Exposed to the natural environment, the steel structure building has been affected by wind, sunshine, light and rain for a long time. Soon, the wall surface appears discoloration, paint peeling, dust and other phenomena. With the passage of time and temperature change, the dust is firmly attached to the wall, and the dust accumulates, resulting in the whole building looks dirty and old.
What is directly related to these phenomena is the coating system of building exterior wall materials, i.e. color coated steel plate. The main factors that affect the performance of coating system are resin, pigment, primer and heat reflection.
Some organic pigments have poor light resistance and strong alkali resistance. Under the influence of sunlight, chemicals and air pollution, the pigments will undergo qualitative change, and some pigment powders will cause the paint film to fade.
Generally, the paint powder on the surface of color steel plate is mainly the aging degradation of film-forming resin, and the phenomenon that resin and pigment are separeted from the surface in particle state. The weather resistance of resin is the key factor to determine the quality of paint powder. Powdering will cause fading and glossiness, thus affecting the appearance of the building.
The falling off of paint film is the aging phenomenon caused by the long-term outdoor use of paint resin. The main causes of paint film falling off are: long-term ultraviolet radiation, the location of substrate surface pretreatment, rough paint formula or improper matching of finish coat and primer.
To sum up, the coating system must select high-quality raw materials, which is very important to avoid or reduce the discoloration and fading of the film.
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