Things You'll Need
Sandpaper and hand sander
Primer and paint (preferably latex)
One of the downsides of a painted door is that with time, wear and tear, the paint starts to chip and peel. The peeling can happen due to poor quality paint, lack of primer, and sometimes, too much moisture in the air. Good surface preparation and the proper choice of paint are important in successfully repainting the door -- and repainting is the only sure way to remedy the peeling.
Scrape off the peeling paint with a paint scraper, then sand down the door with your hand sander, paying extra attention to the areas that were peeling. Make the surface as smooth as possible, even if that means you have to sand off the entire previous coat of paint. Paint sometimes peels because it has another layer of paint or primer underneath that doesn't hold onto the topcoat.
Use a damp, lint-free cloth to clean the dust and dirt off the surface of the door. In some cases, the paint peels because the surface wasn't clean enough before painting. Allow it to dry thoroughly for at least an hour.
Paint one coat of primer on the door carefully. Use a primer especially designed for that type of door material. For instance, if the door is metal, use a metal primer. Take your time, and cover the door from the edges to the middle. Wait a couple of hours to allow the primer to dry.
Coat the door with your paint enamel next. The type of paint you use is key. Use acrylic paint for metal doors. Acrylic (or latex) paint is also resistant to peeling for wood, drywall and other surfaces. After waiting about four to six hours for the first coat to dry, add a second coat and allow it to dry for at least a day before the door is used.
If you feel more comfortable working with the door on a flat surface, take it off the hinges first. Simply remove the hinge pins, slide the door out of the doorway, lay it down on a protected surface and get to work.