Glass Corrosion

Glasses often corrode when they are exposed to moisture for prolonged times. Additionally, many compounds can either directly corrode the glass or act as an accelerator to the process. These compounds, such as sulfur- and nitrogen-containing compounds, can originate from air. Other compounds, such as alkalis, can leached out of concrete.  Corrosion can be often recognized by a haze or by iridescent opalescent layers on the glass.
Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) is a valuable method for the chemical characterization of corroded glasses. The ToF-SIMS depth profile on a glass with a matt haze shows the typical changes caused by glass corrosion (lower depth profile). When compared to a non-damaged glass (upper depth profile), it is clear there is a loss of Na and K in the region close to the surface that is accompanied by an increased water concentration. Na ions in the glass are replaced by hydrogen ions. The structure of the glass built by Si, Na and O is disturbed, causing microscopically thin roughening of the surface. This leads to a change in the optical appearance of the glass. Because of its high sensitivity, ToF-SIMS is able to discriminate between glass corrosion and other changes to the surface, such as surface depositions on top of the glass.