The wall is coated with the specialized Protectam FN® protective coating, which ensures effective, long-term protection against darkening caused by deposits of dust and dirt particles floating in the atmosphere. The protective surface formed by the FN® coating also effectively limits the growth of algae and mold over the long term.
Because the anti-noise barrier is in the close proximity of some very busy roads (20-30,000 cars pass by daily), surfaces that are not treated with the protective coating are very quickly darkened by heavy deposits of dirt. Even after only two years, a difference in color can be seen between areas where the protective coating has been applied and those where it has not.
The speed and intensity with which facades are darkened by deposits of atmospheric dirt in localities suffering from deteriorating air quality (which includes almost all of Prague) is demonstrated by the following table:
So-called “self-cleaning” paints and protective coatings relying on the “lotus effect” (where water balls up on their surface into droplets that easily roll downward) are not effective against darkening of facades caused by deposits of atmospheric pollutants. If there is no rain, soot and other dusty particles of dirt stick firmly to treated surfaces. These particles are usually wrapped in sticky organic materials. In such cases, the “lotus effect” just doesn’t work. Water can’t rinse off the firmly stuck-on dirt particles. In the best of cases there is simply a moderate slowing of the pace of darkening.
Even the most modern protective coatings and paints containing poisonous (biocidal) chemical compounds can’t ensure truly long-term protection (five or more years) of facades and walls from growth of algae and mold. They normally give out after two or three years. Therefore the manufacturers of such coating materials do not offer any guarantee of protection against the growth of algae and mold for more than four years, if they offer any such guarantee at all.
The protective action of the coating used on the Barrandov anti-noise barrier is not based on the “lotus effect,” nor does it rely on any poisonous chemical compounds.
The surface layer formed by Protectam FN® relies on a physical process—photocatalysis. The energy contained in daylight creates special physical conditions on the surface of a wall coated with FN® Coating. These conditions involve the exceptionally efficient oxidation by atmospheric oxygen of molecules and microscopic particles that come into contact with the surface. In terms of chemistry, this is the same process as if they were burned up. Both the long-term, active self-cleaning effect and the protection against mold and algae are based on the same process. Light energy hitting the surface of the coating prevents the establishment and growth of algae and mold and burns up the sticky elements of airborne particles of dirt. Anything left behind is washed away by rain.
The advantages of using Protectam FN® for protection of building facades against growth of algae and mold and darkening by deposits of atmospheric grime include:
1. An exceptionally strong self-cleaning efffct ensures a long-term clean appearance of facades of buildings. (The manufacturer and the firms applying FN® offer a ten-year guarantee against deposition of atmospheric grime and against the growth of algae and mold on vertical surfaces.)
2. Protection of the substrate (natural or painted) against the degrading effects of the ultraviolet radiation contained in daylight—prolonging its lifespan and protecting against changes in color (fading).
3. Protection of facades from deterioration caused by penetration of atmospheric dirt (especially those made of expensive, light-colored stone facing materials). In ten years, pollution can penetrate up to five millimeters deep and become impossible to remove without scrubbing down the stone surface.
4. Exceptionally good permeability of the coated surface—moisture cannot collect underneath it.
5. No poisonous compounds used.
6. Overall extension of the lifetime of facades while maintaining their beautiful appearance, because their surface need not be exposed to repeated abrasive and chemical cleanings.
Because of the extraordinarily high photocatalytic efficiency of the Protectam FN® coatings, the manufacturer is able to offer a ten year guarantee (unique in the marketplace) of the long-term clean appearance of the treated facade of a building. In areas with a lower level of air pollution than Prague, Ostrava or Northern Bohemia, full protective functionality can be assured for a much longer period.
Více zde: https://www.amjtj.com/news/test-wall-set-up-by-advanced-materials-jtj-in-pragues-barrandov-district-proves-to-have-exceptional-self-cleaning-effectiveness-even-after-two-years-under-harsh-conditions/