How to clean a rusty gas tank?

[NCAmother]

I have a lot of rust inside my tank.  I tried white vinegar, 5 gallons and let sit for a week, and it flushed out some of the rust, followed by a water and baking soda mix for the second flush and neutralize .  Then more water, but I still have a good amount of rust, mostly flash.  Is evaporust a good solution, how much would I need?  Muriatic acid?  Thanks in advance

[guzzisteve]

Don't know if Evaporust, but got it at Home Depot, worked great.

[Jack Straw]

In the Stone Age, or maybe Iron Age,  a common method was to drain and flush the tank with parts cleaning solvent then pour in a generous assortment of nuts, bolts, and screws.  Add a couple of quarts of parts solvent, seal the openings and shake the tank, turning it often.  Keep this up until your arms throb and everybody in the shop is yelling at you.  Drain the mess out, rinse, repeat. 

Yeah, it actually did the job circa 1969. 

These days some swear by pour-in sealant coatings specifically meant for the job though some say they're not worth a darn.  I'd look for a fuel tank reconditioning shop if you're close to a large town.

How 'bout a new tank?  If they don't cost $1000 like a V7III........

[Antietam Classic Cycle]

I use a gallon of "milkstone remover" (available at your local farm supply store), then fill the rest of the way with water. 24 hours is usually enough.

[snobear]

I just did my 87 Cali II by filling it full of vinegar for a couple of days with occasional shaking and rolling over.
Then drained it and took it to the carwash with once round of soap and water and then one round of rinse. 
Then setup a space heater and dried it quickly.  There was a little flash rust but nothing to worry about, it was very light.
When I started I thought there was some deep rust but turns out it was all surface rust and the tank interior is very good.
The carwash removed anything that was left after the vinegar round.

[John Croucher]

Buy some copper sulfate used to destroy tree roots. Mix with water and use for final rinse.  It will protect the steel from rusting.

Lava rock for landscaping is a good abrasive mixed with a cleaning solution.  A quart of liquid is enough.  Seal all openings and shake. Rinse and repeat. 

 https://feltmagnet.com/crafts/Patina-Finishes-for-Steel

[Gusable]

I did the KBS coatings kit.  It’s not hard. Little tedious but worth it. Turned out great and the final coat is hard as a rock

[bacongrease]

 Fill tank with nuts and bolts, cover openings.

Strap to your rear tractor tire.   

Go farming.     


         I used the battery charger method.   

[Dr. Enzo Toma]

If you're using a shaker or spinner abrasion method, fish tank gravel is another alternative to nuts and bolts. Just make sure you get it all washed out after. A borescope can be used to verify that.

[chuck peterson]

A pro I’ve met in the moped world sings the praises of Evaporust..standard procedure for all of his remakes

Keeps a family of three going…

[dragger]

I second the milk stone remover. I also try to never use coatings unless absolutely necessary to stop pinhole leaks.

[Scout63]

Pull the petcocks and plug the holes.  Fill the tank to the top with Evaporust or Metalrescue.  Turn the tank in several positions over two days or so, longer if really bad. Drain and flush the tank with water. You will have clean shiny metal inside. Then keep it full of fuel or fog it. I’ve tried everything including tank linings in the past. This stuff is water based, non toxic and doesn’t hurt paint (unless there is rust under paint).

[fotoguzzi]

Can you dilute the Evapo-Rust or do I need to use full strength?  5 or 6 gallons gets sort of pricey.

[Antietam Classic Cycle]

I second the milk stone remover. I also try to never use coatings unless absolutely necessary to stop pinhole leaks.

This ^^^. Sealer as a last resort.

[Antietam Classic Cycle]

Can you dilute the Evapo-Rust or do I need to use full strength?  5 or 6 gallons gets sort of pricey.

Full strength. I've also found that it doesn't work well under about 70 degrees F.

You can make your own "Evaporust", it just works a bit slower than the real thing. https://youtu.be/f9kBdJQMPPI?si=HY3rWiyQS0QnpHxQ

[pressureangle]

Evaporust just makes it too easy.

For sport, if you have a little longer to wait, go to the farm store and get a couple gallons of molasses, like you'd put on horse oats.

[cappisj1]

Not wanting to buy 5 gallons of evaporust. Would it be ok to buy 2 gallons and roll the tank around and sit for the right amount of time so the two gallons touch all of a 5 gallon tank at different times?  Hope that makes sense. 

[bigbikerrick]

I used muriatic acid on the tank from my cal II. left it in about 20 minutes, sloshed it around, drained,and rinse with garden hose, I then repeated it to get a couple of remnant spots. Final rinse, I dumped in half a box of baking soda, then, just lots of water, I then used a leaf blower to dry the inside , and then quickly poured in a few ounces of gas, with 2 stroke oil, to prevent flash rust as much as possible. It seems you always get a little bit.
Rick.

[Antietam Classic Cycle]

There's always electrolysis. I've used that on a bunch of tanks and it works well, if a bit slowly at times.
https://www.thisoldtractor.com/moto_guzzi_loopframe_fuel_tank_cleaning_and_coating.html

[Bulldog9]

Haven't done this in a while, but I've used gravel or a bunch of bolts with acetone or kerosine, sealed all the openings up and shook like mad to remove the rust. Once all was clean and shiny, would generally just run the tank, but I did have a couple tanks professionally coated but that always ended in a mess long term. That was mostly on my Yamaha XS series bikes.

[Scout63]

Can you dilute the Evapo-Rust or do I need to use full strength?  5 or 6 gallons gets sort of pricey.

I’m not sure if you can dilute it.  You can reuse it though. It just gets weaker the more rust is s
Dissolved in it. You can fill the tank half full and turn it over a few times.

[cliffrod]

Evaporust, metal rescue and comparable products remove rust via chelation. Whether as originally concentrated or diluted, once the quantity of available ingredients responsible for chelation are exhausted, the process stops as the solution reaches equilibrium.  Diluting the original concentration will not extend the product, remove more rust or make it last longer. 

[pressureangle]

Not wanting to buy 5 gallons of evaporust. Would it be ok to buy 2 gallons and roll the tank around and sit for the right amount of time so the two gallons touch all of a 5 gallon tank at different times?  Hope that makes sense.

The answer is yes, you can dilute it. I would use distilled water, and assume you'll have to wait twice as long. You can dilute the molasses as well if you have time to wait.

[oranges3]

I have had the best results using this method:

Electrolysis method until metal bar stops pulling rust from the tank.

Then using a 5/1 mix of water and phosphoric acid...this acid turns rust to iron oxide and will not flash rust like other acids or methods after you rinse it.

Final rinse with baking soda and water.

Has nev3r let me down