Removing rust from a gas tank

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Removing rust from a gas tank can be accomplished in a number of ways. Different strategies include using abrasives such as gravel or washers, using acids such as muriatic acid or vinegar, using a battery and washing soda, using a Kreem kit, or using a combination of the aforementioned strategies.

Abrasives

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Acids

Hydrochloric (Muriatic) Acid

WARNING: Wear protective gear during this process (all skin should be covered, long pants/shirt, work boots, gloves, eye protection and filtration mask - the reaction of muriatic acid and rust gives off extremely harmful vapors) if spilled muriatic acid can be neutralized with baking soda. When working with these chemicals, make certain that you have ample ventilation. It's good to have a fire extinguisher handy as well. Always dispose of solvents / hazardous chemicals responsibly, please. And, be safe.

Start by removing the petcock. The aluminum body and rubber internals will have a world of woes with the acid solution.

If you have a pressure washer, fire it up and blast out all the solidified chunks of rust / oil / fuel in the tank. If the outlet becomes clogged by the chunks, use a pair of hemostats to pull out the debris. Continue until the water runs free of debris.

Attach a piece of nalgene hose to the outlet of the tank with a zip tie. Clamp it off with a pair of hemostats.

ALWAYS ADD ACID TO WATER. Start with a more mild solution of 1:1 water / muriatic acid. Be careful not to get the acid on the scoot. Watch it to see that bubbles are being produced in the tank. Let this sit for about an hour.

Drain the tank by removing the hemostats. Flush the tank with water.

If necessary, repeat this process with a solution of 1 part water and 2 parts muriatic acid.

Drain the tank by removing the hemostats. Flush the tank with water.

In a bucket, mix about 1/4 cup baking soda to 2 gallons of water. Fill the tank, let it sit for a few minutes, drain and repeat perhaps 4 or 5 times. You really want to neutralize any remaining acid in the tank, so don't be stingy.

After draining the tank of all available water, seal the nalgene tubing with hemostats and fill the tank with 70% isopropol alcohol. Let is sit for 5 to 10 minutes. The water molecules in the tank will bond to the alochol to avoid further fuel issues. Drain the alcohol and discard responsibly.

Seal the tubing again. This time fill the tank with straight gasoline. Let this sit for five to ten minutes. Drain the fuel and discard responsibly. You may see some minor clouding and sediments, but it should look a lot better than when you started.

If you hadn't done so already, clean out your carburetor with spray carb cleaner and / or Seafoam. Replace the fuel line and make certain that you install a new fuel filter. It's a very good idea to have a couple spares on your shelf. Take a moment to clean your sparkplug and gap it to spec.

Fuel up your scoot with perhaps a quart (max) of fuel or premix, whatever it takes. Prime the carb, say a little prayer and fire the bad boy up. Avoid long rides until you're certain that you have no fuel leaks and good fuel delivery.

Ride safe! Donnie Torok

Phosphoric Acid

WARNING: Wear protective gear during this process (all skin should be covered, long pants/shirt, work boots, gloves, eye protection and filtration mask - the reaction of muriatic acid and rust gives off extremely harmful vapors) if spilled muriatic acid can be neutralized with baking soda.

Behr Concrete Etcher and Rust Remover can be used to clean rust from the inside of a gas tank because it contains phosphoric acid. This can be accomplished by completely filling the gas tank with water and then draining that. Next you plug the hole where the petcock goes, and then fill the tank with the etcher (make sure you mix the etcher with water at a ratio of 1:1). It must be watched carefully, so that it doesn't eat through the good metal. Next carefully drain out the etcher and rinse the tank with water. Next fill it with a solution of water and a small amount of baking soda to neutralize the acid. After 15 minutes, rinse the tank with water again and continue rinsing until the water you pour out of the tank is completely clear. At this point it is important to make sure the tank has no more water in it. This can be accomplished by getting as much water out as possible, adding WD-40 or rubbing alcohol to the tank, and rinsing it out with gasoline. Immediately fill the tank with premix to prevent further rusting.

Vinegar

Vinegar can be used to clean rust from the inside of a gas tank because it contains acetic acid. This can be accomplished by filling the gas tank with water and then draining that. Next, plug the hole where the petcock goes, and fill the tank with the vinegar, leaving it in overnight to dissolve the rust. After pouring out the vinegar, rinse the tank with water. Next fill it with water and a small amount of baking soda to neutralize the acid. After 15 minutes, rinse the tank with water again and continue rinsing until the water you pour out of the tank is completely clear. At this point it is important to make sure the tank has no more water in it. This can be accomplished by getting as much water out as possible, adding WD-40 or rubbing alcohol to the tank, and rinsing it out with gasoline. Immediately fill the tank with premix to prevent further rusting.

Alternatively, a salt and vinegar mixture can be used as these ingredients will react to form a weak sodium acetate and hydrochloric acid solution. This solution should remove rust more quickly than the acetic acid in vinegar alone.

Coca-Cola

This method can work, due to the acidic quality of the drink, but has been questioned due to the sticky sugariness of it.

