The interior of your BBQ lid is aluminum and is NOT painted. We do not coat the inside of our lids with any material that is capable of peeling off. What you are noticing is carbon build-up, a deposit of grease and smoke that collects during normal use. During use, the grease and smoke vapors slowly oxidize into carbon and collect on the inside of the lid. This deposit will eventually peel, and looks very similar to paint. The peeling normally starts in the center of the lid and spreads outward. It may come off in sheets or flakes, and is shiny on one side and dull on the other.
To remove, simply brush off all loose particles with a stiff bristle brush or use a ball of aluminum foil to scrub away the build-up. To prevent future build-up, after every grilling session, while the BBQ lid is warm to the touch—NOT HOT—wipe it with paper towel and a mild soap and water solution. Remember to perform a burn off before using to ensure that the soap isn't being cooked into your food.