高纯铝在含Cl^-溶液中电化学噪声的小波包子带能量特征

SUBBANDS ENERGY CHARACTERISTICS OF ELECTROCHEMICAL NOISE DURING HIGH-PURITY ALUMINUM CORROSION IN Cl^- SOLUTION

建立了基于小波包分解的电化学噪声子带能量表征方法 ,测试了高纯铝在含Cl-溶液中不同条件下的电化学噪声 ,分析了所测电化学噪声信号的时域特征、PSD特征及小波包分解子带能量特征 .PSD分析显示 :随着浸泡时间的增加 ,当蚀孔开始生长后 ,孔核的生长期缩短 ,消亡期延长 ,而SO2 -4 对孔核的生长期及消亡期没有显著影响 .与PSD方法相比 ,子带能量特征向量可以刻画电化学噪声信号的高频“指纹”特征 ,对腐蚀体系、腐蚀类型及腐蚀状态有较强的敏感性 .通过对第一子带能量变化分析显示 ,SO2 -4 会降低高纯铝在含Cl-溶液中孔核的发生频数 .

Various concepts developed in the framework of wavelet transforms have been adapted to the analysis of electrochemical noise measurements (ENM).These new mathematic methods are proposed as an alternative tool to overcome the limitations of FFT in the analysis of ENM.In this paper,a new description method of electrochemical noise (EN)using feature vector subbands' energy obtained by wavelet packets decomposition was described.Both PSD obtained by FFT method and subbands' energy were applied to study the EN signals during high-purity aluminum corrosion in Cl - solution under potentiostatic conditions.From PSD characteristics,it was found that if the immersion time in Cl - solution was prolonged,the activity life of pit nucleus shortened,but the passivation time of pit nucleus lengthened,and SO 2- 4 only influenced the frequency of pit nucleus appeared.Compared with FFT method,subbands' energy feature vector can describe the high frequency 'fingerprint' characteristics of EN signals,which can offer an enhanced ability to categorize different corrosion systems,different corrosion types and different corrosion intensity.