Chemical mechanical planarization (CMP) is one of the most important processes in the semiconductor industry. In a semiconductor manufacturing process, each layer on the wafer needs to be planarized before the next layer is deposited. This planarization is often accomplished using CMP. In order to understand the exact mechanisms of CMP and develop more advanced processes, better understanding of the role of chemical reactions during polishing is required. This work focuses on reactions on the surface of copper, including etching and repassivation. Specifically, surface reactions on copper in nitric- acid based solutions with or without benzotriazole (BTA, a corrosion inhibitor) and/or H2O2 were investigated using electrochemical tools, including potentiodynamic (PD) scans, electrochemical impedance spectroscopy (EIS), and studies of the time-evolution of impedance at different DC potentials. When Nyquist plots are studied for this system, the impedance at the frequencies ~ 100 kHz represents the ohmic resistance. This is the sum of the resistance of the electrolyte, the connections between the electrodes and the power/control units, and any precipitated salt or resistive viscous liquid film on the electrode of interest. Since the first two resistances can be regarded as constant for the conditions studied here, observed changes in impedance at this frequency are interpreted to be the result of the formation of a salt/viscous liquid layer at the electrode surface. The dynamics of the formation of this layer are observed by measuring the changes in the impedance of a bare copper substrate at 100 kHz in different applied DC potentials. The substrate is created when a Teflon-coated copper sample is cut in an electrolyte solution using a guillotine electrode apparatus. This exposes a bare copper surface on which a reaction can occur without any influence of a pre-existing oxide layer, which is exactly what happens during CMP. Using the guillotine electrode, impedance was measured as a function of time at 100 kHz, with different applied DC potentials. The experiments were performed using (I) 1wt% HNO3, (II) 1wt% HNO3+0.02M BTA, and (III) 1wt% HNO3+0.02M BTA+5wt% H2O2. PD scans were performed in each solution in order to characterize the anodic behavior of copper. Different DC potentials from the active dissolution, active/passive transient, and passive region were applied at 100 kHZ while the impedance was monitored. The open circuit potential was also studied in this manner. In solution I, an increase in impedance was observed when higher potentials than the active/passive transient potential were applied. The impedance was constant at the OCP and when potentials in the active region were applied. With solution (II), the exact reverse response was obtained. Complex responses were obtained from solution (III). Interpretations were made for each outcome in terms of surface layer formation and the chemical composition of each system.