16Mn钢局部腐蚀中的电化学噪声特征

FEATURES OF ECN OF LOCALIZED CORROSION FOR 16Mn STEEL

通过测量 16Mn钢在 0 1mol/LCl-+0 5mol/LHCO-3 溶液中的电化学噪声 ,发现在点蚀诱导期 ,亚稳态蚀点的形核速率λ不到 0 0 0 2s-1,噪声电流峰平均宽约 3～ 5s,而噪声电位峰却平均宽达 2 0 0s;在点蚀从亚稳态转变为稳态过程中 ,λ急剧增加 ,且电流噪声峰宽度也开始增加 ,但电位峰宽度却开始减小 .随着局部腐蚀进入稳定发展期 ,噪声中出现了大尺度的波动 ,且噪声电位峰与电流峰宽度基本相等 ,但λ却有所下降 .宏观点蚀的出现导致噪声电阻Rn 迅速下降 ,并在腐蚀进入稳定发展期后逐渐趋于稳定 .

The change of electrochemical noise(ECN)patterns with time of 16Mn steel in 0.1 mol/L Cl -+ 0.5 mol/L NaHCO 3 solution was investigated.The experimental result showed,during metastable pit initiation period,the pitting initiation rate λ was less than 0.002 s -1 ,and the average lifetime of current transient coupled in ECN was about 3～5 s.However,the average lifetime of potential transient was 200 s.During the transition from metastable to stable pitting,λ increased rapidly,with an increase of the lifetime of current transient and a decrease of potential transient.Then,during the stable development of pitting corrosion,the lifetime of current and potential transient become almost identical,and a large-scaled fluctuation in ECN as well as a decrease of λ was observed.In addition,during the transition from metastable to stable pitting,noise resistance R n decreased fast,and R n get stable once the stabilization of pitting corrosion.