Mottling, Fading and Chalking Paints
Generally, original surface is high in humidity or damp plaster is a typical cause of the problem. Other possible causes include having holes or cracks in the wall which allow leakage from above or below area as well as the leakage of water into the walls after painting. These result in deterioration of latex-based adhesives and primary colour pigment. As well, the problem can be caused by ageing paints, low-quality paint or using interior paint, which is not resistant to UV ray, as exterior paint.
Remove corroded paints using a stiff brush and wash with clean water. Alternatively, do the power washing. Should the area be unable to wash with water, wipe clean and leave dry. Fix the holes or cracks with fine wall putty for exterior. Repair the leaks. Apply the primer on original surface and refinish.