PERFORMANCE OF BLACK, GALVANIZED, AND EPOXY-COATED REINFORCING STEELS IN CHLORIDE-CONTAMINATED CONCRETE

The corrosion performance of black steel, galvanized steel, and epoxy-coated steel in concrete was investigated. Samples were exposed to cyclic salt water wetting and drying or to a continuous salt fog. Corrosion assessments included half-cell potential monitoring, chloride (Cl) analysis, and metal loss determinations. Galvanized steel resisted Cl-levels in concrete approximately 2.5 times that which caused corrosion of black steel. Zinc (Zn) provided sacrificial protection for a period approximately 4 to 5 times that for the initiation of corrosion of black steel in equivalent conditions. At the cut ends of galvanized bars, the Zn locally protected the exposed steel to a distance of approximately 8 mm. Epoxy coating imparted excellent overall corrosion protection. However, at points of damage to the coating and at the unrepaired cut ends of bars, localized corrosion on the exposed steel occurred over the same interval and to a similar extent as for uncoated steel. In many instances, corrosion proceeded along the bar under the epoxy coating with subsequent detachment of the coating. Repairs to cut ends of epoxy-coated bars did not delay corrosion of the steel substrate substantially.