Evaluation of the anticorrosive properties of benzotriazole alkyl derivatives on 6% Sn bronze alloy

This paper focuses on the anticorrosive behaviour of surface films formed by different benzotriazole alkyl derivatives on a Cu6Sn bronze (B6), whose composition is similar to materials used for outdoor artefacts. Some alkyl derivatives of the 1,2,3-benzotriazole (BTA) as: 5-hexyl-1,2,3-benzotriazole; 5-dodecyl-1,2,3-benzotriazole and [5-(1-undecyl)dodecyl]-1,2,3-benzotriazole were synthesized in order to investigate the influence exerted by the aliphatic chain on the inhibiting properties of the base molecule (BTA) toward bronze corrosion. The protective efficiency of the organic films, after a preliminary evaluation by electrochemical measurements, was determined by thin layer activation (TLA) and gravimetric techniques on the samples submitted to artificial weathering experiments in acid rain. For TLA measurements a γ-emitting radio nuclide 65Zn (t1/2 = 244 days), used as a corrosion tracer, was produced on the bronze surface by a high energy proton beam. At the end of artificial weathering exposures the radioactivity recovered on the bronze surface, once it was treated with a picking solution, allowed determination of the thickness loss. All the results arising from the different techniques, used in this study, show that BTA molecules bearing long aliphatic chain act as the best corrosion inhibitors.