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[TowerTalk] Exothermic Welding?

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Subject: [TowerTalk] Exothermic Welding?
From: (Bob Wanderer)
Date: Sun, 14 Nov 1999 18:42:53 -0800
While your statements below are correct and 
true, Eric, why take chances?  You usually don't know
what the conditions will be (and how they could change).
An ounce of prevention is worth a pound of cure.  

Realize you can have corrosion occur on (for example) a
guy anchor between the part in the soil and the part in a
concrete block.  You can have problems if the anchor goes
through soil strata which have differing pH's (ask Dave K6LL).

Assume the worst case condition and prepare for that.  If there
is a reason you cannot do so, assume as worst case as possible.
No matter what, never assume a best case scenario.

Bob AA0CY 

From:  Eric Gustafson[]
Sent:  Sunday, November 14, 1999 11:38 AM
Subject:  Re: [TowerTalk] Exothermic Welding?

Hi All,

A lot depends on exactly _where_ this connection must be made.
There is absolutely nothing wrong with connections between
dissimilar metals if there is no possibility that both sides of
the connection will be exposed to an electrolyte (impure water,
wet earth, etc.) for long periods of time.

>From: "Bill Heinzinger" <>
To: <>
>Date: Sun, 24 Oct 1999 20:05:45 -0500
>> For ham radio usage, however, unless you have access via the
>> commericial world or a ham club which wants to make a group
>> use purchase, you can do well enough with mechanical
>> manipulations.  If you must use dissimilar metals, make sure
>> you put a "middle man" between them (e.g. stainless steel).
>> 73,
>> Bob AA0CY

>If the ground rod is copper plated steel: and the clamp is
>brass: and the ground braid is copper:
>are these considered dissimilar metals?

If the plating on the steel is thick enough and remains unbroken
(everywhere on the rod - even after being driven and / or
clamped), they are similar.  But if the connection is to be
covered by dirt, a clamp is not a good idea.  In fact, here at my
new QTH I chickened out completely and used several strands of
#00 copper cable for the ground rods.  No steel to dissolve over

You aren't using braid for lightning safety ground conductor are

>Isn't brass and copper almost the same thing for this situation?

Brass is pretty close to copper in the galvanic series.  Most
fittings are not brass but bronze.  Bronze (depending on the
type) is also close to copper in the galvanic series.  But not
close enough for long term submersion in an electrolyte bath
(earth burial).

There are bronzes on both sides of copper in the series.  Silicon
bronze is below copper.  So it would make copper the sacrificial
member of the connection.  Aluminum bronze is above copper so it
would be the sacrificial member.  Then, (going up or more anodic
in the list) there is brass, and higher still, manganeze bronze.
I have no idea which is in most prevalent use for common panel

>Most UL electrical distribution panels use both brass and copper.

Bronze actually.  And the distribution panels are rarely
submerged in water or filled with wet earth.

There are four main issues for a connection which has both
members exposed to the same electrolyte.

1.  How far apart are the members of the connection in the
    galvanic series?

2.  What is the relative surface area of each material exposed to
    the electrolyte?

3.  How active is the electrolyte?

4.  How long will the connection be exposed to the electrolyte?

Manipulation of those four variables is all the opportunity we
have for increasing the longevity of a connection between
dissimilar metals.

73, Eric  N7CL

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