I use a product called oxysolve. Turns rust into phosphate coating.

Naval Jelly will work also.

Naval jelly...hasn't that been around for years and years? I've never actually used it.. does it leave the area goopy like the jelly itself or does it clean the rust up and kinda disperse?

Yeah Bill, it'* been around for at least 48 yrs. that I know. I've used it a few times over the years. It gets applied to the surface, a waiting period, then wipe off & clean. After that you're rerady for primer. It has a consistency sort of like those paint strippers used on wood furniture.

My Bonne had that problem, except as I picked away at the loose material, I was left with a hole at least 2" wide all the way through the unibody. I didn't catch it quick enough. I swear, rust was the only problem that car had