Environmental Aspects of SCC of High Alloys in Sour Environments

The initiation and propagation of stress corrosion cracking (SCC) of high alloys in sour gas environments were investigated mainly from the viewpoint of cathodic reactions. The most probable cathodic reaction to support the metal dissolution in the pitting and/or cracking process was identified by means of electrochemical measurements. Among various environmental constituents, the influence of elemental sulfur on the dynamics and kinetics of the cathodic reaction was clarified. The role of elemental sulfur in the growth of pits and SCC was examined in detail. A suitable prediction technique to determine the SCC limits of high alloys was also discussed in relation to pitting corrosion as a precursor of SCC.