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topic 4158

Yellow marks on stainless steel after passivation?

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I am trying to get some 316 condition B per Astm B-276 tubes passivated. There has been some concern that the passivation process can cause a "yellow Stain" on the inside of the tube from passivation. Has anyone had this kind of problem before? Can anyone provide passivation and guarantee that this staining will not happen?

Kevin Bourbeau
instruments - Billerica, Massachusetts


We have experienced the same problem in the past, but have come up with a solution for this. Please contact us for further information.

Hunter Cutchin
- Easley, South Carolina


More information is needed -- are you using a chromic passivation? If you use a nitric acid based passivation you shouldn't have any staining, unless your stainless is dirty or oily going in, in which case you'll have to preclean it before passivating. Your quality requirements and the end use of the parts will determine the best passivation method, along with environmental restrictions, of course.

Jeff Watson
Jeff Watson
- Pearland, Texas


Kevin: Most passivation is done in a nitric/hydrofluoric solution and as you can imagine, people are slow to dispose of this mixture. This causes it to be used far past its useful life and leads to the type of problem you describe. Contact me for information on how to correctly passivate stainless alloys.

Dan Weaver
- Toccoa, Georgia

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