Polarization Characteristic of Iron Anode in Concentrated NaOH Solution

Polarization curve, electrolysis curve, and electrochemical impedance spectroscopy (EIS) were adopted to study the polarization of the iron electrode in the concentrated NaOH solution. The results showed that passivation of the iron anode occurred more easily at higher temperature, lower alkali concentration, and greater current density. However, the passivation phenomenon of the iron electrode might become too weak to see under some conditions. The conditions were as follows: temperature 25-35 °C, current density ≤4.7 mA·cm−2, alkaline concentration ≥14.5 mol·L−1. EIS was used to investigate the impedance change of the electrode surface during the above polarization process. Next, the step characteristic of the iron anode polarization during its super-passivation range in the concentrated NaOH solution was described.