Corrosion Resistant Alloys (CRAs) in SOUR Service

The Aim: Appreciation of the requirements for sour service, including materials testing, Standards and Specifications.

CRAs in sour service

• Definition
• Problems – corrosion and cracking
• Cracking mechanisms and avoidance of damage
• Standards and specifications
• Testing of materials

Factors affecting SSC include:

• Metallurgical condition and strength of the material.
• pH of the water phase.
• H2S partial pressure.
• Total stress (residual plus applied).
• Exposure period.
• Galvanic effects.
• Presence of other species – e.g. chlorides, oxygen

CRAs – Corrosion in Sour Conditions

• H2S stress corrosion cracking
• Anodic process, combination of H2S & chloride
• Increases with increasing temperature
• Corrosion
• Temperature, chloride, H2S
• Effect of atomic hydrogen on CRAs
• Hydrogen embrittlement
• Sulfide stress cracking in CRAs
• H₂S stress corrosion cracking of CRAs
• Anodic stress cracking of CRAs
• MR0175 limits for austenitic s/s
• MR0175 limits for duplex stainless steels
• MR0175 limits for nickel alloys
• NORSOK M-001
• Testing for sour service assurance
• Avoidance of SSCC
• Standards and Specifications