Electrode Erosion by Spark Discharges

Theoretical estimates of the areas of electrode hot-spots are made from a consideration of the lateral spread of the electrons and positive ions due to diffusion and their space charge. Areas thus found show that very high current densities of the order 10 6 A/cm 2 are possible in typical short spark gaps at atmospheric pressure. The energy balance at such hot-spots for an equilibrium temperature equal to the boiling point of the electrode material is then considered and, neglecting chemical attack, an equation is set up relating the volume of electrode evaporated per spark (i.e. the spark erosion) to the physical properties of the electrode material.