NACE MR-01-75: Material Requirements for Sulfide Stress Corrosion Cracking
Standard for material selection in sour service environments. While primarily a materials standard, it impacts NDT requirements for equipment and inspection planning in hydrogen sulfide environments.
NACE International (now part of AMPP) writes the corrosion, coatings, and sour-service standards that determine inspection scope for hydrogen-cracking-prone equipment.
NACE MR0175 / ISO 15156 is invoked by every sour-service procurement specification in the upstream and refining markets.
NACE MR-01-75 is invoked when the scope of work matches its title — material requirements for sulfide stress corrosion cracking — and when the contract or regulatory regime cites it as the controlling document. On petroleum and petrochemical equipment, NACE MR-01-75 usually feeds into a written mechanical-integrity program: inspection intervals, examination methods, and acceptance criteria are all traced back to a clause number in the document.
Methods covered
Industries
- Oil & Gas
- Pipeline
- Petrochemical
- Personnel qualification: examinations under NACE MR-01-75 must be performed by inspectors qualified and certified to a recognised scheme (typically ASNT SNT-TC-1A, CP-189, or ISO 9712 depending on jurisdiction), with documented training hours, vision tests, and a controlling written practice.
- Written procedure: every examination requires a written, controlled procedure that names the method, equipment, calibration steps, scanning pattern, and acceptance criteria — and is qualified before first use.
- Acceptance criteria: indications are evaluated against the standard's tabulated limits (length, depth, alignment, frequency); any indication exceeding the criteria is recorded, dispositioned, and either repaired or evaluated for fitness-for-service.
- Documentation: examination reports must include enough information for a third party to reproduce the inspection — equipment serial numbers, calibration records, inspector ID, sketches of indications, and the controlling procedure revision.
- Latest Edition
- ANSI/NACE MR0175/ISO 15156:2020 (3 parts)
- First Published
- 1975
- Scope
- Materials for use in H2S-containing environments in oil and gas production — metallic materials selection and surface limits to avoid sulfide stress cracking (SSC).
- Acceptance Criteria
- Material hardness limits (e.g. ≤ 250 HV / 22 HRC for carbon steels); environmental partial pressure limits.
- Calibration / Qualification
- Hardness testing per ASTM E140 with traceable reference blocks; PMI per API 578.
Key Clauses Inspectors Cite
- Part 1 — General principles
- Part 2 — Carbon and low-alloy steels
- Part 3 — CRAs and other alloys
- Annex A — Environmental severity zones (SSC region 0/1/2/3)
Companion / Parent Standards
NACE TM0177 (lab SSC test) · NACE TM0284 (HIC test) · API 578 (PMI)
Sample Contract Language
“All materials in sour service shall conform to NACE MR0175/ISO 15156:2020 Part 2; hardness verified by PMI on receipt and post-PWHT.”
NACE MR-01-75 is maintained on its publishing organisation's revision cycle. The version cited in any contract or written inspection program should be tracked so that revisions can be reviewed against the existing inspection plan and any clause changes worked into the next procedure update.
A typical refinery turnaround applies NACE MR-01-75 to the inspection scope for high-temperature piping and pressure vessels: corrosion-monitoring locations are read with UT thickness gauges, girth welds on repaired sections are radiographed or PAUT-scanned, and any indication outside the standard's acceptance table is dispositioned through API 579 fitness-for-service before the unit restarts.
What does NACE MR-01-75 cover?
NACE MR-01-75 (Material Requirements for Sulfide Stress Corrosion Cracking) is published by NACE International. Standard for material selection in sour service environments.
Is NACE MR-01-75 mandatory or voluntary?
NACE MR-01-75 is a consensus standard. It becomes mandatory when invoked by a contract, by another code that cites it (for example ASME Section V calling out an ASTM practice), or by a regulator that has adopted it into law in a specific jurisdiction.
Who is qualified to perform inspections under NACE MR-01-75?
Inspections under NACE MR-01-75 must be performed by personnel qualified and certified to a recognised NDT certification scheme — most commonly ASNT SNT-TC-1A or CP-189 in the United States, ISO 9712 in much of the rest of the world, and NAS 410 for aerospace work. The written practice that controls qualification must be in place before any examination is started.
Which other standards are commonly cited alongside NACE MR-01-75?
NACE MR-01-75 is most often cited together with the parent code that brings it into the contract — typically ASME Section V or VIII for U.S. pressure equipment, AWS D1.1 for structural welding, API 510/570/653 for in-service petroleum equipment, or the matching EN/ISO standard for European and international work.
Standard Code
NACE MR-01-75
Organization
NACE International
Methods Covered
1 method(s)
Industries
3 sector(s)
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