[OZ4]

The navel jelly  is easy. Just be careful not to let go into places you don't want or can't clean it out. The worse the corrosion the longer it takes to eat it up. The light stuff is quick only about fifteen minutes. I usually do more than one application for the heavy stuff even overnight. It just can't dry out or it doesn't work.  If the rust is really bad there are pits left behind. After steel wool I like to wipe it down with a damp to wet paper towel soaked with a water-baking soda solution.
Navel jelly is phosphoric acid. It sounds really bad but its not.
It doesn't seem to bother labels or printing much as long as they are not paper.
And the metal should be sealed soon afterwards or it can rust again.

Chris