Electorochemical Analyses on Anodic Dissolution Mechanism of Metal
The author's group has studied the corrosion mechanisms of metals by using various electrochemical methods. In this article, some results concerning with the iron dissolution mechanism by a channel flow double electrode (CFDE) and an electrochemical impedance spectroscopy (EIS) are introduced. The contents of the present article are as follows.
(1) Transient analysis by CFDE in the time and frequency domains
The transient current for active dissolution of iron was separated to the currents for the formations of Fe (II) and the intermediate, calculating the Fe (II) detection current by CFDE in the frequency domain. The fractional coverage of the adsorbed intermediate on the iron surface was estimated from the calculated currents.
(2) Application of laser technique to CFDE
The adsorbed species on the polarized iron electrode were flushed out by the laser impact. The reformation processes of the adsorbed species were investigated.
(3) Determination of dissolved ions by spectrophotometry combined with CFDE
The CFDE was combined with the spectrophotometry with an optical fiber system. The Fe (II) and Fe (III) dissolved from the corroding iron can be determined simultaneously.
(4) EIS study on the iron dissolution
The Fe(II) dissolution efficiency Φdiss was measured with the electrochemical impedance by CFDE. The Φdiss is the frequency dependent parameter regarding with the time constant of the adsorption. The physical meanings of the Φdiss and the Faradaic impedance for iron dissolution were revealed.