Low-temperature plasma polymerization is a promising pretreatment technique to create environmentally friendly coating systems for corrosion protection of aluminum alloys. In this study, the pretreatment effects of plasma treatment and plasma polymerization on corrosion properties of alclad aluminum alloy 2024-T3 ([2A]) were investigated using electrochemical characterization techniques, including cyclic polarization (CP) and electrochemical impedance spectroscopy (EIS). The [2A] panels were coated with an ultrathin layer (similar to 50 nm) of plasma polymers in a direct current (dc) glow discharge of trimethylsilane or its mixtures with one of two diatomic gases (02 and N-2). The CP measurement results showed that the plasma polymer coated [2A] panels exhibited more negative corrosion potentials (E-corr), smaller corrosion currents (I-corr), and no surface passivation when compared with uncoated [2A] control panels. The lower values of I-corr, imply a higher corrosion resistance on the plasma polymer coated [2A]. When investigated using EIS, these plasma polymer coated [2A] panels exhibited higher impedance (/Z/) at lower frequency when first immersed in electrolyte solution, yet degraded quickly to a similar level as uncoated controls within I day of immersion. These results illustrated that thin plasma polymer films provided a certain but very limited corrosion resistance to [2A] substrate; their dominant role in plasma interface engineered coating systems still relied mostly on their adhesion enhancement at metal/paint interface as observed in our previous studies. (c) 2005 American Vacuum Society.