沈阳土壤模拟溶液中SO■对X70管线钢腐蚀行为的影响机制

Effect Mechanism of SO■ on the Corrosion Behavior of X70 Pipeline Steel in Shenyang Soil Simulated Solution

为了探明土壤中腐蚀性离子对管线钢的作用机制,降低油气管道的运行风险,采用交流阻抗技术(EIS)和动电位极化技术研究了SO■对X70管线钢在沈阳土壤模拟溶液中腐蚀的影响,并结合金相显微镜对管线钢表面的腐蚀形貌进行表征。结果表明:在沈阳土壤模拟溶液中,随着SO■浓度的增加,X70管线钢的腐蚀速率变大;SO■浓度由0.01%增至0.02%时,X70管线钢的腐蚀电流密度增幅较大,当SO■浓度达到0.20%时,其腐蚀最为严重,此时试样表面点蚀坑深度较深,腐蚀坑面积扩大且连成一片;在沈阳土壤模拟溶液中Cl^-的存在在改变了X70管线钢表面的电化学腐蚀环境,随着SO■浓度增大,SO■优先于Cl^-吸附于试样表面,将部分Cl^-封存在腐蚀坑中从而加快了X70管线钢的腐蚀速率。

In order to ascertain the effect mechanism of corrosive ions in soil on pipeline steel and reduce the operational risk of oil and gas pipelines,electrochemical impedance technique(EIS)and potentiodynamic polarization technology were utilized to study the influence of SO■ions on the corrosion behavior of X70 pipeline steel in Shenyang soil simulation solution,and the metallographic microscope was combined to characterize the corrosion morphology of the pipeline steel surface.Results showed that in the soil simulation solution of Shenyang,with the increase of SO■concentration,the corrosion rate of X70 pipeline steel became larger.When the concentration of SO■increased from 0.01%to 0.02%,the corrosion current density of X70 pipeline steel increased greatly.When the concentration of SO■reached 0.20%,the corrosion turned into the worst.At this time,the surface pit depth of the sample was deeper,and the corrosion pit area was enlarged and connected into one piece.In the Shenyang soil simulation solution,the existence of Cl^-changed the electrochemical corrosion environment on the surface of X70 pipeline steel.As the concentration of SO■increased,SO■would adsorb on the surface of the sample in priority to Cl^-,which partially sealed parts of Cl^-ions in the corrosion pit and then accelerated the corrosion rate of the X70 pipeline steel.