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Can't passivate 15-5 and 17-4

We are a small manufacturer of helicopter accessories and have struggled to achieve consistent passivation of 15-5 and 17-4, either by outside shops or ourselves. We are researching alternate processes with the goal of improving corrosion resistance. Electropolish looks like it may be a very corrosion resistant option, but we need a matte or dull finish. Any opinions would be appreciated.

Jason Lemmon
Manufacturer - Aerospace - Vancouver, Washington, USA
2004

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First of two simultaneous responses --

Why can't they be Passivated?

You can always try beadblasting and Electropolishing for a bright matte surface.

Bill Grayson
- San Jose, California
2004

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Second of two simultaneous responses --

How are you testing for proper passivation? 17-4 and 15-5 are not as corrosion resistant as, say, the 300 series alloys. You can try pickling in a nitric/HF mixture, after which air drying will produce a passive surface. Electropolishing will probably be your best bet, and a good electropolishing shop can use a process which produces a non-reflective surface, although that is not very often wanted, and they would probably have to set it up just for you.

Jeffrey Holmes, CEF
Spartanburg, South Carolina
2004