Reply #5: Before just the Rustoleum alone, consider stuff like this

[Stinky The Clown]

http://www.eastwood.com/eastwood-rust-converter.html



Eastwood is a high end auto restorer hobbyist supply company. Good enough stuff, but on the costly side. You can probably find a similar product locally, maybe at an auto paint supplier, for a little less, but even at this high retail, it isn't that costly. Given that your door and window grates are less stressed than car parts, it might be a good way to get an extra few years from them. Try this sory of thing and then spray over it with the Rustoleum made for rusty metal.