PSI - Issue 55

Jéssica D. Bersch et al. / Procedia Structural Integrity 55 (2024) 57–63 Bersch et al. / Structural Integrity Procedia 00 (2023) 000 – 000

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2. Methods Initially, an advanced search in the Scopus database with the query string “anti - graffiti AND climate chang*” within the title, abstract, and keywords of scientific papers in English was carried out. Solely one result (Carmona Quiroga et al., 2017a) was retrieved, ensuring the relevance of discussions on the topic and pointing to the need for a broadened search. Therefore, an overview is reported substantiated by the state-of-the-art referring to anti-graffiti products, firstly addressing their application in polluted environments. The subsequent section was focused on their efficiency and durability, for which the search query “anti - graffiti AND durab*” regarding title, abstract, and keywords retrieved 16 journal papers in English from the Scopus database. Lastly, also in the field of sustainability, the choice of anti-graffiti products considering the related cleaning methods is discussed along with the environmental and economic impacts throughout their service life, following topics retrieved from existing research. 3. Results 3.1. Application of anti-graffiti products in polluted environments Air pollution is a decisive variable regarding health and climate change; sulfur dioxide (SO 2 ), nitrogen oxides (NO x ), carbon monoxide (CO), volatile organic compounds (VOCs), and particulate matter lead to massive impacts on the air quality and are mainly resulting from fossil fuels combustion (Kumar et al., 2023). In this context, Carmona-Quiroga et al. (2010b), for example, investigated anti-graffiti solutions as potential pollutant deterrents to be applied to construction materials, considering an SO 2 -polluted environment. An organic inorganic hybrid anti-graffiti product was effective in deterring pollutants when applied to carbonate-based materials, while it was not efficient in preventing SO 2 absorption by cement mortar and brick; on the other hand, another anti graffiti product, water-based fluoroalkylsiloxane, did not influence the SO 2 uptake of any studied substrate (Carmona Quiroga et al., 2010b). Regarding the protected substrates, roughness parameters may, besides impacting graffiti access, affect as well the access of pollutants (Carmona-Quiroga et al., 2017a). Although further studies may be suggested on the performance of anti-graffiti products exposed to other air contaminants, the available information indicates that distinct anti-graffiti products may respond differently to a polluted atmosphere. Furthermore, Gomes et al. (2018) approached the exposure of graffiti paints with different compositions to an SO 2 rich environment, aiming to study its influence as an ageing cause on the effectiveness and harmfulness of graffiti chemical cleaning procedures since the external environment may affect the graffiti paints. Without applying anti graffiti products, the graffiti paints were cleaned with a potassium hydroxide (KOH) solution and a solution of n-butyl acetate, xylene and alcohol isobutyl. Alkyd-based and polyethylene-based graffiti paints had a different behavior when exposed to the SO 2 and moisture-rich environment; the SO 2 ageing of the painted specimens influenced the chemical cleaning efficiency by requiring a higher number of cleaner solution applications in order to reach similar results as on the unaged specimens (Gomes et al., 2018). Therefore, the cleaning effectiveness of graffiti paints may be harmed by continuous exposure to air pollutants, highlighting the importance of prevention measures. 3.2. Efficiency and durability of anti-graffiti products The long-term performance of permanent and sacrificial coatings is considered scarcely known, which is problematic since they are affected by environmental factors and, often, by aggressive cleaning procedures (Carmona Quiroga et al., 2017b). Thus, additional knowledge is needed regarding the behavior of anti-graffiti products under natural exposure in the long run (Gil et al., 2023). The anti-graffiti coatings must be able to keep their effectiveness throughout time, allowing graffiti removal with the lowest possible resulting color and gloss changes within the substrate due to the cleaning actions; furthermore, resistance to solar radiation and chemical and thermal stability are required from the protective products, in addition to environmental and economic compatibility (Rossi et al., 2016). In stone substrates, two anti-graffiti treatments, one composed of a water dispersion of polyurethane with a perfluoropolyether backbone and the other of a water-based crystalline microwax, lost their cleaning efficiency after artificial ageing during 2,000 hours in a chamber with UVB radiation and natural ageing trials in a temperate maritime