The mechanism of hydrogen-facilitated anodic-dissolution-type stress corrosion cracking: theories and experiments

Abstract

A novel concept of hydrogen-facilitated dissolution has been introduced to describe stress corrosion cracking (SCC) in metals under hydrogen, stress and dislocation effect. Related experiments for pipeline steels in dilute bicarbonate solution were conducted to support the proposed mechanism. Slow-strain-rate tests (SSRTs) indicate that pre-charged hydrogen plays an important role in SCC by promoting anodic dissolution and SCC susceptibility. The hydrogen evolution and enrichment around a stress corrosion crack tip were identified using secondary-ion mass spectroscopy and its distribution around a SCC crack was modelled using an elastic–plastic analysis. It is postulated that the presence of hydrogen plus stress makes the anodic dissolution reaction more thermodynamically favourable. A thermodynamic model is proposed which is used to calculate the effect on the SCC growth the presence of hydrogen and stress. The results obtained with the model are in agreement with SSRT measurements.