Experience from Laboratory Testing of Commercial Silicon Bonded Silicon Carbide Materials. Typical Properties and Analyses

Silicon nitride bonded silicon carbide is currently the most common type of sidelining material in aluminium electrolysis cells. The material has replaced carbon due to better chemical resistance, better oxidation resistance, and better thermal performance, which opens for increased productivity. Today, many producers offer carbide based sidelining materials, and the users ask for quality evaluations. During the last two decades, SINTEF and partly NTNU have developed test methods and analyses for quality evaluation. The studies have been financed through national research programs as well as by testing of materials from the different suppliers. The work has contributed to improved characterisation and descriptions of the most important material parameters, as well as better understanding of the industrial performance. The present paper describes our findings regarding typical physical and chemical parameters, based on analyses and tests of several hundred samples from suppliers worldwide. The results from some autopsies of industrial cells for studying the degradation mechanisms are included. Based on our findings and experience, a set of up-dated recommendations and useful specifications for suppliers as well as for users has been worked out.