Letter 25043

Passivation of stainless steel  

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Thought everyone may be interested in this article from Modern Machine Shop magazine. It is about passivation of stainless steel, a confusing subject.

http://www.mmsonline.com/articles/100304.html

We braze 304L stainless steel assemblies. The braze furnace is run at around 2000 degrees F, and has a highly reducing atmosphere. Any protective oxides are wiped out in this process. We have data that shows a brazed stainless part will show a lot more rust in salt spray than stainless before braze. This is normal, and does not usually cause problems, but recently we've had rejections for rust on production parts. We've been looking into this and think moisture in our dunnage may be at fault. In our research, we also found the above article. Any comments?

Tim Neveau
2nd tier automotive - Rochester Hills, MI, USA

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