Abstract
The effects of hydrogen charging on the electrochemical and stress corrosion cracking (SCC) behavior of X70 steel in a simulated deep seawater environment were investigated by using electrochemical measurements, slow strain rate tensile (SSRT) tests, and corrosion morphology characterization through SEM. The results showed that the concentrations of the adsorbed hydrogen in X70 steel after precharging under different hydrostatic pressures increased gradually and tended to be steady with the charging time. High hydrostatic pressures promoted the hydrogen permeation of X70 pipeline steel by promoting the permeating rate and quantity. The SCC susceptibility of X70 steel decreased first and then increased with the hydrogen-charging current density. The area reduction loss (Iψ) and true strain loss (Iε) exhibited the lowest SCC susceptibility at the 25 mA/cm2 hydrogen-precharging current density. The elongation rate loss (Iδ) exhibited the lowest SCC susceptibility at the 50 mA/cm2 hydrogen-precharging current density.
Highlights
Oil and gas will continue to be the dominant source of energy resources across the world in the future
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The effect of the hydrogen permeation on the stress corrosion cracking (SCC) behavior of X70 steel was studied by electrochemical tests, slow strain rate tensile (SSRT) tests, as well as morphology characterizations
Summary
Oil and gas will continue to be the dominant source of energy resources across the world in the future. Due to the aggressive marine environment and the complexity of oil and gas production, there may be a high risk of failure for subsea pipelines caused by the combined factors of corrosion, stress corrosion cracking (SCC), hydrostatic pressure, waves, and currents, as well as some emergency events. Changes in a number of aspects including seabed topography, ocean currents, and geological factors produce additional structural tensile stresses. The disbanding and peeling of coatings lead to the direct contact of corrosive media on the surface of pipeline steels. Under these synergetic effects, it can be strongly confirmed that it is highly risky of SCC failure for subsea pipelines
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