Chloride stress corrosion cracking in martensitic stainless steel -with 12% Cr and 4% Ni 2

[replica]

Dear all,

I have two questions to ask:

1. Can martensitic stainless steel crack due to chloride stress corrosion cracking (ClSCC) similar to austenitic stainless steel?. I was informed that martensitic stainless steel is not prone to ClSCC but prone to hydrogen stress corrosion cracking or hydrogen embrittlement under H2S environment. Is it true?

2. Does ClSCC always exhibit branching and trans-granular cracks?

 

[EdStainless]

1. With any Ni in the alloy it does become susceptible to chloride stress cracking.
We make a superferritic (Sea-Cure) which is 27% Cr and 1.5% Ni (+4.5% Mo) and we have been able to crack it in laboratory testing. Though it has never happened in the field. These alloys still have very good resistance to CSCC. This alloy should be similar to any other 4% Ni stainless grade, such as some of the lean duplex alloys. However since this alloy has low pitting resistance the risk of pitting corrosion and then Hydrogen cracking from that is very real.
And they are also prone to hydrogen cracking mechanisms, some of the best and some of the worst of both worlds.
2. No always, especially in an alloy like this. There will always be some branched TG cracking though even when the combination of stresses and crack rate causes some IGC.

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P.E. Metallurgy, Plymouth Tube

 

[replica]

edStainless...Thank you very much for the useful info

"This alloy should be similar to any other 4% Ni stainless grade, such as some of the lean duplex alloys. However since this alloy has low pitting resistance the risk of pitting corrosion and then Hydrogen cracking from that is very real.
And they are also prone to hydrogen cracking mechanisms, some of the best and some of the worst of both worlds."

Are you referring the above statement to superferritic (Sea-Cure) which is 27% Cr and 1.5% Ni (+4.5% Mo) or 12% Cr 4% Ni?

 

[SJones]

The question is confusing two issues: ClSCC, presumably without H2S, and H2S cracking. Mix the two together and it becomes a slightly different ball game. There is an influence of chloride on the H2S cracking performance of F6NM/CA6NM (S41500) as evidenced by NACE Corrosion 2015, Paper 5477, NACE Corrosion 2004, Paper 04133, and NACE Corrosion 1999, Paper 584. However, pH also comes into play. The three papers have tended to work with room temperature testing where one would expect any hydrogen effects to be more pronounced. Whether chloride becomes a more dominant factor at elevated temperatures remains to be examined. Certainly, one needs to give thought to the blind suitability of the tables under A.6 of ISO 15156-3.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

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

 

[EdStainless]

I was referring to the 12-4 alloy.
The superferritics have outstanding pitting resistance and in those you would never see hydrogen related issues stemming from active corrosion.

I'll second Steve's comment about mixed environments being very complex.
If the pH is acidic, even just slightly then both corrosion modes become much more likely.

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P.E. Metallurgy, Plymouth Tube

 

[replica]

Sjones...thank you for the info...sorry for the confusion..My question if referring Cl and H2S seperately..

EdStainless...thank you for your clarification.