How to Fix Rust Holes in Cars

Written by steve smith
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How to Fix Rust Holes in Cars
Rust holes in cars are often patched with sheet metal. (rouille image by Jacques PALUT from

Rust can eat through metal until there is nothing left, causing a large hole in the body or floor of a car. Rust holes weaken the strength of a car's body panels and might allow fumes and dust to get inside the car. Typically, a sheet metal patch is used to cover and fix automobile rust holes because a sheet metal patch provides more strength than a body filler patch. You can patch a rust hole yourself, but you'll need to set aside several hours to complete this repair job.

Skill level:
Moderately Challenging

Things you need

  • Metal saw
  • Sheet metal, 12-gauge or heavier
  • Tin snips
  • Drill
  • 1/4-inch carbide drill bit
  • Rivet gun
  • 1/4-inch rivets
  • Bondo body filler kit
  • Scraper
  • Sand paper, 200 grit
  • Primer
  • Automotive paint

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  1. 1

    Cut around the hole with a metal saw, removing all corroded metal. Cut right through the existing panelling and get rid of all of the rusted metal until no affected metal exists around the hole's perimeter.

  2. 2

    Center the sheet metal patch so the metal overlaps the hole by two or three inches. Then mark and trim the excess sheet metal with a pair of metal shears.

  3. 3

    Set the sheet metal back on the hole and centre it again. Place it on the underside of the panel if you have access to it. This provides a cleaner final look. Drill through the patch and car panel using a 1/4-inch drill bit with a carbide tip. Make one drill hole every two to four inches along the edge of the patch.

  4. 4

    Attach the sheet metal to the car. Use pop rivets and a rivet gun. Insert one 1/4-inch rivet into your rivet gun, then insert the rivet into the hole and squeeze the gun handle until the rivet forms. Repeat this step in each hole to secure the patch to the car.

  5. 5

    Mix Bondo or another body filler with hardener in a container according to the manufacturer's instructions. Spread the mixed Bondo on the patch and around the edge with a hard scraper. This will cover the patch and seal the seams. It will also blend the repair. Sand the filler after it is thoroughly dry to a smooth and uniform surface with 200 grit sand paper.

  6. 6

    Paint the repaired area with a metal primer. Once the primer dries, sand the primer with metal sand paper. Wipe the area clean and then spray on a matching paint or fibreglass gel coat.

Tips and warnings

  • Large holes may require more surface fillers and supports. Many patches are cosmetic only and will not enhance the structure of your body panels.

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