Degradation factors of a coated impregnated cathode

An M-type cathode has two life-limiting factors: the reduction of impregnants and the degradation of surface coating. The optimum operating temperature and lifetime against the cathode current density are derived for the former. The quantitative temperature dependence on the lifetime of the surface coating is determined by comparing the measured results and theoretical calculations. A comparison of these factors reveals that the lifetime of a coated impregnated cathode is determined by the reduction of impregnants when the cathode is operated at the optimum temperature and with a current density less than 24 A/cm ²