Comparison between NACE MR 0103 and NACE MR 0175
NACE MR0175 / ISO 15156 NACE MR0103 / ISO 17945 Two fundamental standards for materials in H₂S environments, each serving a distinct industrial sector. This comparison clarifies their scope, technical requirements, and correct application.
NACE International, originally the National Association of Corrosion Engineers, began issuing standards under the “NACE” designation in 2001. The most influential standard, MR0175 (Metallic Materials for Resisting Sulfide Stress Cracking in Oilfield Equipment) was first issued in 1975. In 2003, it underwent major revisions: chloride stress corrosion cracking (SCC) was added alongside sulfide stress cracking (SSC). Later in 2003, it became a joint NACE/ISO standard: NACE MR0175/ISO 15156. In April 2003, NACE published MR0103 for the refining industry (Metallic Materials Resistant to Sulfide Stress Cracking in Corrosive Petroleum Refining Environments). In 2015, NACE adopted MR0103/ISO 17945.
📋 NACE MR0175 / ISO 15156 · upstream
upstream · H₂S + Cl‑SCC · mandatory in some regions
Covers both sulfide stress cracking (SSC) and chloride stress corrosion cracking (Cl‑SCC). Environmental limits/constraints are defined for all acceptable corrosion‑resistant alloys (H₂S partial pressure, max temperature, chloride content, free sulfur). Applies only to upstream oil & gas production (drilling, gathering, flowlines, field process). Some U.S. states have enforced it as regulation.
📌 Many end users still specify NACE MR0175‑2002, considering it sufficient.
🏭 NACE MR0103 / ISO 17945 · downstream
downstream · only SSC · no environmental boundaries
Addresses only sulfide stress cracking (SSC). Imposes no environmental limits on materials; they are simply classified as suitable or unsuitable. Uses refining‑industry‑based definitions for sour service. Applies to downstream petroleum refining and petrochemical plants (hydroprocessing, desulfurization). No governmental legal force – industry recommended practice.
📌 Resembles pre‑2003 MR0175 (only SSC, no environmental limits) – reason for rapid refinery adoption.
📑 Key differences — MR0175/ISO 15156 vs. MR0103/ISO 17945
| Parameter | NACE MR0175 / ISO 15156 | NACE MR0103 / ISO 17945 |
|---|---|---|
| Scope & industry | Upstream oil & gas production (wells, flowlines, field processing) | Downstream refining & petrochemical (hydroprocessing, desulfurization) |
| Corrosion mechanisms | Sulfide stress cracking (SSC) + chloride stress corrosion cracking (Cl‑SCC) | Only sulfide stress cracking (SSC) |
| Material acceptance | Environmental limits/constraints (H₂S partial pressure, Cl⁻ ppm, temp, free sulfur) | Binary classification (acceptable / unacceptable), no environmental boundaries |
| Carbon/low‑alloy steel hardness | Base & weld ≤22 HRC | Base & weld ≤22 HRC (strict enforcement) |
| Stainless steels (e.g., 316) | Annealed ≤35 HRC, but tightly restricted by environmental limits (H₂S ≤0.1 kPa, Cl⁻ ≤50 ppm) | No special relaxation; must meet ≤22 HRC if used in SSC service (often listed as acceptable without environment limits) |
| Bolting | A193 B7 prohibited; B7M or other SSC‑resistant required | Same: B7 not allowed, must use SSC‑resistant bolting |
| Welding controls | Some exemptions from hardness testing; heat treatment / process optimization | Mandatory hardness testing per RP0472, carbon equivalent control, or PWHT |
| Legal / regulatory | Mandatory in certain U.S. states; globally adopted | No government enforcement; industry recommended practice |
📌 Important context (MR0175)
Many end users still specify NACE MR0175‑2002, as they consider it sufficient. The most important changes in MR0175/ISO 15156 include extension to Cl‑SCC and environmental limits for CRA.
📌 Important context (MR0103)
MR0103 (ISO 17945) resembles the pre‑2003 MR0175 (only SSC, no environmental limits) – which is why it was rapidly adopted by the refining industry.
✅ Practical application summary
⬆️ upstream
→ use ISO 15156 (MR0175)
Consider both H₂S and chloride; check environmental limits for stainless steels. Welding may follow heat treatment optimization but be aware of Cl‑SCC.
⬇️ downstream
→ use ISO 17945 (MR0103)
Focus on SSC, mandatory hardness testing per RP0472, PWHT common. No need to check Cl⁻ limits, but ensure bolting and welding meet strict hardness.
📌 Since 2010, both integrated into ISO, but differences persist — particularly in environmental limits, chloride coverage, and welding controls. Always select the correct standard based on actual service environment.