Transient ionic mass-transfer rates during the anodic dissolution of an upward-facing horizontal zinc electrode in a 10 wt % (1.95 M) KOH aqueous electrolyte were monitored by holographic interferometry. The anode potential during zinc dissolution was also measured against a HgO/Hg reference electrode. A two-dimensional mathematical model, wherein a supporting electrolyte also takes part in the electrochemical reactions, was developed to characterize the electrolyte transport phenomena. Transient mass-transfer rates of both Zn(OH)(4)(2-) and OH-ions were numerically analyzed, and calculated transient refractive index profiles and anode overpotentials were compared to measured values. The electrochemical dissolution and passivation phenomena of the zinc anode in an alkaline electrolyte solution were discussed.