Metal finishing Q&As since 1989

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Information on Passivate

2002

Hi,

We need information about the make up the bath to passivate a stainless steel part (303), our tanks are: one of 520.00 lts. we are going to use Nitric Acid 10% a Ammonium bifluoride 2%. The 2nd. is 1,200.00 lts. with Nitric acid 10% and sodium dichromate 2%. We need to know if have the right make up.

Thank you for this option! Claudia V. Ortega
Industrial Valle de Saltillo - Saltillo, Coahuila, Mexico

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Claudia,

I am not sure about the Ammonium Bifluoride solution, because the Bifluoride, even in such a small amount will act as somewhat of an etchant, but the 2nd tank on the other hand is very familiar to me, we use the same thing, although you will probably want to us closer to 15-18% Nitric and about 2.5% Sodium Dichromate, it works very nicely when passivated for approximately 20-45 minutes, but be sure to go through the proper precleaning processes prior to passivate(soap, pickle, soap, passivate).

Hope this helps you Claudia.

Tony Schmaltz
- Kent, Washington
2002