For silicon carbide, when exposed to high temperatures in an oxygen atmosphere, passive and active oxidation processes are characteristic, therefore, materials based on SiC must be protected at temperatures above 1300 ° C. Sodium sulfate, the presence of which is possible as an impurity in the fuel, leads to the destruction of the protective layer of SiO2 formed during the oxidation of SiC. Coatings based on the Y2O3 – Al2O3 – SiO2 system are promising for protecting materials based on silicon carbide from the effects of an oxidizing
atmosphere and water and salt vapors. Studies have been carried out on the interaction of coatings
of the Y2O3–Al2O3–SiO2 system obtained by the sol-gel method with water vapor and Na2SO4 salt. As a result of the studies carried out, it was found that coatings based on the Y2O3 – Al2O3 – SiO2 system have good
oxidative and chemical resistance to water vapor and Na2SO4 salt vapor in the temperature range
of 1300 – 1450 °C. The weight gain for coated samples when tested in Na2SO4 salt vapor did not exceed 1 %. The initial SiC substrates are characterized by active oxidation processes with a weight decrease
from 8 to 11 %. DSC analysis in combination with mass-spectrometry of the crystallized sample of the
Y2O3–Al2O3–SiO2 system coating after heating in Na2SO4 salt vapor to a temperature of 1550 °С showed
that at temperatures above 900 °С Na2SO4 decomposes with the release of SO2 and SO3–