Rust is the common term for ferrous or iron oxide. It is formed by iron and oxygen reacting with each other in the presence of moisture in the surroundings. Rusting is also a term often used to refer to the general corrosion of iron, steel and other iron alloys. Rusting is a major problem for cars because not only is it unsightly, but it can also cause your car to malfunction and fall apart. In addition to this, once rusting starts, it's very difficult to stop.
As the saying goes, prevention is better than cure. It is much easier and less time-consuming to prevent rust from forming than having to remove and stop it once it has started. Prevention is especially important in winter if you live in an area which salts its roads because not only does the additional moisture in the winter months facilitate the rusting process, but salt mixed with this water accelerates it.
The basic idea behind preventing rust from forming on your car is cleaning it thoroughly and regularly--salt, dirt and grime that is picked up by your tires as your car travels along the road all contribute to speeding up the rusting process. The undercarriage of your car picks up the most of this dirt because it is closest to the ground and the wheels kick up a lot of debris onto the undercarriage. The undercarriage of your car should be washed at least once a week and should be examined regularly for any small rust spots that have the potential to grow into large ones that could cause major problems.
Repairing Rust Spots
If you find any rust spots on your car's undercarriage, you should remove the rust and repair the area as soon as possible. The same holds for the body of your car -- if small bubbles are forming under the paint, it's likely that rust is forming under your car's paintwork. With rust spots, you first need to remove loose rust and paint by scraping it off with a small razor blade. Be careful not to damage undamaged areas as this will only facilitate the rust in spreading further.
After you have removed the loose paint and rust, wash the area with warm water and car soap to remove any leftover wax and grime. You should be sure to dry the area thoroughly before touching it up. Before painting over the spot, you should apply a primer containing a metal conditioner to the area that will stop further rust from forming and also prepare the area for painting. Primer can be purchased from any auto supply store, just ask for what the store recommends and you should get a good one. Finally, you should paint over the now rust-free spot so that your car looks as good as new. You should be sure to paint or cover the metal or else the exposed metal will quickly rust again, and all your hard work will be undone.