What causes rust on vehicles?
Rust is caused by oxidation, a natural process by which metal turns to rust after exposure to oxygen. Rust occurs most commonly after metal is exposed to water, but time spent in the elements can also cause it. There are three main types of rust: surface rust, scale rust, and penetrating rust.
Surface rust
Surface rust is often found in scratches on your car and can easily be fixed. Your car insurance may cover scratches if you have comprehensive coverage or collision coverage.
Scale rust
Scale rust is the evolution of surface rust. If you don't remove surface rust, it can eat through a vehicle's paint and surface coating and leave the bare metal underneath exposed. Both surface and scale rust are relatively easy fixes.
Penetrating rust
Penetrating rust occurs if you don't address scale rust before it worsens. It eats through the metal of the car and can leave holes or even compromise the entire structural integrity of the vehicle. It's the most expensive type of rust damage to repair and the most dangerous by far. Rain and snow can cause rust on cars, but exposure to salt is one of the main causes — especially if you live in an area where the roads get salted. Salt on the underbody of the car can rust quickly, but it's easy to miss since it's so often on parts of the car that are out of sight.
This is also true if you live near the ocean when natural salt can coat the vehicle's entire body. Learn more about how car insurance covers salt damage.
How much does rust repair cost?
The good news is that small amounts of rust damage are easy to repair — you might even be able to DIY the repairs. However, more serious damage like those caused by penetrating rust can cost thousands, especially if parts of the vehicle need replacing and must be welded into place. A professional must do this repair, which drives the cost even higher when you factor in labor.