用时域法EIS技术研究LY12CZ 铝合金的局部腐蚀

通过周期浸泡腐蚀实验和时域法电化学阻抗谱(EIS)技术研究了LY12CZ铝合金的腐蚀损伤,用金相法测量最大腐蚀深度,用统计分析方法处理实验数据.结果表明,LY12铝合金经周期浸泡腐蚀试验后,低频阻抗倒数1/R_d符合Gumbel分布,1/R_d随腐蚀时间变化的动力学曲线呈S形,该曲线分成点蚀和剥蚀两个阶段,点蚀阶段符合Sigmoidal曲线关系,剥蚀阶段符合线性关系.1/R_d与最大腐蚀深度在空间统计分布和腐蚀动力学规律两个方面都有一致性,因此可以用1/R_d表征腐蚀损伤程度.由此可见,时域法EIS技术可作为一种快速、无损、定量的腐蚀评估手段.

Study on Evaluation of Localized Corrosion of 2024T3 Aluminum Alloy with EIS

Alternating immersion test was applied to 2024T3 Al alloy. Electrochemistry Impedance Spectroscopy (EIS) by time domain method was performed on the specimens. Statistic method was also used to deal with data because localized corrosion is a stochastic phenomenon. The results show that the reciprocal of low frequency impedance (1/R d) was consistent with the Gumbel distribution law. The dynamic variation curve of 1/R d vs. test period was somewhat of S shape which must be divided into two stages to treat the data, i.e. pitting and intergranular corrosion (Sigmoidal curve) and exfoliation (linear line). Compared with the maximum corrosion depth data ( d m) measured by optical microscope, it can be concluded that 1/ R d and d m have similar statistical distribution and time dependent growth. Quantitative relation between the 1/ R d and d m has been established. According to the relation, EIS by time domain method can enable a nondestructive, quantitative and quick evaluation for localized corrosion of 2024 Al alloy.