The morphology of a coating of Ce oxyfluoride on a conductive substrate is improved by addition of yttrium, lanthanum, praseodymium and/or other rare earth metals. Whereas the pure Ce-oxycompound coating shows cracks which frequently extend throughout the entire thickness of the coating, thus exposing finite portions of the substrate to eventual corrosive attack from the environment, the improved coating including the above doping element(s) comprises a substantially impervious structure. Coatings of this nature may be employed with non-consumable anodes in molten aluminum electrowinning cells or as chemical sensors, corrosion protection and other applications.