The Nature of Metal-Electrodes/SF6 Reactions in SF6 Decomposition Due to Direct-Current Interruption under Simulated Circuit-Breaker Conditions

The nature of metal/SF6 reactions under direct-current(dc) simulated circuit-breaker conditions has been examined in orderto explore: 1) the identity of the process(es) responsible for the differentmagnitudes of electrode consumption for various pure metals; 2)the factors determining the different rates of reaction with SF6observed for different metals. It is concluded that high-current arcerosion, which would be expected to consume the metal in the absence ofSF6, is also the primary mode of weight loss of electrodes in thepresence of SF6. The rates of reaction of the evaporated metals seem to berelated to their tendencies to attack SF6 at the sulphur "site" and not,as is generally assumed, at the fluorine "sites." Rather good correlationsare observed between the reaction rates and the heats of formationper equivalent for metal sulphides or the electrode potentials formetal/metal sulphide electrodes.