Stress corrosion cracking: cracking of a normally ductile metal when a susceptible material, tensile stress (often residual weld stress) and a specific environment coincide. Classic pairs include austenitic stainless steel in hot chlorides, usually above about 60 C, buried carbon steel pipelines in carbonate-bicarbonate or near-neutral pH groundwater, brass in ammonia and carbon steel in hot caustic. Cracks are fine, branching and often invisible until a leak or rupture.
Mag particle found a colony of SCC under the disbonded tape at about two o'clock on the pipe.
SCC rarely shows as wall loss, so thickness surveys miss it. Look with mag particle where coating has disbonded and stresses run high.
Also heard as
- stress corrosion cracking
Related terms
Sulfide stress cracking
Cracking of hard steel under tension in wet hydrogen sulfide service, a form of hydrogen embrittlement.
Hydrogen embrittlement
Loss of ductility when atomic hydrogen gets into steel, leading to sudden cracking under stress.
Corrosion fatigue
Cracking under cyclic stress in a corrosive environment, failing at lower stress or fewer cycles than in air.
Cathodic disbondment
Loss of coating adhesion around a holiday caused by the alkali and hydrogen that cathodic protection generates.