Hi, I'm Rachel Yatuzis, and I'm going to tell you why onions remove rust. Rust is made up of tons of hydrogen ions, caused from the oxidation process, that's what causes the rust to begin with. Onions contain a chemical called sulphanilic acid. When sulphanilic acid reacts with hydrogen ions, it causes the rust to just flake away. I will demonstrate. You slice an onion open, you have to use the juicy part of the onion, that, the inside of the onion, and just rub it on any rust parts. There's a little bit on this handle, right here, and if you just make sure to rub that onion really well, on the rusty spots, almost use it as a scrubber itself. The rust will flake off, and maybe some of the onion too. You can get a little piece like that, and it might help you, for some detail work. You may have to let the onion sit for a second, and let it dry a little bit, and then wipe the rust away, but this chemical reaction, will clean any rust stains that you may have around your house, maybe on your car, a fence, anything, and that's it. I'm Rachel Yatuzis, and that is why onions remove rust.