Study of "green" inhibitors on copper alloy artefacts

In order to preserve the surfaces of the metallic artworks from corrosion and degradation, protective systems containing corrosion inhibitors are often applied. These systems must fulfil strict requirements of non-invasiveness from the aesthetic point of view, and shouldn't be dangerous for humans and environment. Benzotriazole (BTA) is the inhibitor usually employed for copper alloys, however it is suspected to be harmful for humans and environment. For this reason, in the last years several "green" alternatives were proposed. In this work, the performances of a selection of green inhibitors have been evaluated. They were applied on polished and artificially patinated copper, an on bronze with natural and artistic artificial patinas, in consideration of the large variability of surface conditions that can be found in cultural heritage field. Their inhibition efficiency was evaluated with electrochemical techniques, while their influence on the surfaces appearance was assessed by means of spectrophotometry in visible light.