Evaluation of chemical resistance/oxidation of Si_3N_4-SiC sidelining materials used in Al electrolysis cells

摘要

Since 1997 SINTEF Materials Technology has tested a large number of commercially available nitride bonded silicon carbide materials. The samples have been tested in a sidelining test cell on a laboratory scale under electrolysis for 50 hours at a temperature of about 955°C. The test pieces were exposed simultaneously to liquid aluminium, cryolite melt, electrolysis gas (CO_2 and CO) and vapour deposit (mainly NaAlF_4). The volume, open porosity and density of each material were measured (ISO 5017) before and after the test. The degree of corrosion was related to the volume loss of the samples during the test, and ranked on a scale from 0 to 10 (0 is best, 10 is worst quality). A review is given of the test results obtained since 1997.