engleski

Modification of self-assembled layer of elaidic acid on copper by gamma irradiation

Copper has been widely used in construction of sculptures and other works of art for ages. When exposed to air a thin oxide layer is formed. This layer offers natural protection to copper. Due to increased environmental pollution copper’s natural protection is not enough. In order to preserve cultural heritage in these conditions it is necessary to apply additional protection from corrosion. Formation of a thin self-assembled protective film (SAM) on the surface of the natural oxide film is a good and practical way to enhance the metal’s natural protective properties. Fatty acids are non-toxic compounds which have an affinity for adsorbing on metals with their hydrophobic end, the carboxyl group. The other end of fatty acids chain has hydrophobic properties and when adsorbed on the metal surface it makes the whole surface of the metal appear hydrophobic. Thus by blocking access for water to the surface the dissolution of the metal is disabled. In this work elaidic acid (EA), a monounsaturated C18 trans fatty acid is used. Because of the specific shape due to the trans form of the double bond EA molecules are close-packed on the copper surface making the coating very compact and water difficult to approach the surface. The EA coating is convenient to be used for cultural heritage protection, because it is very thin and does not change the appearance of the surface. Unfortunately, when exposed to urban outdoors fatty acids tend to degrade and wash-off, and so the protective properties of the SAM are not long-lasting. The aim of this research is to investigate the possibility of using ionizing radiation to modify the structure of the elaidic acid SAM on copper’s surface. By radiation-induced crosslinking the coating would become more stable and durable, while it still would be only physically adsorbed on the surface.

ionising irradiation ; self-assembled monolayers ; corrosion

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