316 stainless and copper corrosion

[zinman]

Will direct connection of Type L or K copper pipe to 316 sst underwater present a corrosion problem?

 

[EdStainless]

What kind of water? what is the conductivity?
Probably, yes.

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Rust never sleeps
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[zinman]

I dont know the conductivity but the water is quite hard. My guess is that the TDS is high for potable water, probably over 600 ppm.

 

[CalvinKelly]

The copper will galvanically corrode.
James Kelly

James Kelly

http://www.rolledalloys.com

 

[EdStainless]

Your copper will not last long.
Even if you electrically isolate the parts you will see preferred attack of the Cu in these conditions.

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Rust never sleeps
Neither should your protection

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[kenvlach]

Under 'normal' conditions, the copper will corrode.
Remember though, only SS in the passive state (usual) is more noble to copper. SS can become active & corrode if the surface oxide passivating film is disrupted by the presence of certain ions or acids. A study of nobility inversion in galvanic corrosion in the Cu-316 SS system caused by Fe(+3):

http://images.katalogas.lt/maleidykla/che24/C-203.pdf

One conclusion (with which I am sure all will agree):
"From the practical point of view, any galvanic contacts of stainless steel, carbon steel and copper in water are undesirable."

For more information on preventing all types of corrosion when using stainless, see

http://www.nickelinstitute.org/inde...+Prevention&ci_id=6579&Submit.x=14&Submit.y=3

 

[zinman]

Thanks to all for your responses. I am going to install a nylon bushing between the copper and the stainless, so there will not be any direct contact.