Corrosion current distribution of macrocell and microcell of steel bar in concrete exposed to chloride environments

The corrosion morphology of rebar in concrete was observed and the corrosion current distribution along the circumference of the steel bar was analyzed theoretically and verified by experiments. The results show that the macrocell corrosion must co-exist with microcell corrosion of reinforcements in concrete. The microcell corrosion takes place in active zone of the rebar surface facing the concrete cover. The macrocell corrosion current Ig between the internal and external surfaces not only further expedites the corrosion process on the surface of the steel bar facing the concrete cover, but also forms cathode protect from the corrosion of the side of steel bar opposite to the concrete cover. Both macrocell and microcell corrosion mechanisms could play significant roles, and the total corrosion could be underestimated if either of them is overlooked. The total corrosion current equals the sum of microcell corrosion current Icorr2 of active steel and anodic dissolution current (ΔIcorrA) caused by Ig.