Hydrogen facilitated anodic dissolution type stress corrosion cracking of pipeline steels in coating disbondment chemistry

摘要

The stress corrosion cracking(SCC) of pipeline steels in coating disbondment chemistry(near neutral pH solution) was studied by using slow strain rate tests(SSRT), polarization techniques, SEM and SIMS (secondary ion mass spectroscope). It was foud that SCC susceptibility increased as the applied electrochemical potential and strain rates decreased. Hydrogen(H) precharging or addition of CO_2 facilitated the process of SCC, suggesting that dissolution and hydrogen ingress are involved in the cracking process. SIMS analysis showed that hydrogen could diffuse into steels around the crack tip during the SCC process, which would facilitate the dissolution rate of the steel and increase SCC susceptibility. A mechanism was proposed which shows that hydrogen enhances anodic dissolution type of SCC in dilute aqueous solution. A thermodynamic analysis of the SCC process was carried out, and was found to be consistent with the experimental results.