SUS304 corrosion by high levels of Chloride content in water 1

[sunergy]

How to avoid corrosion of SUS304 (stainless steel) by higher levels of Chloride content in the water (200mg/Liter) while it comes to Solar Hot Water systems in specific.

 

[kenvlach]

Alloy with Mo and a bit of N.
304 is unsuitable for warm chloride solutions; 316 may also be unsuitable depending upon T & [NaCl]. Probably need to use a duplex stainless steel. See
Saltwater corrosion engineering Forum
304 vs 316 for below waterline marine applications on boats
thread307-178690

Some info on duplex stainless steels:

http://www.stainless-steel-world.net/duplex/ShowPage.aspx?pageID=14

 

[EdStainless]

How hot are you going? 180F?
I have some curves based on experience, basically if you can keep the pH up (7.5-8.5) with 304 you can handle close to 200ppm total Cl in solution. This is a pitting limit.
The problem is that if you have crevices then crevice corrosion will start at lower levels.
The other problem is that chloride stress corrosion cracking is a real risk.
Moving to 316 will not get you better pitting resistance (at this pH and temp) and the CSCC will still be a risk.

You may want to look at lean duplex grades. Both LDX2101 and AL-2003 will give you plenty of CSCC resistance. The LDX2101 has pitting resistance slightly better than 304. The AL-2003 is better than 316. In the case of the duplex grades the data indicates that higher alloy content results in higher pitting resistance under these conditions.


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