How to clean an old gasoline tank

What are the best ways to clean out an old gasoline tank that has sat for 20+ years. It had some gas in it and a lot of crud and probably rust too came out of it. Looks really nasty inside. Outside of tank is in decent shape.

I have used E85 gasoline, works pretty good if not really bad rusty. I have also used muratic acid, but be extremly careful if you use it

You can try cleaning it with E85 and something inside to agitate it, like a short length of chain or some pieces of metal. Shake and tumble it, or devise a way to attach it to a tractor wheel, or a cement mixer, and let it tumble a while.

But, if it's rusted thin, it may reveal leaks, and may be rusted very thin around the outlet fitting, which could break out.

If this is a common tractor or whatever it is on, and a new tank is available, that is your best solution.

Liners, I have never tried, but have heard mixed results.

Another solution is to cut the rusted bottom out, and weld in a new piece.

A word of caution, be careful cutting on a gas tank! Very difficult to get all the gas vapors out. And never use a shop vac to clean out the residual liquids. You can use the exhaust side to dry it out, but don't pull the vapors into the vac!

I've done quite a few, and while I'm certainly no expert, I've learned a few things, and here's what I find works best:

There's a big difference in what works best, depending on whether it's rust or grime. For pure rust, it's hard to beat a good acid. Hydrochloric/muriatic seems to be a popular choice, but I prefer phosphoric (naval jelly) as it converts any remaining bare metal into iron 3 oxide, which is more stable and prevents further corrosion (compared to regular rust, which is primarily iron 2 oxide).

If, however, there is any grime/sludge in there, neither acids nor any off the shelf rust-remover will touch it. I've found the best stuff for this is a high strength degreaser. There's some sort of purple product called 'super clean' that works wonders, but I'm sure others will do just as well. And if there's a combination of rust and sludge, the rust removers and acids won't work until the sludge is removed.

My method is probably not perfect, but I've had good luck with it: First, pressure wash as well as you can to remove all loose/chunkular bits. After pressure washing, drain the water and use the degreaser: Pour some in, swirl it around, let sit for 15 minutes (swirling occasionally), drain, repeat about 3-4 times. Remember that huge volumes of product aren't required. More rinses with smaller amounts of degreaser are far better than pouring a whole pile in and letting sit. One 4 quart jug of the purple stuff is more than enough for one tank.

After draining the degreaser for the last time, air dry as best you can with a blow gun and do an acid wash. Similar process to the degreaser, unless the tank's incredibly rusty, in which case I do what others have suggested: I strap the tank to my cement mixer with the acid and a handful of bolts/length of chain inside and let it tumble itself clean. Make sure whatever you put in there is magnetic as it makes it a lot easier to remove if you can use a magnetic pickup tool. I once foolishly put some stainless bolts in a tank that had a really awkward inset filler cap, and it took ages to shake them out.

Once done with the acid wash, I air dry again with a blow gun as best I can, then do a rinse with WD40. It displaces any remaining moisture (that's what the 'WD' in 'WD40' stands for: Water Displacement). It also coats any bare metal to prevent rusting, and penetrates it's way into any crevises/seams.

The best way to prevent future rusting is to keep it says full, but if for any reason I'm not planning on keeping it full, I'll give it one last rinse with two stroke oil to further coat any bare metal.

Two last notes: I've cometely flip-flopped on my attitude toward liners. I used to love them, but I've bought two tractors now that have had disintegrated liners, and they're a complete nightmare to strip. Not only does it take ages to strip thebold.liner, but they also gum up every portion of the fuel system. It's bad enough for carburetors, but simply awful for injection pumps. I'd be ok using a liner to seal a leak in a tank on a working tractor, but wouldn't use one in a restoration, or anything I intended to hang onto for a few decades.

I've also lost all patience for the store-bought rust removers ('Evap-O-Rust', or similar products). They work marginally ok for light surface rust, but aren't nearly as potent as acids for any heavy rust.

Thank you

A steamer works the best. As in a hottsie.

I strap them to my cement mixer and add a couple handfuls of small nuts and washers and a some water, does a great job

I thought he was asking about a bulk tank.

In 22 years of reading the answers to this question I believe that the most accepted answer is insert nuts and bolts and old chain and attached to the tractor wheel and rive around.

(quoted from post at 20:13:24 01/04/23)

In 22 years of reading the answers to this question I believe that the most accepted answer is insert nuts and bolts and old chain and attached to the tractor wheel and rive around.

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I'm no expert either and have done quite a few with many different methods. Best I have found to work that is the easiest to work with is using Berryman Carburetor Chem Dip in the gallon paint can. If it has light rust and a bunch of grime, it will bring it back to shiny, clean metal. I've done a couple that way now with perfect results. I'll pour the whole gallon in the tank and pour in some nuts and bolts (count them). Shake the tank around by hand for 5-10 min and repeat on each side of the tank. Let sit for a few hours and repeat the shaking. Let sit overnight and repeat the shaking once more the next day. You should be able to drain and rinse at this point, but can let soak for longer if needed. I use a hot water pressure washer to wash and rinse out. I use a paint strainer to filter the chem dip cleaner and put it back in the gallon can to be re-used.

I've used muriatic acid before and its good, but toxic and dangerous to handle, breathe, and dispose of. It will also rust your tank overnight IF you don't neutralize the acid with a base after you drain it. I've strapped them to rear tractor tires and drove them around to agitate them. That also works good, but is very cumbersome to strap down sideways and can be a pain. I've used tank liners before too and they sound great and seemed to work great, BUT I've bought a tractor before that wouldn't run and finally found it had a lined tank that was peeling off internally. I pulled the liner out by the slab with a grab-tool. It was such a nightmare that I bought a good used tank to replace it. I will only use tank liners when I have a pinhole in the tank and replacement is not possible or cost effective. Just my opinion, so hope it helps!

Thanks

I like to take mine to a radiator shop. They have the good chemicals to boil out the rust and crud. And they can seal it

(quoted from post at 14:10:04 01/29/23) I like to take mine to a radiator shop. They have the good chemicals to boil out the rust and crud. And they can seal it

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Problem there is they have almost all closed up.

worked for me 5 years ago. can full of bolts, nuts, washers some liquid (maybe diesel, maybe water?) and bush hog for hours.

I like to blow as much crude out as I can with compressed air. Then I add a screen inside the tank a inline filter. never, never had a problem. inline filters do not restrict the flow or burst into flames! That is an internet old wives tale.

My SC has had a filter on a rubber fuel hose for 33 years.

(quoted from post at 19:13:25 01/30/23) I like to blow as much crude out as I can with compressed air. Then I add a screen inside the tank a inline filter. never, never had a problem. inline filters do not restrict the flow or burst into flames! That is an internet old wives tale.

My SC has had a filter on a rubber fuel hose for 33 years.
<img src=https://www.yesterdaystractors.com/cvphotos/cvphoto146294.jpg>

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xactly! Same BS on inline filters don't work on gravity feed. Not much "head pressure" here & been fine 20 years.