Abstract
The chemical resistance of various silicon nitrides will be determined for several corrosive agents(phosphoric acid, sulphuric acid, soda lye and water) at temperatures between 25 and 100 deg C. The corrosive resistance turns out to be dependent on quantity, composition and structure of the glassy phase. Insignificant formation of layers with body increase without stability changes and more or less complete dissolution of parts of the glassy phase with a significant decrease of weight and resistance can be observed. Whereas in 1-molar 90 deg C hot solutions the chemical stability is highest in soda lye, it is lowest in sulphuric acid. The increased corrosive resistance in 1-molar phosphoric acid in comparison to 1-molar sulphuric acid is attributed to the formation of yttrium phosphates at teh reaction area.