Metal finishing Q&As since 1989

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Medical Device Passivation

We are using nitric acid to passivate a 17-4 orthopaedic device. I would like to propose that we change over to citric acid but am unsure of a couple things. If we laser etch before citric acid passivation, will we lose the etching? Our passivation room is set up for nitric. How difficult/expensive will it be to switch over? How do I figure out the right formulation for out requirements?

Thank you for your help.

Ann Marie Vittorio
Medical Device Manufacture - Massachusetts
2005

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First of two simultaneous responses --

We are familiar with all of the requirements to do this, and it is very easy to switch to citric acid formulations that will work in the same equipment as you now have. 17-4PH grade can present some different needs depending on what kind of stock you are using, but we can handle that easily. We currently handle other orthopaedic devices at a variety of customers.

Using the correct citric formulations and laser marking specifications there is no problem in removing the laser etch mark.

Contact us and we can help you get set up.

Lee Kremer
Stellar Solutions, Inc.

McHenry, Illinois

2005

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Second of two simultaneous responses -- 2005

Ann Marie,

citric acid does slowly remove the black mark from laser etching, but we have found that if you use enough power in the laser you can passivate the area effectively without totally removing the mark. You shouldn't have any problems using a citric formulation with your existing tanks. Information on citric passivation is given in the ASTM A967 specification. Let us know if we can help.

Ray Kremer
Stellar Solutions, Inc.

McHenry, Illinois