ISO 15156-2:2020

Overview

ISO 15156-2:2020 - part of the ISO 15156 series - provides requirements and recommendations for selecting and qualifying carbon and low‑alloy steels (and the use of cast irons) for service in H2S-containing environments in oil and gas production and natural gas treatment. Focused on preventing cracking-related failures, the standard addresses susceptibility to sulfide stress cracking (SSC) and related phenomena including stress‑oriented hydrogen‑induced cracking (SOHIC), soft‑zone cracking (SZC), hydrogen‑induced cracking (HIC) and stepwise cracking (SWC). It supplements but does not replace applicable design codes and is intended primarily for equipment designed using load‑controlled design methods.

Key topics and requirements

• Scope and applicability: Targets equipment in upstream oil and gas production, natural gas treatment and associated field systems (see Table 1 for specific inclusions/exclusions). Not primarily intended for downstream/refining equipment.
• Cracking focus: Concerned only with cracking mechanisms (SSC, SOHIC, SZC, HIC, SWC); general or localized corrosion and mass loss are excluded.
• Material lists and guidance: Annex A provides a list of SSC‑resistant carbon and low‑alloy steels and includes requirements for cast irons (A.2.4).
• Qualification paths: Options for selection include approved material lists and laboratory qualification/testing (see Annex B). Recognized test methods referenced include NACE TM0177, NACE TM0284 and NACE TM0316.
• Fabrication and hardness: Limits and recommendations for hardness of parent metals and welds, plus guidance on fabrication processes and post‑weld treatment to reduce cracking risk.
• Environmental severity: Guidance on assessing H2S partial pressure, pH and alternative parameters (Annex C and D) and on information to supply when purchasing materials (Annex E).
• Design method note: Applies to load‑controlled designs; for strain‑based design consult ISO 15156‑1:2020.

Practical applications and users

Who uses ISO 15156‑2:2020:

• Materials, corrosion and mechanical engineers specifying steels and castings for sour‑service environments
• Procurement professionals needing purchasing information and material specifications
• Inspection and integrity teams evaluating cracking risk in existing assets
• Designers of wellhead, flowline, gathering, water‑handling and gas treatment equipment Practical benefits:
• Reduces risk of catastrophic cracking failures and associated safety/environmental consequences
• Provides a defensible, industry‑recognized basis for material selection and qualification in H2S service
• Helps avoid costly rework, downtime and reputation risk from sour‑service failures

Related standards

• ISO 15156‑1:2020 (general principles; strain‑based design)
• ISO 15156‑3 (CRAs and other alloys)
• NACE MR0175 (historic equivalent guidance) and relevant NACE test methods (TM0177, TM0284, TM0316)

Keywords: ISO 15156‑2:2020, H2S‑containing environments, sulfide stress cracking, SSC, HIC, sour service, carbon steels, low‑alloy steels, cast iron, material qualification.