PURPOSE: To improve binding force and to prevent falling off of the coating agent from the core rod by mixing ≥10wt% colloidal silica of ≤9μ diameter into the binder.

CONSTITUTION: The colloidal silica of ≤9μ diameter is used in a condition like an aqueous solution. The coated arc electrode is manufactured by applying a coating agent which uses only colloidal silica or a kneaded mixture of colloidal silica and ≥10wt% water-glass which has been used conventionally, on the surface of core rod, and then, drying and adhering the coating agent on the core rod.