Organosilane coatings applied on bronze: natural exposure and exposure to temperature/UV cycles

3-mercapto-propyl-trimethoxy-silane (PropS-SH), with or without the addition of nanoparticles, was tested through natural exposure in the coastal town of Rimini (Italy), as a protective coating for outdoor quaternary bronze (Cu-Sn-Zn-Pb). The first results of these tests are presented here: uncoated and coated samples were exposed both in sheltered and unsheltered conditions with respect to the action of rainwater. Sample surfaces were periodically characterized by SEM, EDS, micro-Raman and XRD, and the leaching rain was monthly collected, in order to evaluate the release of the alloying metals by Atomic Absorption Spectrometry (AAS). The results showed that micro-scale cracking and spalling phenomena took place during exposure, partly limiting the protective efficiency. In order to identify the factors responsible for coating damage in outdoor conditions, exposure to temperature/UV cycles in a climatic chamber were carried out. The results showed the strong influence of UV radiation on coating performance