The format of a model designed to predict the probability of near-neutral pH SCC initiation on operating pipelines is described. The model would be used in conjunction with existing site-selection models to improve the prioritization of SCC excavations and to increase the probability of locating SCC in the field. Information being developed as part of the program could also be used to design and select improved alloys and coating systems for new construction. The model is based on the results of a laboratory program aimed at identifying factors that lead to
SCC initiation and early-stage crack growth, resulting in "viable" cracks. To date, five factors have been identified that lead to the earliest indications of crack initiation: inclusions, aligned defects, pre-
existing defects on the pipe surface, persistent slip bands produced by mechanical pre-treatment of the steel, and coating disbondment. These factors produce defects on the surface several grains...
Keywords: stress corrosion cracking, near-neutral pH SCC, pipeline steels, probabilistic model, initiation