[SML] GAC Quandary

[Maia Robbins-Zust]

Question for all you fellow riggers out there:

Just finished doing a rigging inspection at a local school and found
that almost all of the 1/4" GAC cables in the system had a white
powdery substance on them.  The white areas were not uniform and were
scattered across all the cables in a rather random pattern.  My guess
was that this was a residue of the zinc used in the galvanization
process, but why would it be "degrading" like this in such a random
way? (The theatre was built in 2004, so the cables are 12 years old).

I know I've seen GAC that's been left outdoors get a white-greyish
powdery look to them, which I've always associated with the
degradation of the galvanization coating, and I've always thought of
such cables as possibly compromised in some way, but still usable.
However, now I'm questioning my assumption?

So this brings me to my 2 questions:

1) Is this white/grey-ish powder actually from the galvanization?

2) Does this indicate that the cables have been compromised, and if
so, by how much?

Other points of interest: The theatre did have a major "roof failure"
several years ago which resulted in many leaks over the stage house -
however, there's no signs of rust anywhere.  Additionally, I know
that, due to construction delays, the entire steel package for the
theatre rigging system ended up sitting outdoors in crates and under
tarps for a few months before the installation was able to proceed.
Both of these might help to explain a degradation in the galvanization
on the cables?  Also, the last rigging inspection report, done 5 or 6
years ago, does not mention this phenomenon.

Thanks for any help!

Maia Robbins-Zust
Berkshire Production Resources
ETCP rigger - theatre