Rust is a sad fact of life for many steel components. For certain items, replacements are not always readily available, such as for Classic Car restoration projects. Although there are ‘kits’ that can help restore items, they are relatively expensive. Here is a video showing how to dissolve away the rust. It uses electrolysis to convert the rust from red rust to black rust. This restores the component to its original dimensions and as it’s stable it can be treated or painted. Red rust ‘grows’ in contrast making it unsuitable.
All you’ll need is a bowl of water, some soda crystals, a car battery, some steel plates and leads.