Repassivation of corroded rebar by early supply of high corrosion protection current using hybrid galvanic anode

This study aims to clarify the functional characteristics of a galvanic anode system with a zinc core and a built-in DC battery, to establish a practical and rational method for using galvanic anodes. Experimental research was conducted for one year, simulating the repair of chloride-damaged rebar in cover concrete using galvanic anodes. The rebar was pre-corroded, and the concrete was premixed with up to 2 % chloride by mass of cement. The hybrid galvanic anode generated a higher corrosion protection current than the conventional galvanic anode in the early stages due to the built-in battery. During this period, the corrosion protection current and the 24-hour potential shift (depolarization) were more influenced by the type of galvanic anode or voltage of the battery. In the later stages, when the zinc core was the source of the protection current, the current density was higher and the potential shift was smaller in the beams with higher chloride density. After a sufficient supply of electric charge, the rebar was repassivated, with some beams showing a 24-hour potential shift of less than 100 mV and/or a corrosion protection current of less than 1 mA/m 2 . The built-in battery contributed to a significant supply of corrosion protection current in the initial stages, thereby accelerating the repassivation of the corroded rebar. • The hybrid galvanic anode generated a higher corrosion protection current in the early stages due to the built-in battery. • The built-in battery contributed to accelerate the repassivation of the corroded rebar. • After being repassivated, some rebar showed a small 24-hour potential shift and/or a small corrosion protection current.