Comparative Studies of Galvanized and Epoxy-Coated Steel Reinforcement in Concrete

This study describes comparisons of the corrosion performance and pullout strength of black, hot dip galvanized and fusion bonded epoxy coated steel reinforcement in concrete. Accelerated exposure testing confirmed that zinc coating was able to considerably delay the onset of corrosion and epoxy coating effectively eliminated corrosion provided the coating was not damaged. Where coated reinforcement was left with cut ends unrepaired, the epoxy coated bars showed early corrosion of the exposed steel with corrosion progressing along the bar under the coating. Even where cut ends were repaired, the epoxy coated bars showed many sites of breakdown of the repair and corrosion of the underlying steel. For plain reinforcement, the ultimate bond strength of epoxy coated bars is some 17 percent less than that for black steel bars, while that for galvanized bars is some 31 percent greater than for black steel. The ultimate bond strength of deformed bars is up to 50 percent higher than that of plain bars. The passivation of galvanized plain bars by chromate additions to the concrete mix water in the range 15-150 ppm could not be shown to significantly improve the bond strength.