Cathodic Protection Technology Of X80 Steel Based On Hydrogen Embrittlement Sensitivity

The existing cathodic protection standards are based on the traditional low grade pipeline steel.The two and three line pipelines of the western pipeline belonging to West to East Gas Pipeline adopts high grade steel,big caliber and high pressure pipeline steel.The hydrogen embrittlement sensitivity is relatively large,and the hydrogen evolution overpotential is relatively low.In order to ensure the safety of the pipeline,whether the negative critical potential of cathodic protection specified by the existing standards can cause hydrogen embrittlement in X80 pipeline steel and the reasonable negative critical potential of high grade steel pipeline are studied.In this paper,a large diameter X80 steel for pipeline is chosen,and the change law of hydrogen embrittlement susceptibility of pipeline is analyzed by the slow strain tensile test under cathodic protection potential and the cathodic polarization curve.The results show that hydrogen evolution occurs in X80 pipeline steel with the negative polarization potential,resulting in hydrogen embrittlement and cracking;Under the soil environment in Western China,the current density of X80 steel is higher than 4.5A/m~2,and it has hydrogen brittleness risk.The current density reaches 55A/m~2~91A/m~2 and has cracking risk.The research results have great guiding significance for the prevention of hydrogen embrittlement and the setting of negative critical potential for cathodic protection of X80 pipeline steel.