Galvanic Corrosion [RE-wrenches]

[Bill Brooks]

Jim,

I understand the concept of galvanic corrosion and cathodic protection, and
the difference between that and soil corrosion due to soil acidity. I think
your discussion of copper electrodes answers the question. Use copper
electrodes and this is really not much of an issue and will save a lot of
copper in the process.

If lightning is an issue, which it is in many places, I will usually bury a
bare copper grounding electrode conductor connecting the two ground rods
together for maximum protection--no galvanic corrosion because no potential
difference. Also no grounded conductor connection to ground at the array.
Surge arrestors on all conductors (grounded and not grounded).

Bill.

> -----Original Message-----
> From: Jim Easton [mailto:jeaston at ucsd.edu]
> Sent: Thursday, July 19, 2007 8:24 AM
> To: RE-wrenches at topica.com
> Subject: Re: Galvanic Corrosion [RE-wrenches]
> 
> 
> Galvanic (Electrolytic) corrosion caused by DC current flow is different
> from corrosion caused by soil composition.
> 
> Galvanic corrosion such as that caused by a DC ground loop will remove
> metal
> from the side being corroded in virtually exact proportion to the current
> flowing and the time it flows.
> 
> Using copper electrodes can reduce the corrosion since copper has a higher
> electrochemical potential than hydrogen, and the current will
> preferentially
> decompose water rather than corrode the copper. However, any less
> refractory
> metal (i.e. iron, steel, zinc, etc.) exposed to the potential will be
> preferentially corroded leading sometimes to rapid failure. This typically
> applies to steel bolts, nuts, washers, and cores of copper clad ground
> rods
> exposed through abrasion.
> 
> Jim Easton, PE
>  (E 11974)
> 4364 Bonita Road, No. 166
> Bonita, CA 91902-1421
> Tel: 858-527-0240 


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