Study of the catalytic action of heavy metals to understand the phenomenon of sulphation and the formation of black crusts

The degradation of cultural assets exposed in out-of-door environments is a continuous and irreversible phenomenon that is largely accelerated by anthropogenic pollution. Various phenomena of degradation can develop on stone surfaces among which one of the most important is the formation of black crusts that are created in areas protected from runoff. The development of these degradation patinas is very complex and understanding their genesis could be fundamental in preventing the decay of monuments. This research shows the results of a second exposure campaign in accelerated ageing chambers in order to understand the role of catalysts that trigger the sulphation process and the formation of black crusts. This study was developed by analyzing samples of Carrara marble treated with metal cation solutions and PM 2.5 that were exposed for three weeks in corrosion and irradiation chambers.