用电化学噪声研究16Mn钢的亚稳态孔蚀特征

ELECTROCHEMICAL NOISE CHARACTERISTICS OF METASTABLE PITING OF 16Mn MILD STEEL

采用电化学噪声 (ElectrochemicalNoise ,ECN)和极化曲线方法研究了 16Mn钢在Na2 CO3+NaHCO3 溶液中的亚稳态与稳态点蚀特征 .测量加入Cl-前后 ,由亚稳态点蚀形核引起的ECN谱特征 .发现电位与电流噪声具有典型的快速增加缓慢恢复的暂态峰 (Transient)特征 ,且随Cl-的增加 ,亚稳态蚀点溶解电流与寿命显著增加 .丝束电极 (WireBeamElectrode,WBE)的研究表明 ,钝化电极表面电流与电位分布随Cl-加入向不均匀发展 。

The fluctuation of potential and current of 16Mn carbon steel were monitored in NaHCO 3+Na 2CO 3 aqueous solution with and without 0.5 mol/L Cl -.Noise current and noise potential patterns were experimentally observed which related to the incubation and die of metastable pitting,where the 'transient' in ECN had generally characteristic of 'fast down and slow recovery'.The amplitude and lifetime of transient in ECN increased when addition of 0.5 mol/L NaCl.In addition,Surface potential and current mapping on passive film of 16Mn steel was also measured simultaneously by wire beam electrode,and the result showed the number of surface active points increased with addition of Cl -.Furthermore,dynamic potential scanning indicated that the addition of 0.5M Cl - would cause the passive film breakdown at more negative potential.