Organic films for protection of copper and bronze against acid rain corrosion

In this paper, the anticorrosive effects of surface films formed on copper and bronzes by different organic inhibitors (mainly benzotriazole derivatives) are evaluated. Several alloys, nominally similar in composition to ancient artistic bronzes, were studied in comparison with copper. The protective efficiency of the organic coatings was tested by electrochemical ac and dc measurements performed both in acid and neutral rain. The experimental data show that benzotriazole derivatives with a long aliphatic chain form thin and very protective films on copper. The presence of the alloying elements (e.g. Sn, Zn, Pb) and multiphasic structures decrease the organic film performances. Nevertheless, among the compounds used, the most efficient, 5-octyl-1,2,3-benzotriazole (C8), seems to be a promising coating in the bronze conservation field.