316l stress corrosion cracking elevated temperature

[KevinNZ]

Can someone please recommend a reference for 316L corrosion resistance at elevated temperature.

We have a system with 316L water pumps operating at 110C and would like pump same fluid at 207C @18bar. What is the change in SCC resistance over this temperature range? Water cl- ~ 2140 mg/l.

Note the water is oxygen free and all the piping and valves are carbon steel.

I have done research and found

"temperature should be seen as a key indicator for susceptibility to
CLSCC"
"If free from oxygen, solutions will not cause CLSCC"
"The 316L stainless steel did not exhibit any evidence of IGSCC in 500°C deaerated supercritical water"

 

[EdStainless]

You do need to be careful because 'oxygen free' mean sub-ppb levels, something that in above ground systems is almost impossible to achieve without using oxygen scavengers.
The supercritical water that you refer to has a total impurity load (all anions and cations and particulate) of <2ppm. No iron in that system.
If there is active corrosion then there is a risk of SCC. I would consider pitting in 316L at 207C and 2000ppm Cl to be rapid. In fact I cannot imagine 316L surviving 2000ppm Cl at room temperature for long.
I don't think that SCC should be your first concern here.

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P.E. Metallurgy, consulting work welcomed

 

[KevinNZ]

Thanks EdStainless

The water source is from underground. We have no problems with this fluid and 316L and 110C.

 

[cap1a79]

Reference from Figure A8-2 "Material Selection for hydrocarbon and chemical plant, David Hansen" (Note that it is a guideline of Cl SCC.)

1. Time to failure at 2,200 ppm of chloride at 250 C - 20 hours

2. Time to failure at 2,200 ppm of chloride at 150 C - 15,000 hours

3. Time to failure at "4,000 ppm" of chloride at 100 C - above 100,000 hours (more than 10 years)






SiHyoung Lee,

 

[KevinNZ]

Thanks for your input.
Our client when with super duplex for this duty. One reason was the quote from the corrosion consultant to report on 316L was more the cost of the super duplex option.

 

[cap1a79]

FYI

https://www.steeltank.com/Portals/0/Pressure Vessels/SSWseminarOct2012/Relative Cost 4 15 2012.pdf

SiHyoung Lee

 

[EdStainless]

Just curious, did they have a thorough specifications with corrosion or impact testing required on all raw materials and as part of the weld qualification?

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P.E. Metallurgy, consulting work welcomed

 

[CH. Lee]

Kev, i wouldn't use 316L to handle 200 'C chloride-laden fluids.
ClSCC is the possible threat, alongside with other damage mechanisms, e.g. pitting, crevice.

SDSS would certainly a better option, with a much higher chrome content, hence the higher PREN, CPT and CCT. The mechanical properties are also more superior that that of 316L. I am not sure why your client claimed that 316L costs more though?


CH. Lee, PhD P.E
Lead Materials and Corrosion Engineer
Intecorr Consultancy

http://www.intecorr.com

twitter.com/intecorr

 

[EdStainless]

A superduplex (>25% Cr) will cost a lot more than 316L, but 2205 should be very close as you will reduce the wall thickness by at least 40%.
The real problem in this application is that if there is a leak, even a microscopic one you will have saturated brine at 200C and oxygen. Both pitting and CSCC will take off rapidly in 316L, and only a bit slower in 2205.

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P.E. Metallurgy, consulting work welcomed

 

On google image search, enter the terms 'venn diagram' and 'stress corrosion cracking' and it will yield the results of 100,000 undergraduate engineering reports.

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