Thermal Stability of Organic Coatings for Aluminium and Its Environmental Aspects

Thermal stability of organic coatings for aluminum plays a key role not only in specific applications, but also in the recycling process of aluminum scrap. For production of secondary aluminum it is necessary to remove coatings from scrap. Rests of unremoved coatings affect the quality of final aluminum. Most of methods for coatings removing are based on thermal decomposition. This process leads to emission of various organic compounds which present potential risk for human health and also for environment. Thermal stability of all tested coatings with increasing temperature was study with use of thermogravimetric analysis (TGA). Significant degradation of coating started at temperature 200 degrees C and at temperature 450 degrees C was most of the tested coating degraded and remained only inorganic part of coating. Inorganic part render approx. 30 % of the original coating mass. Degradation of tested coatings was also confirmed by Fourier transform infrared spectroscopy (FTIR) analysis. This work also deals with study of inorganic/organic ratio of hybrid coating on real sample of scrap for recycling. The thermolabile part of coating is degraded during heating, which lead to emission of organic compounds and products of degradation which can affect human health and also the environment.