孔蚀过程中的电化学噪声特征

FEATURES OF ELECTROCHEMICAL NOISES DURING PITTING CORROSION

研究了几种钝态金属在合有活性离子的中性缓蚀剂体系及硫酸体系中发生局部腐蚀时的电化学噪声行为。结果表明:在研究的所有腐蚀体系中,饨态表面孔蚀过程中腐蚀电位波动噪声的功率密度谱(SPD)曲线都具有相同特征,即在极低频率下为白噪声,随频率升高,逐渐转变为1/f^n 噪声。视金属材料不同,测得的表观 n 值在2.2—3.4之间。SPD 曲线上最高频率 f_c 与溶液中 Cl^-浓度关系呈现三种类型。提出了一个解释实验结果的 SPD 的数学模型.

An investigation on the features of electrochemical noises during pitting corrosion of aluminium,iron,carbon steel and two kinds of stainless steels in various passivating solutions with different concentrations of pas- sivators and Cl^- ion was carried out.All the electrochemical noises obser- ved are low frequency noises.The highest frequency f_c observed for a given solution usually increases with the increasing of Cl^- concentration.It seems that the higher the value of f_c is,the more easily the pit initiates,and that it is possible to evaluate the effectiveness of passivatorsor the resis- tance of metals against pitting corrosion by comparing f.Sometimes there is a maximum on the curve of f_c varying with Cl^- ion concentration, and pitting corrosion occurs before the maximum while general corrosion occurs after the maximum.All the spectral power densities measured show that the electrochemical noise is 1/(f^n) noise,though the value of n is somewhat different for different metals.A mathematical model for the spectral power density has been proposed.