NACE MR0175/ISO 15156
Definition
The international standard for materials selection and qualification for sour oil-and-gas service. Sets hardness limits, alloy restrictions, and testing requirements to prevent SSC and related sulfide-assisted cracking.
- Scope
- Materials selection for sour oil-and-gas service
- Sets
- Hardness limits and alloy restrictions
- Purpose
- Prevent SSC and sulfide-assisted cracking
- Standard type
- International joint NACE/ISO standard
Common questions
Why does hardness matter for preventing sulfide stress cracking?+
Higher-hardness microstructures are more susceptible to hydrogen-induced cracking because hardened steel has less ductility to accommodate hydrogen trapped at grain boundaries and defects, so the standard caps hardness to keep material tough enough to resist crack initiation in sour service.
How is this standard used in a forensic failure investigation?+
An investigator checks whether the failed component's material, hardness, and heat treatment actually complied with the standard's requirements for its service environment; noncompliance is strong evidence pointing to material selection or manufacturing as a contributing cause of an SSC-related failure.
Does compliance with NACE MR0175/ISO 15156 guarantee a component will never crack?+
No, it substantially reduces risk for the conditions it covers but does not eliminate it, since factors like unexpected H2S concentration, residual stress, or welding defects outside the standard's assumptions can still lead to cracking even in compliant material.
Related terms
- Hydrogen-Assisted Cracking (HAC)
- The general term for crack initiation and propagation facilitated by absorbed atomic hydrogen. Encompasses hydrogen embrittlement, sulfide stress cracking, and hydrogen-induced cracking.
- Hydrogen Embrittlement (HE)
- Loss of toughness and ductility in a metal due to absorbed atomic hydrogen, resulting in brittle fracture at stress intensities below the...
- Hydrogen-Induced Cracking (HIC)
- Planar crack arrays that form parallel to the steel rolling direction when high levels of hydrogen are absorbed. Common in pipeline steels...
- Liquid-Metal Embrittlement (LME)
- Brittle fracture of a normally ductile metal when it is in contact with a specific liquid metal. Not hydrogen-related but mechanistically analogous:...
- Sulfide Stress Cracking (SSC)
- Hydrogen-assisted cracking specific to H2S-containing environments. Sulfide ions poison the recombination reaction at the steel surface, forcing more atomic hydrogen to enter...