Polymeric Smart Coatings for the Active Protection of Modern Bronze Artefacts

Marino LAVORGNA, CNR IPCB

Contemporary art is a major challenge for conservators and scientists since there is still a significant lack of established conservation methodologies. Nowadays, emerging approaches envisage that the coating formulations have to confer further protection even when the coating barrier properties fail. In this sense, the main goal of this work, which is carried out in the framework of the WP4 “Protection of the surfaces” of the NANORESTART project (Nanomaterials for the restoration of Works of Art), is the development of smart protective coatings able to actively protect the surface of modern copper-based artefacts from corrosion. The protective coatings under development are based on polymers obtained from renewable sources: chitosan (CS) and amorphous poly(vinyl alcohol) (HAVOH). The obtained results suggest that the coatings, which are optically transparent and easily removable, effectively preserve the surface characteristics of bronze substrates during accelerated corrosion tests, and thus represent a promising solution for the protection of Cu-based alloy artworks stored or exhibited in an indoor environment. Specifically, a cooperative effect has been observed between the polymer matrix and traditional inhibitors based on either benzotriazole or mercaptobenzothiazole. Alternatively to some selected ionic liquids characterized by a chemical structure that favors their dispersion in the coating formulations and replicates the structure of common inhibitors are also under investigation. In-vitro biological tests have confirmed that these compounds are safer for human health, as demonstrated by a non-cytotoxic response on human fibroblast cells (HDNF) and lower inflammatory response than the common inhibitors. Moreover, the use of nanocarriers guarantees the storage of the inhibitors that will be released under stimuli related to the beginning of the corrosion processes. The controlled release of corrosion inhibitors allows to hinder degradation phenomena and to develop long-lasting protective coatings.

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