Thermal analysis techniques are useful to evaluate physical properties, curing behavior and degradation stability of powder coatings. The composition products of powder coatings were studied by the system composed of the thermogravimetry/differential thermal analysis coupled gas chromatography/mass spectrometry (TG/DTA-GC/MS). The system couples the thermal analysis with a gas chromatography separation and mass spectrometry identification methods. This system improves the analysis of the decomposition products of powder coatings and the identification of toxic products arising from their degradation. The TG curves recorded at different heating rates showed that the epoxy resin-based coating and the polyester-based coating are stable in air around of 210 degreesC when the degradation is started. The values of the activation energy E-a of the epoxy coating (159.8 +/- 11 kJ mol(-1)) and the polyester coating (162.9 +/- 5 kJ mol(-1)) were determined by Ozawa's method.