PVA-based peelable films loaded with tetraethylenepentamine for the removal of corrosion products from bronze

tThe removal of corrosion products from bronze artifacts is still an open challenge, in particular whenstubborn corrosion patinas are found on surfaces with pronounced cavities and reliefs. Highly vis-cous polymeric dispersions (HVPDs) of polyvinyl alcohol (PVA) are able to adhere to highly textured3D surfaces, forming films that can be easily peeled off. Here, PVA-based HVPDs were loaded withtetraethylenepentamine (TEPA), whose copper(II) complex has a stability constant four orders of magni-tude higher than that of EDTA tetrasodium salt, traditionally used by conservators for cleaning bronze.TEPA promotes alkaline hydrolysis of acetyl groups in PVA, leading to the association of the polymerchains into more ordered structures, reducing significantly the time needed for the formation of films ascompared to HVPDs loaded with water. Besides, the solubility of TEPA in most polar solvents allows toupload higher quantities of chelating agent in the HVPD, as opposed to EDTA. The confinement of TEPAinside the PVA matrix allowed the effective and progressive removal of copper corrosion products froma 16th century Italian bronze masterpiece, preserving the natural cuprite patina of the historical bronze,in times drastically shorter than traditional cleaning methods.