Natural corrosion of the uranium-colored historical glasses

The historical uranium-colored glasses have been collected from the dumps of former glassworks. Buried in the soil the glasses have been exposed to natural weathering for approximately 150 years. Uranium content ranges from 0.089 to 0.556 wt% depending on the particular glass type. Two types of natural corrosion crusts were distinguished: (1) The leached glass that is hydrated and depleted of alkalies: Affected layer is up to 0.56 mm thick. The corrosion involves leaching of alkali ions from the glass. In comparison with the primary glass the corroded part shows higher uranium content. Uranium concentration in the leached layer increases because (UO2)2+ sorption on the residual glass. (2) Laminated outer layer of residual glass and newly formed aluminosilicate along with calcite: The surface layer system of newly formed phases and leached relics of glass is at most 30 μm thick. With respect to the glass composition the research suggests that the Ca2+ and Al3+ ions forming new phases have been provided by the natural leaching solution. The uranium concentration in the corrosion crust is significantly lower. Alpha spectroscopy demonstrated the isotopes 238U and 234U in the products of the glass corrosion are at the radioactive disequilibrium.