The electrochemical redox kinetics of the CoB alloy electrode was investigated in 6 M KOH solution by electrochemical impedance spectroscopy (EIS) together with cyclic voltammetry (CV). The results show that the reversible electrochemical capacity of CoB alloy electrode is from the reaction Co/Co (OH)(2). The EIS reflects the following four steps in the process of Co (OH)(2) -> Co: the conduction step in the micropores of the electrode, two successive charge transfer steps and the diffusion of OH- away from the electrode, and the process is considered to be under the diffusion control. The EIS obtained from the process of Co -> Co (OH)(2) only show the responses of the conduction step and two electrochemical steps, and the second charge transfer step Co (OH)(ads)/Co (OH)(2) is regarded as the rate-determining step in the process. However, CVs reveal that the process of Co -> Co (OH)(2) is entirely under the diffusion control. This inconsistency could be due to the different formation mechanisms of the oxide layer under potentiostatic and potentiodynamic conditions. (C) 2014 Elsevier B.V. All rights reserved.