De-rusting gas tank

BrianK · Jan 11, 2026

While the tank is off pending engine work, I took a look inside and was dismayed to see a fair amount of rust. So I've had it full of a white vinegar mixture and now a brush inserted through the gas cap will easily brush off the rust revealing nice clean metal underneath.

Of course, that brush doesn't reach in very far. I'm thinking of using the traditional (?) method of dropping in a bit of chain or handful of nuts and shaking. But more than a little apprehensive of an end of that chain or some of those nuts getting stuck in some nook or cranny, for which, with the baffling and all, there appears to be plenty of opportunity.

Has anyone tried this method, with or without success?

And any other suggestions?

Thanks as always - BK

NPeteN · Jan 11, 2026

Evaporust, pour in, pour out.

Jdub · Jan 11, 2026

Use Metalworks in Eugene, Oregon or a similar outfit. Very inexpensive and your tank is returned clean as you could wish with a protective coating. I've used them three times and they are the best value for your money. I have tried self-cleaning and it is a mixed result. Absolutely recommend clear Caswell applied on a warm day but not too hot - viscosity and vigorous and strategic movement returns the best coating. I have an Interstate tank hanging up right now that has three years on it and looks as good as the day it came out of the tank.

concours · Jan 11, 2026

I use nuts. Have for years. Multiple norton tanks, no trouble.

Tornado · Jan 11, 2026

I used aquarium gravel and soapy water, then dried with isopropanol (rubbing alcohol). A bit light oil or wd40 to coat insides for storage if not back on bike.

BrianK · Jan 11, 2026

Thanks all - BK

NORTSTER1974 · Jan 11, 2026

concours said:
I use nuts. Have for years. Multiple norton tanks, no trouble.

You're right on Concours. Just make sure you count them before you put them in, so you have the same amount coming out

Shelby-Right · Jan 11, 2026

I used electrolysis, on my GL1000 tank, if you want to try this method, go get some bulk washing soda, 1/2 a cup or so, just use it with water, I put a piece of tube inside a piece of push bike tube whith a couple of notches in the rubber, hook up your battery charger negative to tank, and positive to electrode tube to the bicycle tube to insulate it from the metal at filler neck. Cheers

BrianK · Jan 12, 2026

I tried electrolysis, did nothing. I think I may have put too much electrolyte in. Anyway, on to vinegar, which seems to be working. Thanks!

batrider · Jan 12, 2026

I've not tried electrolysis inside a gas tank but the advantage is that it does not remove any steel - just the rust. Vinegar is acid and will remove the base metal. Maybe OK if not left for too long.
Most of my experience in comparing the two methods is with small engine parts and cast iron frying pans.

Shelby-Right · Jan 12, 2026

BrianK said:
I tried electrolysis, did nothing. I think I may have put too much electrolyte in. Anyway, on to vinegar, which seems to be working. Thanks!

I tried industrial vinegar the 9% acetal acid, it didn't work, I know it can, I've used it on other smaller things and it removes mill scale.

Shelby-Right · Jan 12, 2026

BrianK said:
I tried electrolysis, did nothing. I think I may have put too much electrolyte in. Anyway, on to vinegar, which seems to be working. Thanks!

I think the soda just makes the water conduct, an electrolyte. I. Probably used too much as well, there was nothing scientific going on when I did mine.

marshg246 · Jan 12, 2026

If really heavily rusted do the nut and bolt thing first.

Then here's my crazy method (be sure to keep off the paint or immediately rinse with water):
1. Put on big boy shorts
2. Put in good bit of Muriatic Acid (get it at the hardware store for cleaning bricks) and seal it up (I leave petcocks in and close the lid.)
3. Do not breath fumes!
4. Turn every which way - around 2 minutes.
5. Dump out and immediately put in a water hose (power washer better) and flush thoroughly
6. Pour in some WD40
7. Turn every which way
8. Dump out WD40
9. Repeat 7 and 8 until you don't see water.

I can't find the picture, but after the nuts and bolts there was a mound of rust about 8" across and 2" high and then I did the treatment above. The bike is still on the road today with no tank leaks. That's an original tank.

Onder · Jan 13, 2026

You need a old school battery charger to do the electrolysis method but it works well. You have to move the
lead around the tank to make sure it gets all the rust.
Phosphoric acid is another approach and also works well. Flash rust is a problem I tried washing it afterwards
with WD40. Water will make it flash even faster.

baz · Jan 13, 2026

Best method I have used so far is food grade citric acid
Pour 1kg in the tank
Fill to the brim with water
Give it a shake and let it sit for a few days then flush out with fresh water
Then a liberal coat of wd40 or just start using it with a full tank of petrol

De-rusting gas tank

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