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 two years. The variables investigated were the effects of coating damage, the effects of coating the cathode steel, and two repair techniques. For 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 protectoin throughout the period of exposure when the coating was applied to all the steel in the specimens. Substantial levels of corrosion were observed when only one layer of the steel was coated. The zinc silicate coating performed well, especially when any damage to the coating was repaired prior to placement of the concrete.