Electrochemical Impedance Spectroscopy (EIS) was used to assess the ability of two different epoxy die attach adhesives to prevent corrosion of copper. Incorporating corrosion inhibitors in the adhesives was shown to reduce but not eliminate corrosion. EIS revealed that high water absorption in adhesives with low crosslink density significantly increased corrosion. Chloride impurities in the adhesives also increased corrosion. The diffusion coefficient of chloride in the epoxy was found to be 5 to 6 orders of magnitude lower than water. The presence of two time constants in the EIS scans correlated well with more corrosion.