孔蚀发展期的电极阻抗频谱特征

FEATURES OF AC IMPEDANCE OF PITTING CORRODED ELECTRODES DURING PITS PROPAGATION

对不同孔蚀体系的实验证明,在孔蚀发展期,电极交流阻抗的根Sluyters图上呈现具有两个时间常数的容抗曲线。这是蚀孔中的弛豫过程与孔外钝化表面上的弛豫过程平行叠加的结果。为进一步证实这种双容抗谱乃是孔蚀发展期的电极阻抗频谱特征,用模拟孔蚀电极的复合电极证明了这一现象。建立了相应的等效电路模型。使用本实验室中建立的IFP软件对实验数据拟合并考察了等效电路与孔蚀状态的相关性。

Features of AC impedance of passivated mild steel and stainless steel electrodes suffering from pitting corrosion are studied.For the electrodes during pits propagation, the Sluyters diagrams are composed of two capacitive loops.Based on the assumption that the impedance for a pitting corroded electrode is composed by parallel connection of the impedance within pits and the impedance of the passive surface outside of pits, an equivalent circuit to interprete the features of the impedance of pitting corroded electrodes during pits propagation has been proposed.By the IFP technique developed in this laboratory, the parameters in the equivalent circuit can be estimated.Variations of these parameters with the conditions of electrode surface are studied both for real pitting corroded electrodes and composite electrodes simulating pitting corroded surface.The latter are made of Ni-plated iron electrode with predetermined number of holes (φ0.3mm) drilled through the Ni layer.Results are discussed.