Flame retardancy (FR) in polycarbonate (PC) and polypropylene (PP) was obtained through the application of an intumescent coating on the polymeric substrate. A better performance was obtained with PC, a char former and highly viscous polymer, compared to with PP. Indeed, whereas 61 μm was required to obtain good FR (by the UL94 V0 rating, in particular) in the case of PC, at least 158 μm needed to be used to give FR to PP. The aging of the coated materials induced by UV-filtered light radiation was then studied. This exposure led to a decrease in the FR. This effect was more pronounced in the case of PP compared to that of PC. The decrease in the FR was attributed to a decrease in the adhesion of the coating on the polymeric substrate because of its suspected physical aging. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39566.