[TowerTalk] Rohn U-bolts

john at kk9a.com john at kk9a.com
Sat Jul 29 15:44:36 EDT 2017

Electroplated zinc parts typically have a chromate conversion for additional
corrosion protection but as Grant said it is a poor choice for anything
outdoors. I have had better luck with Cadmium plated hardware however due to
the toxic nature of the process this has become rare. My preferred hardware
choice for towers and antennas is stainless steel and second is Armor Coated

John KK9A

To:	Rob Atkinson <ranchorobbo at gmail.com>, towertalk
<towertalk at contesting.com>
Subject:	Re: [TowerTalk] Rohn U-bolts
From:	Grant Saviers <grants2 at pacbell.net>
Date:	Sat, 29 Jul 2017 11:43:17 -0700

Zinc corrodes about 1/30 the rate of steel per year when exposed outdoors.
Add salt to the air and erosion is much faster. Zn is also sacrificial
relative to iron so small scratches in the coating has the steel still

There are two principal forms of zinc on steel - electroplating and hot dip.

Electroplating is cheap and fast and thin enough the steel as plated
dimensions change very little. It is usually 0.0002" for spec'ed fasteners,
probably less from hardware store stuff from China, and will protect the
steel outside for a year or two.

Hot dip is usually specified around 0.005" thick so lasts about 25 times as
long. Parts are cleaned, fluxed and dipped in a molten Zn bath. Just like
soldering. The Zn is thick enough that bolts and nuts need to be sized
differently to fit together. Also, holes tend to get Zn droplets inside when
hoisted from the molten Zn kettle, so may need filed or reamed for bolts to
fit. The design of the parts to be HDG has to consider they will be immersed
in molten Zn above 800 deg F.

Ace Galvanizing in South Seattle had a minimum charge of $125, or $1.25 per
pound of steel, whichever is larger, when last I was there a year ago. Great
folks, easy to work with but a very busy place with many tons dipped per

Grant KZ1W

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