I don't think the frames of the grills are as prone to rust as the sheet metal of a car (especially here in the rust belt where so much salt is out there you get high blood pressure just walking outside). Eastwood and POR15 are quite expensive but in the automotive environment there is no substitute for how well they work. The stuff just stops rust dead in it's tracks period (I find the Eastwood better than POR15 BTW). Where other treatments just slow it down at best the Eastwood drops it dead with no special pre treat either. I just blow out loose stuff with air and spray Eastwood in. Done................period. I even tried their frame version of RE on the frame of my old Infiniti QX4 and with no pre treatment other than spraying with brake cleaner to remove grease it formed a hard ceramic like coating that stopped all the rust dead. Hard as nails too. So yes, expensive. Worth it? You bet! On a grill? It depends.............If it's a lifelong "keeper" sure if a flip no