A novel coupling of electrochemical impedance spectroscopy with atomic emission spectroelectrochemistry: Application to the open circuit dissolution of zinc

• A novel coupling of electrochemical impedance spectroscopy with on-line detection by inductively coupled plasma optical emission spectrometer is demonstrated.
• The system is demonstrated for Zn in 0.1 M NH4Cl which shows that the electrochemical current and Zn oxidation are closely coupled.
• Analysis of the Zn dissolution rate and electrical current versus potential allows an independent determination of the anodic and cathodic Tafel constants.
• No correlation is observed between Zn oxidation and dissolution for Zn in 0.5 M NaCl.
• The results are interpreted in terms of the existence of oxidation product film intermediates.

A novel coupling between atomic emission spectroelectrochemistry (AESEC) and electrochemical impedance spectrometry (EIS) is demonstrated. In this way, it is possible to distinguish situations in which the oxidation of the metal leads directly to the formation of dissolved ions or passes through a slightly soluble film intermediate. It was found that Zn dissolution 0.1 M NH4Cl occurs without any significant solid intermediate as evidenced by the excellent correlation between the AC components of the electrical current and the zinc dissolution rate. Analysis of the dissolution rate and total current transients as a function of potential directly yields the anodic and cathodic Tafel slopes for this system. In contrast, for Zn/0.5 M NaCl, electrochemical oxidation leads directly to the formation of an intermediate corrosion product film with subsequent dissolution.

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