The compositions of industrial soda lime glasses were optimized according to customer needs and technical specifications. For standard applications, weathering or corrosion problems are rather rare and always connected to wet conditions during storage and/or transport where the stuffy atmosphere favours a high rate of humidity.
The involved mechanisms are different from those of the most studied alteration, which is in immersion conditions. Indeed, the alkali and alkaline-earth cations released from the alteration reactions cannot diffuse away. They stay on the surface or in the alteration layer of the glass. They can lead to the formation of alteration salts on the surface by reacting with atmospheric gases. These salts are the classic outward sign of weathering: microscopic crystals of sodium and calcium carbonates.
Glass weathering issues are crucial for coated products. The influence of the glass composition is not so obvious to study as the manufacturing process spontaneously generates at the subsurface a specific gradient of composition depending on the process conditions (as well illustrated for the bath / atmosphere sides in the float process). We will present the results of weathering studies of lab model glasses (PhD thesis of Amandine Serve), which allow us study the influence of the different oxides on glass weathering behaviour for standardised melting and preparation conditions