To stop a wall from Chalking you should prepare the surface before painting and make sure the surface is clean and apply a good quality primer and use a high quality paint.
You should also use lighter paint colors that absorb less UV radiation.
Regularly clean and maintain the painted surface to prevent any excessive chalking of the paint over time.
To treat chalking walls and fix chalking walls you can wipe down the surface of the wall with a damp cloth to remove any dust.
Then skim apply a coat of pva to seal the surface of any of the remaining chalk.
You can also apply a wall stabilizer such as everbuild 496 prior to the skimming.
Wall chalking is a paint defect which occurs when the painted surface develops a white and chalky residue.
The wall chalking is caused by the paints film breaking down over time and is often caused by exposure to ultraviolet light, moisture and other environmental factors.
To reduce chalking of the walls and paint when painting.
Use inorganic pigment colors which don't react strongly to UV light.
Use lighter colors which are less UV absorbent.
Don't thin the paint for external applications.
Apply a good quality primer to the surface after preparing the surface really well.
And choose a good quality paint.