Glass Surface Analysis by an Optimized Sequential Chemical Etching Technique Using the Corrosive Agent HF/HNO₃

The characterization of the early reaction steps of the corrosion process in liquid media represents a tremendous challenge within the field of chemical analysis. In response to this, some known instrumental methods like AFM, SIMS and SNMS have proven themselves useful. Within the present work on the subject, we will introduce an optimized direct chemical etching technique which allows the quantification of the primary removed glass surface layers. It is based on the established etching procedure using hydrofluoric acid in combination with other mineral acids. The above mentioned method is modified and appropriately extended by enhancing the precision of the selected exposure time with the help of an automatic dipping device. Other improvements include the minimization of the dissolution rate by lowering the test temperature to -10 degrees C and also the decrease of the aqueous activity by adding alcohol instead of water into the acid solutions. Furthermore, by applying sequential etching with low concetrations of HF and HNO3, very small removal depths within the range below 10 nm per step are obtained. The equivalent components from the dissolved surface layers of the examined float glass are determined by subsequent chemical analysis of the etchants via AAS and ICP-OES. Their dissolution character can be well distinguished through a comparison between the gravimetric mass loss q(gravim) and the so-called normalized mass release per surface area q(sol), calculated from the chemical composition of the corrosive solutions.