NACE MR0103 / ISO 17945: Sulfide Stress Cracking Requirements for Sour Refinery Service
NACE MR0103, published now as ISO 17945 and current under the designation ANSI/NACE MR0103-2015 / ISO 17945:2015, sets the materials requirements for resisting sulfide stress cracking in metallic equipment exposed to corrosive petroleum-refining, or wet-H₂S, environments. It spells out which alloys are acceptable, along with hardness limits, heat-treatment conditions and welding controls, so that vessels, piping, valves and instrumentation can hold up under aqueous hydrogen-sulfide service without cracking.
MR0103 covers downstream and refinery work; it's the counterpart to NACE MR0175 / ISO 15156, which handles upstream oil-and-gas production. Both address sulfide stress cracking, but the split by sector is exactly where most of the confusion about this standard comes from. And MR0103 itself is a materials requirements standard, nothing more. It isn't a pressure spec, a dimensional spec, or a product-testing spec.
Crestflo builds instrumentation fittings, valves and manifolds in stainless, duplex and high-nickel alloys, engineered to meet refinery sour-service material requirements. Heat-number traceability comes standard, and every part ships with EN 10204 material test certificates. This page lays out exactly what NACE MR0103 requires, how it differs from MR0175, and which components conform.
Also Known As: MR0103, ISO 17945, ANSI/NACE MR0103-2015
Specifiers reference this standard under several designations. It shows up as MR0103, MR-0103, NACE MR-0103, and ANSI/NACE MR0103, and by edition as NACE MR0103-2015 (current) or NACE MR0103-2012 (prior). Its ISO twin is ISO 17945 or ISO 17945:2015, and the full current designation reads ANSI/NACE MR0103-2015 / ISO 17945:2015. Engineers on the ground call it the refinery sour-service materials standard, the SSC refinery standard, or sometimes the downstream wet-H₂S cracking standard. Different names, same document.
NACE MR0103 at a Glance: Designation, Scope & Hardness Limit
| Attribute | Value |
|---|---|
| Standard name | NACE MR0103 |
| Current designation | ANSI/NACE MR0103-2015 / ISO 17945:2015 |
| ISO equivalent | ISO 17945:2015 (technically identical content) |
| Governing body | Originally NACE International; now AMPP (Association for Materials Protection and Performance) |
| Full title | "Metallic materials resistant to sulfide stress cracking in corrosive petroleum refining environments" |
| Type of standard | Materials / SSC-resistance requirements (not dimensional, pressure or product-test) |
| Damage mechanism addressed | Sulfide stress cracking (SSC) in aqueous (wet) H₂S |
| Sector | Downstream & midstream, petroleum refining, petrochemical, amine plants, gas processing |
| Environment trigger | Aqueous H₂S, with or without hydrocarbons |
| Key hardness limit | 22 HRC max for carbon & low-alloy steel base metal |
| Covered equipment | Pressure vessels, heat exchangers, piping, valves, pump & compressor cases and associated components |
What NACE MR0103 Covers: Refinery Sour Service & Covered Equipment
NACE MR0103 covers the downstream and midstream sector: oil refineries, petrochemical units, amine treating plants and gas-processing facilities where process streams carry aqueous hydrogen sulfide. The trigger is wet (aqueous) H₂S, whether or not hydrocarbons are present alongside it.
The standard covers the metallic construction materials for equipment exposed to that environment, including:
- Pressure vessels and columns
- Heat exchangers
- Process piping
- Valves and instrumentation components
- Pump and compressor cases and associated pressure-containing parts
A key modeling difference sets MR0103 apart from its upstream sibling: MR0103 treats refinery sour service as inherently severe, so it skips the H₂S partial-pressure severity thresholds that MR0175 / ISO 15156 uses to decide when its rules kick in. If the refinery stream is wet and sour, the material rules apply.
Sulfide Stress Cracking: The Mechanism MR0103 Guards Against
Sulfide stress cracking, or SSC, is a form of hydrogen-induced cracking. When steel corrodes in an aqueous H₂S environment, atomic hydrogen forms at the metal surface. Sulfide ions slow the recombination of that hydrogen into gas, so more of it works its way into the metal. Once inside a high-hardness, high-strength microstructure under tensile stress, the absorbed hydrogen embrittles the material and triggers brittle cracks, often with little warning.
Because susceptibility climbs fast with hardness and strength, controlling hardness is the main lever MR0103 uses to keep SSC from happening. That's why the standard's core requirements focus on hardness caps, heat-treatment condition, and weld/heat-affected-zone control, rather than wall thickness or pressure rating.
NACE MR0103 Requirements: Hardness Limits, Heat Treatment & Welding
NACE MR0103 Hardness Limits (22 HRC) by Material Category
| Material category | Requirement | Notes |
|---|---|---|
| Carbon & low-alloy steel | ≤ 22 HRC base metal | Weld and heat-affected-zone hardness controlled per the standard and NACE SP0472 |
| Austenitic stainless (e.g., 316/316L) | Supplied solution-annealed; hardness controlled | Cold-worked/high-hardness conditions restricted |
| Duplex, super-duplex & nickel alloys | Per the standard's alloy-specific provisions | Refer to the applicable MR0103 / ISO 17945 material tables |
The 22 HRC maximum on the Rockwell C hardness scale for carbon and low-alloy steel base metal is the figure people cite most when they talk about MR0103, and it anchors the standard's whole approach to SSC resistance. Values follow the applicable standard, but the final material and hardness condition can be tailored to what's needed.
