Leaching of lead silicate glasses in acid environment: compositional and structural changes

Lead silicate glasses (45.3 weight % of lead oxide) were leached in aqueous static solutions of HNO3 at pH = 2 and T = 90 .C for different leaching times, to study the weathering mechanism of lead glasses in an acidic environment. The leached surface was analysed by different analytical techniques like RBS (Rutherford backscattering spectrometry), XPS (X-ray photoelectron spectroscopy) and SEM-EDS (scanning electron microscopy-energy dispersive spectrometry). Even the leaching solutions were analysed by ICP-AES (inductively coupled plasma-atomic emission spectroscopy) to measure the amount of lead and other ions that migrate from the glass to the solution. The results obtained show that the leached layer, depleted of lead and alkaline ions, is some hundreds of nanometres thick. It is about ten times thinner than the one obtained on richer glasses (66 weight % of lead oxide), but the kinetics of the leaching process is exactly the same: a stabilisation takes place after two days of leaching and a Pb-enriched surface thin layer (a few nanometres thick) is formed.