The electrochemical quartz crystal microbalance (EQCM) was used to directly measure the dissolution rate at cathodic potentials, and thus the cathodic corrosion rate, of thin film analogs of phases in AA2024. Thin films of pure Al, Al-4%Cu, and Al2Cu were studied in 0.1 M NaCl containing 0, 10-4, or 10-2 M Cr2O7-2. A range of cathodic potentials was studied for each material. The true cathodic current density was calculated from the difference of the net current density and the dissolution rate, which was determined by the EQCM. The presence of dichromate in solution decreased both the cathodic corrosion rate and the cathodic current density on these thin film analogs. In particular, it decreased more effectively the cathodic reaction rate on Al2Cu, which can support faster cathodic reaction rates. In order to understand the initial mass increase observed on the Al2Cu analog, experiments were performed with Au electrodes, which do not exhibit extensive oxide film formation or dissolution. In addition, open circuit exposure of the polyurethane-coated Au electrodes in 0.5 M NaCl was also performed to study the usefulness of the EQCM as one of the possible tools for assessment of the corrosion degradation in coated metal systems.