Regarding the 'passivation' of stainless steel

[Walt Welch]

A recent thread mentioned the 'passivation' of stainless steel:
http://www.bladeforums.com/ubb/Forum54/HTML/000489.html

The mechanism of action of this process was said by the author to be the oxidation of Cr, which enhances corrosion resistance. I had always thought that passivation was a process used only on austenitic stainless, but the thread was concerning martensitic stainless.

Further, I have read that the actual mechanism of action was somewhat controversial, and Cr oxidation might not be the primary factor:
http://www.finishing.com/faqs/sstpass.html

The above URL is a site where metallurgists share their real world experiences with this process. The exact effect of 'passivation' is variously given as the removal of any carbon steel, or the removal of organic compounds and 'tramp' metals such as Al, and other considerations are mentioned as well.

Have any of you posters had experience with this process, and can you comment on just what it accomplishes, and how it does so?

Thanks, Walt

 

[UffDa]

I'm no expert, but I remember from classes when I was an apprentice tool and die maker that passivating was an acid bath to remove any traces of carbon steel from stainless.

I know that carbon steel can start a rusting process in stainless that is hard to stop. I
also know that aluminum can cause cause stainless steel to corrode, especially in transmitting antennas.

There may be more to it then that, but that's all I remember

 

[mikeS]

As a weldor thta works stainless , any contact with carbon steel would show up as rust, chipping guns, chains, cables,grinding wheels that previously had been used on carbon steel were forbidden as they would cause problems. Some special jobs were built under a tent in the shop to steel dust drom the air off the unit(customer specs), even magic markers and duct tape were not allowed because of chlorine contamination. I believe, and I did not have anything to do with the process that passivation remove the contaminated (skin) or chrome oxide that the stainless produces and allows a fresh (uncantaminated skin) oxide to develop.

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