The electrochemical behavior of Al in phosphoric acid base slurry was investigated under chemical mechanical polishing (CMP) condition. The effect of applied potential on the CMP metal removal rate was also evaluated. The results from potentiodynamic polarization curve measurements indicated that a contact pressure in the range of 3 to 9 psi greatly modified the passivation behavior of Al in 5 vol % H3PO4 + 0.5 M citric acid + 5 wt % Al2O3 slurry by a decrease in corrosion potential and an increase in passive current density. The experimental results also showed that CMP removal rate strongly depended on the contact pressure and potential applied. The potential dependence behavior of the removal rate could be divided into three regions depending on the direction of polarization and the magnitude of potential applied. The results of electrochemical impedance spectroscopy and Auger electron spectroscopy examinations showed that passive film formation on Al in the resting slurry was affected by the applied potential, which in term caused a change in the relative contribution of the corrosion and mechanical abrasion to the total removal rate of Al.