[Boatanchors] Rust, Coatings, etc.

[Michael D. Harmon]

I've been reading the thread about rust converting coatings, and I 
remembered something from about 35+ years ago that I've always wondered 
about.

Westinghouse built a factory back in the Seventies in Jefferson City, MO 
when I lived there (later bought by ABB).  They manufactured big 
industrial transformers and switchgear, as I recall.

Once they had the exterior of the building completed, they treated it 
with something that made it rust.  Yes, that's right - as in the 
reddish-brown iron oxide.  As first it looked pretty bad but after a 
while it settled into a deep red-brown color and actually looked sort of 
unobtrusive.  Not what you'd expect from a big steel building covering 
several acres.  I asked someone why they did that and was told that the 
rust was only surface deep and permanently protected the underlying 
steel from further corrosion.

I'm wondering if any of you have ever heard of a similar situation where 
rust was used as a protective coating?  Does the process have a name?  
Does it work somewhat like gun blue?  Gun blue uses phosphoric acid and 
creates a deep blackish-blue protective coating (iron phosphate?), but 
can rust if you leave salty fingerprints on the surface and don't keep 
the surface protected with a light film of oil.  You don't find many 
shops that do hot-dip bluing any more, because the salts and solutions 
(and fumes) used in the process are pretty noxious.

Mike, WB0LDJ
mharmon at att dot net