A method of using an activator in a compact discrete sacrificial anode assembly that is assembled within an anode cavity in concrete is described. The method includes providing a sacrificial anode, and an activator to activate the sacrificial anode, and a backfill to embed the sacrificial anode and the activator in an anode cavity in the concrete. The activator is provided as a discrete contained unit for dispersion through the backfill to surfaces of the sacrificial anode, and the unit at least in part separates the activator from any electrolyte in contact with the sacrificial anode. The activator is separated from the backfill prior to use. The advantages of this invention include limiting corrosion of the sacrificial metal element prior to use, containment of the health and safety risk presented by an activator, and providing a facility to control the quantity of activator installed in a sacrificial anode assembly. A surprising benefit results from a transient increase in the temperature of the assembly.