[TowerTalk] Rohn U-bolts

[Grant Saviers]

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 protected.

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 day.

Grant KZ1W



On 7/29/2017 9:27 AM, Rob Atkinson wrote:
> I've heard that you have to be careful sourcing hardware for a tower,
> especially from a non-tower manufacturer.  It has to do with the
> galvanizing.  From what I've been told, the non-tower intended
> hardware has shall we say, "casual galvanizing" and the tower stuff is
> galvanized to be up in a hard to get to place for a long time.
>
> Rob
> K5UJ
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