In previous works we have observed that during the passivation of zinc electrode in KOH solutions under potentiostatic control the anodic dissolution current decreased gradually with time. We ascribed this phenomenon to a change of the properties of the initially formed zinc hydroxide on the zinc surface, i.e. to a "surface phase change" on the electrode. In this work we attempt to further prove this assumption kinetically. We measured the courrent-time curves of the zinc electrode during passiviation under potentiostatic conditions and in KOH solutions of different concentrations. The experimental results are in agreement with the derived kinetic equations, showing that during the anodic passivation of zinc electrode under potentiostatio conditions, the initially formed (Zn(OH)2)ad on the surface was gradually changed, with participation of OH- ions, into the less soluble (ZnO)ad, which caused the decrease of anodic dissolution current. This process of surface phase change is catalysed by the OH- ions, its reaction order with respect to OH- is unity,

Key words: ELECTRODE, PHASE TRANSFORMATION, ZINC ION, ANODES, SURFACE PHASE, POTASSIUM HYDROXIDE