^^ +1, water gets in the door via the windows sits at the bottom and rusts.
If you do get new doors or fix the old ones take the door panels off and spray sealer in the bottom of the door, but first look at the underside of the bottom of the door and you should see drain holes, or plugs or both, remove the plugs and put something in the drain holes so they won't get clogged, then spray the sealer.
This will prevent water from sitting directly on the metal.
Also check the window gaskets, shouldn't get alot of water in there.
Navel Jelly uses Phosphoric acid to convert red rust(iron oxide) into black ferric phosphate(not rust, lol).
It will remove paint and tarnish chrome so be careful and wear gloves.
But grinding down to bare metal is always best.
Coke has Phosphoric acid in it, it is good to clean chrome