Characterization of the Anti-Graffiti Properties of Powder Organic Coatings Applied in Train Field

Stefano Rossi,Michele Fedel,Simone Petrolli,Flavio Deflorian

doi:10.3390/coatings7050067

Abstract

The widespread prevalence of the phenomenon of graffiti and the growth of the removal cost—in particular in public transport systems—has pushed the research for technical solutions to this problem. Suitable solutions to address graffiti-related concerns are needed in order to reduce the cleaning costs as well as the downtime of trains. Graffiti are a big problem for painted metal, because the protective coatings and graffiti have the same chemical nature (polymeric matter). A permanent coating is expected to be able to resist the highest possible number of cleanings of the graffiti without modifying its aesthetic and corrosion protection properties. The purpose of this study is to develop a methodological approach for the characterization of graffiti-resistant organic coatings. For this purpose, a critical review of the existing standards is carried out. The anti-graffiti properties of a polyurethane organic coating were investigated before and after accelerated weathering. In order to understand the behavior of the coatings during cleaning, the aging of the coating in contact with the remover was carried out. The effect on the corrosion protection properties was assessed during the accelerated aging. The resistance of the coating was proved to be strongly affected by the surface finishing. UV exposure modified surface properties and graffiti removal efficiency.

Highlights

The problem of graffiti originated in the second half of the last century, causing a lot of damages to transport vehicle bodyworks as well as to buildings and public areas [1,2,3]
It is possible to see that the polar solvent (MEK) cannot remove the graffiti over the fourth cycle without producing a color change outside the ASTM threshold
After about 60 min of exposure, delamination of the paint from the substrate was observed, followed by the occurrence of cracks after about 200 min. These results suggest that the contact time with the organic solvent can be dramatically detrimental for the corrosion protection properties

Summary

Introduction

The problem of graffiti originated in the second half of the last century, causing a lot of damages to transport vehicle bodyworks as well as to buildings and public areas [1,2,3]. The cost of graffiti removal is very high. In 2014, a study reported that the cost of cleaning Milano (Italy) of graffiti would have been 100 million euros [5]. Trenord (the railroad agency of the Lombardia region, Italy) evaluated the cost of vandalism including the graffiti removal to be approximately 8 million euros [6]. The first one consists of a “sacrificial” layer (commonly wax-based coatings) which is removed during the cleaning. The second technological solution is a permanent layer which is not solubilized during graffiti removal. This solution is well considered, on metallic substrates, and on stone and concreate [10,11]

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