Here in California all the paint products sold have to meet clean air standards. The old formulations that had good reputations are now different, but have the same names. It makes it confusing for us to know what is now best. I have had experience with some of the old names new products which were disappointing. Compounds that worked well in the past for rust prevention were toxic and had to be eliminated. We formerly used zinc chromate to prime aluminum or galvanized steel with great results. I also used the Rust Destroyer brand of red primer with very good result on steel for both clean and rusty metal. I don't know how well the newer formulation works, but will probably try it. The old Rustoleum red primer performed well in the past and we are using the new brush on version on some projects in our shop, but don't know how well it will do. The new top coat oil based Rustoleum paints don't seem to be lasting as long as we would like. Sun fades it, and gets chalky in a couple of years. I used it to repaint our Scamp frame about 3 years ago. I guess we are all guinea pigs!
I'm not slamming Rustoleum, as the new laws make it challenging to figure out new ways to get good performance. Other companies are having the same issues.