The authoritative public forum
  for Metal Finishing since 1989
-----

Determining Max. Temp SS304 Experienced From its Blue Color?

September 29, 2008

Does anybody know how I can determine the temperature that a piece of SS304 has experienced based on the surface color ?
I am working with a pressure vessel that have an internal screen of this material and I found some holes and warpage in an blue colored area after some time in operation (radial flow reactor), we actually know that this vessel was above 950°F but we would like to determine the maximum temp peak that we experienced.
The steel have not scales so I think it was between 1000°F and 1600°F.
Do you know if is possible to find a chart like that one that exist for "temper colors of carbon steel" but applicable to SS304?

I understand the stain color in heat affected SS will depend on the thickness of the oxide layer but if possible to have it related with temperatures?

Thanks in advance for your help

Luis Marcano
Facilities Engineer: piping, valves, vessels - Long beach, California USA

I don't think so. Even if there was a complete equation and you had it, you could not find the value of a variable without knowing the others. I would imagine the oxide thickness and color is also a function of exposure time, amount of oxygen present vs. affected area, other gaseous species present, previous condition of the surface, among others.

Guillermo Marrufo
Monterrey, NL, Mexico
October 7, 2008