Stainless is nice.
If you have an iron one and the rust and scale is getting bothersome contaminating the water prematurely, you can line it w/ aluminum foil.
If done very carefully and used with extra care,,it will work just like a stainless tank.
Use the extra-wide, heavyduty foil (18 or 24"?). A one piece job of lining the tank is done.
Careful not to tear the stuff. The ends are just tucked in X-mas wrap style. The top edges folded over the tanks edges.
Water weight will push out the wrinkles so don't worry too much about that. Avoid placing objects directly onto the bottom, you don't want to tear the foil.
Works just like a stainless tank.
It does take extra care in emptying. I used to bail it out till almost empty, then carefully dump the rest. A liner lasted several bbl bluings before I replaced it with another one. Just another sheet of foil after all.
Better than the (crusty)old iron tank,,which was one step better than the 36" fiber-glass window flower box heated w/2 electric hot water tank elements hooked up to 110 I used before that.
I finally did get a stainless tank about 20 yrs. But it's amazing what you can accomplish when you have to make do with what you have.