REMOVING GRAFFITI: A CRYSTAL-CLEAR REMEDY FOR VANDALISM

…or to prevent the defacement of its property in the first place.

Railroad cars are the preferred targets of illegal sprayers, so it is coating locomotives and railcars with polysilazanes. These molecules harden into an extremely smooth and durable layer.    

Thick, dark tears run down the sheet metal, pausing briefly on the edge of the railcar body. Then gravity pulls the shimmering bluish-black mixture of paint and cleanser downward. The heavy drops fall on the absorbent paper that Kwasi Ofosu and Kaya Gaffar have previously spread out as the top layer of a three-layer structure. Under the paper are special textile mats and, at the very bottom, a sheet of plastic. This padding absorbs the pasty mixture that is created when these professionals remove graffiti from vandalized railcars.    

Every swipe made by the two railcar cleaners reveals a bit more of the urban train’s red paint. Early that morning, the Series 423 train was still covered by a garish graffito left behind by unknown sprayers in the night. Ofosu and Gaffar know they have a morning of hard work ahead of them to fully remove the 45 square meters of black, blue, white, yellow, and red spray paint. But there are even worse cases — for example, when the sprayers carry out a concerted “bombing” action and vandalize one side of an entire train. 

The two men, who are wearing white overalls and protective masks covering their noses and mouths, are experts when it comes to dealing with the questionable street art that sprayers leave on trains, mostly at night. Documenting the damage, preparing the surface, applying the cleanser, waiting seven minutes, and then removing the dissolved paint — every move made by the duo to remove the graffiti is perfectly coordinated. “One train, one team — that works,” says Kwasi Ofosu as he applies a brush full of transparent cleaning paste to a stubborn spot of paint residue.

The original paint job of the urban train, a pattern of rich red and brilliant white, is emerging from under the graffiti. This is not to be taken for granted, as the traditional methods of chemical and mechanical cleaning used to leave visible tracks. Behind the anti-graffiti team stands a railroad car with faded paintwork. Dull red and brownish white in the places that have been cleaned several times show that this railcar will soon need a completely new paint job. For a complete railcar set, that can cost up to € 15,000. Amounts of this kind quickly add up: In 2014, sprayers left their traces on the trains and infrastructure of Deutsche Bahn about 20,000 times. That year the resulting damage amounted to more than € 8 million.    

In order to mitigate the damage, today more and more railcars are being covered with a microscopically thin protective coating of polysilazanes that will make it easier to remove any graffiti sprayed on them in the future. In 2014, Merck KGaA, Darmstadt, Germany acquired AZ Electronic Materials, a producer of these polymers. Since then, the company has supplied the special chemicals, which are also known as Durazane, to the paint industry.

The formulation that is made from these chemicals is a runny solution that is usually wiped or sprayed on surfaces. There the mixture hardens into a smooth, hard layer that is similar to glass. Graffiti does not stick very well to this barrier and cannot diffuse into the paint layer covering the railcar. As a result, the graffiti can be removed with relative ease. The fresh red color of the urban-train car that has just been cleaned is a brilliant example.    

Time is also an important factor for Deutsche Bahn in the struggle against graffiti, says 57-year-old Hans-Jürgen Zanger, who is responsible for the cleaning of the electric multiple units (EMUs) at DB Regio in Frankfurt am Main.

These EMUs include primarily the Series 423 and 430 urban trains as well as the Series 442 regional train sets. The EMU workshop, which is located in Frankfurt’s former postal service train station, serves all the trains that travel to and from Frankfurt within a radius of about 80 kilometers. 

“Our job is to remove all the graffiti from our trains within a period of 24 to 72 hours,” says Zanger. That’s because the vandalized cars disturb the passengers and create a feeling of insecurity. In addition, this robs the sprayers of the feeling of success they would get if they saw their illegal creations displayed on the rails for weeks on end.

All over the world, interest is growing in this specialist chemical product with its strong protective effect. That’s because its layers, which are between two and five micrometers thin, do more than just build a barrier against destructive graffiti sprays, according to Sergej Nell, an applications specialist for functional materials in paints at Merck KGaA, Darmstadt, Germany. Nell explains that surfaces of every kind benefit from this treatment, because it makes them more attractive visually and more resistant to environmental impacts.

For example, vehicle paint is protected against the dreaded “chalking” of the pigments caused by ultraviolet light — that is, the separation of the pigments from the surface of the paint. Even glass can be covered with a layer of glassy polysilazanes in order to protect its surface. Because of the similar behavior of both substances, this is known in the industry as a glass-on-glass technique.    

As a result, the use of this technique is widespread today. In addition to locomotives and railcars for public transportation, polysilazanes also have various other applications, such as the protection of building façades, ship hulls, stainless steel sinks and showers, works of art in public spaces, and classic automobiles.

According to Bergheuer, a chemical engineer, other areas of application will be added in the future. That’s because Merck KGaA, Darmstadt, Germany is expanding its portfolio of polysilazanes, which have different properties depending on their individual modification. Such developments could also give Deutsche Bahn an additional advantage in its endless cat-and-mouse game with the sprayers.