Bronze artefacts constitute a fundamental portion of cultural heritage, but there is a lack of effective methodologies for the removal of corrosion layers, such as those produced by the “bronze disease”. In this contribution, networks of poly(2-hydroxyethyl methacrylate) (pHEMA) semi- interpenetrated (semi-IPN) with polyacrylic acid (PAA) or polyvinylpyrrolidone (PVP) loaded with tetraethylenepentamine (TEPA) are proposed for the removal of copper corrosion products. Alkaline pH causes the ionization of carboxyls in PAA increasing the swelling and the porosity of the pHEMA/PAA semi-IPN. In pHEMA/PVP, increasing the pH leads to the co-presence of the enol and enolate forms of PVP, along with significant changes in the macroporosity and a decrease in the mesh size. 2D FTIR imaging indicates that TEPA interacts with carboxylates in PAA, and with polar or charged CO groups in PVP. The kinetics of Cu(II) ions uptake by the semi-IPNs showed that the ion-matrix interaction is stronger for pHEMA/PAA. The process likely follows two stages, i.e. an initial diffusion-controlled step followed by diffusion in smaller pores or adsorption at less available sites.<br/>Upon application of the TEPA-loaded gels onto corroded bronze, copper oxychlorides dissolve and migrate inside the gels. Cu(II) ions probably form ternary complexes with TEPA and carboxylates in PAA or CO in PVP. The application of the semi-IPNs allowed the gradual and effective removal of oxychlorides, leaving unaltered patinas of cuprite that are needed to passivate bronze against corrosion. Loading the semi-IPNs with TEPA provides a much higher cleaning efficacy than traditional EDTA, opening new perspectives in the restoration of bronze works of art.

pHEMA/PAA and pHEMA/PVP semi-IPNs: effect of pH and loading with tetraethylenepentamine for the removal of bronze corrosion products

ACS Fall 2021

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