干湿循环下低碳钢亚稳态孔蚀电化学噪声混沌的分析初探.pdfVIP

The 6th China Corrosion Conference Characterization of Metastable Pitting on Mild Steel during Wet-Dry Cycles by Electrochemical Noise Analysis Based on Chaotic Theory 1 1,* 1 1,2 Anna CHEN , Fahe CAO , Jianqing ZHANG , Chunan CAO 1 Department of Chemistry, Zhejiang University, Hangzhou ，PR China 2State Key Laboratory for Corrosion and Protection, Institute of Metal Research, The Chinese Academy of Sciences, Shenyang, PR China * Email of the corresponding author: nelson_cao@zju.edu.cn Abstract: Electrochemical noise EN was used to investigate the metastable pitting behavior of mild steel Q235 in 0.1 M Na SO and 0.1 M NaCl aqueous solutions during wet-dry cycles. The chaotic parameter 2 4 Largest Lyapunov Exponent LLE of electrochemical current noise ECN , whose positive percentage is able to represent the number and value is associated with sites of metastable pits, was calculated. The calculation results show chaotic oscillations of ECN are more plentiful in wet cycles and in Na SO solution, 2 4 indicating larger numbers of pit embryos and a more uniform distribution of metastable pits. The corrosion of Q235 in NaCl solution is localized with lower LLE values. Keywords: electrochemical noise; metastable pitting; mild steel; chaotic theory 干湿循环下低碳钢亚稳态孔蚀的电化学噪声混沌分析初 探 1 1,* 1 1,2 陈安娜 ，曹发和 ，张鉴清 ，曹楚南 1 浙江大学化学系，杭州，中国，310027 2 金属腐蚀与防护国家重点实验室，沈阳，中国，110016 ? 通讯作者：Email: nelson_cao@zju.edu.cn 摘 要：本文用电化学噪声法检测低碳钢 Q235 在0.1 M NaCl 和0.1 M Na SO 溶液干湿循环腐蚀试验 2 4 中亚稳态点蚀的发生特性。电流噪声（ECN ）的混沌分析中最大Lyapunov 指数（LLE ）正值的百分率 越高，亚稳态点蚀的数目越多；LLE 数值越正，亚稳态蚀点分布越均匀。文章对监控的 5 天 15 个干 湿循环内，每小时 15 分钟后 11 段电流噪声进行先降噪后计算 LLE 的处理。LLE 计算结果可预测在 Na2SO4 溶液中，低碳钢表面将发生大量亚稳态蚀点的产生和修复过程，并且由较大的 LLE 正值显示 这些蚀点的分布较在NaCl 溶液中均匀。同时，电流噪声LLE 计算结果表明Q235 在湿循环中比干循 环中产生更多可修复的亚稳态点蚀且湿循环中蚀点的分布更加均匀。 关键词：电化学噪声；亚稳态点蚀；低碳钢；混沌分析 1 引言 碳钢上亚稳态点蚀通常引发电流先迅速上升后指数衰 减回到基线。通过理论计算，此类电流峰功率密度谱 众所周知，亚稳态蚀点的成核、生长、灭亡将引 衰减斜率为-2 mA2 2 [3] /Hz . Speckert 等人 的研究表明， 起电位、电流的波动