The aim of this study was to compare the weathering performance of two commonly refinish coatings used in a domestic car manufacturer based on polyurethane (PU) and acid-catalyzed alkyd-melamine resins. The replacement of the alkyd-melamine refinish with the PU system was shown to largely lower the reported fading behavior of the monocoat system. For better comparison between the refinish coatings, an original equipment manufacturers' (OEM) topcoat, Cured at production line, was also used. Different characterization methods including DSC, atomic force microscopy, thermo gravimetric analysis, DMTA, and Fourier transform infrared spectroscopy were performed to elucidate the changes observed in the optical, mechanical, and weathering performance Of studied coatings. It was found that the main reason for the inferior behavior of the acid-catalyzed coatings compared with that of the PU and OEM was due to its low crosslinking density. The poor weathering resistance of the former coatings was attributed to its incomplete curing reaction and therefore, to its immatured film formation. (C) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 111: 2946-2956, 2009