NACE MR0103 Heat-Treatment Requirements
MR0103 lays out the delivery condition and heat treatment for each alloy category. Carbon and low-alloy steels get annealing, normalizing or stress-relieving; austenitic stainless steels get the solution-annealed condition. It's the heat-treatment condition that actually produces the low, uniform hardness the limits call for.
NACE MR0103 Welding & SP0472 Weld-Hardness Control
Welding is where uncontrolled hard microstructures show up most often. MR0103 requires that weld metal and the heat-affected zone (HAZ) stay within the standard's hardness limits, with fabrication and post-weld practice aligned to NACE SP0472 (control of weld hardness for SSC resistance). Qualification and testing of SSC resistance draw on methods such as NACE TM0177 and TM0284.
NACE MR0103 vs NACE MR0175 / ISO 15156: Downstream vs Upstream
MR0103 and MR0175 draw the sharpest line in one place: where the material ends up in the process. Ask people what separates them, and the answer boils down to this: MR0103 / ISO 17945 governs downstream refining; MR0175 / ISO 15156 governs upstream production.
| Feature | NACE MR0103 / ISO 17945 | NACE MR0175 / ISO 15156 |
|---|---|---|
| Sector | Downstream, refineries, petrochemical, amine & gas processing | Upstream, oil & gas production / extraction |
| ISO twin | ISO 17945 | ISO 15156 |
| Environment model | Refinery sour service assumed severe (no H₂S partial-pressure exemption thresholds) | H₂S partial-pressure / severity thresholds define applicability |
| Primary damage mechanism | Sulfide stress cracking (SSC) | SSC plus broader cracking modes (SCC, HIC) |
| Typical equipment | Vessels, exchangers, piping, valves, pumps | Wellhead, tubulars, production / field equipment |
| Governing body | AMPP (formerly NACE) | AMPP (formerly NACE) / ISO |
If a producing well or field equipment is involved, the standard to reach for is NACE MR0175, or its ISO counterpart, ISO 15156. Refineries, petrochemical units and amine units fall under a different rule: MR0103 / ISO 17945 governs there.
NACE MR0103 Editions & Where to Get the Standard
The current edition is ANSI/NACE MR0103-2015 / ISO 17945:2015; earlier editions include MR0103-2012 and revisions before that. The ISO adoption, ISO 17945:2015, carries content that's technically identical. The authoritative, copyrighted document, the official NACE MR0103 PDF, comes from AMPP, the ANSI Webstore, and ISO (listed there as ISO 17945). Always get the PDF from these official publishers, not from third-party or pirated copies.
Materials That Meet NACE MR0103 for Refinery Sour Service
Crestflo covers stainless, duplex and high-nickel/CRA alloys for instrumentation work, the practical choice for wet-H₂S refinery and petrochemical streams. The MR0103 material set itself is broader, spanning carbon and low-alloy steels, austenitic stainless steels, duplex grades and corrosion-resistant nickel alloys. Carbon and low-alloy steels fall within the standard's scope, but not within Crestflo's US instrumentation material range.
| Alloy | UNS | Role in sour / refinery service | Grade page |
|---|---|---|---|
| 316 / 316L | S31600 / S31603 | Baseline austenitic stainless for moderate wet-H₂S service | 316/316L |
| 904L | N08904 | High-alloy austenitic for chloride + H₂S resistance | 904L |
| Duplex 2205 | S32205 | Duplex for combined chloride + sour service with strength | Duplex 2205 |
| Super Duplex 2507 | S32750 | Super-duplex for aggressive chloride + H₂S environments | Super Duplex 2507 |
| 254 SMO | S31254 | 6Mo super-austenitic for high-chloride sour service | 254 SMO |
| AL-6XN | N08367 | 6Mo super-austenitic alternative for severe media | AL-6XN |
| Alloy 20 | N08020 | Acid-resistant austenitic for sulfuric/process streams | Alloy 20 |
| Inconel 625 | N06625 | Nickel CRA for the most demanding sour + chloride duty | Inconel 625 |
| Inconel 825 | N08825 | Nickel-iron-chromium CRA for sour and acid service | Inconel 825 |
| Monel 400 | N04400 | Nickel-copper alloy for reducing / H₂S conditions | Monel 400 |
| Hastelloy C-276 | N10276 | Nickel-moly-chromium CRA for extreme corrosion resistance | Hastelloy C-276 |
UNS numbers are the standard published Unified Numbering System designations. Final grade selection can be customized to requirement.
NACE MR0103-Compliant Instrumentation Fittings, Valves & Manifolds
Crestflo supplies NACE-compliant instrumentation components in the stainless, duplex and high-nickel alloys above, made to the sour-service material and hardness requirements that apply to them. That includes NACE MR0103 / ISO 17945 conformance, stated on the material certificate on request. Conforming product families include:
- Tube & compression fittings, single and double-ferrule, up to 2″ (50 mm) OD; fittings qualify to ASTM F1387 and are supplied NACE compliant.
