INFRARED MICROSPECTROSCOPY AS A COMPLEMENTARY TECHNIQUE TO ELECTRON-PROBE MICROANALYSIS FOR THE INVESTIGATION OF NATURAL CORROSION ON POTASH GLASSES

Natural corrosion crusts on potash-lime-silica glasses, that have been buried in soil for very long periods, were examined using infra-red reflectance microspectroscopy and electron-probe techniques. Individually these techniques are useful: infra-red provides information on which functional groups are present, but is not good at distinguishing between cations; electron-probe microanalysis reveals the composition of a sample, but cannot explain how the elements are combined. By using both techniques on the same sample areas the corrosion was shown to be composed of layers of amorphous silica gel with precipitates such as carbonate-substituted calcium phosphate, calcium sulphate and manganese dioxide.