What I have seen, it is only the portion closest to the surface that corrodes.
I have found iron pieces buried for hundred of years with only slight
corrosion. Scrap iron, stored laying on the ground, has almost disappeared in
no time. I believe it is a combination of water, "dirt", and air that is
causing this.
When installing fence with steel poles, a concrete "plate" is made around the
pole just at the surface. It is sloped on the top to allow water run-off. If
you don't do that the pole will corrode at the surface and eventually break
there.
The rebar in concrete is "protected" by the concrete but will corrode if too
close to the surface. In the same way the fence pole is "protected" by the
concrete plate.
Maybe some concrete poured around anchor can extend the life-expectancy of the
anchor.
Next: What method or how would you inspect an anchor for corrosion damages?
Just digging around it?
Hans - N2JFS
-----Original Message-----
From: Mark Robinson <markrob@mindspring.com>
To: Jim Thomson <jim.thom@telus.net>; towertalk <towertalk@contesting.com>
Sent: Thu, Jun 20, 2013 11:36 am
Subject: Re: [TowerTalk] Screw Anchor Experience
Jim wrote
> ## why mess with screw in anchors ? Only power company’s + telco’s use
> em. Even then
> they use eggs in the EHS guys. A 40’ tall utlility pole is already 6
> feet into the ground. No
> anodes used.
>
> ## The rohn type rod anchors are in contact with the soil, where it is
> trenched, so that portion
> of the rod needs to be coated with roofing tar pitch. Those GAC series
> anchor rods involve
> excavating a huge hole, that is then trenched. The concrete slab needs to
> be poured, then the
> entire mess is bakfilled with dirt.
>
I reply...
They weren't screw anchors. They were the Rohn supplied anchors set in
concrete per the Rohn specifcations (as you describee) BUT they are still
vulnerable to corrosion. I have read dubious accounts of using tar on the
buried metal parts - the tar can fail and then the corrosion will be
concentrated in the failed areas
My opinion/guess is that the sacrificial anodes are a better way to go but
only time will prove me right or wrong.
Mark N1UK
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|