Where the
world gathers for metal finishing
Q&As since 1989


-----

316 corrosion in pressure vessel

I work for a small residential water filtration company. Our main product, a filter housing, is manufactured by deep drawing 316 sst. The housing is annealed after drawing but not passivated. Since this is a residential water filter, the corrosive solution is chlorinated water. We are observing localized corrosion in the contact areas between the sst and sealing components. The sealing components are either an nbr o-ring or a tpe washer. Is it possible the sealing components are accelerating the corrosion? is the corrosion caused mainly by the chlorinated water? aside from passivation, are there alternatives to preventing this type of corrosion.

John Manocchio
manufacturer - Sparks, NV
2005

---

Your posting seems to imply that passivation is an impossibly big deal, John. It's a cleaning, a dip and thorough rinsing. What am I missing that you seem to be working so hard to avoid it?

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2005

Hi Ted. thanks for the response. It is not that I am trying to avoid passivation. My current supplier indicated that he felt passivation would not solve the issue. Do you feel that passivation would resolve this issue? thanks, John

John Manocchio
manufacturer - Sparks, NV
2005

---

The simple stainless steels such as 316 don't like chlorides.

Perhaps you should look to a duplex stainless steel such as 2205, or even a super-duplex such as 2507.

Bill Reynolds [deceased]
consultant metallurgist - Ballarat, Victoria, Australia
We sadly relate the news that Bill passed away on Jan. 29, 2010.
2005

---

John,
Given the presence of chlorinated water, no, passivation wouldn't be a permanent solution. It would stave off the corrosion for a while longer than you're seeing now, though. Periodic repassivation of the housing would enable you to still use 316 and keep it corrosion free. citric acid based passivation chemistry would allow your customers to safely perform this as part of the standard maintenance procedure. Let us know if we can help.

Regards,

Ray Kremer
Stellar Solutions, Inc.

McHenry, Illinois

2006