After many years of use, a microwave may begin to decline in appearance and operation. One possible issue that may arise is the peeling of the interior paint. Since peeling paint can both become a fire hazard and contaminate food you cook in the unit, it's important to prevent and repair the interior paint when it peels.
When food splatters onto the interior of a microwave and you don't clean right away, it can bake onto the surface of the microwave interior and harden, creating a "hot spot." These hot spots get warmer than the rest of the microwave's interior during the cooking process, which can lead to the deterioration of the paint in that area of the microwave. Sharp utensils may also scratch the paint off the oven cavity walls.
Aside from causing the flaking of the interior paint of the microwave, hot spots that form in a microwave can create other issues. The spots where food baked onto the surface, or where the interior paint was scratched by a utensil, may spark when you run the microwave. If paint is peeling and hanging from the inside of the microwave, this creates a possible fire hazard. To prevent this sparking, the interior of the microwave must be smooth.
Prevention is the best course of action when it comes to peeling paint on the inside of a microwave. You can stop peeling paint before it starts by always cleaning up spills or splatters from the inside of the microwave as soon as they occur. Once peeling begins, though, use fine-grit sandpaper to remove the hanging pieces of paint from the microwave's interior to prevent further peeling. The microwave is safe to use in this condition, although the scratched areas may rust over time if not repainted.
To fully repair a microwave with peeling paint to like-new condition, you not only must remove the paint that is peeling but also repaint the microwave so that it doesn't rust. You can buy paint made specifically for microwave interiors at appliance stores, but you also can use any standard gloss enamel paint to cover the exposed areas of the microwave interior. Test the paint in a small area first. Apply the paint, then run the microwave containing a cup of water on HIGH for about a minute; the painted area should not be any warmer to the touch than the rest of the oven after you remove the water. After painting, allow the microwave to dry for at least 24 hours before use.