Abstract :
A thermodynamic model was developed to
clarify the interactions of hydrogen, stress and anodic
dissolution at crack-tip during near-neutral pH stress
corrosion cracking in pipelines by comprehensively
considering the electrochemical reactions occurring in
the pipeline steel in deoxygenated, near-neutral pH
solution. By analyzing the change of the free-energy of
steel due to the presence of hydrogen and stress, it is
demonstrated that a synergism of hydrogen and stress
promotes the cracking of steel. The enhanced hydrogen
concentration in the stressed steel significantly
accelerates the crack growth. An exact expression of
the hydrogen concentration factor, i.e., the dependence
of anodic dissolution rate of steel at crack-tip on the
hydrogen concentration, is essential at the quantitative
prediction of the crack growth rate.
