plating, anodizing, & 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 [affil link] . 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
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
Accurate Anodizing Inc.
Compton, California, USA
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.
Stellar Solutions, Inc.
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 [adv: item on eBay & 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
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
Some AMS specs let you use copper sulphate instead of Sodium Dichromate. It is not a replacement in ASTM A967 [affil link] but maybe if they do their homework they could get away with using AMS2700 [affil link]B instead. Just a thought from me.Kevin W. Gallich
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