Rationale: Industrial TNT contains substances other than 2-4-6-trinitrotoluene that are of primary interest for military applications. The degradation of industrial TNT by aging and by contact with steel surfaces, which represent real situations of use of the material, was investigated. There is practical knowledge about this degradation, but the literature lacks details of this process. Methods: Small steel samples used in military ammunition were covered with TNT and heated at 75 ºC for 30 days under vacuum. Some of the samples were previously painted with a red alkyd paint coating that protects the metallic surface. After aging, the TNT was scraped off the metal pieces and analyzed by scanning electron microscopy, Fourier-transform infrared spectroscopy and gas chromatography-mass spectrometry. Results: The results showed in detail how the integrity of the TNT is maintained even under thermal stress and in contact with the steel surface. Although some changes were observed in the surface appearance of the TNT, all the analyses indicated the maintenance of the chemical integrity of the industrial TNT. The only change in composition identified is related to the contamination with degradation products of the alkyd paint coating and not with the degradation processes of the TNT itself. Conclusions: Our results indicated that although there are many TNT degradation processes reported in the literature, for cases involving thermal stress degradation of TNT in solid phase in contact with metal, these processes are irrelevant. Thus, it is possible to elucidate the safety of TNT when packaged in steel artifacts, which represent the majority of military ammunition.