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Problem connecting galvanized steel to steel brackets and setting both in concrete

August 15, 2009

Hi,

Am erecting a used antennae tower made of galvanized steel. In order to anchor it to the concrete, I am attaching 2" x 2" (1/4" thick) steel angle iron to each of the tower's three legs. Also, to stablize the tower better, I thought it good to sink about 4" of the tower as well into the concrete.\

Is there any danger of a chemical adverse reaction between the galvanized and non galvanized steel and the concrete itself?

Also, would there be a need to ground the tower, and if so, how could this most easily be done? I need a quick opinion if possible and thanks.

Giles Allan
Private Contractor - Moncton, New Brunswick, Canada

I would coat the angle iron in a coal tar pitch to cut down corrosion and any attack from the concrete.

Terry Hickling
Birmingham, United Kingdom
August 18, 2009

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Whether or not to ground the tower is a decision based on the electrical requirements of the antenna and whatever is connected to the antenna. It is not relevant to corrosion of the tower.

If indeed you choose to ground the tower, it should be done by a clearly visible grounding strap/cable/braid from the tower to a ground point near but separate from the concrete in which the tower itself is set.

Bill Reynolds [deceased]
consultant metallurgist - Ballarat, Victoria, Australia
We sadly relate the news that Bill passed away on Jan. 29, 2010.
August 21, 2009

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August 25, 2009

As Bill says, grounding is a requirement of the equipment on the tower, but you could also consider lightning. If its a tall tower and in a lightning prevalent area, then provide earthing for that reason too perhaps.

On joining ungalvanized steel to galvanized, you didn't say how you join it, but presumably welding. That will destroy the galv at the point of the weld, but as thats submerged in concrete perhaps not so important.

For ungalvanized steel in concrete, the amount of cover is an important factor. Concrete is partly porous, so ungalvd steel close the surface of the concrete will rust and cause concrete failure.

Galvanized steel has been successfully used on reinforcing in concrete in many countries and for many years without problems. But ungalvanized steel is also common inside concrete.

This doesn't sound like a problem.

Geoff Crowley
Crithwood Ltd.
Westfield, Scotland, UK