TRANSPASSIVE DISSOLUTION OF IRON IN ACIDIC SOLUTION INVESTIGATED BY CHANNEL FLOW ELECTRODE

摘要

The transpassive dissolution of iron in acidic solution (pH 1) was investigated by electrochemical impedance spectroscopy (EIS) with channel flow double electrode (CFDE). CFDE is one of hydrodynamic technique which has similar principle to a rotating ring disc electrode (RRDE). The species dissolved from the iron were determined by CFDE and spectrophotometry, and it was found that both Fe(Ⅱ) and Fe(Ⅲ) dissolve from iron during transpassive dissolution. The electrochemical impedance shows the capacitive loop, inductive loop and negative resistance. A dissolution efficiency of the iron electrode in the frequency domain was obtained by calculations using dynamic collection efficiency N(ω). Nyquist plots of the dissolution efficiencies of Fe(Ⅱ) and Fe(Ⅲ) show the semicircle, indicating the adsorptions of intermediate and passivating species.