POR-15 is just like any other coating in that the better the surface prep the better the results. If you use the phosphate coating after a good bead blasting you'll get good results. I use the High temp silver alot and you need to make sure you get it heated to cure it. I use a heat gun if i'm not going to fire up the motor. I've even used it inside my headers as a heat reflector. Remember moisture from condensation can come from the inside out. I have a Flathead that I used the silver High temp on the exhaust and the silver paint on the motor and its just now starting to show need of a touch up after 3 seasons of use. This motor was really bad cosmetically when I coated it , so I'm happy with POR-15. I also like the Corrolless that Eastwood sells for inner fender wells. Brian [Non-text portions of this message have been removed]