Effectiveness and durability of anti-graffiti products applied on ETICS: towards a compatible and sustainable...

External Thermal Insulation Composite Systems (ETICS) are widely used constructive solutions which aim at enhancing the building thermal performance. Nevertheless, ETICS can often present anomalies (e.g., stains and microcracks) throughout their service life, and vandalism actions, as in the case of graffiti, are rather common in urban areas. The removal of undesired graffiti is generally carried out through invasive chemical-mechanical methods, which may affect the durability of the ETICS. The adoption of anti-graffiti products can be a feasible protection method; however, no comprehensive studies were already addressed on these substrates. This study aims at evaluating the effectiveness, compatibility, and durability of three anti-graffiti products (with permanent, semi-permanent, and sacrificial properties) when applied on different ETICS. The removal of aerosol graffiti paints was carried out with a low-invasive and eco-friendly removal method (i.e., low-pressure steam jet). The water transport properties, as well as color, gloss, and roughness, were evaluated before and after graffiti removal. The durability of the anti-graffiti was also assessed by artificial aging cycles. Results showed that graffiti removal was rather efficient on ETICS with acrylic-based finishing coats and when using (semi) permanent anti-graffiti products (with ΔE*_ab < 5, i.e., not macroscopically visible, when comparing cleaned and reference surfaces), although these products can reduce their effectiveness after aging. Conversely, unsatisfactory graffiti cleaning was observed on ETICS with lime-based or silicate-based finishing coats (with ΔE*_ab > 5), with considerable alteration also of the water transport properties (reducing water absorption and slowing down the drying kinetic).