Bare Copper EGC in Metallic conduit

[c_picard]

Do you feel this applies, and this is a violation:

358.12 Uses Not Permitted.EMT shall not be used under
the following conditions:
(1) Where, during installation or afterward, it will be subject to severe physical damage.
(2) Where protected from corrosion solely by enamel.
(3) In cinder concrete or cinder fill where subject to permanent moisture unless protected on all sides by a
layer of noncinder concrete at least 50 mm (2 in.) thick
or unless the tubing is at least 450 mm (18 in.) under
the fill.
(4) In any hazardous (classified) location except as permitted by other articles in this Code.
(5) For the support of luminaires or other equipment except conduit bodies no larger than the largest trade size
of the tubing.
(6) Where practicable, dissimilar metals in contact anywhere in the system shall be avoided to eliminate the
possibility of galvanic action.

 

[iwire]

No I do not and no it is not.

If we say a bare copper in EMT is a problem we would also have to say bare copper is also a problem in galvanized junction boxes and other enclosures.

 

[c_picard]

Great point iwire, and I like the simplicity of the argument.

The problem lies in that "where practicable" bit.

 

[George Stolz]

It would lend some credence to the practice of insulating water pipes that come in contact, however. Never pondered that one long enough to look it up.

 

[Smart $]

...The problem lies in that "where practicable" bit.

Not actually. They have to qualify as dissimilar metals first. Galvanizing is zinc. Tinned copper coating is a zinc alloy. These manufacturing processes would not be used if the metals were dissimilar.

 

[don_resqcapt19]

Not actually. They have to qualify as dissimilar metals first. Galvanizing is zinc. Tinned copper coating is a zinc alloy. These manufacturing processes would not be used if the metals were dissimilar.

This chart shows a corrosion risk to the zinc when in contact with copper. In your example, the tinning process would prevent the electrolyte from getting between the copper and the zinc alloy.

This chart shows a copper/zinc cell voltage of ~0.9 volts and says, that cell voltages greater than 0.5 volts can result in corrosion issues.

 

[kwired]

What are typical steel device boxes coated with? We put a grounding screw in the hole and make a direct copper to zinc?? junction with our bonding jumpers all the time in these boxes.

 

[Smart $]

This chart shows a corrosion risk to the zinc when in contact with copper. In your example, the tinning process would prevent the electrolyte from getting between the copper and the zinc alloy.

This chart shows a copper/zinc cell voltage of ~0.9 volts and says, that cell voltages greater than 0.5 volts can result in corrosion issues.

Busted hmy:

 

[acrwc10]

What would you think of bare copper in aluminum rigid.

 

[iwire]

What are typical steel device boxes coated with? We put a grounding screw in the hole and make a direct copper to zinc?? junction with our bonding jumpers all the time in these boxes.

Precisely my point

We need to stop looking for problems where there are none.

 

[kwired]

What would you think of bare copper in aluminum rigid.

I don't see a galvanic corrosion type of problem there, aluminum components are used to connect to copper quite often. Thermal expansion is the bigger issue with copper to aluminum connections.

 

[GoldDigger]

I don't see a galvanic corrosion type of problem there, aluminum components are used to connect to copper quite often. Thermal expansion is the bigger issue with copper to aluminum connections.

As a practical matter, the result would depend on whether the contact(s) took place in a dry, damp, or wet environment. With a dry clean contact point and no soil or other contact with the wire and raceway there will be no galvanic corrosion.

Tapatalk!

 

[iwire]

As a practical mater when I start seeing issues with these ....

... I will start worrying about bare copper in EMT.

 

[GoldDigger]

When you expose that to sea air, you will see problems. But that will seldom happen except in outdoor raintight boxes.
Remember too that outside conduit can be a wet environment.

Tapatalk!

 

[iwire]

When you expose that to sea air, you will see problems.

If I expose that box, or EMT to sea air, or a pool pump room I will see as problem regardless of copper contact or not.

 

[kwired]

As a practical matter, the result would depend on whether the contact(s) took place in a dry, damp, or wet environment. With a dry clean contact point and no soil or other contact with the wire and raceway there will be no galvanic corrosion.

Tapatalk!

So in a moderately clean and dry location you are saying we are missing an electrolyte to help the process along?

 

[GoldDigger]

Yup. If you cannot "dissolve" some of the metal into ions, you have no electrolytic action.
Kind of like a battery without electrolyte generates no current.

Tapatalk!

 

[kwired]

That means the dissimilar metal issue with water pipes likely means they corrode from the inside where nobody sees anything until it is too late.

 

[GoldDigger]

That means the dissimilar metal issue with water pipes likely means they corrode from the inside where nobody sees anything until it is too late.

:thumbsup: 100%
You see external corrosion once a little bit of water starts to leak out or if the environment is damp.


Tapatalk!

 

[iwire]

So we have established water speeds corrosion.