dissimilar metals

[wireday]

If copper piping touches the EMT that would be a problem? If aluminum MC touches the copper piping that is ok? Correct?

 

[Dennis Alwon]

Well, I don't know for sure but there is galvanic reaction between copper and aluminum. I do know that roofers have had issues with aluminum flashing and copper roofs.

 

[mopowr steve]

Not sure but I had an inspector tell me to put separation between a piece of EMT and copper water line that were touching not to long ago.

 

[drcampbell]

If there's any moisture present, zinc in contact with copper will corrode quite quickly. Steel will also corrode quickly, but less so.



http://www.atlassteels.com.au/documents/TN7-Galvanic_Corrosion_rev_Aug_2010.pdf

 

[Carultch]

If there's any moisture present, zinc in contact with copper will corrode quite quickly. Steel will also corrode quickly, but less so.

View attachment 17918

http://www.atlassteels.com.au/documents/TN7-Galvanic_Corrosion_rev_Aug_2010.pdf

Aluminum and stainless are on opposite sides of that chart. Yet stainless is the most common fastener used with aluminum base materials. What is the explanation for why this is an acceptable material combination? And is galvanized steel on aluminum an acceptable combination?

Another mystery is that tin is often used as a buffer material between copper and aluminum, such as tin coated aluminum lugs being dual rated for both copper and aluminum wire, yet tin is no closer to aluminum than copper.

 

[MiElectrician]

I asked foreman about the mc being run near copper pipe in a bathroom and he said to tape the pipe so they don't actually touch

 

[rlundsrud]

I asked foreman about the mc being run near copper pipe in a bathroom and he said to tape the pipe so they don't actually touch

This would eventually fail as the two metals would move through heating and cooling cycles and wear through the tape over time. Having enough space to prevent contact is really the best method.

 

[big john]

For electrolysis to occur, you need an electrolyte like water.

I think in a dry environment galvanic corrosion will be very minimal. It's honesty not something that would worry me.

 

[kwired]

This would eventually fail as the two metals would move through heating and cooling cycles and wear through the tape over time. Having enough space to prevent contact is really the best method.

Enough tape and it is going to take a very long time.

I've seen copper tubing strapped with EMT straps many times - those that know what they are doing will wrap the tubing with tape before putting such a strap on it, and they put several wraps not just one layer.