Discoloration in an SS pipe
Discoloration in an SS pipe
(OP)
We have a problem of internal dicoloration in a duplex SS pipe. That appears after welding the external reinforcement or saddle of the pipe support.
Can it be avoided with an argon internal atmospher or Nitrogen atmospher in the internal side while welding the saddle?.
Our client has complaint about it.
Regards
Luis
Can it be avoided with an argon internal atmospher or Nitrogen atmospher in the internal side while welding the saddle?.
Our client has complaint about it.
Regards
Luis





RE: Discoloration in an SS pipe
In fact, you must either purge or pickle or mechanically remove the stain.
The brown discoloration associated with welding heat in an air atmosphere compromises the corrosion resistance. I'm sure Special Metals has some papers about it. Search on "heat tint".
Mike Halloran
Pembroke Pines, FL, USA
RE: Discoloration in an SS pipe
Practical Guidelines for the Fabrication of Duplex Stainless Steels, 2nd Edition (16000)
http://www.nickelinstitute.org/en/TechnicalLiterat...
RE: Discoloration in an SS pipe
About cleaning internally(because the dicoloration is only internal) there will be places not able to be reached,
Can be trust in a chemical cleaning with a liquid solution and pasivation?.
A mechanical cleaning and passsivation is standard in a buttweld. But for this case not all weld affected sectors can be cleaned in a mechanical way
Regards
RE: Discoloration in an SS pipe
Mike Halloran
Pembroke Pines, FL, USA
RE: Discoloration in an SS pipe
ASTM A380
ASTM A370
ASTM A923
ASTM E92
ASTM E562
ASTM G48
this practice is common place in desaliantion plants where duplex and super duplex stainless steels are common place.
If sea water is used for hydrotesting and remains stagnant in the piping then corrosion will occur.
Refer tot he gold Coast Desalination Project debacle where many millions of dollars were spent replacing the stainless steel because of these issues.
http://www.couriermail.com.au/news/queensland/tugu...
http://www.couriermail.com.au/news/features/corros...
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