316L和HR-2不锈钢在盐酸液膜环境中的钝化与点蚀

Passivation and Pitting of 316L and HR-2 Stainless Steel in Hydrochloric Acid Liquid Membrane Environment

基于自行设计组装的盐酸液膜腐蚀模拟装置,采用腐蚀挂片、电阻探针、Tafel极化、电化学阻抗等方法,研究了316L和HR-2不锈钢在浓度分别为1、0.5和0.1 mol/L,温度分别为90、70和60℃的盐酸蒸汽环境中的钝化和点蚀行为,并利用金相显微镜、XRD对腐蚀试样和腐蚀产物进行了分析。结果表明:两种不锈钢的腐蚀速率随时间先加快后减慢最后趋于稳定,316L不锈钢的腐蚀速率相对较高;两种不锈钢均能形成稳定钝化区,且维钝电流密度相差不大,HR-2孔蚀电位的钝化区间总体都比316L不锈钢高,说明HR-2不锈钢更耐腐蚀;另外,两种不锈钢表面腐蚀产物成分基本相同,316L不锈钢表面的腐蚀产物更多更密集,这是由于O的吸附被C1-所取代,钢体表面上的钝化膜难以形成或破坏,并且更可能导致不锈钢点蚀。

With a home-made facility,the corrosion behavior of 316 L and HR-2 stainless steels at60~90℃beneath thin films of condensate HCl steam of 1,0.5 and 0.1 mol/L HCl solutions was assessed by means of mass loss method,resistance probe,Tafel polarization measurement,electrochemical impedance spectroscopy,metallographic microscope and XRD.Results show that the corrosion rate of the two stainless steels accelerates with time in the initial stage,then slows down and finally stabilizes.The corrosion rate of 316 L is faster.Both stainless steels can form stable passivation zone with more or less the same maintaining passivity current densities.The passivation interval of the HR-2 steel is higher than that of 316 L steel,indicating that former is more resistant to corrosion.In addition,the corrosion products of the two stainless steel surfaces are basically the same,however,the corrosion product on the316 L steel is much dense.Due to the fact that the oxygen in the corrosion product scale is replaced by the competition of Cl-,correspondingly,the passivation film on the surface of the steel may tend to crack and be difficult to be healed,therefore,pitting corrosion may be initiated of the stainless steels.