In article ,
Roy Lewallen wrote:

- You may not be able to clean it enough to re-establish a good contact

- The copper may be gone from the portion of the rod which is beneath
the soil surface, and hence your ground conductivity may be shot.

Surely the ground conductivity doesn't depend on that thin plating of
copper, does it? Isn't the conductivity of rust better than the dirt
it's in contact with?

The conductivity of the rod itself will certainly decrease by some
amount, if when the copper is gone. I don't have a quantitative
figure for this. Whether the rust (from the corroded steel) is more
or less conductive than the soil surrounding it will probably depend
to some extent on the soil conditions... but both will surely be less
conductive than uncorroded metal (be it steel or copper). Every extra
ohm in the current pathway is going to result in an increase in
voltage rise across the grounding system if/when the system takes a
hit.

From what I see (based on a quick skim of the DoD-issued MIL-HDBK-419A
on grounding and lightning protection), the copper plating serves two
important purposes: compatibility with the copper wire, and protecting
the steel of the rod from corrosion. By itself, it doesn't seem to be
critical for carrying the current.

If the copper's gone, and the steel is in direct contact with the
soil, I'd be concerned about the rod suffering some fairly serious
corrosion over a period of a few years. You might end up with a
ground rod which was, in effect, only a foot or so long... it could
break or be badly narrowed by corrosion not far below where it's
hammered into the ground. This might seriously compromise its ability
to shunt the charge of a lightning strike into the soil and keep the
voltage rise on the attached wires to a level that minimizes damage.

It probably depends a lot on the soil chemistry... e.g. acidic soils
would probably be harder on an unplated ground rod that more alkaline
soils, and would degrade it more rapidly.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!