Corrosion Performance of a Second-Generation High Ratio Zinc Silicate Coating in a Reinforced Concrete Environment

The macrocell method was used to evaluate a high ratio zinc silicate coating for corrosion performance on concrete reinforcing steel. Twenty-seven macrocells were constructed and subjected to cyclical chloride exposure for 364 days. The variables investigated were the effects of coating damage, the effects of coating the cathode steel, and two repair techniques. As a comparison, galvanized steel was used in six of the specimens, and epoxy-coated steel was used in three specimens.

It was found that the zinc silicate coating provided good corrosion protection throughout the 364 days of exposure when the coating was applied to all the steel. Substantial levels of corrosion were observed when only some of the steel was coated. The zinc silicate coating performed significantly better than the galvanized coating, although less corrosion was observed on the epoxy specimens than on the zinc silicate specimens due to the excellent initial condition of the epoxy coating.