SCC of Stainless Steel in H2S service

[avinas...@gmail.com]

Dear All,

 

I require your expert guidance on the below matter.

 

As we all know SS matl is prone to SCC (Stress corrosion cracking) in presence of Chlorides.

Now, as per various articles on the net, when this matl is additionally subjected to wet H2S service, the damage due to SCC is increased significantly.

 

So susceptibility of SS to SCC, is more in wet H2S /Sour service.

 

Can anyone put a light on this subject, as to why/how this happens?

 

Regards

Avinash

[Shomenath Bagchi]

Simply put, applied stress (stress energy stored in material) aids corrosion and expand small fissures in cracks.

---

From: "avinas...@gmail.com" <avinas...@gmail.com>
To: material...@googlegroups.com
Sent: Wednesday, June 19, 2013 4:28 PM
Subject: [MW:17980] SCC of Stainless Steel in H2S service

--
To post to this group, send email to material...@googlegroups.com
To unsubscribe from this group, send email to materials-weld...@googlegroups.com
For more options, visit this group's bolg at http://materials-welding.blogspot.com/
http://www.linkedin.com/groups/MaterialsWelding-122787?home=&gid=122787&trk=anet_ug_hm
 
The views expressed/exchnaged in this group are members personel views and meant for educational purposes only, Users must take their own decisions w.r.t. applicable code/standard/contract documents.
---
You received this message because you are subscribed to the Google Groups "Materials & Welding" group.
To unsubscribe from this group and stop receiving emails from it, send an email to materials-weld...@googlegroups.com.
For more options, visit https://groups.google.com/groups/opt_out.
 
 

[avinas...@gmail.com]

Dear Sir,

 

Thanks for your reply.

I agree that  SCC (Stress Corrosion cracking) damage in Stainless steel is multiplied because of STRESS.

 

But my query here is that this SCC effect (because of chloride and stress) is even more damaging in Presence of H2S (sour service).

 

Can you please explain this phenomenon?

 

Following is an extract from NACE MR-0175/ISO-15156 "

"stress corrosion cracking SCC

cracking of metal involving anodic processes of localized corrosion and tensile stress (residual and/or applied) in the presence of water and H2S.

NOTE Chlorides and/or oxidants and elevated temperature can increase the susceptibility of metals to this mechanism of attack."

Regards

Avinash Araj

[Shomenath Bagchi]

H2S is a worse corroding medium for SS than chloride. SCC depends both on corrosive medium and stress.

For details, please check on SCC in Metals Handbook or net.

---

From: "avinas...@gmail.com" <avinas...@gmail.com>
To: material...@googlegroups.com

Cc: Shomenath Bagchi <snba...@ymail.com>; snba...@ymail.com
Sent: Thursday, June 20, 2013 1:47 PM
Subject: Re: [MW:17985] SCC of Stainless Steel in H2S service

[pgoswami]

Avinash,

 

Traditionally offshore  oil and gas production involves both sour (High H2S) and chloride environment (due to high salinity of sea water). Sour service especially in the presence of wet H2S , generates tremendous amount of "nascent hydrogen" which charges on to the materials used for construction.

 

MR -0175 explains in great length what're the consequences of this "nascent hydrogen charging " which causes various forms of hydrogen induced cracking. Hardness control, heat treatment, cleanliness , good welding practices are required to mitigate this.

 

As austenitic S.S is prone to chloride SCC, one has to be very careful about selection of these alloys for sour service. 

 

Table A-2 in  ANSI/NACE MR0175/ISO 15156-3:2009 addresses these  concerns related to both"Chloride Conc" and "H2S partial pressure" and " Max recommended Design Temperature(60 to 149 Deg C)".

 

Note temperature is very critical to avoid Chloride SAC. The 300 series alloy/s  commonly  accepted for sour service is SS 316/316L.

 

The attached document gives a good description of  sulfide stress cracking.

 

Thanks

 

 

 

Pradip Goswami, P.Eng,IWE

Welding & Metallurgical Specialist

Ontario, Canada

pgos...@quickclic.net

pgos...@sympatico.ca

 

 

---

From: material...@googlegroups.com [mailto:material...@googlegroups.com] On Behalf Of Shomenath Bagchi
Sent: Thursday, June 20, 2013 5:23 AM
To: material...@googlegroups.com
Subject: Re: [MW:17986] SCC of Stainless Steel in H2S service

[Arunachalam A]

some useful files on the subject.

--

Arunachalam.A,