Palladio writes:
<< Your guy (or guyette) should remove (via sandblast, grinder, or other) all
 the rust down to bright metal, and apply the best damn paint he can get >>

whereas, Brunelleschi writes:
<<Rusted iron can be stabilized with tannic acid (rust converter) which will
produce a rather attractive black skin.  It only converts iron oxide so do
not remove the rust. >>

Submitted by,  Huntley Brinkley