Rust-Oleum good stuff. I use the rusty metal primer (rust color) to maintain my steel gates. While the neighbors refinish theirs entirely every 2 years with primer and pain, I just go out with a 1 inch and touch up rusty spots LOL.
Oops back on topic, you make me want to make my own canopy, and I have 1 that came with my 80 tank that needs repair from water damage.