title: Durability of anti-graffiti coatings on stone: natural vs accelerated weathering.
abstract: Extending the use of novel anti-graffiti coatings to built heritage could be of particular interest providing the treatments are efficient enough in facilitating graffiti removal and long-lasting to maintain their protective properties without interfering with the durability of the substrates. However, studies of the durability of these coatings are scarce and have been mainly carried out under accelerated weathering conditions, the most common practice for assessing the durability of materials but one that does not reproduce accurately natural working conditions. The present study aimed to assess the durability of the anti-graffiti protection afforded by two anti-graffiti treatments (a water dispersion of polyurethane with a perfluoropolyether backbone and a water based crystalline micro wax) on Portland limestone and Woodkirk sandstone after 1 year of outdoor exposure in the South of England with periodic painting and cleaning episodes taking place. A parallel study under artificial weathering conditions in a QUV chamber for 2000 hours was also carried out. Changes to the coatings were assessed by measuring colour, gloss, water-repellency, roughness and microstructure, the latter through micro-Raman and optical microscope observations, periodically during the experiments. The results show that both anti-graffiti treatments deteriorated under both artificial and natural weathering conditions. For the polyurethane based anti-graffiti treatment, artificial ageing produced more deterioration than 1 year of outdoor exposure in the south of England due to loss of adhesion from the stones, whereas for micro wax coating there were no substantial differences between the two types of weathering.
authors.affiliation: School of Geography and the Environment, University of Oxford, Oxford, United Kingdom.
authors.forename: Paula M
authors.identifier: http://orcid.org/0000-0002-9583-7131
authors.initials: PM
authors.lastname: Carmona-Quiroga
authors.affiliation: Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Oxford, United Kingdom.
authors.forename: Robert M J
authors.initials: RM
authors.lastname: Jacobs
authors.affiliation: Departamento de Espectroscopía Nuclear, Vibracional y de Medios Desordenados, Instituto de Estructura de la Materia (IEM-CSIC), Madrid, Spain.
authors.forename: Sagrario
authors.initials: S
authors.lastname: Martínez-Ramírez
authors.affiliation: School of Geography and the Environment, University of Oxford, Oxford, United Kingdom.
authors.forename: Heather A
authors.initials: HA
authors.lastname: Viles
mesh_terms: D002119:Calcium Carbonate / Q000737:chemistry; D008420:Manufactured Materials / Q000032:analysis; D010151:Paintings; D013499:Surface Properties; D014887:Weather
chemical_list: D002119:Calcium Carbonate