My hitch receiver has some kind of plastic coating thiat is flaking off and some cases coming off in sheets. It looks like it is 3-5 layers thick. Underneath the coating there is a lot of rust but the metal is not comprised. Should I be worried about this rust? Can I just spray it really well with rust oleum or do I need to take the whole hitch receiver down grind it to the metal and then apply many coats of rust oleum primer and then paint?