New strategies for conservation of cultural heritage under climate change conditions

Outdoor Cultural Heritage (CH) materials are exposed to chemical, physical, and biological stressors, including liquid water, water vapor, temperature fluctuations, solar radiation, pollutants, and microorganisms. Climate Change affects these parameters, potentially increasing or decreasing degradation risks. Concurrently, environmental policies adopted at European level contributed to influence atmospheric emissions trends leading to a decrease in atmospheric SO2, thereby increasing the relative relevance of non-climatic stressors like NOₓ and atmospheric particulate matter (PM). This new multi-pollutant scenario must be considered in risk assessments for CH conservation, leading to the need for updated approaches to evaluate material degradation and the durability of protective treatments. This thesis investigates degradation mechanisms and assesses the durability of innovative protective coatings for outdoor bronze and carbonate stones under updated climatic and atmospheric conditions. An accelerated ageing methodology was implemented based on environmental parameters derived from real monitoring data, thus including an updated synthetic rain formulation and reproducing conditions representative of southern Europe. The performance of a novel polyester-urethane cutin-based coating for bronze was evaluated via laboratory ageing simulating rain exposure (stagnant and run-off), and temperature/relative humidity/UV cycles. A multi-analytical approach allowed to assess corrosion processes and coating durability. Results demonstrated that the cutin-based coating performed comparably or better than commercial references. The effects of atmospheric PM on bronze corrosion were studied using both ambient and synthetic PM. Multivariate analysis enabled development of a preliminary predictive model correlating PM ionic composition with corrosion-induced mass loss. Chemical analyses confirmed that synthetic PM effectively reproduces corrosion phenomena, highlighting the importance of PM composition over deposited mass and validating its use in laboratory ageing procedures. For carbonate stones, various functionalization for an hydroxyapatite-based coating were tested, to assess antibacterial and anti-staining properties. The proposed methodology improves the reliability of laboratory ageing tests and better predicts real-world material performance.