How to Repair a Scratch in a Cast Iron Bathtub or Sink

Cast iron bathtubs and sinks are beautiful and can be expensive. Although they are not easy to scratch, once a scratch occurs it should be fixed immediately. Untreated, scratches in cast iron could begin to rust, causing stains on your once white bathtub or sink.

In order to repair the scratch, purchase an enamel repair kit for a cast iron bathtub. It won't matter if you use the materials in the repair kit for your kitchen sink: it should have almost everything you need to complete the job properly.

Step 1: Clean the scratched area, as well as the surrounding enamel with acetone to remove any residue. Wear gloves during this step to protect your skin.

TIP: Keep in mind that acetone is highly noxious and flammable: dispose of any saturated paper towels carefully. Also, be sure to properly ventilate the area during the entire project. Wearing a respirator and eye protection is also a very good idea.

Step 2: Apply the porcelain filler from the cast iron scratch repair kit with a plastic edged putty knife. You may have to mix the filler before completing this step.

Step 3: Smooth the top of the fill carefully, then allow it to dry for 2-4 hours.

Step 4: Lightly sand the filler with fine grit sandpaper. Try to avoid sanding the surrounding enamel that covers the cast iron sink or bathtub.

Step 5: Apply the primer to the scratched area, using a small paint brush. Try to cover only the filler. If you extend the primer too far, you can correct the mistake with acetone. Some kits include small cans of spray primer: if your kit contains this type of primer, use painter's tape to tape off the surrounding areas and only expose the filler for paint. Allow the primer to dry.

Step 6: Paint the area with the primer using the included enamel paint. You should plan on applying 3 coats, allowing for drying time between each coat. Remove any painter's tape after the last coat has been applied and clean up the acetone as necessary. Let the paint dry for 24 hours before using the bathtub or sink.