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Green rust on welded corners

I recently have a problem with 'green rust' on some of my stainless steel products. It usually happens on items that are welded in the corners. For welding,we use OK Tigrod 16.30 as the filler on 316 SUS sheetmetal. The product is also later dipped into a chemical that contains nitric acid (10-30%), hydrofluoric acid (<10%) and acetic acid ⇦this on eBay or Amazon [affil links] glacial(<10%). I need to find out what exactly is causing the green rust and what can I do to prevent a reoccurence? Thank you!

Sem Chan
Engineering - KL, Selangor, Malaysia
2005

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Sounds like you are dissolving the metal into nickel and chromium salts by your acid treatment. The acid may be getting into porous welds and when the water evaporates, it leaves the salts behind.

Flush the treated area with hot, then cold water to try to get the salts out of the pores.

  
Tom Pullizzi
Falls Township, Pennsylvania
2005