Hydrogen Embrittlement of X80 Pipeline Steel under Negative Interference of UHVDC Discharge Environment

A simulation test of ultra high voltage direct current (UHVDC) ground electrode discharge interference and cathodic protection was conducted on X80 pipeline steel in Guangzhou soil environment with water content of 50%. The effects of interference interval and interference frequency on the hydrogen embrittlement sensitivity of X80 pipeline steel were studied by means of thermal desorption spectroscopy (TDS) and slow strain rate test (SSRT). The results show that under the condition of interference alternating with cathodic protection, the hydrogen entering the X80 pipeline steel escaped during the interval of interference, but the hydrogen content in the material was basically stable when the interval time exceeded 24 h. The hydrogen content in the X80 pipeline steel increased with the increase of interference frequency, and the change of hydrogen content was dominated by diffusible hydrogen. The percentage of reduction area and percentage elongation after fracture of X80 steel decreased with the increase of interference duration, indicating the increase of hydrogen embrittlement sensitivity of the material.