Corroded (?) Ground

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  #1  
Old 10-31-05, 08:23 PM
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Question Corroded (?) Ground

My newly purchased 1967 home has a standard basement with an addition/dirt crawlspace done ~1985. House has been upgraded to 200 amp service which I presume was done at the same time. Breaker box has two grounds which appear to be aluminum (house wiring is copper). One goes to copper water lines and the second goes thru the crawl space and is connected to a ground rod (someone referred to these as 'white' metal?).

This second ground is broken and appears distressed - almost etched or corroded perhaps - with a light coating of white residue not too dissimilar to that build-up on car battery poles on parts of it - residue does not seem to be acidic like battery poles. I am confused - aluminum is relatively non-reactive. Can this be some other material?

Any idea what the cause is? Am I okay running a copper ground from the box to the ground rod? I would also replace the second ground to the copper water lines with copper. Should I replace the ground rod as well since it is not copper but some greyish metal?
 
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Old 11-01-05, 09:22 AM
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Join Date: Jul 2005
Location: Central Indiana
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There are a couple possiblities that come to mind. One is that the corrosion is simply a natural reaction of copper oxidizing in the ground, which I understand can happen often. Another possibility is that the direct connection between the aluminum grounding electrode conductor to a (I'm assuming) copper ground rod with a non-listed Cu-Al connector is causing electrolysis between the dissimilar metals. Now that I have thrown out my crazy theories, maybe an electrician can shed some light on how this can be corrected in the field, or some other possibilities.

On a related subject, the ground rod has been under fire in the electrical community for what safety related purpose it actually serves, so it's up for discussion on whether or not you need to be worried about this.

Dave
 
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