Duplex SS for SRB corrosion

[andygo11]

I have a question regarding the metallurgy for SRB corrosion protection. It was extensively reported that SRB corrosion can eat stainless steel and casue localized corrsoion, like 304L. I am wondering if duplex SS has the same problem in SRB enviroment? Since it is harder than austenite alloys. Thanks.

 

[metengr]

Yes, it will suffer the same problem. MIC will affect almost all metals with the exception of Ti alloys.

 

[gr2vessels]

There is some extended resistance to the H2S cracking of Duplex Stainless Steel compared with Austenitic Stainless Steel, but it depends on the partial pressure (less than 10 kPa abs), temperature, additional chlorides, low pH, etc. Look up in NACE MR0175, there are also extensive studies on the topic on the net.
Cheers,
gr2vessels

 

[EdStainless]

When you get to highly alloyed SS grades (superaustenitic, superferritic, superduplex) you will find functional resistance to MIC related corrosion.
The strength or hardness of the alloy has no role in this.
It is simply the chemical stability of the alloy.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[andygo11]

Any reference to support the conclusion that SRB corrosion can deteriorate duplex ss?

 

[metengr]

Search the internet and you will find what you need.......................

http://www.nace.org/cstm/Store/Product.aspx?id=a4d8e4ad-7270-de11-ae9c-0017a446694e

 

[stanweld]

MIC (SRB) related corrosion has been reported on duplex stainless steel and nickel-chromium-molybdenum alloys as well as a host of other materials.

 

[SJones]

Don't forget that the 'I' in MIC stands for 'influenced.' This choice of wording is to convey the concept that the microbiology itself doesn't necessarily have to be corrosive; it can simply create the conditions for other types of corrosion to take place. The duplex parent material may have a higher inherent corrosion resistance than the 304L, but any welds could still be susceptible.

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.

 

[mrfailure]

You also do not need MIC necessarily from SRB. For example, I evaluated a duplex pump impeller shaft exposed to stagnant water. Selective MIC attack occurred primarily on the martensitic layer while ferrite was left alone. I did not confirm SRB in this instance.

 

[OGMetEngr]

Wait a minute, "on the martensitic layer while the ferrite was left alone"? Duplex is ferrite and austenite, not martensite and ferrite. And there is no "layer", only austenite islands in a ferrite matrix.

 

[metengr]

There are duplex ferrite/martensite steels, as well as duplex stainless steels.

Example;

http://www.sciencedirect.com/science/article/pii/S0142112304001951

 

[EdStainless]

When we speak of duplex SS we are talking about Austenite in Ferrite. No other phases.
The F/M SS are martensitic stainless alloys that don't fully harden. Different animals all together and not referred to as duplex.


= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[metengr]

As I said you can have duplex ferrite/martensite (DFM) steels, which are high strength lamellar texture and have absolutely nothing to do with duplex stainless steels. Some of these high strength duplex phase steels have been used in the automotive industry.

 

[gr2vessels]

Andygo11,
You have asked for Duplex SS SRB corrosion. The comments have slided off the track. The Duplex Stainless Steel is the ferrite and austenite alloy at approx 50% (ideally).
Yes, it can be affected by SRB, under specific conditions. Look up the NACE MR0175 for restrictions of use, also check out reputed studies available on the internet. Refer also to the Outokumpu corrosion handbook for further guidance.