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What does NACE MR0175 require?
Short answer
NACE MR0175 / ISO 15156 sets requirements for metals in oil and gas production containing H₂S. Carbon and low-alloy steels must meet hardness limits, typically 22 HRC maximum, and corrosion-resistant alloys are qualified within limits of temperature, H₂S partial pressure, chloride and pH. Buyers must state sour service on the order.
Carbon and low-alloy steels
Corrosion-resistant alloys
What buyers should specify
State "NACE MR0175 / ISO 15156 compliant" together with the part and the environmental conditions. Require hardness testing and certificates confirming compliance.
Three parts of the standard
- Part 1: general principles for choosing cracking-resistant materials
- Part 2: carbon and low-alloy steels, and cast irons
- Part 3: corrosion-resistant alloys and other alloys, with environmental limits for each family
MR0175 vs MR0103
MR0175 / ISO 15156 covers oil and gas production. NACE MR0103 (ISO 17945) covers refining environments. They are similar in approach but not interchangeable, so the order must name the right one.
Materials in this guide
Related guides, comparisons and articles
Guides
Frequently asked questions
Is sour service the same as HIC testing?
No. HIC testing (NACE TM0284) checks plate and pipe for hydrogen-induced cracking; MR0175 compliance covers hardness and material limits. Projects often require both.
Does stainless steel meet MR0175?
Many stainless grades do within stated limits. Duplex and super duplex, for example, are qualified within temperature and chloride limits.
Is B7 bolting acceptable in sour service?
Not where bolts are exposed to the sour environment. Hardness-controlled B7M with 2HM nuts is used instead.
Are corrosion indices enough to select a material?
No. Indices such as PREN rank alloys, but temperature, crevices, flow, contaminants and fabrication quality all matter. Use service experience, corrosion data or testing for critical applications.