Metal finishing Q&As since 1989

-----

I Need Concrete "Cons" to Nitric 1 Passivation with Sodium Bichromate. Please Help!

At this time our Passivation shop uses these methods according to ASTM A967. Nitric 2-5, and also citric acid passivation. It has been proposed that we add Nitric 1 as a service. I am nervous about this. I would like to hear pro's and con's.. to be honest, mostly cons about this method. I appreciate your help!

Faith R. Starks

2006

---

The biggest con is that it introduces another source of hex-chrome into your process: given the fact that OSHA is getting pretty harsh on hex-chrome, the profit potential would have to be pretty huge to make it worthwhile. The second biggest con is that it is more complex to maintain because of the mix of chemicals.

Jim Gorsich
Compton, California, USA
2006

---

With the proper citric based procedures, you shouldn't need nitric baths at all to passivate anything you need to. Adding another nitric bath would just be redundant.

Ray Kremer
Stellar Solutions, Inc.

McHenry, Illinois

2006

Also look at the health issues with Sodium Dichromate. Look up the MSDS and then decide if it is worth it. Check out using copper sulphate [on eBay or Amazon]instead. You may need to do some homework but it may be worth while for you... You also stand the chance of not being RoHS compliant as well.

Kevin W. Gallich

2006

---

Thanks, Kevin, but what are you referring to in mentioning copper sulphate? Surely you can't passivate stainless steel with it?

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2006

Some AMS specs let you use copper sulphate instead of Sodium Dichromate. It is not a replacement in ASTM A967 but maybe if they do their homework they could get away with using AMS2700B instead. Just a thought from me.

Kevin W. Gallich

2006