How to solve the problem of efflorescence in exterior wall paint?

Analysis:
1. The alkalinity of the substrate is too high, so the coating is applied directly without alkali removal.
2. The wall appears cracked or seeps, and water pours into the putty layer and base layer. Moisture carries alkaline substances from the wall to the coating, creating a white substance on the surface. At the same time, its high alkalinity corrodes the coating layer. Causes discoloration, fading and peeling of the coating.

Solution:

1. Take necessary waterproofing measures, paying special attention to roof gutters and low walls.
2. Eliminate the alkalinity of the base layer: Mainly water and maintain the mortar plaster layer (3-4 times). If the cement is completely polymerized, its alkalinity will quickly decrease.
● If watering conditions are not available and natural rainwater and natural aggregation are relied upon, the drying time will be longer. It takes at least 20 days (may take more than 30 days in winter). Therefore, watering and curing the mortar plaster layer is the best method to reduce alkali.
● Qualified cement is the basis for eliminating the alkalinity of the base layer.
3. Eliminate the alkalinity of the putty layer: The key to eliminating the alkalinity of the putty layer is to choose good quality putty. This kind of putty has good hardness, is water-resistant, and is not highly alkaline (PH value less than 10).
At the same time, it is necessary to water 1-2 times in time after the putty is constructed. The cement in the putty layer can be completely polymerized and hardened. This way the pH value can also be lowered.
4. Choose a sealer with good performance. Penetrating and sealing the base layer and putty layer makes it difficult for alkaline substances to penetrate into the coating along with water vapor. This is a temporary solution. However, if the penetration and sealing performance is not good enough, or there are too many alkaline substances in the base putty (PH>10), efflorescence will still occur.