Susceptibility to Hydrogen Embrittlement of X65 Steel Under Cathodic Protection in Artificial Sea Water

Abstract

Hydrogen permeation behavior and its effect on cracking mechanism of X65 steel under cathodic polarization were studied in artificial seawater by means of electrochemical hydrogen per- meation test and slow strain rate test (SSRT). Results show that the calcium magnesium deposits formed on the steel during cathodic polarization would significantly decrease the hydrogen diffu- sion coefficient; the effective hydrogen diffusion coefficient (Deff) was calculated by Fourier meth- od, modified Laplace method and time-lag method respectively, which give an average value 1.49× 10 -7 cm 2 ·s -1 ; the hydrogen concentration (C0) in the sub-surface of the steel showed an exponential relationship with the polarized potential; the crack propagation was influenced by the synergistic ef- fect of anodic dissolution and hydrogen evolution under thesoftpolarization conditions; howev- er, if the polarized potentials were extremely negative, the concentration of hydrogen would in- crease sharply, as a result, the X65 steel became sensitive to hydrogen embrittlement.