WHAT IS RUST
Rust is a form of corrosion, and it can also occur on the battery as well as the car body.
Rust can be caused by the accumulation of road salt, dirt, moisture or chemicals in those places not normally reach by day-to-day cleaning. Or by chips, scratches and any damage treated or painted metal surfaces resulting from minor accidents or abrasion by stone and gravel. Dust control chemicals, sea air or industrial pollution will also accelerate corrosion, as will high humidity, particularly when the temperature is just above freezing point.
Moisture that stays in certain areas of the vehicle for extended periods may also promote corrosion even when the rest of the vehicle is dry. And high temperatures will also cause corrosion to other parts of the vehicle that aren't ventilated well enough for quick drying.
HOW TO PREVENT IT
1. Keep your vehicle clean with frequent and thorough washing.
2. Keep the underside as clean and dry as possible.
3. If you drive on salted roads, the car should be washed at least once a month during winter.
4. If you live near the ocean, wash your car at least once a month during the year.
5. Remove any foreign material, such as chemicals, salt, bird droppings, tar and so on, from the painted surface of your car. Use a proper cleaning fluid (see section on cleaning)
6. Regularly inspect your vehicle for scratches, dents and chips and repair as soon as possible with touch up paint. If these marks have gone through to the metal, have them repaired properly at a body shop.
7. Keep the passenger and luggage compartments of your car clean. Moisture, dirt or mud may accumulate under floor mats, so check these often. More checks are needed if the vehicle is used frequently during wet weather.
8. Transport items such as salt, fertilisers and chemicals in sealed containers.
9. Do not park your vehicle in a damp, poorly ventilated area. If you often wash your vehicle in the garage, or drive it in the wet, the garage may be damp and the high humidity will accelerate corrosion.
Warning: Do not apply additional undercoating or rust preventive coating on or around the exhaust system components like the exhaust pipe or catalytic converter. A fire could start if the undercoating substance heats up.