On the formation of stress corrosion crack colonies with different crack population

The aim of this research was to understand why the cracks in a stress corrosion cracking (SCC) colony developed in the pipeline steels exposed to near-neutral pH environments, can be either very dense or sparse, a key puzzling feature of SCC cracks found in the field. Results showed that crack population in a crack colony was increased with increasing the area of mill scale coverage and the length of time the damaged mill scale can be maintained on the steel surface. Various mechanical, chemical and physical conditions that can preserve or remove the mill scale from surface have been studied.