Corrosion of Constantan or Copel at elevated temperatures
Corrosion of Constantan or Copel at elevated temperatures
(OP)
I am trying to develop a device that would use a Copel/Chromel thermocouple in a application that might see temperatures up to 1500°F (815°C). I understand that the Copel or Constantan material would be at or exceeding it's upper limits, so I am looking for an alloy that may extend the life of the thermocouple at elevated temperatures. I see there are a few variations of Constantan, but not sure which one would resist corrosion.
Constantan - 44Ni 54Cu
Copel - 43Ni .05Cr 1.75MN 55Cu
Copel X - 45Ni .05Cr .05 Mn 55Cu
Copel XM - 43Ni .05Cr .7Mn 55Cu
Copel XS - 44Ni .9Mn 53 Cu
I can guess that the Ni and Cr are there for corrosion resistance, but such small variation in Mn have to be there for a reason.
The Chromel should be good up to 1100°C at least from what I have found.
Constantan - 44Ni 54Cu
Copel - 43Ni .05Cr 1.75MN 55Cu
Copel X - 45Ni .05Cr .05 Mn 55Cu
Copel XM - 43Ni .05Cr .7Mn 55Cu
Copel XS - 44Ni .9Mn 53 Cu
I can guess that the Ni and Cr are there for corrosion resistance, but such small variation in Mn have to be there for a reason.
The Chromel should be good up to 1100°C at least from what I have found.





RE: Corrosion of Constantan or Copel at elevated temperatures
People like 'E' because it has a high mV/deg output, and this makes it good for use below RT.
However the output curve is very non-linear (9th order) and they are very sensitive to contamination.
Any exposure in dry hydrogen, vacuum, or any sulfur (even small traces) will accelerate the drift of output.
I should add that the Chromel will undergo significant changes as well. These have been documented starting around 1,000F.
The Cr and Mn are there to manage the properties. You can't afford to make ultra-high purity wire for TC use.
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P.E. Metallurgy, Plymouth Tube
RE: Corrosion of Constantan or Copel at elevated temperatures
RE: Corrosion of Constantan or Copel at elevated temperatures
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P.E. Metallurgy, Plymouth Tube
RE: Corrosion of Constantan or Copel at elevated temperatures
RE: Corrosion of Constantan or Copel at elevated temperatures
Many in flame detection service use 30-60 junctions to give 500mV-1V output.
http://www.aqpl43.dsl.pipex.com/MUSEUM/POWER/therm...
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P.E. Metallurgy, Plymouth Tube
RE: Corrosion of Constantan or Copel at elevated temperatures
RE: Corrosion of Constantan or Copel at elevated temperatures