Development and evaluation of new treatments for outdoor bronze monuments

This research is aimed at testing innovative treatments and comparing them with those traditionally applied for the protection of outdoor bronze monuments. The protection and corrosion inhibition of bronze monuments depends intrinsically on the nature of the patina and corrosion behaviour, which should be fully characterized and understood before any treatment is applied. To this regard a change in conservation approaches is proposed which takes into account existing differences in patina composition and the stability of corrosion products. This may result in the selection and adoption of different type of treatments to be applied on the same bronze monument. The performance of currently applied corrosion inhibitors (benzotriazole) and protective coatings has been compared with new treatments based on organo-silanes, the formation of artificial cuprite patinas, the production of artificial copper oxalate patinas induced by fungi, and limewater as potential corrosion inhibitor. Both reference and new treatments have been applied on artificially patinated and naturally aged bronze coupons exposed to aggressive urban and marine environments. A complement of analytical techniques was used to evaluate the proposed treatments' performance (FTIR microscopy and ATR mapping, environmental scanning electron microscopy (ESEM), electron impedance spectroscopy (EIS), colorimetry). Treated coupons will be monitored over an 18 month exposure to a marine environment as well as after submission to different cycles of artificial ageing, in order to evaluate their long term corrosion resistance.