Continuous low level current (CLLC) measurements are used to investigate the vulcanization of natural rubber (NR) with sulfur (S), 2-mercaptobenzothiazole (MBT) and zinc oxide (ZnO) in the presence and absence of stearic acid (StAc), At elevated temperatures, the mixtures show increased conductivity attributable to the presence of ions. Current curve maxima characteristic of transitory ionic species are detected. Possible ions are discussed in connection with references in literature. For the mixture N/S/MBT/ZnO/StAc, the comparison with the rheometer measurements exhibit a relationship between the formation of ionic intermediates and crosslinking of the polymer, The suitability of this electrochemical method for the investigation of ionic species in crosslinking reactions is demonstrated.