Lead patination in the atmosphere of Athens, Greece

Abstract: Pure metallic Pb foils were exposed to the atmosphere of Athens for different periods of time (up to 150 non-rainy days) in the summer of 2005. The interacted Pb surfaces were probed using the 12C(d,p)13C reaction (E d: 1100keV) at the Tandem accelerator of the NCSR “DEMOKRITOS”. Laser-μRaman and SEM–EDS were also complementary applied. Using the above methodology we recorded surface carbon profiles and concentrations as a function of the exposure time, corresponding to the evolution of the carbonate layer formed onto Pb foils due to the interaction with atmospheric H2O and CO2. The C-containing surface layer was found to be stabilized after ∼120days. Further investigation by means of laser-μRaman and SEM–EDS indicated that the patina initially consists of Pb-hydroxycarbonates (hydrocerussite) overgrowing Pb-oxides, whereas Pb-sulfates (anglesite) and possibly basic Pb-sulfates are formed at the end of the patination process. The crystal growth of Pb-sulfates, or most likely the transformation of hydroxycarbonates to sulfates, is attributed to the pollution of Athens atmosphere by SO2. [Copyright &y& Elsevier]