Battery and Washing Soda

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The Details

What do you need to make this work? Not much, really:

  • A large non-conductive container that will hold the part in water - A Rubbermaid tub, a plastic bucket, or a large non-metal trash can all work great as long as they don't leak.
  • A battery charger or other source of 12V DC power.
  • Wires or cables to connect the electrodes together
  • Sacrificial electrodes - iron re-bar works great, stainless steel is very bad (and the result is illegal and dangerous).
  • Arm & Hammer LAUNDRY Soda, also known as washing soda.
  • Some chains or steel wire to suspend the part in the solution - copper wire is bad and messy.
  • Water

The basics are pretty simple.

  1. Find a container big enough to hold your part, plus some room to spare for the electrodes - they must not touch the part for this to work.
  2. Fill the container with water and add 1/3 to 1/2 cup laundry soda per every 5 gallons of water. Mix thoroughly.
  3. Position the sacrificial electrodes around the edge of the container and clamp them in place so that you have at least 4" of electrode above the water to connect to. The more the merrier - this is essentially a "line of sight" process between the part and the electrodes.
  4. Wire all of the electrodes together so they are, electrically speaking, one big electrode. Make sure all connections are on clean metal and sufficiently tight to work.
  5. Suspend your part in the solution using the wire/chains so it is not touching the bottom and is not touching any electrodes. The part must be electrically connected to the support mechanism and not connected to the electrodes for this to work.
  6. Attach the battery charger NEGATIVE lead to the part and the POSITIVE lead to the electrodes. Do not get this backwards! If you do, you'll use metal from your part to de-rust your electrodes instead of the other way around -the positive electrodes are sacrificial and will erode over time. That's how the water becomes iron-rich.
  7. Double check everything to be sure the right things are touching, the wrong things are not touching, and the cables are hooked up correctly.
  8. Turn on the power - plug in the charger and turn it on.

Within seconds you should see a large volume of tiny bubbles in the solution - these bubbles are oxygen and hydrogen (very flammable!). The rust and gunk will bubble up to the top and form a gunky layer there. More gunk will form on the electrodes - after some amount of use, they will need to be cleaned and/or replaced - the electrodes give up metal over time. That's why re-bar is such a nice choice - it's cheap and easy to get in pre-cut lengths.

The process is self-halting; when there is no more rust to remove, the reaction stops. This is handy because you don't have to monitor it, and because you can do large parts where they are not totally submersed at one time without worrying about "lines" in the final part.

Once you are done, the part should immediately be final cleaned and painted - the part is very suspetible to surface rust after being removed from the solution. There will be a fine layer of black on the part that can be easily removed, and once it is removed, the part can be primed/painted as needed.

Safety Precautions

You're playing with serious stuff here, so stay safe. It's not rocket science, but if you're new to this, you might not know all of this - so read up before you do any of this.

  • This process produces highly flammable and explosive hydrogen gas (remember the Hindenburg?), so do it outside, or in some other well ventilated area. Hydrogen is lighter than air (like natural gas), so it will collect near the ceiling - not sink to the floor like some other flammable vapors will (like propane and gasoline). If you have open flames near this (Hint: gas appliances like water heaters and furnaces have pilot lights!) you will most likely severely injure or kill yourself (and others near you) and become a contender for the Darwin Awards in the process.
  • Assuming you used re-bar and steel wire/chain like you were told to, the waste water resulting from this is iron-rich - it's perfectly safe to pour it out onto the grass and your lawn will love it. Beware of ornamental shrubs that don't like iron-rich soil though, unless you like making your wife mad at you.
  • Make sure the battery charger (or whatever source of power you use) stays dry. All of the usual cautions about any electrical device in a wet environment apply here.
  • The solution is electrically "live" - it is a conductor in this system. Turn off the power before making adjustments or sticking your hands into the solution. You can get a mild shock if you stick your hands into the water with the power on.
  • The solution is fairly alkaline and will irritate your skin and eyes. Use gloves and eye protection. Immediately wash off any part of your body the solution comes into contact with with plenty of fresh water.
  • Don't use stainless steel for the electrodes. The results are toxic and illegal to dump out.
  • Don't use copper for the electrodes and anything else in the water - the results are messy.

If you are unsure of any of this or unsure about your safety - STOP! Get help before you do something stupid. Use common sense, be smart about what you're doing, and stay safe so you can finish your restoration project and enjoy it.

Kreeme

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Kreeme is a commercial product for coating the inside of a tank with a chemical compound resistant to the corrosive effects of gasoline. For long lasting results, this product should be avoided.

POR-15

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POR has a kit available that includes all the chemicals to clean, prep, and coat a tank. The most challenging part of PORing tank is the tedious drying process. After the cleaning and prepping, which adds a charge to the metal so the coating will adhere to it, the tank must be completely dried. If this step is not done correctly the entire process will fail. The most effective ways to dry a tank seem to be running a source of hot air through it, while setting it out in the sun. Once the tank is dry, the coating may be applied. Once dry, the tank will last for years without worry of rust(some user's have experienced 15+ years of no rust). POR is highly recommended above Kreeme, as Kreeme has a tendency to fail after time, while POR does not (when done properly).