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Ted Mooney, P.E. RET
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for Metal Finishing 1989-2025
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Too much passivating
2007
Hi Everyone,
We are starting a passivation line to finish the assemblies we build here. Each requires passivation prior to assembly and then again after welding is complete.
My question is, why is it necessary to passivate the pieces prior to welding and assembly? The whole assembly is 321 stainless. Any ideas would be helpful.
Finishing Company - Savannah, GA, USA
Cleaning of the weld area and at least 1/2" on each side (more for thick sections) avoids weld contamination. In addition to precleaning to remove organics, pickling or mechanically cleaning of stainless steels to remove any heat treatment oxide, carbon steel or embrittling elements such as zinc, lead, sulfur, cadmium, etc., is advised. The Welding Handbook (p. 79 in Vol. 4 of the 7th Edn.) specifically mentions pickling with a nitric acid solution as an acceptable method. Check American Welding Society or ASME guidelines or codes that may apply for your product.
Ken Vlach [deceased]- Goleta, California
Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from.
2007
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