AbstractThe erosion of arc cathodes is caused by evaporation and by forced fluid motion of the molten metal layer at the spot surface. The gross erosion rates (X1X2) of both components are derived from the equations of stationary and non‐stationary cathode spot models in a first approximation. These rates depend mainly on thermal properties of the metal, the atomic mass and the ionization state of the cathodic plasma. The calculated total gross ratesXtare between 67 μg/As (Be) and 3300 μg/As (Bi); the measured net rates (X̃) amount to about 10% ⃛30% of these gross rates. The range of the ratioX2/X1=vis 0,56 (Cd) ≦v≦ 2,64 (Mo). The various gross ratesX1.2tare strongly correlated with the net rates X̃ the relative rms deviations σrelfrom a power law fit are between about 15% and 30%. Resistive heating results in a worse correlation of the rates than ion impact heating. Probable causes of the deviations from exact functional dependencies a