Rust spots on SS316L weld joints

I use 316L ss for the fabrication of exhaust ducts. Any reason why there are rust spots developing at the weld joints?

Vijay Shenoy
- Houston, Texas

Yes there are lots of reasons.

Top of the list is carbon steel contamination of your weld joints. If you used a carbon steel shipping hammer or carbon steel brush or any tools made of carbon steel you will get rusting.

The parts need to be passivated. Search this site and you will find lots of posts that deal with this issue.

If you have weld color on the stainless steel after the welding process this will prevent the steel from passivating. In this case you need to remove the weld color prior to passivating, or, you need to pickle the parts.

Hope this solves your problems.

John Holroyd
- Elkhorn, WI

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