Originally Posted by Cnphoto
it doesnt really look like oxidization but ive never seen brass in the early stages of oxidization, and its only at the top closest to the coals not the bottom
It is heat induced oxidation, which is a slightly different chemical reaction than oxidation that occurs with exposure to room temperature air. You can get rid of it by removing the surface layer but you will also risk removing the plating/painting.
Your quad metal cover is now becoming a quint metal cover.