Chloride level for SS 1

[andygo11]

Hi, this may be a old topic. But I met a situation that the original pipe inside a overflow tank was CS + coating. It is produced water service with 0xyen ~ 1ppm and chloride ~270 ppm. pH is about 8. Op. Temperature is ~80C. Now the field consider to choose SS to replace the old CS+coating pipe to save money. If it is austenite SS, chloride is not good news to them. I am thinking to recommend duplex SS instead of austenite SS. Is there any good reference we can got o for this issue? Thanks.

 

[EdStainless]

Is the pH always over 7?
Is there any risk of scale formation?
If the answers are 'yes' and 'no' then at this level you should be able to use a lean duplex grade (2202. 2101. and so on).
Considering how strong these alloys are you can use much thinner walls than with 316L, so the cost difference should be minimal.

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P.E. Metallurgy, Plymouth Tube

 

[SJones]

Don't forget the external environmental conditions in your choice of material. Depending on location, there could be plenty of chloride on the outside. Painting might help, but that introduces an inspection and maintenance burden. The more robust alternative of thermal spray aluminium will not be cheap.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

All answers are personal opinions only and are in no way connected with any employer.

 

[Chumpes]

hello
i would advise not to use austenitic stainless steel 316L in water with [O2] = 1ppm, pH > 8 and [Cl-] = 300ppm above 50°C.
regards

 

316L is not advisable, and at 80°C I have doubts about duplex SS as well.


"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[EdStainless]

If the pH is actually 8, then The questions come down to risks with welds, fittings, and other weak spots.
For more margin you could use 2205, though I still feel that the lean duplex grades have a reasonable chance of working well.
The impact of pH is strong, each change in value by one point is similar to a 30C temp differential.
I do agree that I wouldn't use a 300 series alloy. The risks of pitting and SCC are too great.

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P.E. Metallurgy, Plymouth Tube

 

[Chumpes]

hi
DSS 2205 should be adapted to aqueous environment with [O2] = 1ppm, pH > 8, chlorides = 300ppm up to 150°C, in absence of stagnant conditions, abnormal active chlorine concentration or excessive fouling.

references :
- outokumpu corrosion handbook (free paper version available after consultation of outokumpu)
- arcelormittal : L’acier inoxydable et la corrosion (free download)

regards