- Instrumentation valves, needle, ball, check/NRV, relief and bleed valves; valves qualify to the applicable ASME B16.34 / API valve standards.
- Valve manifolds, 2, 3 and 5-valve manifolds and double-block-and-bleed, 100% seat & shell leak tested.
Every part carries a heat/lot number for full traceability, backed by an EN 10204 3.1 material test certificate (3.2 is available on request). PMI (positive material identification), in-house NDT and third-party inspection can all be arranged. For documentation detail, see EN 10204 material test certificates and heat-number traceability, the MTC itself covers the certification side, while the traceability page walks through how each heat number is tracked.
Need MR0103-conforming fittings, valves or manifolds for refinery sour service? Send your specification and we will quote conforming components. Request a quote or request a sample.
Why Crestflo for Sour-Service Instrumentation
Crestflo is the instrumentation arm of an export house with four decades behind it, recognized by the Government of India and carrying a solid delivery record across the Middle East. That heritage stands behind a manufacturing brand built for critical service. We supply US customers with:
- The right materials for refinery sour service, SS, duplex, super-duplex and high-nickel CRAs, made to the applicable NACE sour-service requirements and customizable to your spec.
- Full traceability, every part carries a heat/lot number plus an EN 10204 3.1 MTC (3.2 on request). PMI, NDT and third-party inspection are all available.
- ISO 9001, ISO 14001, ISO 45001 & PED certified manufacturing.
- Honest origin, Indian origin, with US / European melt available on request and full material traceability.
- Delivery you can plan around, ready stock for standard items, made-to-order for specials, 6–8 week delivery.
Standard product comes from Indian mills. If you need domestic-melt or TAA-aligned material, US or European melt is available on request. Talk to our engineering team about your refinery or petrochemical sour-service scope, we build confidence into every fitting, valve and manifold we ship.
Frequently Asked Questions About NACE MR0103
What is the difference between NACE MR0175 and MR0103?
Downstream petroleum-refining service (wet-H₂S) falls under NACE MR0103 / ISO 17945, while upstream oil-and-gas production falls under NACE MR0175 / ISO 15156. Both standards address sulfide stress cracking. MR0103, though, treats refinery service as inherently severe, and it skips the H₂S partial-pressure thresholds that decide when MR0175 kicks in.
What are the NACE MR0103 requirements?
MR0103 caps hardness at 22 HRC maximum for carbon and low-alloy steel base metal. It mandates specific heat treatments, anneal, normalize or stress-relieve, by alloy category, requires austenitic stainless to be in the solution-annealed condition, and controls weld and HAZ hardness in line with NACE SP0472.
What is the latest version of NACE MR0103?
The current edition is ANSI/NACE MR0103-2015 / ISO 17945:2015. The ISO adoption, ISO 17945, matches it point for point in technical content.
Is NACE MR0103 the same as ISO 17945?
Yes. ISO 17945:2015 is the ISO-adopted version of NACE MR0103, technically identical to it. That's the reason the standard carries the designation ANSI/NACE MR0103-2015 / ISO 17945:2015.
What does NACE mean for valves?
A "NACE" valve uses materials and hardness conditions chosen to resist sulfide stress cracking in wet-H₂S service, per MR0103 for refinery service or MR0175 for production. Crestflo supplies NACE-compliant instrumentation valves and manifolds, and they qualify to the applicable ASME B16.34 / API valve standards.
Which alloys meet NACE MR0103 for refinery service?
Common alloys for this kind of work include 316/316L, 904L, Duplex 2205, Super Duplex 2507, 254 SMO, AL-6XN and Alloy 20. Nickel alloys round out the list too: Inconel 625/825, Monel 400 and Hastelloy C-276. Crestflo supplies all of these in instrumentation forms.
Does Crestflo supply NACE MR0103-compliant fittings and valves?
Crestflo manufactures NACE-compliant compression and tube fittings, needle, ball, check, relief and bleed valves, manifolds and double-block-and-bleed assemblies, in stainless and high-nickel/CRA alloys. These are produced to the applicable sour-service material requirements, with EN 10204 3.1/3.2 material test certificates and heat-number traceability. Specify MR0103 / ISO 17945 conformance on your RFQ.
What is the lead time on MR0103-conforming parts from Crestflo?
Ready stock covers the standard items. Made-to-order specials take 6–8 weeks to deliver. Send us your specification and we'll get you a quote.
Related Standards & Resources
- NACE MR0175, the upstream production sour-service materials standard.
- ISO 15156, the ISO version of the upstream standard.
- EN 10204 material test certificates, 3.1 / 3.2 MTC documentation.
- ASTM F1387, performance qualification for compression tube fittings.
- Sour-service material selection (NACE), how to pick alloys for MR0103 / MR0175 service.
- Downstream refining applications and petrochemical & chemical, context for refineries and amine service.
- All instrumentation standards, the full standards hub.