There are many sources leading to the surface rust that appears on cars. Small metal shavings, known as industrial fallout, can come off car brakes, embed themselves in the surface of car paint and eventually lead to rust stains. Or, if your car was transported by train, small metal shavings that come off railroad tracks, known as rail dust, might have become embedded in your car. No matter the source, you want to remove the rust from the finish, especially if you have white car paint that is particularly vulnerable to unsightly rust spots and stains.
Wash your car in the shade to remove any dirt or contaminants while keeping the surface cool. Leave a little water on the car to help lubricate the abrasive clay.
Spray a small amount of the lubricant on a 10-inch to 12-inch area of the affected paint.
Break off a chunk of abrasive clay and rub it gently back and forth over the area. Do not rub up and down or in circular motions. Pressing too hard with the abrasive clay can cause surface damage. Repeat until no dark rust spots remain. This removes the rust particles but you may still see a slight stain. If during this process you drop the clay in the dirt or notice it is becoming embedded with particles, discard and break off a new chunk.
Wash your car again to remove any remaining clay or particles of rust.
Use paint remover to remove any residual stains before polishing and waxing your car. Using a sealant will not prevent your car from being stained again, but will offer a modicum of protection.