Graffiti
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Anti-graffiti Policy is the most important part of preventing graffiti. It requires resources and committment. Any surface that is tagged must be cleaned within 24 hours of being reported. If tagging is repeated, the area must be policed to try and apprehend the tagger.
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To remove graffiti by pressure washing, select a pressure washer with a tip that creates a spray that will remove the graffiti without damaging the substrate. On porous surfaces like brick or wood, direct the spray at the wall at an angle so that the paint is not driven deeper into the surface. The substrate of the surface (brick, concrete, aluminum, acrylic) will determine the right tip, pressure and angle. Run a trial on a small area on the bottom or edge to make sure of the results, and then start the work. Try pressure washing first, and then mask over the graffiti with an acrylic coat that is color matched to the substrate color.
Anti-Graffiti Coatings
on Concrete
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Acrylic coatings are the most common coating applied to achieve uniform color on concrete noise barriers. To mask graffiti on a wall coated with an acrylic stain, the coating is simply re-applied over the graffiti to mask it. The wall will look best if a color matched coating is applied to keep the noise barrier looking good as new.
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Sacrifical coatings are typically wax based materials applied over the finished surface of a noise barrier when first completed. When the wall is tagged, the wax surface is removed with a hot water pressure wash. The wax material is then re-applied. Wax based materials do not last forever and may need to be renewed after about ten years. Local conditions will vary this life widely.
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Aliphatic urethanes are superior coatings, providing hard, dense surfaces that are long lasting. One or more coats of material may be required for the initial application (base coat, intermediate and top sacrificial coat). Some allow removal of graffiti by pressure washing. Some use a solvent to dissolve the sacrificial to coat, which then must be reapplied.
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Proprietary materials containing fluoro-polyol are expensive to purchase and apply but have the advantage of being unpaintable. Manufacturer's literature shows paint literally dripping of the surface.
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ASTM D6578 Standard Practice for the Determination of Graffiti Resistance is a test method for a smooth surface which may not be applicable to coatings applied to porous brick or concrete. But if the anti-graffiti coating like an aliphatic urethane achieves a smooth surface, then this test method may prove useful. Check the product label to see if it claims satisfactory results per ASTM D6578.
Powder Coated Aluminum - Powder coatings are baked on urethanes, polyesters or fluoropolymers. Many paint removers are suitable for use, but it is best to ascertain the specific material recommended by the supplier of the powder coated panels to be sure the solvent is compatible with the powder coated surface. Some powder coatings claim anti-graffiti properties. These can be confirmed by testing per ASTM D 6578.
Clear Acrylic - Removal of graffit from clear acrylic noise barriers is accomplished with materials specified by the supplier of the acrylic sheet. It is best accomplished soon after the graffiti is first applied.
