From the following site:
http://www.galv.co.uk/appearanceguide.html
A thin brown surface staining sometimes occurs in service when the
galvanized coating comprises entirely zinc-iron alloys as discussed under
'Dull grey coating'
1.Dull Grey Coating
General comment:Acceptable.
A dull grey appearance is caused by growth of the zinc-iron alloy
layers through to the surface of the galvanized coating. Grey coating may
appear as localized dull patches or lacework patterns on an otherwise normal
galvanized coating or may extend over the entire surface. Dull grey coatings
usually occur on steels with relatively high silicon content which are
highly reactive to molten zinc.
Dull grey coating are often thicker than the normal bright or spangled
coatings and therefore give longer life. It is rarely possible for the
galvanizer to minimise or control the development of dull grey coatings
which is dependent basically on steel composition.
Doug - K1ZO
----- Original Message -----
From: <K7LXC@aol.com>
To: <towertalk@contesting.com>
Sent: Wednesday, September 12, 2012 4:13 PM
Subject: [TowerTalk] Brown colored galvanized surface?
Howdy, TowerTalkians --
On lots of old galvanized towers sometimes you wind up with a brownish
colored surface. Can anyone tell me what it is? It's not rust but
something else. Just curious. Tnx.
Cheers,
Steve K7LXC
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