The invention relates to an aqueous paint composition comprising a mixture containing: (1) an aqueous paint; (2) a colloidal dispersion of a cerium compound, having a pH of at least 5 and comprising a water-soluble or water-dispersible polymer (i) which is obtained following the polymerisation of at least one monomer (I) corresponding to (I) an ethylenically-unsaturated, aliphatic, cyclic or aromatic, linear or branched monocarboxylic or polycarboxylic anhydride or acid and, optionally, a monomer corresponding to (II) a polyoxyalkylene ester of an ethylenically-unsaturated carboxylic acid; and (3) a base. The invention also relates to paints and varnishes containing said composition.