Inhibitive action of ferricyanide complex anion on both corrosion and passivation of zinc and zinc–nickel alloy in the alkaline solution

Abstract

The corrosion of zinc and Zn–0.5Ni alloy in strong alkaline solution (7M KOH) in the absence and presence of [Fe(CN)6]3− complex anion (1×10−3–1×10−2M) as inhibitor has been studied. Tafel plot, potentiodynamic, potentiostatic and electrochemical impedance spectroscopy (EIS) techniques were used, and complementary by EDX and SEM investigation. It is observed that, the corrosion current density (Icorr) decreases, and the inhibition efficiency (IE%) increases as the concentration of inhibitor is increased. The shift of breakdown potential to less positive direction, indicating that the reduction of oxide layer on the alloy surface occurs somewhat easier in the presence of [Fe(CN)6]3− complex anion. The impedance measurements have shown that the increase of the inhibitor concentration in the alkaline solution reduces the corrosion rate in the active region. Accordingly, addition of [Fe(CN)6]3− complex anion to KOH solution can be considered as an important criteria for a good battery anodes. This behavior is due to its high negative open-circuit potential, less corrosion rate and higher self-catalysis in the passive region compared with those in its absence.