High-temperature process streams combined with sour service put both API 941 hydrogen-attack limits and NACE sulfide-cracking limits on the table at once.
| Dominant Failure Mode | High-temperature hydrogen attack, sulfide stress cracking |
| Governing Standard | API 941 Nelson curves, NACE MR0175 |
| Typical Material Default | Alloy Steel (Cr-Mo), Inconel 625 for severe service |
| Typical Structural Type | U-Tube for highest-pressure/temperature process units |
Petrochemical service often combines high temperature with sour or hydrogen-rich streams.
They define the maximum operating temperature and hydrogen partial pressure combinations a given steel can tolerate without hydrogen attack — material selection for high-temperature hydrogen service is checked directly against these curves.
Often yes for moderate combinations, but severe combined conditions may push the requirement toward Inconel 625 or similar — this is exactly the kind of combined-condition case that needs engineering review rather than a default assumption.
Only for H₂S-bearing (sour) service specifically — confirm whether your process stream is classified as sour before assuming NACE documentation is required.
Every enquiry is checked against governing code, material compatibility and manufacturing feasibility before a quote is issued. Use our product, material, grade and standards guides to freeze the RFQ — then confirm with engineering.
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