材料期刊网

通过极化曲线和交流阻抗谱测试以及OM表面腐蚀形貌观察、SEM和TEM的组织观察,研究了Cl-和SO42-离子对X70和X80两种管线钢腐蚀过程的作用机理与规律。结果表明：Cl-有强穿透性,极易引起点蚀,两种钢的自腐蚀电流密度都随着Cl-浓度的增大而增大,点蚀和全面腐蚀也随之进一步加剧,X70钢在较低浓度的NaCl溶液中出现全面腐蚀和点蚀,X80钢仅在高浓度NaCl溶液中出现明显的点蚀,且在各种不同浓度溶液中腐蚀程度均没有X70钢严重。SO42-在金属表面吸附能力比Cl-强,少量SO42-在金属表面的吸附,造成Cl-的局部含量高,更易引起点蚀,而大量SO42-在金属基体表面覆盖,能阻碍Cl-的影响。X80钢比X70钢有更强的耐腐蚀性,X70钢对SO42-和Cl-的作用更为敏感。

Corrosion mechanism and corrosion process of Cl-and SO42-ions on grade X70 and X80 pipeline steels were studied by means of polarization curves,electrochemical impedance spectroscopy,OM,SEM and TEM.The results show that Cl-has a strong penetrability,leading to pitting corrosion.The corrosion current density of the steels increases and pitting and general corrosion is aggravated with the increase of Cl-concentration in the solution.Pitting and general corrosion of X70 steel occurs in the NaCl solution of low concentration and only obvious pitting corrosion of X80 steel in the NaCl solution of high-concentration is observed and corrosion degree of X80 steel is less than that of X70 steel in same concentration solution.The adsorption ability of SO42-on the surface of metal is stronger than Cl-,a small amount of SO42-that adsorbs on the surface of metal to cause higher local content of Cl-causes more pitting,however a large amount of SO42-can cover on the surface of metal to hinder the influence of Cl-.X70 steel is more sensitive to the effect of SO42-and Cl-compared with X80 steel,and X80 steel exhibits higher corrosion resistance than X70 steel.