That sounds like a good way to get most of the rust out. Buit even if you get all the rust out, understand that rust is an electro-chemical reaction... rust is iron oxide.
If you have iron, oxygen and water rust will form.
Iron is the tank, oxygen and moisture come from the air. That tank will rust again.
You must coat the (iron) tank with something to prevent air and moisture from contacting the metal if you want to stop it from rusting again.
Keeping the tank full to the top with fuel will do it. Kreeming the tank will also do it.