[Mr_Rich]

I originally started using a product called Metal Etch that I was able to buy at hardware stores. I can't find the product any more. CLR is similar and slightly weaker but succeeds in prepping the metal surface for painting. I've been using POR-15 like this for many years. It holds up better than most products I've found in a spray can. Standard Brands used to sell big spray cans of black urethane that I painted the engine compartment in my old Firebird. That stuff held up over time (20+ years), but it's long gone. Paint formulations change over time and a lot of products don't exist any more.