Was looking on a site and found this stuff.

Oxisolv Rust Remover
This specially formulated Rust Remover is a powerful, rust-fighting liquid created to meet the needs of auto restorers. It reaches even inaccessible areas, quickly dissolving iron oxide completely and leaving a zinc phosphate coating. Rust Remover can be sprayed, brushed, or used as a parts dip. It is non-toxic, non-flammable and reusable. This is not a primer. Treated surfaces should be wiped with PRE Painting Prep (10041 Z) or thinner before priming and painting.

Anyone used it?

What is Zinc Phosphate?

If its used on an exhaust that isn't thin enough to punch a key through but is still very rusty...is it actually going to work?

Scot
So many questions today!

Hello,
This product sounds much like what POR-15 calls "Metal Ready". I did some frame painting and the Metal Ready is the second step of the painting process. The product does remove some surface rust, but for complete rust removal the metal part has to soak in the product for a long time. A white film is left behind on the metal that is supposed to retard rust. I just recently painted, so I don't know the long term results of the product. I'm unsure that it would be of use on your rusted exhaust system.
Regards,
Tom

Zinc oxide is the similar chemical to the zinc used to make Galvinized metal. It leaves a chemical barrier to rust and corrosion. If you get through the paint, instead of the metal rusting, the zinc produces a chemical reaction that leave yet a third chemical on the surface, that will not rust or corrode. It works very well, if it's a good product. This is one of the steps the newer cars are using to prolong the life of the car body. If you break through the zinc coating to the metal, it will rust or corrode.