Performance Assessment of Graphene Oxide as a Protective Coating for Historical Stone

Stone cultural heritage faces significant deterioration from environmental factors, necessitating protective treatments that preserve both functionality and appearance. In this study, graphene oxide (GO) was evaluated as a protective coating for both natural and artificially aged Euganean trachyte and Vicenza stone samples. GO was applied as a low-concentration aqueous dispersion (0.5 mg/mL) by brush, and samples were subsequently exposed to UV light for 7 h to simulate weathering. Performance was assessed in accordance with European standards through measurements of water capillary absorption, water vapor permeability, contact angle, and color variation; further characterization was conducted using FT-IR, Raman spectroscopy, SEM, and XRD. Results indicate that GO coatings reduce the water capillary absorption coefficient by up to 49% for Euganean trachyte and 22% for Vicenza stone, while maintaining vapor permeability close to that of untreated samples. Although UV exposure permanently darkens the coating, it slightly enhances hydrophobicity, likely due to differential photoreduction of thin surface layers versus thicker pore-associated GO domains. These findings suggest that, while GO, particularly after UV weathering, shows promise for stone protection, further research is crucial to optimize coating uniformity and assess long-term durability under realistic environmental conditions.