Electrochemical Corrosion Behavior of SSC Resistant OCTG in H2S Environment
The effect of H2S on the corrosion behavior of 110S OCTG without external stress was investigated using polarization curve and electrochemical impedance spectroscopy(EIS)technology.The effective hydrogen diffusivity coefficient and sub-surface hydrogen concen-tration were obtained by electrochemical hydrogen permeation method.The sulfide stress corrosion behavior of 110S OCTG loaded to 95%actual yield strength(AYS)was studied by electrochemical noise(EN)technology in the acetate acidified NaCl solution containing saturat-ed H2S.The fracture morphology was analyzed by scanning electron microscope(SEM).The results show that the H2S reduces corrosion re-sistance of 110S OCTG by increasing the polarization current density and decreasing the charge transfer resistance.Both effective hydrogen diffusivity coefficient and sub-surface hydrogen concentration are enhanced significantly in acidic solution,when 2 mA/cm2 constant current hydrogen charging is carried out.The electrochemical potential noise peaks of SSC have the characteristics of rapid decline and slow rise.The potential noise peak lifetime and amplitude increase during crack initiation and propagation.The sulfide stress corrosion cracking origi-nates at the pitting corrosion caused by anodic dissolution and continues to expand until fracture.
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