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).
Definition
SCC is a major in-service degradation mechanism: chloride SCC of austenitic stainless steel, caustic SCC of carbon steel, amine SCC, polythionic acid SCC, and ammonia SCC of copper alloys. SCC is detected by PT, ET, and UT, and is described in detail in API 571.
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
- 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.
- Corrosion Under Insulation (CUI) — Corrosion under insulation is external corrosion of carbon and low-alloy steel piping and vessels hidden beneath thermal insulation, caused by water ingress that accelerates corrosion in the 60–175 °C temperature range.
- API 571 Damage Mechanisms — API 571 is the recommended practice describing damage mechanisms affecting refining and petrochemical equipment, including general/uniform corrosion, localized corrosion, environmentally assisted cracking, metallurgical degradation, mechanical damage, and high
Further reading
stress corrosion cracking scc detection methods
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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