It is always best to repair surface rust as soon as it appears. The fix is very similar to a general paint repair.
Using sandpaper or an abrasive wheel, sand down the rusty spot thoroughly. Sand it down until bright metal is visible.
After sanding the spot, apply primer according to the manufacturer's directions.
Apply paint to the area. Again, follow the manufacturer's directions. Give it plenty of time to dry.
After the paint dries, apply a clear coat to protect the new paint.
It is important to remove surface rust as soon as possible, because left alone, rust quickly eats through metal, leaving holes in the vehicle's body. Once holes appear, the only two options are to replace the affected part or cut away the affected pieces and weld new pieces in their place. Both of these are more expensive and complicated repairs.
Rust tends to develop in areas of the body such as the top inside edge of the fender well, the lower section of the quarter panels and the front and rear corners of the rocker panel. Experts recommend checking for rust in these and other areas as part of a regular inspection schedule.Learn more about Car Parts & Maintenance