Corrosion of 85-5-5-5 bronze in natural and synthetic acid rain

In order to investigate the decay of bronzes exposed to acid wet depositions, a comparative study has been performed by following the corrosion behaviour of different sets of bronze specimens exposed either to natural rain or to a similar solution, without organic compounds, artificially reproduced in laboratory. The as cast G85 bronze specimens were exposed to aggressive solutions for different periods through a wet-dry technique. The pH trend of the solutions and the amount of metals transferred into the solutions were periodically monitored. OM, SEM, XRD, RAMAN analyses and ac electrochemical measurements were performed on the artificially weathered specimens. Preliminary results, showing the difference between the ageing in natural and synthetic rain, suggest the influence of the organic components on the corrosion process. In particular, the growth of a more uniform protective layer of corrosion products on the metal surface exposed to the natural rain could be attributed to these components. PACS 82.45.Bb; 82.33.Tb