Not much. I painted this spare tire rim 5-10 years ago and its been installed almost 3 years on the '65 Formula S while it was being stripped, sandblasted, and painted. Has some overspray from the body shop on the outside of the rim. Cleaned it up today with some Simple Green.
looks great for 5-10 years out in the elements. I got a set of stripped Rallies in the yard and they are looking a little rusty.
All I know is I painted the underside and trunk area with the brush on stuff and it's hard as nails. Almost like epoxy paint.
I used it on the undercarriage on my car. And the floors. The floors I painted black but the undercarriage i left just red primer.
Years ago, before all the 2 part primers. We (bodyshop) did a test on primer and the red oxide primer was far superior for rust protection than White,Gray,Black primers.
Usually if things are safe, they don't work, if they work, they'll make you grow a tail.... on your forehead... Good question though.
And old paints and primer had LEAD decades back, it kept the rust down! Rustoleum had lots of solids, thats good. But unlike auto paints nothing to deter UV right? Great for inside floors and underside. Works for me.
