Electrical discharges in a pulsed vacuum arc system at low pressure were produced using a peak current of 100A with pulses of 30 ms. Discharges were carried out applying a voltage of 104 V between the electrodes. Materials used as cathode were Ti, Zr, Ni, Cu, Mo and W. The cathodes morphology after the discharge production was studied using the scanning electron microscopy (SEM) technique. Ti and Zr presented the highest erosion. Moreover, circular craters on Ni and Mo cathodes were observed and a region of the Zr cathode, with high erosion and great quantity of craters was analyzed. The discharge voltage for each material was measured, obtaining arc voltage values. Finally, relationships between arc voltages and some material characteristics as melting point and boiling point were observed, presenting an exponential tendency.