The effect of Mn, Fe and Cu ions on potash-glass corrosion

The corrosion products of potash-glass with manganese, iron and copper ions were studied by analysing the glass surfaces after being in contact with static water or using a stirrer for different periods. Glass samples with 56 mol.% SiO2, 24 mol.% CaO and 20 mol.% K2O were prepared, with 1 mol% of the different metal oxides. The basic composition of these glasses is analogous to the composition of the medieval stained glasses of the XV century from the Monastery of Batalha. The corrosion products were characterized using Ion Beam Analysis, Optical Microscopy and Fourier Transform Infrared spectroscopy. The experimental conditions used reproduced well the corrosion processes found in ancient glasses of similar composition weathered through five centuries. A silica-rich-layer and calcium carbonate were identified on the surface. It was also detected that more than one silica-rich-layer has developed during the longer immersion periods. The elemental profiles for Si, K, Ca, Cu, Mn and Fe were obtained by means of Rutherford Backscattering Spectrometry in the attacked surface region of the glass, while hydrogen profiles were obtained by Elastic Recoil Detection. It is shown that a layer forms that is richer in the transition elements and that copper containing glasses displayed faster initial glass corrosion.