Rust

I just soaked a bike chain in Vinegar yesterday, cleaned it up enough to have it flex again and go through the derailer. The bottom of the pan was coated with rust flakes. Good stuff. That's the same way they tell you to apply other rust products (evaporust), wet towels and plastic sheeting. There was a guy who took 5 gallons of something and put a hood in a kiddie pool and used a fountain pump to let the stuff just flow over the hood for a day. Worked great. Not an option for a hood of course.