engleski

Corrosion Protection of Bronze Patina by New Non-Toxic Organic Inhibitors

From antiquity bronzes have been widely used to produce sculptures and others objects of art. Bronze objects are generally covered with a patina. The patina layer can be described as a coloured corrosion products film with various physical, chemical and electrochemical properties. The patina formed in a long term exposition acquired often a certain protective effect of the substrate metal, but a recent increase of air pollution and/or acid rain damage the bronze exposed in urban environment. A method that reinforces a protective effectiveness of patina becomes therefore necessary. To obtain a patina in a short period and representative of certain type of natural patina on bronze, we have synthesised patina electrochemically in a solution composed of sulphate and bicarbonate. The morphology and crystallographic structure of artificially obtained patina were examined with Scanning Electron Microscopy (SEM) and X-ray Elemental Energy Dispersion Spectroscopy (EDS) analyses. In order to preserve metal works from the aggressive atmosphere, protective films of organic inhibitors are often required. Organic inhibitors normally produce very thin chemisorbed films that lead to a remarkable decrease of the corrosion rate due to slowing down the electrochemical reaction kinetics. Most of commercially available inhibitors are toxic compounds that should be replaced with new environmentally friendly inhibitors. Our research aims at making compounds with low toxicity and good inhibition efficiency against copper corrosion. The protective effect of two non-toxic organic inhibitors: 1-phenyl-4-methylimidazole and 1-(p-tolyl)-4-methylimidazole on the patina were examined by potentiodynamic methods and the electrochemical impedance spectroscopy as well as spectroscopic methods. The results of these investigations have shown that both studied inhibitors protect patina in aggressive media.

synthesised patina; EIS; patina structure; imidazole derivatives

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