NEC - Dielectrics and galvanic corrosion

Ever wonder about how dielectrics are part of the National Electrical Code? I was doing some research and found this article on transorbelectrical.com talking about how the National Electrical Grounding Research Project (NEGRP) did some studies on how dissimilar metals resulted in galvanic corrosion, which lead to NFPA updating article NEC 250. 

The article basically covers why a galvanic grounding rod needs to be a 0.625" (5/8") diameter, while a copper grounding rod only needs to be a 0.5" (1/2") diameter. The two rods were buried in the same soil for ten years, one was copper bonded and the other was galvanized. When they dug it up the galvanized rod was mostly eaten away while the copper bonded was corrosion-free. 

I don't know if this corrosion was caused by the soil or from being tied to a dissimilar metal, there was a chemical reaction that caused an anodic reaction.

Under the same reasoning, aluminum alloy clamps are not allowed because they would simply corrode by a galvanic cathode (such as copper). If you ever want to check out what metals are good to use, just google "Galvanic Table". Items listed as Anodic have a tendency to corrode. 

If for any weird reason we would need to use dissimilar metals I heard of using a Sacrificial Anode. This is basically tying a piece of magnesium  or a even coating your anode with something more anodic (higher in the Galvanic Table). Otherwise try to use something closely related in the Galvanic table to minimize the corrosion. Same would apply to nuts, bolts, etc.

Reference: http://www.transorbelectrical.com/pq/technical/NECCompliantGndRodR8.pdf

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