This is one I know you are going to like. Many times we find gas tanks rusted on the interior and generally not useable because of this rust. I will be adding pictures to help this all make more sense as time allows.

I will show you just how to get one of these tanks clean again and return it to service again.

Materials you will need:

Muriatic Acid (HCI)

Hazards associated with Muriatic Acid (HCI)-

READ THIS STUFF AS IT WILL SAVE YOU A WORLD OF HURT AND POSSIBLE INJURY

Muriatic or hydrochloric acid causes severe irritation or burns to skin and eyes.
Vapors may irritate respiratory tract.
Handling

Wear clothing that covers exposed skin areas. Use gauntlet-style acid-resistant gloves and eye protection when working with acid.
Use only in well ventilated areas.
Always add acid to water…never add water to acid.
Do not mix muriatic acid with any other chemicals.
Management Options

Do NOT dispose down the drain or in storm drains.

Do NOT dispose of in the trash: liquid wastes can leak in a trash truck and react with other chemicals.

Wastewater treatment facilities routinely use muriatic acid. Call your local facility to see if they will accept it.

Take to a HHW collection or commercial hazardous waste facility.

1. Remove the petcock form the fuel tank. Failing to remove the petcock will destroy the inner seals of the petcock during the acid step.

2. Block the openings of the fuel tank. Use a piece of steel to cover the hole. Use a small amount gasket sealer around the opening then fasten your plate with two bolts.

3. Move the tank to a WELL VENTILATED AREA. This is important as one lung of muriatic acid in this next step will probably lay you out flat on the ground.

4. Add 1/2 Gallon of water to the tank.

5. Add 1/2 to 3/4 Gallon muriatic acid. AFTER ADDING ACID TO THE TANK, NEVER ADD WATER TO THE ACID.

6. Close the fill cap and slowly turn the tank over. Allowing the acid to slowly contact the rust and remove it. I usually roll the tank on the lawn nice and slow so it does not end up dripped on me. Turn the tank 1-2 times and then open the cap to allow the gas to vent. Be careful not to breathe this stuff.

7. Continue to turn the tank periodically. On real rusty tanks I usually allow the acid to sit for about 5-10 minutes with the cap open (so no gas is allowed to build up).

8. Repeat as needed. Sometimes it is necessary to use nuts and bolts to break the heavier rust loose.

9. Let the acid sit in the tank and crush up some Tums and mix with about 1/2 gallon hot water.

10. Now recover the acid from the tank as best as you can.

At this point if you are intending to line the tank with kreem, follow the directions on your Kreem or other tank lining product.

11. Dump the Tums and hot water in the tank and swish around. This will neutralize the acid and stop it from further etching the metal.

12. Now rinse out the tank with a garden hose. Rinse it with about 5-8 gallons of water. At this point letting the tank sit flat on the ground, just insert the hose and let her rip for about 10 minutes. As the water bubbles out the top it will circulate enough to clean the tank out.

13. Dump out the water from the tank.

14. Now add 1/2 quart of oil to the tank and about 1/2 gallon of gas. Make sure this is swished around so it gets into all of the recesses of the tank inside.

15. Now remove the blocking plate and carefully recover the oil and gas mix.

16. Install the tank with a new inline fuel filter and fill up the tank completely with fuel. I use the ones I can take apart and clean for the first few runs. This allows us to keep from eating up the more expensive and smaller filters.