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What are the different ways of passivation for SS 316 L and SS 314 L?
I want to remove rusting form 316L SS and 314L SS. I want to know what are the different types of PASSIVATION and which is the best method for it.
If possible please describe method in detail to get the best result.
Hello Hirak. Please patiently search this site and you will find dozens of inquiries, responses, and opinions on this subject. Three passivation methods include citric acid , nitric acid, and electropolishing. There is rarely such a thing as 'best' because the concept is too simplistic. Good luck.
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
If you see rust on stainless steel, I suggest removing the rust as one step and following up with a subsequent passivation. Avoid heavy mechanical removal methods as this may smear the rust into the metal. I have some electrolytic rust removal methods but they aren't commercially available overseas.
In my experience, Nitric acid just doesn't do a good job removing existing rust. Chelant passivation chemicals do a much better job removing rust but are slow. An acid rust remover including phosphoric, glycolic and other ingredients may remove the rust quicker.
After removing the rust, follow up with a final passivation step. I prefer the chelant chemistry.
Passivation of Stainless Steel conventionally is done with about 20-50% Nitric acid. In case rust is present on the Steel it is better if a light re-pickling is carried out on the material and after a thorough water wash to passivate it in a bath of HNO3.Muralidhar Y
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