Bill:
In general, yes, a passive, sacrificial anode material can be used to
protect against electrolytic corrosion. But you have to know a lot more about
the material to be protected and its environment than we have so far discussed
here on TT.
You can also use an active system in which a sacrificial anode is
connected to the material to be protected but through a DC supply, usually in
the vicinity of 100 Volts and adjustable. This minute DC current (typically a
couple hundred mAs) offsets the natural Galvanic current generated by the
reaction of the metal in the wet electrolyte of the ground. The anodic
material and the set point for the DC rectifier feeding the whole shebang is
determined a priori through measurements of the potential difference between
the protected elements (ground rod, anchor screw, etc) and remote earth ground.
I designed a few of these cathodic protection systems for the electric
utility I worked for some years ago. Most of our Korean-War era substations
had been built with buried ground systems made of scrap boiler steel pipes -
copper was in short supply, needed for jacketing for ammunition at the time.
It was only at these 1950's substations where we had to install active cathodic
protection systems. Never had occasion to design another one since, though.
If you have an underground pipeline (gas or oil) running through your
region, you might want to check with their local engineer. He/she might be
able to give you some pointers about cathodic protection in your area, and
maybe, for some coffee and doughnuts, give you a brief tutorial.
73 de
Gene Smar AD3F
-------------- Original message ----------------------
From: Bill Coleman <aa4lr@arrl.net>
>
> On Jan 16, 2006, at 2:16 PM, k0dan wrote:
>
> > The tower NEVER moved or
> > wobbled; retensioning of guywires never was necessary due to anchors
> > "floating", occasional retensioning only due to stretch of the wires
> > themselves It was a great installation. But, once that slow, hidden
> > galvanic
> > action went past a critical point, BOOM!
>
> Can't one use a sacrificial anode to avoid exactly this sort of
> galvanic action?
>
> Bill Coleman, AA4LR, PP-ASEL Mail: aa4lr@arrl.net
> Quote: "Not within a thousand years will man ever fly!"
> -- Wilbur Wright, 1901
>
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