the exterior wall painting is fading with alkali, and it has great destructiveness to the exterior decoration effect. after the heavy rain, the color of the paints often becomes flower and white. serious wrinkles will appear, even the paint film will disappear. this is actually the reason why the exterior wall paint is alkaline.
if a large amount of unpolymerized cement or lime is contained in the base and the putty, the rain will pour into the putty and the base, and the water vapor will bring these alkaline substances to the coating and form a layer of white material on the surface. at the same time, because of its high alkalinity, the pigment in the coating will change color and fade.
solving method of pan alkali in exterior wall coating
1, the elimination of basic alkali is mainly the maintenance of mortar plastering layer, can be watered for 3-4 times, so that the cement completely polymerized, its alkalinity will soon decline. if water conditions are not available, the drying time will be longer, at least for more than 20 days (or more than 30 days in winter). therefore, the water maintenance of the mortar plastering layer is a better method of reducing alkali. of course, the choice of cement is also very important. the selection of qualified cement is the foundation.
2. to eliminate the alkalinity of the putty is mainly the selection of good leveling putty. this putty not only has good hardness and water resistance, but not high (ph value less than 10). the key is to improve the amount of adhesive (latex) in putty and reduce the amount of cement. at the same time, the putty should be poured in time 1-2 times after the putty is well constructed, so that the cement in the putty can be completely used. polymerization of hardening, so that the ph can also be reduced. on the market, some low-end putty (1000 yuan / tons below) completely rely on cement to improve the cohesive force, and no timely rain maintenance, resulting in ph up to 10 (some 14), this situation will certainly appear in the case of alkali.
3. choose a good primer to seal the base layer and putty layer, so that it is difficult for the alkaline material to permeate the coating with water vapor. this is a temporary solution. however, if the primer is not well sealed or the basic substance of the base putty is too much (ph>10), there will be a common alkali phenomenon. to make the primer better permeate the primer, the size of the primer is fine and the viscosity is low.