Gas Tank Varnish/Rust

[Hamie]

I have a Trike Shop Runabout that has been sitting in a garage for years do you have any suggestions on how I can get this gas tank cleaned? Thanks.

 

[Zammy]

I've never had to do this Hamie but here's one idea:

https://www.denniskirk.com/blog/2020/06/12/how-to-remove-rust-from-inside-a-motorcycle-gas-tank/

 

[Sidecarbill]

Electrolysis, then a gallon or so of phosphoric acid. Put a lid on it and turn it every which way but loose. Turn it every once in awhile. You should leave it in there for a couple hours. When you look inside the metal should look clean like new. Empty the acid, rinse with a quart of alcohol. Dry the inside immediately with compressed air, you're trying to avoid flash rust. Give the tank overnight to make sure it's dry. I always buy a quart of por15 sealer. I put at least two coats in the tank drying between each one. Leave it dry for at least a week. You're done.