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Will 316 SS corrode/rust when immersed in hard water environment?

Q. We intend to use 316 ss for making products which are used inside water for long duration and heat ~ 90DegC (SS is immersed in Hard water/normal water).

Question is will there be corrosion on this material? if "yes" is there any other SS grade which can withstand corrosion/rust under these conditions.

The material has to be formed and needs blanking process.

Suresh [last name deleted for privacy by Editor]
- Singapore

A. You will need to have the unit passivated and I would prefer that it was electropolished, otherwise it will rust.
You might see it become coated with salts from the hard water over a long time.Years.

James Watts
- Navarre, Florida


A. Answer: It depends upon the composition of the water, whether the SS is stress-relieved after forming and welding, and whether there are any joints with crevices. My guess is that 316 SS is marginal for this application; a more suitable grade is UNS S31803 (Alloy 2205). See the graph 'Pitting Corrosion in Marine Applications' at

Pitting of 316 SS at 90°C occurs above 200 ppm chloride, and at lower concentration at welds, bends and crevices. As S31803 is roughly twice as strong and more corrosion-resistant than 316 SS, thinner material can be used to offset the higher price.

Ken Vlach [deceased]
- Goleta, California

contributor of the year honored Ken for his countless carefully researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at, continue to benefit from.

Q. Hello Sir,

First of all thank you for your wonderful answers. I have a question. I am working on a project where I have to use some conducting metal rods (say SS316) inside the water. The rods will be inside water for years and it should conduct all the time. So it must be highly corrosion resistance and at the same time it should not be expensive. Can you please suggest me a suitable material that can be used for this application?

Sameer Chouksey
- Bangalore, India
March 21, 2015

A. Hi Sameer. If it's "just water", I think 316SS is fine. As James says, it should be passivated, which would be normal manufacturing procedure I would hope.


Ted Mooney,
Ted Mooney, P.E.
Striving to live Aloha - Pine Beach, New Jersey
March 2015

March 26, 2015

A. Sameer,
When you say "conducting metal rods" are you implying electric current? Depending on the set-up that can be a quick way to destroy many types of metal.

ray kremer
Ray Kremer
Stellar Solutions, Inc.
supporting advertiser
McHenry, Illinois
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