An investigation of new inhibitors to mitigate rebar corrosion in concrete.

Rebar corrosion in concrete is the most costly and performance-limiting problem facing the nation's infrastructure. One of the most practical and economical approaches to this problem is to use corrosion inhibitors in a quality concrete mix for new construction. This investigation examined the corrosion inhibition characteristics of a series of compounds in a simulated pore solution (SPS), saturated calcium hydroxide, using rebar samples. The compounds were selected based on qualities of either low water solubility, good performance in alkaline environments, or promising results in the literature. The compounds were compared to strontium chromate and three commercial inhibitors in SPS. After approximately 1 week of rebar exposure, sodium chloride was added periodically over 2 weeks to simulate the gradual accumulation of chloride in concrete. Inhibitor performance was assessed using the open circuit potential, the polarization resistance, and a semiquantitative analysis of visible corrosion. Disodium beta-glycerophosphate and barium metaborate showed excellent inhibitor performance that was comparable to that of the chromate-based compound and surpassed the commercial inhibitors at comparable concentrations. Based on this screening, the authors recommend that the effect of these compounds on the curing and strength properties of concrete, as well as their corrosion inhibition characteristics in concrete, be examined.