Effect of Microstructures on the Corrosion Behavior of Reinforcing Bars (Rebar) Embedded in Concrete

This work aims at understanding the effect of microstructures (coarse, medium and fine ferrite–pearlite, martensite and tempered martensite) of a reinforced (rebar) steel developed by various heat-treatments (furnace cooling, air-cooling, force air-cooling, quenching, and tempering, respectively) on its corrosion behavior in freely aerated 3.5% NaCl + 3.5% FeCl₃ solution. The impressed current technique was used for forcing corrosion of the rebar, which was embedded in concrete coupon, so that correlation could be drawn between microstructure and corrosion behavior in short duration. Corrosion susceptibility increased from force air-cooled–quenched–air cooled–furnace cooled–tempered steels. The crack formation in the concrete was directly related to the rust composition and thickness, presence of crack in the rust, alpha/gamma* ratio and critical corrosion amount.