Duplex stainless steels (22Cr duplex and 25Cr super duplex) are susceptible to hydrogen induced stress cracking (HISC) under cathodic protection (CP). Industry subsea failures have resulted from HISC under load-control scenarios where local strain levels exceed a critical strain threshold. Load-control situations occur in the absence of restraints on continuous material straining, such as for thermal growth and free spans. Residual stress levels from fabrication and installation, coating system integrity, and defective material microstructures contribute to initiation of HISC.
What can be done to avoid HISC?