X-ray Photoelectron Spectroscopy as a tool to investigate silane-based coatings for the protection of outdoor bronze: The role of alloying elements

Giulia Masi (1) , Andrea Balbo (2) , Jérôme Esvan (3) , Cecilia Monticelli (2) , José Avila (4) , Luc Robbiola (5) , Elise Bernardin (1) , Maria Chiara Bignozzi (1) , Maria C. Asensio (4) , Carla Martini (1) , Cristina Chiavari (1)

1 UNIBO - Alma Mater Studiorum Università di Bologna = University of Bologna
2 UniFE - Università degli Studi di Ferrara = University of Ferrara
3 CIRIMAT - Centre interuniversitaire de recherche et d'ingenierie des matériaux
4 SSOLEIL - Synchrotron SOLEIL
5 TRACES - Travaux et recherches archéologiques sur les cultures, les espaces et les sociétés

Application of a protective coating is the most widely used conservation treatment for outdoor bronzes (cast Cu-Sn-Zn-Pb-Sb alloys). However, improving coating protectiveness requires detailed knowledge of the coating/substrate chemical bonding. This is particularly the case for 3-mercapto-propyl-trimethoxy-silane (PropS-SH) applied on bronze, exhibiting a good protective behaviour in outdoor simulated conditions. The present work deals with X-Ray Photoelectron Spectroscopy (XPS) and Electron Microscopy (FEG-SEM + FIB (Focused Ion Beam)) characterization of a thin PropS-SH film on bronze. In particular, in order to better understand the influence of alloying elements on coating performance, PropS-SH was studied first on pure Cu and Sn substrates then on bronzes with increasing alloy additions: Cu8Sn as well as a quinary Cu-Sn-Zn-Pb-Sb bronze. Moreover, considering the real application of this coating on historical bronze substrates, previously artificially aged (''patinated'') bronze samples were prepared and a comparison between bare and ``patinated'' quinary bronzes was performed. In the case of coated quinary bronze, the free surface of samples was analysed by High Resolution Photoelectron Spectroscopy using Synchrotron Radiation (HR-SRPES) at ANTARES (Synchrotron SOLEIL), which offers a higher energy and lateral resolution. By compiling complementary spectroscopic and imaging information , a deeper insight into the interactions between the protective coating and the bronze substrate was achieved.

Mots clés: X-ray Photoelectron Spectroscopy; Bronze; Silane coating; Atmospheric corrosion; Conservation-restoration; Cultural heritage

Domaines: Génie des procédés; Matériaux

Giulia Masi, Andrea Balbo, Jérôme Esvan, Cecilia Monticelli, José Avila, et al.. X-ray Photoelectron Spectroscopy as a tool to investigate silane-based coatings for the protection of outdoor bronze: The role of alloying elements. Applied Surface Science, 2018, 433, pp.468-479. ⟨10.1016/j.apsusc.2017.10.089⟩. ⟨hal-01997469⟩