HTHA and H2-H2S Corrosion 1

[CoCoE]

Hello my dear Fellow members,

I am daily coming across both HTHA and H2-H2S Corrosion material review , and I do use the Nelson's curve and Couper Gorman curves for my selection. The question coming to me daily is that why don't we verify HTHA in an H2S containing environment? And Today my question came to the interest since I have met such an interesting service. In the current service (which contains approx 8% H2S and 710 psi H2 partial pressure), CS is suitable if I consider couper Gorman curves, but when I cross checked with HTHA, then I can't use CS, rather I must go for at least Low alloys.

What is your opinion in this? Is there any alleviation of damage by the presence of H2S in a Hydrogen containing environment sometimes? In my experience, I feel presence of H2S aggravates the damage.

this is wonderful for me, hope for you too. So give me some advise.

Cococa

 

[SJones]

They are two different degradation mechanisms: one occurs at the metal gas interface, the other occurs within the metal itself. It is possible that the generation of the corrosion product from the reaction at the metal gas interface could influence access of the hydrogen to subsurface regions, thus influencing the rate of development of HTHA. Why not try a literature search?

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.

 

[CoCoE]

Jones, Great to see your reply.

I have already done many searches, and I could not find a convincing answer on this. I need to fix my philosophy of material selection in judging HTHA on H2-H2S service also. It's not a walk in the park for me even many feel otherwise.

Cococa

 

[SJones]

If you have no reliable objective evidence for a reduction in degradation severity, then assume the worst case and determine what the value implications are. The technical safety specialist then has something to work with for demonstrating ALARP.

http://www.hse.gov.uk/risk/expert.htm

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.

 

[blacksmith37]

For what it's worth ; I can promise you that Al Couper never considered hydrogen attack when developing corrosion curves.

 

[Chumpes]

Dear Cocoe
you ve got 2 different types of damage here :
- generalized corrosion due to sulfur species at high temperature (couper & gorman, McConnomy, other curves from API 939-C)
- hydrogen attack (Nelson)

you ve calculated that you can control generalized corrosion with selection of carbon steel, but it cannot be finally selected because it is not suitable regarding Nelson curves.

thus you should now evaluate the material induced by Nelson curves (low alloy steel) and check if it is suitable regarding couper&gorman (it will if carbon steel is)

I hope it helps
regards

 

[DBreyer]

Cocoe,

if anything H2S will make HTHA worse since it acts as a dissociating agent, leading to the formation of atomar hydrogen from H2 which can diffuse more easily into the metal. Additionally the H forming in the corrosion reaction btw.H2S and the steel may diffuse into the steel.

Daniel Breyer
Inspection Engineer

http://lnkd.in/dFcQA-w

 

[Chumpes]

quote :
DBreyer (Materials)
Cocoe,

if anything H2S will make HTHA worse since it acts as a dissociating agent, leading to the formation of atomar hydrogen from H2 which can diffuse more easily into the metal. Additionally the H forming in the corrosion reaction btw.H2S and the steel may diffuse into the steel.

end quote

true that H2S enhance HTHA but then I think DBreyer maybe make a confusion between higth temperature sulfidation and wet H2S cracking processes ?
H2S is poisonous for atomic H recombinattion thus increase hydrogen permeation rate in wet H2s environements