How to Repair a Rusty Gas Tank

Restoring a car involves redoing every part of the vehicle, including the gas tank. Many times, old vehicles have rusty gas tanks that don't appear to be salvageable. Fortunately, there are lots of restoration technologies out there to make that old gas tank look and perform like new again. This is a fairly easy project, but it will take a some time to do correctly, as there's a lot of drying time in between steps.

Things You'll Need

  • 3/8-inch ratchet and socket set
  • Flathead screwdriver
  • 2-foot metal chain
  • Hose and water source
  • Gas tank sealer kit
  • Bucket
  • Muriatic Acid
  • Acetone
  • Baking soda
  • Rubber gloves
  • Gas tank paint
  • Air compressor, hose and air nozzle
  • Red scuffing pad
  • Unbolt the gas tank from the vehicle using the 3/8-inch ratchet and sockets. When it's lowered from the vehicle, use the flathead screwdriver to disconnect the gas lines from the tank, and unplug the wiring from the tank as well.

  • Unbolt the gas tank sender unit from the center of the gas tank using the 3/8-inch ratchet and socket set. Place the sending unit to the side, as you may be reusing this part. Place the chain into the gas tank, pick it up and shake it up to bounce the chain around the tank. This will knock off any loose rust from the interior of the tank. Pour the rust out of the tank and remove the chain as well.

  • Put on rubber gloves. Mix the metal wash from the gas tank sealer kit in a bucket with two gallons of hot water. Then pour the bucket into the gas tank and swirl it around the entire tank, making sure to coat all surfaces. This will remove any gasoline that has turned into varnish from the tank. Then pour out the metal wash, and place a hose inside of the tank. Turn on the water and let it run for five to 10 minutes. This will completely flush out the tank.

  • Pour 64 ounces of muriatic acid into the bucket and mix it with a half-gallon of water. Then pour that bucket into the gas tank, and slosh the contents around the tank for five to 10 minutes. When you're done, the surface of the tank should be a gray color. Pour out the contents into the bucket and pour the baking soda into the bucket to neutralize the acid.

  • Place the etching liquid from the gas tank sealer kit in the gas tank, sloshing the contents around the interior of the tank. Make sure it hits all surfaces, so the etching liquid can do its job. Then pour one quart of acetone into the tank. Slosh the acetone around in the same manner. Then pour the contents out into a bucket.

  • Pour the sealer product from the gas tank sealer kit into the tank. Work it around the interior of the gas tank, coating all surfaces. Let the tank sit for eight to 10 minutes, then bolt the sending unit back into the tank and rotate the tank onto its top, and let sit for eight to 10 minutes. Repeat this process for all sides of the gas tank. Pour any excess sealer into a bucket.

  • Set the compressor to output 5-10 psi. Then put the air nozzle on the air compressor hose, and place the nozzle into the tank. Set up the nozzle so that it stays on for a while, as it's important that airflow goes through the tank while the sealer is curing. Allow the tank to sit for 48 hours to cure.