Letter 33054

440C VAC MELT Stainless Steel rusting after passivation process  

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We're having a problem with parts we machined out of 440C VAC MELT stainless steel rusting.

These parts are machined, grinded, heat treated and then passivated. Our customer wants these parts delivered clean, without any oil or WD40 on them. We've done this in the past but the parts rusted and we had to make them again, obviously at a total loss of profit. Our passivation process is very efficient and the parts are cleaned at least twice prior to passivation.

Any suggestions or ideas on how to provent rust using this material would be greatly appreciated.

Thanks,

Thomas Osborne Sr.
- Bainbridge, New York, USA

Try to use electrochemical anodic cleaning. Degreasing will go simultaneously with passivation, and corrosive resistance will probably increase.

Anna Berkovich Russamer Lab Pittsburgh, Pennsylvania

Thomas, what hardness are you achieving in your hardening step? 440C at Rockwell C 60 has far better corrosion resistance than 440C at Rockwell C 55, in my experience.

While not related to your question, why the vacuum melt? Are you looking to reduce stringers (it will) or improve fatigue life? (It won't).

Good luck!

Lee Gearhart metallurgist East Aurora, NY

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