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topic 8703

HOW TO PASSIVATE STAINLESS STEEL SURGICAL INSTRUMENTS


(2001)

Q. PLEASE HELP ME Dear Sir,

I am the maker of Surgical Instruments and am supplying in the local market. I have started my business in April 2000. I am using the local as well as Japanese stainless steel for manufacturing the instruments.

From the last two months, One of my customer had complained to me that at the very first round of autoclave of the instruments, my instruments have caught rust, but the other test have gone well. One of my friend has suggested me that he learnt that such problems of stainless steel is dealt by PASSIVATION PROCESS. But neither me and my friend know about the Passivation process, nor we know about which chemicals are to be used.

I have real trouble because I am unable to selling my instruments. Yesterday I have made a search on the internet and your kind personality was appeared to me with a hope that you will be able to help me in this swear problem.

I request you to kindly guide me how I could come over to this problem and oblige me. Thank you very much for your kind co-operation and will always remind me of your great love for me.

Yours truly,

SULTAN MEHMOOD
- SIALKOT, PAKISTAN


simultaneous (2001)

A. Hello Sultan!

Passivation is a process in which you remove stray iron particles from the surface of stainless steel, and/or enhance the formation of the chromium oxide layer that makes stainless steel resistant to corrosion. It is commonly done in nitric or citric acid formulations.

The first thing that you want to do is go to Finishing.com's home page, and look in the Frequently Asked Questions area- that's Section 4. There is a FAQ on Passivation of Stainless Steel that is worth reading.

Another source of information is the US Federal Specification QQ-P-35C [link is to free spec at Defense Logistics Agency, dla.mil], which you can get free from assist.daps.mil. Click on the Quicksearch button, and type in the "QQ-P-35", and it will get you the document in pdf. It lists only the nitric acid formulations. Several citric acid recipes are given in ASTM A967 [link by ed. to spec at TechStreet] (available from the ASTM at astm.org) and in AMS2700 [link by ed. to spec at TechStreet] (available from the SAE at sae.org).

I hope this helps!

lee gearhart
Lee Gearhart
metallurgist

----
Ed. note 5/29/12: That mil specs page has moved around several times over the years, but is currently at assist.daps.dla.mil/quicksearch/
Ed. note May 2013: make that quicksearch.dla.mil


(2001)

A. Dear sir,

By saying "passivation" I believe you mean the thin protective coating film formed on the articles.They are primarily chromium oxides(Cr2O3).We require a minimum level of 12%Cr to ensure a passive layer. Your query does not indicate the "grade" of stainless steel you have used. I feel "austenitic" stainless steel is the best choice. If you have already used this grade then the problem could be some thing else for which I need the exact description of the "corrosion" pattern and how it looks like on the instrument...

Regards,

C.K.Sekar
- Chennai, Tamil Nadu, India


(2001)

A. Sulton:

Much of the surgical instrument industry has gone to using citric acid based products for passivation. These instruments are commonly 410SS or similar, with laser etching. The laser etching is a very weak point in the corrosion problem and must be passivated to pass the autoclave tests.

The trick is to get the passivation required without removing the laser etch marks that the manufacturer wants to remain. This can be attained with a significant improvement in corrosion resistance over the old nitric acid methods laid out in QQ-P-35C.

adv.
Contact us if we can be of assistance.

Regards,

lee kremer
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Lee Kremer
Stellar Solutions, Inc.
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McHenry, Illinois
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June 8, 2009

A. Dear Sultan,
Passivation is removal of free iron and other contaminants from the surface of stainless steel to make it corrosion resistant.
But other factors according to the product and manufacturing practice is also to be considered.
Best Regards,
M. Jahangir

JAHANGIR Mirza
- Sialkot Pakistan



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