Anodic dissolution of copper in arginine and hydrogen peroxide based medium suitable for chemical mechanical planarization (CMP) slurry formulation was investigated using Electrochemical Impedance Spectroscopy (EIS). Potentiodynamic polarization and impedance data were acquired for copper dissolving in hydrogen peroxide and arginine. Reaction Mechanism Analysis (RMA) was employed to determine the mechanistic pathway of copper dissolution. The results indicate that there is no stable passivating film formation on the copper surface and direct dissolution was also ruled out. A two step mechanism involving cupric oxide as an intermediate species is proposed. The simulated data for this mechanism captures the essential features of the impedance spectra at various overpotentials. © The Electrochemical Society.