Rust in fuel tanks

[Alan G]

If a bike has substantial surface rust inside the tank, but purely surface rust, nothing deep or flaking, would you clean or leave it?

If you cleaned it would you then attempt to line it with some ethanol friendly sealant, or leave as bare metal and try to keep the tank well topped up.

Thanks.

[will_curry]

Just make sure sure you've a decent in-line fuel filter and otherwise just leave the tank alone.
That's what I've been doing for many years.

[charles.bulloch]

You can electrolyse the rust with washing soda. This replaces the rust with iron.

[mark.prizeman]

This stuff is pretty good at keeping tanks going

https://bilthamber.com/product/gas-mac/

[nevhunter]

Even the oil tanks gave rusted out the Bottom occasionally. Condensed water goes to the bottom of the oil. Chroming the Tank can result in rust from the Pickling process. The Mid 60 Velocette Venom was Notorious for it Phosphoric acid will convert rust. The thing is to get right into the Corners. Clever people might consider electroplating ZINC on the inside. That will give GALVANiC protection. The best. Nev

[Alan G]

Love it! Options covered in the replies so far:
Leave it
Additive to fuel
Treat with chemical to convert rust
Electro plate

What no one has suggeated is using one of the ethanol freindly tank lining paint treatments. I know some of the earlier treatments became troublesome when ethanol was introduced - but some of the newer treatments are ethanol compliant.

Good call on the oil tank. I guess water could sit under the oil unnoticed for years in storage.

[Simon.Gardiner]

Any form of rust removal will be problematical unless you take the bottom off the tank ('cos that's the only way you'll guarantee that you've got complete internal coverage - even if you try and submerge in a bath eg of citric, which works quite well as a rust remover although it's even better with a dash of washing soda, you'll have a lot of fun avoiding air or gas pockets).
I'd always be wary of putting any coating over rust, it will carry on rusting under the coating although it might be slowed down.
I've used phosphoric a lot and in my experience it doesn't get into pits (pretty good on fairly light rust though and I do use it to deal with the flash rust you get after cleaning off most of the rust removers, although as more of an etch primer...).
That Bilt-Hamber product looks interesting (I use some of their stuff, I've not seen that one before, must be new) but as with Will I've had some kind of rust on the inside of the (now) 650 tank ever since it's been in my possession (which is now rather longer than I care to put down) and although I sometimes have a worry about it that tank still seems pretty sound.

SG

[JohnnyBeckett]

hi i use POR 15 KIT it cleans and etch and seals the tank i have used it for years on all my motorcycles and classic cars