Deposition of Ce-Al-O coatings on Al 2024-T3 alloy substrates was conducted by magnetron co-sputtering of CeO2 and Al targets. The incorporation of Al into the CeO2 film resulted in an amorphous or nanocrystalline structure with binding energy states different from Al, Al2O3, and CeO2. Electrochemical measurements indicated that the amorphous or nanocrystalline Ce-Al-O coating increased the corrosion resistance of bare Al 2024-T3 substrates by more than three orders of magnitude, and exhibited a very different cathodic and anodic protective mechanism compared to Al and CeO2 coated and as-polished Al 2024-T3 samples. The oxygen reduction cathodic reactions on the Al alloy surface have been significantly suppressed, and the tendency for pitting corrosion of Al alloy substrate has been significantly reduced by the Ce-Al-O coating. The improved corrosion performance is attributed to the unique microstructure and the resulting interaction and redox reactions of the Ce, Al, and O atoms within the Ce-Al-O coatings. (C) 2016 The Electrochemical Society. All rights reserved.