Comparative analysis of corrosion of borosilicate glasses in water vapor

Abstract

A comparative analysis of interaction of various borosilicate glasses with water vapor is carried out in the work. The fundamental dependence of the observed processes on the concentration of alkali metal oxides as well as glass formers B2O3 and Al2O3 in glass is shown. The relative content of alkali oxides determines which processes dominates. The absence of alkali metal oxides leads to the fact that no hydrated or hydrogenated layers are formed on the surface of the glass. At a concentration of alkali metal oxides above ~15% by weight, hydration of the glass surface is observed as a result of the ion exchange reaction of water protons and alkali ions; the hydrated layer grows with time of hydration according to a parabolic law. However, at a concentration of alkali metal oxides below about 8% weight, the ion exchange reaction stops after formation of a 20 nm thick hydrated layer due to a sharp decrease in the “solubility” of alkalis in a thin water layer adsorbed on the surface due to an increase of pH factor, and due to a radical decrease concentration gradients for Na and H in the glass and in the solution. And then the formation of a hydrogenated layer with the formation of silicon hydroxides in the NaBSixOy molecular complexes is observed. The top surface hydrated layer acts as a source of protons for this reaction. The growth of the hydrogenated layer occurs with time according to a linear-parabolic law.