Review on Get Rid of Rust with POR-15 Rust Remover: 1 Quart - Effective Rust Dissolving Solution, Reusable, Biodegradable, Safe for Delicate Metal, Plastic, PVC, Viton, and Paints by David Gonzalez

This stuff is great! I had a bunch of rust on the inside of the trunk lid in hard to reach places. I sealed the edges, poured in almost a full gallon and waited. It took 8 hours and almost all the rust disappeared! You can see before and after photos of the same area. In the last picture you can see the rust line showing exactly where the grout was and was working before I had to turn it. I can see how expensive this will be in bulk if you are making large slabs but if you are restoring a car and want to keep most of the original metal then this is a great deal. A little thought about how to store the product is all it takes to keep this stuff going for a long time.