Summary for 316 ss corrosion in hard water Discussion
316 ss corrosion in hard water is discussed as a case that depends heavily on the water chemistry and fabrication details. Suresh asked whether 316 stainless steel used immersed in hard water at about 90°C would corrode, and whether another grade would be better for parts that must be formed and blanked. James Watts advised that the parts should be passivated and preferably electropolished, warning that otherwise they may rust and may eventually pick up salt deposits from hard water. Ken Vlach added that 316 is only marginal for this service if chlorides are present, especially at welds, bends, and crevices, and suggested UNS S31803 (Alloy 2205) as a more corrosion-resistant alternative. In a later question about rods in water for years, Ray Kremer said that if it is “just water,” 316SS should be fine, again assuming normal passivation.
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
2006
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
2006
2006
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 https://www.assda.asn.au/asp/index.asp?pgid=17991&cid=34299&id=56951
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
Finishing.com 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 finishing.com, 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.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
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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
Stellar Solutions, Inc.
McHenry, Illinois
