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采用电化学阻抗谱(EIS)技术对电沉积Ni-Co镀层在3.5%NaCl溶液中的腐蚀失效过程进行了研究,发现可采用4种等效电路对镀层的失效过程进行拟合:浸泡初期,镀层耐蚀性能良好,可以简单的等效为镀层电阻与镀层电容的并联;浸泡一段时间后,镀层/金属界面上发生腐蚀反应,引入了双电层电容和界面电荷转移电阻;浸泡后期,界面上的腐蚀产物产生积累,引入反映腐蚀产物信息的Warburg电阻元件;当腐蚀产物的积累影响到腐蚀介质的扩散时,引入了扩散电阻和扩散电容。通过对失效过程中镀层电阻和电容随时间的变化曲线进行分析,发现Ni-Co镀层在3.5%NaCl溶液中的失效过程可分为3个阶段:腐蚀介质的渗透阶段,界面金属的腐蚀阶段和镀层的失效阶段。
Electrochemical impedance spectroscopy (EIS) was used to study the corrosion failure process of electrodeposited Ni-Co coating in 3.5% NaCl solution. Four kinds of equivalent circuits were used to fit the failure process of coating: The corrosion resistance of the coating is good, which can be simply equivalent to the parallel connection of the coating resistance and the coating capacitance. After the immersion for some time, the corrosion reaction occurs on the coating / metal interface, and the electric double layer capacitor and the interfacial charge transfer resistance are introduced. On the corrosion products of the accumulation of introduction of corrosion products reflect the information of the Warburg resistance element; when the accumulation of corrosion products affect the diffusion of corrosive media, the introduction of diffusion resistance and diffusion capacitance. Through the analysis of the curve of the resistance and the capacitance of the coating during the failure process with time, it is found that the failure process of the Ni-Co coating in 3.5% NaCl solution can be divided into three stages: the infiltration stage of the corrosion medium, the corrosion stage of the interface metal and Coating failure stage.