An environmentally friendly inhibitor, cerium cinnamate (CeCin), was studied as an additive to an epoxy coating. The effects of corrosion inhibition on AA 2024-T3 provided by cerium cation and cinnamate anion were investigated by electrochemistry impedance spectra (EIS) and polarization tests. It was found that cerium ion and cinnamate group have synergistic inhibiting effects. The EIS results show that CeCin is an effective inhibitor pigment for improving the corrosion resistance of epoxy coatings on AA2024-T3, as reflected by the much higher coating resistance than that of the blank epoxy coating. The inhibiting effect of CeCin during the onset of corrosion in defects of the epoxy coating was verified using scanning vibrating electrode technique (SVET), which is in agreement with the EIS results.