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Passivating 304V SS single-use medical device

We have a single use medical device (a guidewire), that uses 304 SS. We are unsure if this device will need passivation. The device has a machined tip that is welded onto a spring, which has a core running through it. All components are 304 SS. This assembly gets stress relieved at approximately 670F. We would like to know if the heat treating process would produce an inert layer acceptable for human use or do we need to passivate?

Thanu Anidharan
Medical Device - Conshohocken, Pennsylvania
2006

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Thanu:

It is not likely that the heat treating process will form the proper level of passive film. I would recommend testing of the surface to determine the level of passivation existing on the surface.

This testing can be done in a number of ways, and I would recommend running at two tests, including an ESCA evaluation of the surface chemistry, especially for determination of the chromium to iron ratio (should be greater than 1.5). Also, run a corrosion test, like a salt spray test or a CPT (critical pitting temperature) test to determine the corrosion resistance of the surface.

From our experience with welded surfaces, you will find it necessary to passivate the surface after welding and heat treating, unless the heat treat process included a passivation process or exceptional gas chemistry controls.

Thanks,

Daryl L. Roll
Costa Mesa, California, USA
2006

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It would be highly advise to passivate this part. Most medical and surgical application require this. There are easy, excellent performing citric products available that should give you what you need. Let us know if you need help.

Lee Kremer
Stellar Solutions, Inc.

McHenry, Illinois

2006