AMS 2700 Method 1 Type II Passivation for Medical Device
Q. We are quoting passivation of a medical device manufactured from 17-4 H-900 stainless steel. Is anyone aware of any restrictions on the use of nitric acid w/ sodium dichromate to passivate medical devices.
We are set up for this process but not the high concentration-high temp nitric process.
- Colorado Springs, Colorado, USA
A. Type II passivation works well with 17-4. I personally prefer the type VIII because I don't like mucking about with the sodium dichromate. Yet I never had any problems when we did use type II, and a few of our parts were H900 condition.
September 28, 2016
Q. REF: 416 SS passivate per AMS2700 [link by ed. to spec at TechStreet] Method 1, Type 2.
Hello, we've sent many parts to our different passivation vendors and keep getting parts that are "Flash attacked" or etched. This has been a hit and miss for us with the different companies. Is there anything we can do or suggest so that this doesn't continue happening?Jessica Fritter
- Fort Lauderdale, Florida, USA
A. Hi Jessica. You used a gmail e-mail address and haven't supplied company or industry information, so I don't know if your company must comply with this spec or you are the author of the job requirements. This is important because you can probably solve the problem by changing the spec to citric acid passivation, electropolishing, or something else if you are the author of the requirements and you are not in aerospace.
If your vendors must comply with AMS 2700 Method 1, Type 2, one suggestion is that the parts be cleaned better before passivation because some people claim that even minuscule traces of oils can cause this etching, perhaps by generating some sort of organic acid which etches the parts.
Ted Mooney, P.E. RET
Pine Beach, New Jersey
Striving to live "Aloha"
Passivation, but not per AMS2700E suggested typeNovember 4, 2016
I'm creating a passivation series of tests for this, I have to passivate various CRES steels. But I have a Problem with the steel 1.4034 (AISI 420/UNS Code S42000).
In the Standard AMS2700E it's recommended to use Method 1 Type 1-3 (citric is no choice for us), to passivate the specimen. But our favorite choice would be Type 8. Do you have any experience in passivating parts unlike in the AMS suggestions? Do we have to expect degradation of the mechanical properties or something similar?
materials student engineer - Pfäffikon, Switzerland
November 7, 2016
Go ahead and try a small piece of 420 in the Type 8 bath. You'll probably see for yourself why it's not a good idea. (Usually mismatching nitric bath types and stainless grades results in the part being ruined and/or emission of large quantities of toxic NOx gas.)
Citric passivation does have the advantage that if you set it up properly, you can use one bath to handle all your different grades.
Stellar Solutions, Inc.
November 30, 2016
Q. Hey guys,
thanks to your input. I persuaded my Supervisor to at least try the citric solution for the 1.4034.
Our common passivation suppliers don't have much experience with citric acid and asked us for the desired bath temperature/immersion time, citric concentration and whether the bath Needs "additional wetting agents and Inhibitors as applicable".
Do you have any recommendations for us (a little bit more detailed specifications than these in the AMS2700 [link by ed. to spec at TechStreet] would be great)?
Thanks a lot,
- Pfäffikon, Switzerland
December 2, 2016
The parameters you are asking about are given within the 2700 standard, though for 420 you're probably going to want to be at 20 minutes or more even at 65 °C. Of course testing with your parts against desired performance levels is recommended as well.
As far as the additives, they aren't absolutely necessary, but I like to think they do help quite a bit, since that's essentially what my product is. If you are interested, click the link next to my name and you can get my contact information, then I can direct you to my distributor in Germany.
Stellar Solutions, Inc.
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