Dissimilar metal threaded joints-SDSS to CS & Cu-Ni to CS
Dissimilar metal threaded joints-SDSS to CS & Cu-Ni to CS
(OP)
Dear Experts,
Pls help me with this, I have a threaded connection in the Fire Fighting system where we are connecting CS Blind 2" flange with a 3/4" threaded hole where we are connecting SDSS/CuNi 3/4" Nipple/Pipe NPT(M).
I believe we will have a corrosion issue if we do this because of dissimilar metal joining together.
Can anybody support me here quickly?
Pls help me with this, I have a threaded connection in the Fire Fighting system where we are connecting CS Blind 2" flange with a 3/4" threaded hole where we are connecting SDSS/CuNi 3/4" Nipple/Pipe NPT(M).
I believe we will have a corrosion issue if we do this because of dissimilar metal joining together.
Can anybody support me here quickly?
Thanks & Regards,
Abhijit





RE: Dissimilar metal threaded joints-SDSS to CS & Cu-Ni to CS
The result will be accelerated corrosion of the CS.
How accelerated depends on the water.
If the water is high conductivity the situation will be worse.
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P.E. Metallurgy, Plymouth Tube
RE: Dissimilar metal threaded joints-SDSS to CS & Cu-Ni to CS
RE: Dissimilar metal threaded joints-SDSS to CS & Cu-Ni to CS
Thanks & Regards,
Abhijit
RE: Dissimilar metal threaded joints-SDSS to CS & Cu-Ni to CS
These joints are made all of the time, in fresh water.
If this water is more corrosive then you have bigger issues (the CS piping).
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P.E. Metallurgy, Plymouth Tube
RE: Dissimilar metal threaded joints-SDSS to CS & Cu-Ni to CS
RE: Dissimilar metal threaded joints-SDSS to CS & Cu-Ni to CS
RE: Dissimilar metal threaded joints-SDSS to CS & Cu-Ni to CS
What is often forgotten in galvanic corrosion issues in pipe is earthing/grounding. If both ends of the pipe are earthed by, say, intimate contact with pipe shoes or the like, then isolating the joint between dissimilar materials does no good anyway.
RE: Dissimilar metal threaded joints-SDSS to CS & Cu-Ni to CS
RE: Dissimilar metal threaded joints-SDSS to CS & Cu-Ni to CS
RE: Dissimilar metal threaded joints-SDSS to CS & Cu-Ni to CS
http://www.fppi.com/assets/documents/data/PipeFit_...
RE: Dissimilar metal threaded joints-SDSS to CS & Cu-Ni to CS
Thanks so much for the info. However, why just can't we eliminate the route cause which creates the possibility of leaks due to corrosion.
So I am thinking of elimination this threaded joint itself.
I have asked Material Engg for the same, will keep you all updated.
Thanks & Regards,
Abhijit
RE: Dissimilar metal threaded joints-SDSS to CS & Cu-Ni to CS
Btw we ignore the advice not to use it in combination with Teflon tape, based on the advice of a Dow spec. Twenty years in, we have found that the combination of dense Teflon tape top dressed with anaerobic sealant is the best thread sealant combination- everything else we've tried, and we've tried them all, is inferior.
RE: Dissimilar metal threaded joints-SDSS to CS & Cu-Ni to CS
I will have to try the combination.
RE: Dissimilar metal threaded joints-SDSS to CS & Cu-Ni to CS
This is making it a better joint-No corrosion issues.
Thanks for all the replies, it helped me a lot.
Thanks & Regards,
Abhijit