Project Riddler's Ride - 1976 Plymouth Duster
POR-15 is designed to work best over the rust to bite into it, I was told years ago after I sandblasted the frame on my Power Wagon, that it works best if you just wire brush off the scale and that by blasting the metal I defeated the purpose of what the product was designed for. Since your tank is nice and smooth un-rustable metal I would look for another durable product to put on it.