This paper examines plasma-sprayed aluminum oxide and chromium oxide layers as well as aluminum phosphate-sealed layers by means of thermogravimetric analysis in order to determine both the stability of plasma-sprayed layers and the phosphate reaction as a function of the temperature during the sealing process. The thermogravimetric analysis of aluminum oxide layers showed no changes in weight in the layer during the heat treatment. In the case of chromium oxide layers, on the other hand, the thermogravimetric analysis showed an increase of 1.7 percent by weight due to oxidation of the sprayed layer. The thermogravimetric analysis of sealed layers showed weight losses of approximately 14%, which agreed well with the behavior of the pure seal. In the case of aluminum oxide layers, the behavior differed from that of sealed chromium oxide layers as a result of the reaction between the seal and the aluminum oxide layer. Paper includes a German-language abstract.