This is a 48-hour review of citric acid.
The fuel pump is less effective because of the gasket, but the same effect is expected if the gasket is removed and only the fuel pump is submerged separately.
The tank sealer is not yet in use.
I'm not promoting a specific product, so don't misunderstand the intention. I recommend the product with the best reviews.
How to remove rust in fuel tank?
Fill the container with 5 gallons of water.
Mix 4 pounds of citric acid in water.
Empty the fuel tank. It doesn't matter if there's a small amount of gasoline left.
Fill the fuel tank with citric acid mixed water and seal it and wait more than 24h.
(In my case, I sealed the bottom with a fuel pump. It's also possible with duck tape.)
(The water was leaking out little by little, so I turned the tank upside down for 24 hours.)
Dry it well and coat the inside of the fuel tank with a coating chemical.
The process is over when the coating chemical dries well.