[Milsurplus] Plated steel in WW II

[aGEnuine ham]

John:

There were two processes generally used in that time frame, cadmium
plating and galvanizing.  Zinc plating was not yet common.  Galvanizing
(dipping prepared steel in hot molten zinc) was the process of choice for
steel which was fully exposed; garbage cans, farm windmills and towers
being my favorite examples of continuous exposure.  Cadmium, now
classified as a hazardous substance as it falls into the heavy metals
category, was easier to plate on complicated shapes, and was used for
indoor stuff and small hardware.  Zinc in galvanizing provides an
electrochremical resistance to rust, even when scratched or worn away,
but cadmium must be a solid coating, like paint, to provide protection. 
Visually, it is often possible to identify galvanizing by the visible
crystalline structure of the zinc, or by the obvious remains of runs
while the zinc was still molten.  This is usually obscured in old
surfaces, however.  New galvanizing is shiny, also, and it takes some
weathering for it to develop the soft gray look.  Compare an old garbage
can with a new one for the difference in looks.  Cadmium, on the other
hand, was pretty dull from the get-go, or at least it didn't take long
for it to become dull.

I don't know if there are any cadmium platers left because of the
hazardous materials problem.  Galvanizers still exist, but part of the
preparation process is boiling in strong acid, so be sure the base
material is up to that.  Zinc plating, a more recent process may be your
best bet, but you will have to get some of the antique restorers to tell
you how to turn it dull more rapidly.  Finally, cold galvanizing spray
comes out pretty dull, and from a distance is difficult to tell from real
galvanizing, but it has little resistance to mechanical damage, so it
isn't satisfactory where parts rub together, or are walked on, for
example. 

Zinc and cadmium respond differently to hydrochloric acid (muriatic acid,
acid core solder, swimming pool cleaner), but I don't remember which
response is which.   One turns black, while the other foams.   

George W5VPQ
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