engleski

Self-Assembling Monolayers of Organic Acids for Protection of Bronze from Polluted Urban Atmospheres

Cultural heritage made of bronze can be found exhibited in cities all around the world. Such artefacts, after long-term exposure to air and humidity, form a thin film of corrosion products with a characteristic greenish colour, called patina. Patina protects the substrate bronze, but also enhances its beauty. Such works of art are exposed to the aggressive effect of polluted urban environments. Different ways of treating and protecting both bronze and its patina are common: coatings, mainly waxes and varnishes, and corrosion inhibitors. Since protection is applied to artefacts that are cultural heritage and exposed in urban outdoors it is expected for the protection to have additional characteristics beside corrosion inhibition: it should not change the aesthetics of the work of art, as colour or surface structure, it should be easy to apply and it should not be harmful for the restaurateur. This is the reason why application of self- assembling monolayers of organic acids is interesting in this field of application. Organic acids are not harmful, a monolayer on the metal’s surface cannot be seen with bare eyes and the fact that these molecules are self-assembled by pure exposure of the bronze artefact to the solution containing molecules with self-assembling properties makes it easier to apply then any other protection. Two types of organic acids are investigated for protection of CuSn6 bronze and its patina: stearic and palmitic acid. They are both dissolved in ethanol and bronze is exposed to the solution. The corrosion inhibition efficiency is investigated by electrochemical methods (potentiodynamic polarization and electrochemical impedance spectroscopy) in a solution simulating urban atmospheres. Different concentrations are investigated on bare bronze and the optimal concentrations are applied for patinated bronze. The corrosion products of both bare and patinated bronze exposed to the corrosion test solution are investigated by SEM and EDX.

corrosion; bronze; patina; self-assembling monolayers

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