the lead-silicate glasses have been corroded in acidic solutions. In these conditions, silica is always less soluble than all other glass components. In each glass family, the effect of the silica content on the glass dissolution rate has been studied. The three series display a similar behavior as a function of the glass composition, namely a sharp increase of the dissolution rate with the content in soluble oxides. These experimental results have been explained in the framework of a Monte-Carlo simulation of glass dissolution. The simulations show that the fast extraction of the soluble species as compared to that of silica generates a porous surface layer, which becomes thicker and thicker when the percentage of soluble oxide increases in the glass. This increases the interface area between the glass and the solution, and consequently the dissolution rate in the same proportion. The numerical simulations reproduce quite well the experimental variations of the dissolution rates with glass composition.