Abstract
In this work, the use of atomic emission spectroelectrochemistry (AESEC) coupled to electrochemical impedance spectroscopy (EIS) is presented as a method of revealing dissolution mechanisms. To illustrate the method, the dissolution kinetics of Al cations from an Al-Zn pure phase (Zn-68 wt.% Al) was investigated in an alkaline solution. In the cathodic potential domain, a nearly direct formation of dissolved Al3+ was observed, while in the anodic potential domain the Al dissolution occurred by migration across a ZnO/Zn(OH)2 film. It was demonstrated that this methodology can be applied to a nonstationary system during a potentiostatic experiment for a lower Al content phase (Zn-22 wt.% Al). The nature of the charge transfer mechanisms depended on the applied potential and could be identified by comparing the direct current and alternating current faradaic yield using AESEC-EIS.
Highlights
Since its introduction to the corrosion field by Epelboin et al.[1], electrochemical impedance spectroscopy (EIS) has proven itself an essential and ubiquitous technique in corrosion research
At the onset of Zn dissolution, there is a notable decrease in the jAl, that we previously termed a negative correlation effect (NCE) in ref
We have demonstrated the application of combined atomic emission spectroelectrochemistry (AESEC)-EIS to identify and quantify different anodic dissolution processes for a multielement system, Al-Zn pure phase in 0.1 M NaOH
Summary
Since its introduction to the corrosion field by Epelboin et al.[1], electrochemical impedance spectroscopy (EIS) has proven itself an essential and ubiquitous technique in corrosion research. For steady-state corroding systems, EIS may provide a direct measurement of the corrosion rate[1], and the form of the EIS spectrum may reveal the underlying mechanisms resolved over a wide frequency range of time constants[2]. The difficulties of EIS alone are the inability to identify the specific faradaic reactions that occur during charge transfer and the requirement of steady-state system. To resolve these difficulties a variety of couplings, such as EIS–Raman spectroscopy[3] have been developed. The theoretical development of such techniques has been addressed in the development of a generalized EIS transfer function[4]
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