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Thermal Passivating

We are looking for a shop that does "thermal passivating." Our print call for thermal passivation at 800° . Who does this? The material is stainless steel.

DEBBIE SIEMERING
- UNION, NJ
1998

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I am not familiar with a process such as that. SS will oxidize at that temp in an air environment and probably give a light tan or buff color. This nickel or chrome oxide formed is quite corrosion resistant to many, but not all, environments.

Neglecting certifications, anyone with an air atmosphere oven that will get to that temp could do it.

800 F is in the oven category and they are not horribly expensive on the used market.

800 °C is a furnace and are significantly more expensive than ovens.

Vacuum furnaces do the exact opposite, giving an oxide free surface if the temp is high enough.

James Watts
- Navarre, Florida
1998

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Debbie:

Look to a local heat treater for this process. It sounds like a heat treat process called Nitriding or Nitriting, in which steel is subjected to an atmosphere of ammonia ⇦ this on eBay or Amazon [affil links] and nitrogen at elevated temperature to harden and corrosion inhibit the steel.

Someone out there that knows heat treating will know what the process is.

Good Luck,

  
Craig Burkart
- Naperville, Illinois
1998

 

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1998

Debbie,

The semiconductor equipment industry thermally passivates stainless steel to make a thick dense oxide layer. It is normally done at 550 °C in very dry air (-100 °C dew point). If you don't use dry air you will get a nodules. Consult Handbook of Vacuum Technology [on Amazon affil links] (1996) edited by Dorothy Hoffman et al or Handbook of Physical Vapor Deposition (PVD) Processing [on Amazon or eBay or on AbeBooks --> affil links] (1998) by Donald M. Mattox for references. I don't know what would happen at 800 °C though you would certainly anneal the stainless steel.

Donald M. Mattox
Society of Vacuum Coaters
Albuquerque, New Mexico

I am trying to find a thermal passivation process for 434L SS powder metal material which will improve corrosion resistance. Can anyone help me out - is this possible? What are the temp, atmosphere, type of furnace, etc use for such a process.?

Michael Gersmeyer
- Bartlett, Illinois, USA
2000