Behavior of B in passivating gels formed on International Simple Glass in acid and basic pH
Résumé
International Simple Glass altered for years in silica saturated conditions develops a passivating gel, which retains some B and Ca in its the inner region. These elements could impact the way the gel limits glass alteration. However, the retention mechanism, speciation, and diffusion properties of these elements are still unknown. First, we found that the presence of B and Ca in solution can dramatically slow down glass alteration. However, splitting the B and Ca into two different solutions with other glass elements did not give similar protection against glass alteration. Further experiments in basic and acid pHs revealed that i) water diffusion is not dramatically affected by the retention of B and Ca in passivating gels, and ii) slow diffusion and high retention of B is observed only in gels formed in basic pH. This mechanism could explain how passivating gels control the residual rate.