Articolo in rivista, 2023, ENG, 10.1016/j.polymdegradstab.2023.110575

Improvement in the sustainability and stability of acrylic protective coatings for outdoor bronze artworks

G. Pellis, B. Giussani, P. Letardi, T. Poli, P. Rizzi, B. Salvadori, A. Sansonetti, D. Scalarone

Department of Chemistry, University of Torino, Via Pietro Giuria 7, Torino, Italy Science and High Technology Department, Università degli Studi dell'Insubria, Via Valleggio 9, Como, Italy Institute of Anthropic Impacts and Sustainability in the Marine Environment, CNR, Via De Marini 6, Genova, Italy Institute of Heritage Science, CNR, Via Madonna del Piano 10, Sesto Fiorentino, Italy Institute of Heritage Science, CNR, Via Roberto Cozzi 53, Milan, Italy

Outdoor bronze artworks are an entrenched part of our urban landscape. They are usually covered by a patina resulting from their exposition to the environment. This patina plays an important aesthetic role and may provide some passivation on the surface, nonetheless it does not prevent the degradation processes promoted by external factors such as pollution, light and humidity. One of the strategies to slow down these unwanted processes is the application of protective coatings. The products currently available have some limitations due to the loss of effectiveness over time and poor environmental sustainability. With the aim of proposing more performing alternatives, coatings based on Paraloid® B44 modified with corrosion inhibitors and light stabilizers were prepared and characterized. Two non-toxic corrosion inhibitors were studied, 5-mercapto-1-pheniltetrazole (MPT) and 5-ethyl-1,3,4-thiadiazol-2-amine (AEDTA), comparing them with the traditional benzotriazole (BTA). The approach used aimed to identify the blend providing the most stable coatings. The chemical and physical properties of the coatings, such as colour, solubility, glass transition and composition, were studied and monitored over time. All coatings have shown adequate visual properties; however, corrosion inhibitors degrade some other properties of the coatings and need to be used in conjunction with light stabilizers. The permanence of corrosion inhibitors in the coatings over time was also studied by investigating the role of the support. The establishment of specific interactions between inhibitors and the bronze surface lengthens their permanence in the coatings compared to what happens with inert supports. Especially for AEDTA, the inhibitor retention within the coating and at the coating-bronze interface is better than for BTA and MPT. The effect of each of the additives on the photooxidation stability of the coating was evaluated and the most promising inhibitor and stabilizer combination was identified.

Polymer degradation and stability 218

Keywords

metal protection, corrosion inhibitors, light stabilisers, photooxidation, heritage, conservation

CNR authors

Sansonetti Antonio, Salvadori Barbara, Letardi Paola

CNR institutes

ISPC – Istituto di Scienze del Patrimonio Culturale, IAS – Istituto per lo studio degli impatti Antropici e Sostenibilità in ambiente marino

ID: 488890

Year: 2023

Type: Articolo in rivista

Creation: 2023-11-23 18:04:50.000

Last update: 2023-11-23 19:11:45.000

External IDs

CNR OAI-PMH: oai:it.cnr:prodotti:488890

DOI: 10.1016/j.polymdegradstab.2023.110575