Cathodic protection causes generation of hydrogen atoms on the cathode (structure) surface. As the structure-to-water potential at the metal surface becomes more negative, hydrogen generation increases. Hydrogen generation can cause hydrogen embrittlement in many high strength steels, stainless steels and non-ferrous alloys. This phenomenon, when combined with high tensile loads or internal stresses can also induce stress corrosion cracking. The presence of hydrogen sulfide also induces formation of hydrogen at the metal surface.
While the hull and most appurtenances should be constructed of alloys generally not conducive to hydrogen embrittlement at anticipated cathodic protection levels, the use of high strength steels and/or corrosion resistant alloys susceptible to hydrogen embrittlement from cathodic protection may be required for appurtenances or interfacing components such as risers.
Cathodic protection compatibility should be reviewed for each of these components during the material selection process to identify alloys that may be susceptible to hydrogen embrittlement when exposed to the levels of cathodic protection anticipated during the service life. Where materials susceptible to embrittlement are identified, provisions for alternative materials, coatings, electrical isolation, and/or other measures for mitigation of hydrogen embrittlement should be implemented accordingly.