Estudio del comportamiento de dos tratamientos antigraffiti como protectores de materiales de construccióninteracción antigraffiti-substrato, propiedades y durabilidad

Abstract

The damage caused by the traditional agents of construction material decay, namely water, air pollutants, biological agents and so on, is accentuated by direct human action in the form of graffiti and soiling. While graffiti can be found on nearly any surface in cities, their effects – visual impact and deterioration – are especially pernicious in buildings, historic buildings in particular. Anti-graffiti coatings have been developed to combat this problem by protecting the surface of construction materials to prevent paint from penetrating their pore systems or from adhering to the surface, thereby facilitating subsequent cleaning operations (with pressurized water, chemical products and so on). The present report evaluates the behaviour of two such anti-graffiti coatings, a new compound synthesized at the Ceramics and Glass Institute (a Spanish National Research Council, CSIC, body), Zr Ormosil, and a commercial fluorinated product (Protectosil Antigraffiti®, manufactured by Degussa). They were tested on five construction material surfaces: cement mortar, lime mortar, limestone, granite and brick. The parameters studied were compatibility (modification of petrophysical properties), interaction (penetration depth, chemical bonding and modification of active centers, effectiveness (paint and water repellence) and durability (resistance to freeze-thaw cycles, UV radiation and polluted air) under the project “Surface treatments for the conservation of construction materials: scientific fundamentals and design of new multipurpose products” (MAT 2003-08343). The inverse gas chromatography findings showed that of the two coatings, Protectosil (more highly concentrated) reduced the surface energy in lime mortar, limestone and granite more effectively. This would explain the more thorough cleaning of graffiti attained in the materials impregnated with this product, a result that was clearly related to the porosity, cohesion and especially the roughness of the substrates.