Peeling is the loss of adhesion from the surface of the paint coating. When there is a primer and topcoat, or multiple coats of paint peeling may involve some or all coats.
All surfaces prior to painting have to be wash to remove any grease, oil or other surface contaminants.
Peeling can also affect galvanized metal due to the same circumstances. To solve this issue we need to choose the correct products to be applied. The products depend of the status of the metal: new, weathered, rusty.