Evaluation of Multiple Corrosion Protection Systems and Stainless Steel Clad Reinforcement for Reinforced Concrete

Abstract

The corrosion performance of multiple corrosion protection systems and stainless steel clad reinforcement is compared and evaluated in this study. Conventional steel and conventional epoxy-coated steel coated with 3M™ Scotchkote™ 413 Fusion Bonded Epoxy are used as “control” systems. The corrosion protection systems, which are compared to the control systems based on macrocell and bench-scale tests, include stainless steel clad reinforcement, conventional epoxycoated reinforcement cast in concrete containing one of three corrosion inhibitors (DCI-S, Rheocrete 222+, or Hycrete), epoxy-coated steel with the epoxy applied over a primer coat that contains microencapsulated calcium nitrite, epoxy-coated steel with the epoxy applied after pretreatment of the steel with zinc chromate to improve adhesion between the epoxy and the steel, epoxy-coated steel using improved adhesion epoxies developed by DuPont and Valspar, and multiple coated steel with a zinc layer underlying the DuPont 8-2739 Flex West Blue epoxy layer. Macrocell tests are conducted on bare bars and bars symmetrically embedded in a mortar cylinder. Bench-scale tests include the Southern Exposure, cracked beam, and ASTM G 109 tests. The results indicate stainless steel clad reinforcement exhibits very good corrosion performance when the cladding is intact. In uncracked mortar or concrete containing corrosion inhibitors, corrosion rates and losses are lower than observed using the same mortar and concrete with no inhibitor. For concrete with cracks above and parallel to the reinforcing steel, the presence of corrosion inhibitors does not provide an advantage in protecting the reinforcing steel. In uncracked concrete, a lower water-cement ratio results in corrosion rates and losses that are lower than observed at the higher water-cement ratio. In cracked concrete, a lower-water cement ratio provides only limited additional corrosion protection when cracks provide a direct path for the chlorides to the steel. iii When adhesion loss between epoxy and steel is not considered, a 230-mm (9 in.) deck reinforced with conventional epoxy-coated steel or one of the three high adhesion epoxy-coated steels is the most cost-effective. When the potential effects of adhesion loss are considered, at a discount rate of 2%, the most cost-effective option is a 216-mm deck containing stainless steel clad reinforcement.