Optimization of an industrial chemical cleaning process for glass lenses

The chemical cleaning of glass constitutes an extremely complicated problem, since its exposure to chemical attack by either water, acid, alkali salt solutions or even gases in the atmosphere may result in corrosion. In reality, corrosion generally occurs in a combination of ways simultaneously. This is particularly true with respect to industrial chemical cleaning of glass lenses, in which the absolute cleanliness (and spotlessness) of the surface of the lenses is the primary condition for further processing and/or fitness to the ultimate use. This paper presents data of a selected industrial field study (in vivo conditions) in which an application, optimization, and assessment of the chemical cleaning process (and its results) of glass lenses involving various surfactant-based formulations has been carried out. With a high level content of polyphosphates (i.e., sodium tripolyphosphates), the phosphate ester-based formulations were found to perform better than formulations based on other classes of surfactants (i.e., anionics and nonionics). The best results were achieved with 2.5–3.5% solutions of the formulation that contained ca. 3% of surface active agent. The optimal ratio of alkali-phosphate in the formulations was found to be in the range of 1:1.7–1:2.4. The results are discussed and conclusions with regard to the “real world” of such industrial processes have been drawn.