http://www.eastwood.com/rust-solutions/treatment/eastwood-rust-converter.html
Or, the Home Made way:
Homemade Rust Remover # 1: Ketchup
Two of the most commonly found household items,
washing soda and tomato ketchup when used together are helpful in removing rust. It cleans off rust from metal furniture like tables and chairs quite easily. Take washing soda in a spray bottle and spray it generously over the rust. Similarly take some tomato ketchup and spread it on those areas where washing soda has been applied. Keep the solution on the furniture for at least two hours before you wash it off with warm water. Let it dry completely before you use the furniture.
Homemade Rust Remover # 2: White Vinegar
White vinegar acts as an excellent rust remover and removes rust from all kinds of machinery and equipments made of metals including your bike. Take white undiluted vinegar in a spray bottle and spray it over the rust marks. Allow the
vinegar to settle on the rusted surface for almost two hours. Then rub the surface with the help of a wire brush untill all the rust is removed from the surface. Wash off with clean warm water and then leave it under the sun for drying or you can just wipe off the water from it. The process can be repeated if some of the rust stains are left behind after
cleaning. Do not use any other types of vinegar as they often leave behind stain marks on the materials on which they are applied
Homemade Rust Remover # 3: Borax
The best part of borax as a rust remover is that it is not harsh on the surface where it is applied. It is commonly available in the market. Borax can be combined with different other substances to prepare an effective homemade rust remover. In a clean bowl, mix one quarter cup of borax, one teaspoon cream of tartar and sufficient amount of
hydrogen peroxide so that a thick paste can be formed. For thorough mixing of these three substances, you can take the help of a mixing rod. Apply this thick paste on those spots of rust in the form of a thick layer. Leave the paste on the rust for half an hour. Then wipe it off using a damp sponge and you will see the rust spots have disappeared. If required, you can repeat the process. If you do not have borax at home, you can replace it with
baking soda.
Borax, when combined with lemon juice is also good on rusts. In a container, prepare a mixture of lemon juice and borax, using half cup of lemon juice and one-fourth cup of borax. Mix the two ingredients to make a thick solution. Pour the solution on the rusted surface evenly and leave it like that for half an hour or so. If the rust is a stubborn one, you can keep it for some more time. Finally, rub off the surface with a rag to get a rust-free surface.