Initiation of transgranular stress corrosion cracking in linepipe steels was studied in near- neutral pH environment. The effects of surface condition, composition, inclusions, pre-existing defects, mechanical factors, and hydrogen production at the surface were studied. In addition, the effects of spacing between inclusions and of pre-existing defects on crack coalescence were examined. Crack initiation was associated with pitting. Crack size increased with time of testing, and crack density increased with increase in applied stress. Possible mechanisms oflow-pH SCC are advanced in this paper. Plasticity localization and
localized dissolution are the two major aspects of crack development. These two processes occur on the same crystallographic planes, and thus, mutually enhance each other during crack development. Hydrogen is discharged and enters the steel under the exposure conditions, possibly influencing the cracking process by facilitating plasticity localization. The importance of crack initiation sites is discussed with respect to implications for field inspections and for assessing the integrity of a pipeline containing cracks. Keywords: stress corrosion cracking, near-neutral pH, cyclic stress, SCC colony, coalescence,
initiation, crack nucleation.