Materials Engineering 08 Jul 2026
H₂S Compatibility with Elgiloy® Alloy in Sour Gas Service
Technical guidance on fatigue resistance and stress corrosion cracking (SCC) of Elgiloy® alloy components in H₂S and sour gas applications.
Elgiloy® superalloy (Co-Cr-Ni-Mo / UNS R30003) is renowned for outstanding mechanical fatigue endurance and exceptional resistance to sulfide stress cracking (SSC) in sour gas (H₂S) environments. This technical appraisal outlines its optimal engineering application.
Technical Compatibility Matrix
✅ Highly Recommended
Internal regulator springs, sensing diaphragms, and dynamic elastic elements undergoing high cyclic loading.
⚠️ System-Level Validation Required
Not typical for valve bodies. The resilience of Elgiloy® alone does not compensate for incompatible elastomeric seats or stem packings.
Critical Process Parameters
- H₂S Partial Pressure: Requires strict compliance with NACE MR0175 / ISO 15156 hardness thresholds and heat treatment profiles.
- Associated Electrolytes: Free water condensation and chlorides dramatically increase pitting and stress-oriented hydrogen-induced cracking (SOHIC).
- Mechanical Stress State: Cold-worked components must receive certified stress-relief heat treatment to prevent crack propagation.
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