MechChem Africa

WACKER has developed a new, highly effective anti-graffiti product, which permanently protects surfaces with a thin film of silicone. Graffiti and stickers can be readily washed off with just cold water.

It’s a scenario replicated in cities all around the world: under cover of darkness, a graffiti artist whips out a spray can and gets to work. The pitch-black paint etches its way mercilessly into the masonry. The fine pores of the sandstone soak up the acrylic paint like a sponge. After a few minutes, the culprit has disappeared – leaving a personal memorial on what was once a natural stonewall.

WACKER anti Grafitti coating

“In porous masonry, the paint can penetrate down to a depth of about one millimetre,” says Professor Helmut Weber, founder of the Competence Center for Building Protection and Renovation in Ebersberg near Munich, Germany. “It literally clings to rough sandstone surfaces and is highly tenacious,” notes the construction expert. A great deal of water, special chemicals and a high-pressure cleaner are needed to remove the graffiti. Even so, the outlines of the inscriptions can often still be seen afterwards. The only remedy in such cases is to resort to sandblasting. “But that, of course, strips away the building fabric,” says Weber. “If you do that after every graffiti attack, the building itself will eventually suffer.”

Year after year, graffiti and wild posters inflict huge damage on public buildings, bridges, underpasses and house walls. They are not only time-consuming and expensive to eliminate. They lower the value of these structures, too. The Deutscher Stadtetag (Association of German Cities) estimates the damage done in Germany at €200-million every year. In the United States, the Department of Justice puts the annual cost at some US$12-billion.

“Spray paints are becoming cheaper and thus affordable for everyone. Consequently, the spotlight is increasingly being turned on technologies that can provide buildings with long-lasting protection against graffiti and other defacements”, explains Marianne Kreuzpointner, a marketing expert in construction chemicals at WACKER’s production site in Burghausen, Germany. “We’re receiving more and more requests from customers about whether we supply products that offer permanent surface protection and enable graffiti to be removed for a low cost.”

One such WACKER product is already available in the USA. Applications engineer Hartmut Ackermann and his research colleagues have taken this pioneering technology and enhanced it further. “Like most anti-graffiti systems, our new product forms a continuous film on the substrate, where it acts as a barrier between the substrate and the spray paint,” says Ackermann.

“The graffiti is unable to develop permanent adhesion to the silicone and so can be removed with cold water and a cloth or a high-pressure cleaner,” explains the chemist. Tests in the Upper Bavarian town of Burghausen prove just how well the product works. An underpass there for cyclists was treated with the new anti-graffiti coating. “We deliberately chose a concrete wall that is a favourite target for graffiti artists,” says Albert Gunthner, head of the department responsible for the town’s upkeep. “The sprayers usually slip in here unnoticed and have plenty of time to create memorials.”

When the 20 m² test area was cleaned, Gunthner witnessed for himself how effective the anti-graffiti protection is. “Before this, we had to use sandblasters to clean the defaced concrete walls, because the paint penetrates so deeply into them. What’s more, the frequent cleaning was exacting a heavy toll on the structural fabric. Thanks to this new anti-graffiti product from WACKER, all we need now is a high-pressure cleaner and cold water. It is very impressive”, he says.

“The protective film is about 0.2 mm thick and can be stretched by up to 160% before it tears. This allows cracks and irregularities to be bridged effectively, while the substrate is protected from damage by the paint,” explains Ackermann. The extendibility of the silicone is also important for another reason: building materials are always under tension. They expand during the day as the wall warms up and contract at night when it gets cold. This is a constant challenge for the protective coating. Another is posed by heat and UV light. The silicone must remain transparent even under a scorching sun and it must not turn yellow or embrittle.

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