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Ted Mooney, P.E. RET
Pine Beach, NJ

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Stainless steel "Tea Staining"

Dear all,

Any one with experience about Stainless Steel can tell me what is the meaning of "tea staining"? Any help would be really appreciated.

Brian Kelley
- Melbourne, Vic, Australia

Brian:

I have heard this term used for a variety of things, but the bottom line is that it is a yellowish brown (like tea) stain on the surface of stainless steel that is usually iron oxide formed from long aging or improper passivation. It can also be sulfides if you are using a high sulfur grade like 303 or other free machining grades. Customers have used this term to us for any staining like this.

Depending on which it is, the treatment is different. You can test this by soaking in 5-10% NaOH overnight. If the yellow stain is gone, it was sulfides or sulphates. You can accelerate this by heating the NaOH (careful!).

Lee Kremer
Stellar Solutions, Inc.

McHenry, Illinois

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