Comparing the corrosion resistance of thermo-mechanically treated rebars of low alloy and mild steels embedded in chloride-contaminated concrete mortars

THE CORROSION characterize of mild steel (MS) and low-alloy steel (LAS) embedded in mortars have been studied in the presence and the absence of chloride ions. Electrochemical DC polarization, AC impedance, acoustic emission, and scanning-electron microscopy studies were performed to characterize the steels. It was observed that the low-alloy steel has a corrosion resistance about 1.5 times better then the mild steel. Impedance, galvanic corrosion, cyclic polarization, and SEM studies confirmed that the improved resistance of LAS over MS is due to the formation of impervious and compact trust layer on LAS. The results show that the rate of increase in corrosion rate with chloride content in mortars is considerably higher for MS than the LAS. Neither of the two steels were observed to be in a completely passive state in the presence of chloride ions; the dissolution current density in the pseudo-passive zone was, however, about ten times lower than LAS than for MS.