Atmospheric corrosion of fire-gilded bronze: corrosion and corrosion protection during accelerated ageing tests

Fire-gilded bronze (replicating the materials of Lorenzo Ghiberti's Paradise Door (Baptistery of Florence, 1452)) was aged in runoff/stagnant conditions by accelerated exposure tests in synthetic acid rain. After preliminary electrochemical investigations, a detailed characterization of gilded bronze samples before and after artificial ageing tests followed. Surface and cross-sections analyses were performed by FIB/FEG-SEM, SEM/EDS and micro-Raman spectroscopy. The protective efficiency of a coating based on 3-mercapto-propyl-trimethoxy-silane was also quantitatively assessed by GF-AAS through analysis of metal release, while the aesthetical appearance of coated and uncoated gilded bronze before and after ageing was evaluated by colour measurements.