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How can I passivate stainless steel part without destroying silver solder joints

 

Need to passivate a small stainless steel part that has fittings that are joined by food grade safe silver solder. The problem is that the passivation solution attacks the solder. I have tried both the standard nitric solution and even Citri-Surf, with Nitric being the most aggressive. Any suggestions?

Charles Brown
Fabrication Concepts Inc. - Tamaqua, Pennsylvania, USA

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Clean the part very well and it will autopassivate. Honest this is the right answer.

I suppose I should tell you the rest of the story. One of the reasons for passivating using nitric acid or citric acid is to remove free iron from the surface. Just giving the part a good clean will not remove the free iron. You could however passivate prior to performing the silver solder operation and then just clean very thoroughly after silver soldering and get a good result. By cleaning thoroughly I mean so that you get good sheeting action with water over the surface. Beading is bad and if you get beading or a rapid water break your part is not clean enough.

Good luck and I hope this helps.

John Holroyd
- Ellkhorn, WI

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Charles:

The silver solder should not be attacked by the CitriSurf. We have millions of parts being made and passivated with this product without a problem in this area. Maybe you are using the wrong product. If you contact us we will get you to where you need to be.

Regards,

Lee Kremer
Stellar Solutions, Inc.

McHenry, Illinois

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I agree with the guy from Elkhorn, given that the soldering is low temperature and any fluxes are able to be removed without attacking the silver. Is this part body jewelry, by chance?

Jeff Swayze
- Kelowna, B.C., Canada