Spark decomposition of SF6/H2O mixtures

The spark decomposition of mixtures of SF₆ (partial pressure from 100 to 500 kPa) and water (concentrations between 600 and 2000 VPM) has been studied. The sparks were generated between a point (stainless steel) and a plane (aluminum) either under 50-Hz AC voltage or by discharging a capacitor. Owing to the high water content the only stable gaseous oxyfluorides detected were, in order of decreasing importance, SOF₂ and SO₂F₂. The yields of these two byproducts have been measured as a function of the number of sparks, the SF₆ pressure, and the H₂O pressure. When the sparks additionally struck a solid insulator (polytetrafluoroethylene or biphenolic resin), CF₄ was detected. Its appearance was paralleled by a sharp increase in the yield of SOF₂, whereas that of SO₂F₂ remained unchanged