CHLORIDE S.C.C IN 316 SS - AMBIENT TEMPERATURE.

[ibf]

Dear Fellows:

We are manufacturing a 316 SS slurry tank which will be working at ambient temperature (78 F ). The amount of chloride in the water process is ~ 2000 ppm . It is not a pressure vessel, and there will be constant exposure to the atmosphere. The water will be constantly agitated with the slurry.
We have suggested the client to use at least 316-L grade , and have the tank passivated. The client refused both suggestions.

Questions: At the above-mentioned conditions , am I at risk of having S.C.C ?

Please let me know if you need further data to answer my question.

 

[TVP]

Yes.

 

[ibf]

TVP : Could you please give me more details. What is the minimum temperature to avoid SCC to happen with that amount of chloride ? I mean , what is the threshold limit (temperature wise) for that amount of chloride ? Is there a literature where I can find more info about the correlation of ppm x temperature ?

Thanks.

 

[EdStainless]

What is the pH?
I doubt that CSCC will be your biggest problem. At high Cl levels and high stresses (these will happen somewhere in the tank) I have never seen non-sensitized 316 crack at temps below 120F. Are you sure that no part of the tank can get warmer?

There is no Cl threshold. I have seen 304 and 316 cracked in the lab in 1ppm solutions and less.

I am assuming that crevice/under deposit corrosion will get you first. Any place that the slurry can settle will create crevice conditions and you have plenty of chlorides to drive that

How thick is the tank? Could you reduce the walls with stronger material? I suggest that you look at lean duplex grades like LDX2101 and AL2003.

= = = = = = = = = = = = = = = = = = = =
Corrosion, every where, all the time.
Manage it or it will manage you.

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[ibf]

Thank you Ed.

1. PH is higher than 7 (alkaline condition).

2. It is not supposed to have temperature higher than 30 C.

3. Tank will be made out of 316 L by using 3/16" - thick plates.

4. We always used rubber-lined thicker carbon plates w/o. any problem at all. In this case it`s a customer request, and we are trying to change its mind to go back to carbon.

 

[EdStainless]

The high pH does help you, some.
Thr problem with SS is that if this gets shut off and just left to sit, or if someone cleans it with the wrong stuff it is history.
Though it does get you away from the risk of liner damage.
I would still prefer a lean duplex for this application. Though I don't know how much lighter you want to make the walls.


= = = = = = = = = = = = = = = = = = = =
Corrosion, every where, all the time.
Manage it or it will manage you.

http://www.trent-tube.com/contact/Tech_Assist.cfm