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316 Passivation

We are manufacturers of Grade 316L hot water tanks, approx. 1000 per month. We pickle using a cold HF/Nitric Acid solution, 6 tanks per dip of about 30 minutes, and then rinse internally and externally using tap water through a high pressure cleaner. Should we be using demineralized water? Should we be dipping in a neutralizing bath after the acid and before rinsing? Any assistance would be appreciated.

Many Thanks,

Tyrone Bagg
- Perth, Western Australia
2003

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2003

What is the problem?

Whether you need to revise your practice depends on whether the end result complies with specification. The specification might deal with corrosion resistance, or mechanical properties, or cosmetic appearance, or many other properties. You know what specification you need to comply with but we don't know, nor do we know whether you are actually achieving compliance. And if you are not achieving compliance, what aspect is deficient?

Bill Reynolds [deceased]
consultant metallurgist - Ballarat, Victoria, Australia
We sadly relate the news that Bill passed away on Jan. 29, 2010.

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Passivate by dipping in nitric acid and wash with water.

Syed Farooq Quadri
mfgr. of costume jewelry- Hyderabad, Andhra Pradesh, India
2003