How-To: Paint Chip Repair
Despite the technological advances in paint over the last hundred years, an automobile's exterior comes under heavy assault the instant the car rolls off the production line. Door dings, bird droppings, corrosive rain, winter road salt and ocean fog all take their toll on that thin layer of color that protects your vehicle's steel body from the elements. Rock chips are especially damaging, as unlike contaminants that slowly eat away at the paint, rock chips cut all the way down to bare metal without prior warning. That allows moist air immediate access and surface rust soon follows. Worse yet, the rust can spread like a cancer beneath previously undamaged paint, so it's best to fix the damage and seal the hole as quickly as possible.
Clean the Injury
Begin by thoroughly cleaning the repair area with a standard car detergent and water solution. Rinse all soap residue from the area and allow to dry completely. Using a fiberglass pencil (available at most auto parts stores in the paint and body department), carefully remove rust and loose paint from the chipped area. Fiberglass dust is a severe irritant, so be sure to wash your hands when finished and don't breathe or allow the dust to contact your eyes while working. Hopefully the chip is fresh and rust hasn't had a chance to take hold, but if the metal has been exposed to the elements for some time, it may be necessary to use a tiny piece of 800-grit sandpaper to remove all traces of rust from the area.
Fill the Crater
Determine the manufacturer's color code for your vehicle (check owner's manual to find out where the data plate is located) and obtain a small bottle of touch-up paint from your local dealer or auto parts store. Brush thin coats of paint across the repair area, allowing each coat to fully dry before applying the next. If the chip is very small, you can use a sliver of thin cardboard to dab the paint into the hole. Fill in the chipped area one layer at a time until the new paint is higher than the surrounding factory paint. Allow at least 24 hours for the final coat of paint to harden.
Blend the Repair
Starting with a small piece of 1500-grit wet/dry sandpaper wrapped around a small foam-rubber sanding block, slowly sand down the raised touch-up paint. Dip the sandpaper into a container of water regularly to rinse removed paint from the abrasive. Try to sand only the touch-up paint, as the factory paint surrounding the chip is quite thin and will not handle very much sanding. As the touch-up paint nears the same height as the factory paint, change to 2000-grit wet-dry paper for final sanding. The paint in the area will take on a matte appearance, which is then polished to a glossy finish using a small amount of rubbing compound on a clean cloth. Follow with your usual auto wax or polish to give the fresh paint a protective coating. The quality of the repair will depend on your work and how well the touch-up paint matches your factory paint. But regardless of results, the ugly crater will be filled and your vehicle's sheetmetal will be protected from additional exposure. And if the repair goes well, no one will notice that the chip was ever there!