engleski

Testing of new protective wax-based coating systems for outdoor bronze monuments using EIS

Outdoor bronze sculptures are vulnerable to atmospheric corrosion environments from acid rain containing sulfates and carbonates in urban-industrial environment, to chlorides, which are main cause of “bronze disease”, in marine environmental exposure [1, 2]. The present protection coating systems utilized by conservators do not provide adequate protection under many circumstances. Best coating system used is still benzotriazole (BTA) with a top coat of wax. As known, benzotriazole showed to be toxic, thus many efforts were done to replace BTA with some non-toxic corrosion inhibitors [3]. In this work, the protective properties of coating systems formed by three natural organic inhibitors (Neem tree, Mimosa and Chestnut extract) and wax were evaluated by Electrochemical Impedance Spectroscopy (EIS). EIS technique was proven to be most adequate technique for the evaluation of the protective properties of surface films and coatings in corrosion science [4]. Measurements were performed in rural, urban-industrial and marine simulated environment on Cu-6Sn bronze coupons, similar in composition to artistic bronzes. The experimental data showed that all three plant extracts have increased corrosion resistance of bronze in simulated environments more than wax applied alone but in comparison with traditional coating system (BTA+ wax) inhibition efficiency was much lower. Nevertheless, among the compounds used, the most efficient, Neem tree extract, seems to be a promising coating compound in the bronze conservation field.

bronze corrosion; coatings; EIS

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