Electrochemical H permeation tests were performed to in order to measure the H permeation current through X-65 pipeline steel in electrolytes simulating soil conditions to initiate near-neutral pH stress corrosion cracking in pipelines. The H permeation current was analyzed following the constant concentration model. It was shown that, AQDS, simulating the organic compound in the soil, inhibited H permeation by decreasing the sub-surface H concentration, while sulfide promoted H permeation by inhibiting the H recombination and thus increasing the sub-surface H concentration. The steel specimen was more susceptible to stress corrosion cracking in the soil solution with a higher sub-surface H concentration, indicating that H was involved in near-neutral pH stress corrosion cracking in pipelines. It was suggested that H promoted the cracking of the steel, accompanying with the anodic dissolution on the crack sides and at the crack tip.

Analysis of Electrochemical Hydrogen Permeation through X-65 Pipeline Steel and its Implications on Pipeline Stress Corrosion Cracking. Y.F.Cheng: International Journal of Hydrogen Energy, 2007, 32[9], 1269-76