Behaviour of various glass-ceramic sealants with ferritic steels under simulated SOFC stack conditions

Under experimental conditions simulating SOFC stacks, it appeared that excessive internal Cr oxidation of the ferritic steels, sometimes accompanied by external Fe-oxide formation, only occurred in the case of glass-ceramics containing minor amounts of PbO. This internal oxidation finally resulted in a volume change of the ferritic steel, which was manifested in bulging of the steel. As a consequence, the glass-ceramic was pushed away from the steel surface and crack formation at the glass-ceramic-steel interface occurred. The rate of corrosion attack strongly depended on the detailed steel composition. Increasing Si content apparently increased the rate of the corrosion attack, and thus possibly decreasing the time for the occurrence of short-circuiting.