Aluminium alloys are widely used in architectural, aeronautic and car industries. They are usually protected by the formation of a thick oxide layer (anodization) or by applying an organic coating. In the latter case, a particular type of corrosion called filiform corrosion can occur. This corrosion is characterized by a paint adhesion loss and the occurrence of threads at the interface substrate-pretreatment-coating. As the reduction of oxygen and chloride initiation play an important part in filiform corrosion, the idea developed in this work was to use the efficiency of cerium pretreatments (widely described in literature) to prevent development of filiform corrosion for aluminium alloy 1050 coated with a cataphoretic painting. Three methods have been followed : electrophoresis in aqueous colloidal cerium sulfate solution, phosphoric anodization followed by cerium electrophoresis and sulfuric anodization in a mixed H2SO4/Ce(SO4)(2) solution. Initial properties and their evolution during immersion in NaCl were recorded by EIS. Spectroscopic ellipsometry has allowed to characterize the conversion layer for the electrophoresis treatment. The efficiency of Ce treatment towards filiform corrosion was not as expected with a cataphoretic paint. This is due to an important damage of the pretreatment during painting. But the good evolution of sample properties during exposure to NaCl allow us to think that these pretreatments could be efficient with anaphoretic or electrostatic painting.