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topic 2135

Passivate vs. Bisulfate

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since most everybody agrees that passivating is more of a cleaning process, why is it that no one can tell me for sure why a passivate treatment for cleaning only and then performing a Bisulfate treatment after is not practical.

i believe in my experience that the Bisulfate treatment takes off any passivate treatment previously done.

it seems useless to do both when the 2nd treatment is for adhesion purposes, therefore the parts should be cleaned well enough just with the one treatment?

ken neuts


Sorry, Ken, but I can't understand your inquiry. By 'passivation' are you referring to the chromate treatment that is done on zinc and cadmium plating, or are you referring to the nitric acid treatment that is done on stainless steel? I'm afraid that trying to answer a question I don't understand will only muddy the waters :-)

Ted Mooney, Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey


have been looking for a alternative to nitric acid must also conform to gov spec for passivate would like to also have information on getting a brighter finish on stainless steel most 302 series

gary wasielewski
lee spring - Bristol, Connecticut


Citric acid passivation is an alternative. Type 'passivation' into the search field in our Directory of Chemicals and you will find at least two suppliers of alternatives.

Ted Mooney,
Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey


Dear Sir,

I am currently in the semiconductor industry and would like request for the following information. Q: what is the thickness or depth of penetration for both type of process ?

Thanks & best regards

Joseph Yeo
- Singapore


What is the primary purpose of passivating stainless steels? Is it the coating properties or the removal of surface oxides. We primarily passivate after machining process, but shouldn't it also be accomplished after other processes such as welding?

Kevin Evers
aeropower - New Port Richey, Florida


Kevin: The purpose of passivating stainless is to remove iron from the surface and expose more chromium allowing a chrome rich oxide film to form that protects the surface from corrosion. I have several papers on the subject that I would be happy to share with you.

Dan Weaver
- Toccoa, Georgia


Hi, Dan,

If you have copyright control, we would publish them in our library here, if not, we could post the articles names and magazine here.


tom pullizzi portrait
Tom Pullizzi
Falls Township, Pennsylvania


Is the passivation coating on steel an electrically conductive layer or an insulating layer?

Colin Bugden
- England

March 25, 2009

In reading the previous responses, I really felt that there was not a direct answer to whether; Does the passivation of a stainless steel connector shell make the part non-conductive?

Thomas Brown
- Muskegon, Michigan

March 26, 2009

Hi, Colin and Thomas. I can't give you the hard numbers that you'd probably like to have, but passivation only surface enriches the stainless and builds a uniform tarnish layer on it. The contact resistance might be slightly higher than a "fresh" stainless steel, but it is not an insulator.


Ted Mooney, Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey

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