Potentiodynamic and potentiostatic polarization, and the rotating disk electrode technique were used to study the reduction characteristics of iodate (IO3-) ion on copper (Cu). Depending on the relative concentrations of IO3- and H+ two pH regimes were observed. The cathodic current in the first regime (pH > 3) was controlled by H+ diffusion from the solution to the metal surface. In the second regime (pH < 3 and up to 10(-2) M IO3- concentration) the cathodic current was found to be under mixed control, involving reaction control via the electrochemical reduction of IO3- and transport control via the diffusion of I-2 (aq). It was concluded that IO3- was an effective oxidant for Cu chemical mechanical polishing (CMP) with strongly acidic (pH < 3) slurries but it was not convenient reagent as an oxidant for Cu CMP with weakly acidic (pH > 3) slurries.