西气东输二线X80管线钢内腐蚀行为的研究

Study on internal corrosion behavior of X80 pipeline steel used in the second West-East Pipeline Project

关键词:  西二线  X80钢  内腐蚀  极化曲线  交流阻抗  内腐蚀机理 

Key words:  West-East Pipeline Project(WEPPⅡ)  X80 steel  internal corrosion  polarization curve  electrochemical impedance spectroscopy (EIS)  internal corrosion mechanism

摘要:

以西二线X80管线钢为对象,采用动电位极化和交流阻抗技术研究了不同质量分数的Cl-和SO2-₄在西二线清管产物模拟溶液中X80钢内腐蚀行为,探讨了西二线管道内腐蚀机理。实验结果表明,X80管线钢在只含不同质量分数的Cl-模拟溶液中的极化曲线都呈明显的活化控制,且随着Cl-质量分数的增大,X80钢的腐蚀电流密度i_corr大幅增大,X80钢的腐蚀速率增大；X80在含质量分数为0.05%Cl-、不同质量分数的SO2-₄模拟溶液中的极化曲线同样呈明显的活化控制,但是随着SO2-₄质量分数的增大,X80钢的腐蚀速率呈现先增大后减小的趋势,SO2-₄质量分数为0.50%时,腐蚀电流密度i_corr达到最大值,腐蚀最为严重；当模拟溶液中同时含有Cl-和SO2-₄时,X80钢的腐蚀电位与只含Cl-时相比均有所降低,腐蚀电流密度均增大； 当Cl-和SO2-₄共存时,随着SO2-₄质量分数的增加,SO2-₄能快速地吸附在金属表面,阻碍Cl-的吸附,减小了Cl-对金属的腐蚀。 

Abstract:

Taking the X80 steel used in the second West-East Pipeline Project(WEPPⅡ) as a study object, this paper researched the effects of Cl- and SO2-₄ with different concentration(wt%) on internal corrosion behavior of X80 pipeline steel in stimulated solution for pigging product,discussed the internal corrosion mechanism of WEPPⅡby potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) experimental. The results showed that, in the stimulated solution only containing different Cl- mass fraction, the polarization curves of X80 pipeline steel have typical characteristics of active dissolution, the corrosion current density(icorr) and the internal corrosion rate of X80 steel increases along with the increase of Cl- mass fraction; in the stimulated solution containing both 0.05% Cl- and different SO2-₄ mass fraction, the polarization curves of X80 pipeline steel also have typical characteristics of active dissolution, but the internal corrosion rate firstly increases and then decreases with the increase of SO2-₄ mass fraction. When the mass fraction of SO2-₄ is 0.50%, the icorr reaches the maximum value while polarization resistance reaches the minimum value, and the corrosion behavior of X80 steel is the most serious at this time; when the stimulated solution contain both Cl- and SO2-₄,the corrosion potential of X80 steel decreases while the icorr increases than the stimulated solution only containing Cl-, with the increase of SO2-₄ mass fraction; when the stimulated solution contain both Cl- and SO2-₄, with the increase of SO2-₄ mass fraction, SO2-₄ can adsorb on the metal surface faster than Cl-, which decreases the corrosion aroused by Cl-.