Corrosion Performance of Epoxy-Coated Reinforcement in Aggressive Environments

The objective of this research was to investigate the integrity and corrosion performance of epoxy-coated reinforcement in aggressive environments. A series of experimental studies were conducted: a) hot water immersion and knife adhesion testing for assessment of coating adhesion; b) materials and procedures for repairing coating damage; c) degree of mechanical damage caused during concrete placement when using metal head and rubber head vibrators; d) accelerated corrosion of coated bars embedded in macrocell and beam specimens placed in a corrosive environment for more than four years. The effects of coating condition and amount of damage, repaired vs. unrepaired damage, bar fabrication, and concrete cracking were studied.

Regardless of coating condition, the performance of epoxy-coated bars was better than that of uncoated bars. Unlike black bars, coated bars did not exhibit deep pitting or substantial loss of cross section at crack locations. Damage to epoxy coating was the most significant factor affecting corrosion performance. Bars with coating in good condition, without any visible damage, performed best. The greater the size and frequency of damage, the more severe and extensive the amount of corrosion. The performance of bars that were fabricated or bent after coating was worse than that of coated straight bars. Mixing coated and uncoated bars in the same concrete member led to undesirable performance. Patching damaged coating reduced but did not prevent corrosion, particularly at bar ends. The most important factor in coating repair was the type and properties of the patching material. Surface preparation prior to coating had little effect. The absence of cracks in the concrete delayed, but did not prevent the onset of corrosion of coated bars. During consolidation of concrete, rubber head vibrators caused less damage to epoxy-coated reinforcement than did comparable metal heads. Hot water and adhesion tests were useful and practical for evaluating coating adhesion after production. An adhesion test procedure was developed and is recommended for quality control. A set of recommendations for proper quality control, design, and construction practice of structures with epoxy-coated reinforcement was proposed.