Acorn clamp dissimilar metal

Merry Christmas
kwired said:
Good question. Looking around I can find similar clamps that say they are rated for copper, galvanized, stainless or steel rods,rebar, etc. which makes sense for the clamp itself that is usually bronze, but what keeps the copper conductor that is in direct contact with the rod from having galvanic corrosion with the steel rod? Most other clamps listed for use with rebar have separate contact surfaces for the rod and the conductor and the rod and conductor are not in direct contact within the clamp.
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Physics wise -- the only thing that keeps the connection from corroding is initially it's gas and water tight, due to the compression face to face copper to steel. That's it.

But we all know that rebar rusts quite quickly even without help, and anything near the ground is going to be wet. Eventually that rust will reduce the margin of contact as it eats between the steel and copper.

Galvanic corrosion happens at very low voltages: like tenths of a volt. And you can easily have that voltage difference between true ground and the GEC. You thus have all the elements of galvanic corrosion. The steel will be the sacrificial anode, the copper and brass will be fine.

en.wikipedia.org

Cathodic protection - Wikipedia

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In field inspections this effect is very pronounced near water heaters (inside and out). Encased in concrete who knows? Concrete is porous to water vapor and moisture and is conductive. Maybe we just throw away buildings in the USA too fast to notice. Go to the UK with 900 year old pubs and inns, and find the one with the oldest ground connection and check.....
 
When it comes to the connection to rebar with an acorn there is really no concern for corrosion between the copper and the steel. The reason being if you look at how they're connected together there is more surface contact between the acorn and the copper conductor than there is to the rebar. On the other side of the acorn the bolt (when properly tightened) is actually digging into the metal of the rebar. So even if there were a somewhat poor connection between the rebar and the copper the conductor is still adequately connected to the rebar through tightening of the acorn.
 
Yup. I don't have a cad weld kit. So I braze. It's solid. Any inspector who understands silver solder at high temp knows is a lifetime bond.

There is a special solder for bonding ferrous to non-ferrous. It has a special blue flux on the rod
 
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