[Bell Historians] Canon removal and faculties

[Roderic Bickerton]

>
> Certainly the WBF steel headstocks, and probably those by other
> manufacturers as well, are all galvanized as standard, which
> completely alleviates the problems of corrosion.

Unfortunately this is factually incorrect.
Hot dip galvanising is a Sacrificial coating and has limited life.

70 years would be a reasonable expectation.
A bit short, considering the number of reasonably sound timber parts that
have survived 300+ years.


I have found a life chart at:
http://www.galvanizeit.org/resources/files/AGA_root/pdf_files/pubs/PR-SLC-05.pdf,
or http://www.metalplate.com/galvanizing/TIS5.HTM
Life may be better than the chart because it is subject to condensation and
spray but not direct weathering.
The performance of Galvanised beam ends buried in tower walls can be much
reduced depending on how damp and chemically active the wall material is.
There is a lesson from the building industry regarding galvanised cavity
wall ties which have in some cases failed completely in less than 50 years.
Great care must be taken if differing materials, which will be displaced
from Zink on the electrochemical table are in contact with the Zink coated
part.