[GreenKeys] Evapo-Rust

[Web Williams]

We used to use a product called Ospho at my dad's motel
on two sets of cast iron staircases that were exposed to salt
air (next to the ocean). I have fond memories of lugging 50
gallon trash containers up and down those steps! (No elevator,
four floors...) The name was "Ospho". They still are in business-
I had forgotten about them. http://www.ospho.com/

You can squirt the stuff on with a spray bottle, let it dry, and paint.
The process does NOT remove any rust, it merely converts the
rust into something that you can paint, and the rust itself will not
"grow" any further (as long as your coat of paint seals off the rust
from moisture ingress).

This is probably not what you're looking for, as I imagine cosmetics
will be as important as anything else.

Our process was to beat the rust down to bare metal as best we could
with hammers or hatchets until no more would come off, then spray the
metal with Ospho to convert as much of the remaining rust into a paintable
surface, then paint with a coat of red-lead based primer (you can still 
get it,
regardless of what you might think, it's just tightly controlled), 
followed by
two coats of Alkyd enamel based paint. The stairs are still in use 
today, 40
years after being put into service! (Most iron stairs that are not 
treated in
this manner last about five years in our salt-air environment.) They
did get a major overhaul at about 25 years (nuts/bolts/railing replaced).

I suspect naval jelly is probably going to be more along the lines of
what you need to use. It's a lot less destructive than hammers and 
hatchets,
but will take a LONG time to get you down to bare metal. You would
think that in this day and age, some chemist would come up with some
rust-dissolving spray-on chemical that would completely remove all traces
of rust down to bare metal in a few minutes without harming the metal
substrate!

Best of luck, -Web (AJ4VM)