The whitening and fading of exterior wall paint is the most common and widespread quality problem in the paint industry. And it is the most destructive to the appearance of the decorative effect. So what can be done to avoid it?

Whitening of paint

Reason

It rains when there is no topcoat or the topcoat is not completely dry.

Treatment

1. Check whether the bottom alkali efflux and whitening are caused by insufficient or missed alkali-resistant primer. If it is caused by alkali efflux and whitening, the project can only be redone.

2. If the whitening is caused by the emulsion not being completely dry, this is the initial water-resistant whitening of the emulsion. When the temperature rises, the whitening will automatically recover. If you need to quickly restore the original color. After the exterior wall paint is dry, you can try to use a topcoat roller or spray it once.

3. Some whitening is caused by uneven spraying of exterior wall paint. It looks like whitening from the side. In this case, you can find a place first. Spray it again at the original whitening position. After drying, see if the color is consistent. If it is possible, spray it over a large area more times.

Paint alkali efflux

Cause

When it rains, rainwater will flow into the putty layer and the base layer. After the weather clears, the water vapor will bring these alkaline substances to the coating. A layer of white substance is formed on the surface. At the same time, due to its high alkalinity, the pigment in the coating changes color and fades.

Prevention

1. Eliminate the alkalinity of the base layer: mainly the maintenance of the mortar plaster layer. If watering can be done 3-4 times to make the cement completely polymerize. Then its alkalinity will drop quickly.

If there are no watering conditions, relying on natural rainwater and natural polymerization. The drying time will be longer, at least more than 20 days (may be more than 30 days in winter). Therefore, watering and curing the mortar plaster layer is the best way to reduce alkali. Of course, the choice of cement is also very important, and the selection of qualified cement is the basis.

2. Eliminate the alkalinity of the putty layer mainly by choosing a good quality leveling putty. This putty has good hardness, is water-resistant, and has low alkalinity (PH value is less than 10). At the same time, after the putty is constructed, water should be applied 1-2 times in time so that the cement in the putty layer can be completely polymerized and hardened, so that the pH value can also be reduced.

3. Use a sealing paint with good performance to penetrate and seal the base layer and putty layer. It is a temporary solution to make it difficult for alkaline substances to penetrate into the coating with water vapor. However, if the penetration and sealing performance is not good enough or there are too many alkaline substances in the base putty (PH>10), alkali efflorescence will still occur.