engleski

Protection of electrochemical and chemical patina in aggressive environments containing chlorides

Protection of electrochemical and chemical patina in aggressive environments containing chlorides K. Marušić, T. Kosec*, H. Otmačić Ćurković Faculty of Chemical Engineering and Technology, University of Zagreb, Croatia * Slovenian National Building and Civil Engineering Institute, Ljubljana, Slovenia Numerous cultural and historical artefacts are made of bronze. In humid and unpolluted air bronze is protected with oxide films, called patina. However, in urban atmospheres the aggressive air species concentrate in acid rain which dissolves patina and the bronze itself. This leads to enhanced deterioration of bronze artefacts. In protection of historical and cultural artefacts, only methods that do not change the visual appearance of the artefact itself can be applied. Such methods include protection of bare metal as well as the patina covering it. One of the possible methods is the use of corrosion inhibitors. Recent research has shown that imidazole based inhibitors can be succesfully used to protect patinated bronze. The aim of this study is to investigate the use of imidazole and benzotriazole type inhibitors (MBI, TMI, BTAH) in protection of bare and patinated bronze and to compare it to other methods of protection, such as lacquers or natural and synthetic waxes that are in use in conservation practice. The possibility of prolonged service-life will be evaluated for the corrosion inhibitors tested. Since the studies can not be performed using cultural and hystorical objects, patina similar to patina naturally formed in marine environments will be synthesized electrochemically.Also, chemical patina will be applied to bronze surface. Morphology and structure of the patinas will be determined using SEM/EDX and Raman spectroscopy. Then both chemical and electrochemical patina will be studied in environments that simulate agressive marine environment. The protection properties of corrosion inhibitors in combination with various surface finishes such as lacquers, natural and synthetic waxes will be evaluated on differently patinated bronze samples. Electrochemical results together with corrosion test chamber results will show the different inhibiting actions of different applied finishes in a certain environment. SEM /EDX analysis as well as Raman spectroscopy will be used to evaluate the differently formed patina before and after the electrochemical experiments. The combination of electrochemical and spectroscopic techniques will enable the study of inhibition mechanisms and inhibition efficiency of the chosen protection method.

bronze patina; acid rain; corrosion inhibitors; electrochemical methods

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