I understand that the cap is plastic with a copper coating. Will that coating patina like 100% copper?

Hello Aimee, Some people might say that the finish discolors (turns a grayish-green), but we call that a beautiful patina. The following information is straight from the product page's Installation Manual: • In its natural state, copper breaks down in the elements and develops a patina. In general, copper progresses from a natural salmon color to a series of russet browns and grays, and finally to a blue-green or gray-green patina. • To maintain the shiny look, apply a car wax immediately after purchasing the cap and reapply every 3 to 6 months. • To remove an already tarnished finish, remove the old coating with mineral spirits and grade 0000 steel wool. Buff with grade 0000 steel wool for a satin finish. For a mirror-like finish, apply a car wax or spray with a clear lacquer or polyurethane and let dry, and then apply a car wax. • To encourage a natural patina, remove the lacquer with mineral spirits and grade 0000 steel wool. However, if you do not wish to hasten the patina-development process, skip the removal of lacquer and let the cap weather naturally. Thank you for your inquiry. Your Deckorators Team