I've found electrolysis to be especially destructive in the construction of
some of those High Rises with the aluminum skins. I used to ride up and down
the outside of those buildings looking for corrosion. We replaced lots of
bolts and used a phenolic washer so the bolt didn't contact the aluminum.
I always make sure my 'sacrificial anode' on my boat motor is patent.
How could we utilize that concept of 'sacrificial anodes' to protect our
----- Original Message -----
From: "Roger Borowski" <K9RB@bellsouth.net>
To: <TOWERTALK@contesting.com>; "Bill Steffey" <email@example.com>
Sent: Wednesday, February 06, 2002 4:08 PM
Subject: Re: [TowerTalk] Universal Freestanding Tower
> Actually, Bill, its a phenomenon called electrolysis that caused the steel
> bolts to appear to be "rotten in the middle", as you say. It is caused not
> by the steel, the aluminum, or the rain, but a combination of the three.
> When two dissimilar metals, such as aluminum and steel come together at a
> junction, a small electrical voltage is created and over time one
> in this case the steel of the bolt, becomes the sacrificial anode, while
> aluminum tower becomes the cathode. When you add moisture to the mix, from
> rain and humidity, the electrolysis is accelerated and the sacrificial
> gets eaten away at the junction area, while leaving the bolt head and
> exposed surface of the nut appearing fine. The area of the bolt in contact
> with the aluminum tower was rapidly corroding away but was hidden from
> sight. You could actually take a millivolt meter and measure the voltage
> created by these junctions, measuring from the head of the bolt to the
> leg. The "electrolyte" created from these junctions of dissimilar metals
> acidic, which further accelerates the corrosion of the sacrificial
> in this case, the bolt shanks.
> Steel bolts, being plain, cadmium plated, galvanized (zinc coated), or
> whatever is a poor choice of fasteners against an aluminum surface but the
> degradation could be slowed significantly by the utilization of a
> type of coating, such as penetrox or noalux on the bolts or better yet,
> using this type of coating on stainless steel hardware, which also
> the stainless steel hardware from galling upon assembly and disassembly.
> Stainless Steel fasteners should never be installed dry as galling will
> occur guaranteed! When coated with an anti-seize paste stainless steel
> hardware for fastening all antenna and towers applications will last a
> The above facts can be verified in any primer books on metallurgy. The
> minute voltages created by dissimilar metal junctions is the principle of
> which thermocouples operate.
> 73, -=Rog-K9RB=-
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