Role of Microstructures on Stress Corrosion Cracking of Pipeline Steels in Carbonate-Bicarbonate Solution

Stress corrosion cracking (SCC) on the external surface of pipelines contributes to the major failure of pipelines. The great majority of SCC is intergranular and occurs in a carbonate-bicarbonate environment. Metallurgical factors affecting SCC are still vague and therefore have been studied. Uniform microstructures, not mixed structures, are favorable for suppressing SCC. Low-C steels produced in a process such as thermomechanical-controlled processing are less susceptible to SCC. The presence of locally soft micro-structures decreases resistance to SCC (mixed structure and decarburized structure). However, SCC resistance is high on hard layers, like grit-blasted surfaces.