How To Repair Rust on a Car

Shop for supplies

• First, find the car manufacturer’s paint code.
  • Note: The paint code can be on the body, in the engine compartment or trunk, or elsewhere. Use either of these online resources to find instructions on locating your paint code: automotivetouchup.com or duplicolor.com.
• Buy automotive touch-up paint in pints and quarts to use in a spray gun, aerosol cans or roller ball applicators.
  • Pro tip: Even if you know how to use a spray gun, mixing automotive paint with a reducer to match the temperature and humidity conditions can be tricky. We don’t recommend it. Instead, buy aerosol cans for larger repairs and brush-tip applicators to fix small scratches.
  • Note: Most late-model vehicles were painted with base coat/clear coat paint. The base coat contains just the pigment and binding resins. The clear coat is the layer of paint that goes over the color coat, giving the surface a glossy appearance.
• Buy equal amounts of both base coat and clear coat.
• You’ll also need an epoxy self-etching primer to bite into the bare metal and a lacquer primer to hold the paint.
• Buy 60-, 120-, 400-, 600- and 1,000-grit sandpaper, a sanding block, grease and wax remover, poly sheeting, painter’s tape, a tack rag and a microfiber cloth.

Mask off the repair area

• Tape the leading edge of poly sheeting a few feet away from the repair so you’ll have room to blend the touch-up paint into the good areas.

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Remove the rust

• Remove any blistered paint with a scraper.
• Sand through the rust spots down to the bare metal using 60-grit sandpaper. If you have one, use a random orbital sander for this part.
• Switch to 120-grit and enlarge the sanded area so you’ll have space to feather the edges.
• Feather the edges of the repair area with 220-grit sandpaper.
• Finally, lightly sand the entire repair area with 400-grit.
• Use a tack rag to remove particles from the unmasked area.

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Clean with detergent

• If the rust has created pits in the metal, you can fill them now with body filler or wait until the epoxy primer dries and apply multiple coats of filler primer. Here are a few tips for choosing the paint for rusted metal.
• Clean the entire unmasked area with a grease-cutting dishwashing detergent, followed by a clean water rinse.
• Wipe the area with a lint-free cloth to remove any remaining dust or lint, and let it dry.

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Apply epoxy primer, then filler primer

• Spray the filler primer in heavier coats to cover the entire repair area. Self-etching epoxy primer provides a strong bond to bare metal, so use it as your first coat.
• Move the can away from the surface slightly and blend it into the surrounding painted area.
• Spray two to three medium coats, allowing the recommended wait time listed on the label (usually 15 minutes) between coats.
• Wait a full hour for the epoxy to dry to the touch (longer if it’s humid outside).

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Sand the primer

• Starting with wet 600-grit sandpaper, smooth the primer and feather the edges.
• Switch to wet 1,000-grit sandpaper to do a final sand of the entire repair, including the blended areas.
• Wash with clear water and let dry.
• Wipe the dried epoxy primer with a lint-free cloth.
• Apply two to three heavier coats of lacquer filler primer, allowing drying time between each coat.
• Let the lacquer primer dry until it’s dry to the touch—at least one hour—before sanding.
• Sand drips and sags with 320-grit sandpaper.
• Then, final-sand the entire repair area.

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Apply the colored base coat

• Holding the spray can 10 to 12 in. away from the surface, spray the repaired area.
• Start at the bottom of the repair and apply the color coat in left-to-right rows, overlapping each pass by about one-third.
• Slowly build the color into the repair and surrounding areas in two to three coats, allowing 10 to 15 minutes between each coat.
• Allow the base coat to cure until it’s dry to the touch. This process can take as little as 60 minutes but can be significantly longer in humid conditions.
  • Pro tip: Once you’ve achieved a good color density and have it feathered nicely into the surrounding area, do not sand the base coat (especially metallic colors) unless you’ve created runs or sags. In that case, lightly wet sand the blemish with 400 grit paper and then respray the touched-up areas.

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Spray on the clear coat

• Apply several thin coats of clear coat, allowing the recommended drying time between coats.
• Gradually feather the clear coat into the surrounding areas for a smooth blend line.
  • Note: This is the hardest part because all clear coats run easily, and that’ll ruin the look of your paint job! Practice spraying on a scrap piece of cardboard to get a feel for the nozzle and the application speed. If you create a run in the clear coat, you’ll have to let it dry for at least 48 hours before attempting to fix it with 400- or 600-grit sandpaper. Then you’ll have to respray the sanded area.
• If time allows, let the repair cure for 48 hours before driving the vehicle and at least a week before finishing the job with the polishing compound.

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Buff the repair

• Hand-buff the repaired area using an old cotton T-shirt or microfiber cloth charged with polishing compound.
  • Pro tip: Don’t use a polishing machine or buffing wheel for this step.
• If you have more than one grit of polishing compound, work your way up to the finest grit (usually swirl remover), using a fresh cloth for each one.
• Wipe the entire area with a clean microfiber cloth to remove any residual polishing compound.
  
• Wait at least 30 days before applying any car wax or ceramic coating.