Sulfide Stress Cracking (SSC)

Sulfide stress cracking is hydrogen-assisted brittle cracking of high-strength steels in wet H2S environments, principally affecting hardened steels above approximately 22 HRC such as fasteners, valve internals, and high-strength pipe.

Definition

SSC is governed by NACE MR0175 / ISO 15156, which limits hardness and chemistry of steels used in sour service. SSC is prevented by material selection and post-weld heat treatment that reduces hardness.

Related terms

  • Hydrogen-Induced Cracking (HIC) — Hydrogen-induced cracking is a stepwise internal cracking in carbon and low-alloy steel pipelines and vessels exposed to wet H2S service, in which atomic hydrogen accumulates at inclusions and recombines, generating high internal pressure that causes blister-l
  • Stress Corrosion Cracking (SCC) — Stress corrosion cracking is the brittle cracking of a normally ductile material under the combined action of tensile stress and a specific corrosive environment, propagating along grain boundaries (intergranular) or through grains (transgranular).
  • Hydrogen Embrittlement — Hydrogen embrittlement is the loss of ductility and load-bearing capacity of a metal caused by the absorption of atomic hydrogen, typically affecting high-strength steels, titanium alloys, and some nickel alloys.

Further reading

hydrogen assisted cracking in welds detection

More defect terms

Crack · Lack of Fusion · Lack of Penetration · Slag Inclusion · Porosity · Undercut · Overlap · Burn-Through · Weld Spatter · Lamination

Where this comes up in practice

Terms like this one appear in three places that matter commercially: the written practice that governs how your personnel are qualified, the procedures and technique sheets that define how an examination is actually performed, and the evidence an auditor or client asks for when they want to know why an inspection was accepted. Getting the terminology right is the easy part; being able to produce the qualification record, the calibration traceability and the procedure revision that applied on the day of the inspection is the part that decides audits.

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