Environmentally assisted cracking of pipeline steels in CO2 containing environment at near-neutral pH

The paper summarizes the results obtained by authors concerning near-neutral stress corrosion cracking (SCC) phenomena on buried pipelines. Stress corrosion tests according to different methodologies and fatigue propagation tests were executed on traditional steel grades. Tests were performed also on specimens precorroded according to a procedure developed to produce localized attacks similar to those observed during failure analysis on pipelines, acting as preferential sites for crack nucleation. Electrochemical tests were carried out in order to evaluate the influence of environmental parameter on pit formation. The main role of continuous plastic deformations on near-neutral SCC is confirmed. The effect of pH, CO2, and bicarbonate concentrations on pitting formation is discussed.