Corrosion Protection of Steel Rebar

Steel corrosion is a major concern for any society with reinforced concrete structures. More specifically, the United States, with its vast infrastructure of concrete and steel bridges, superhighways, and reinforced concrete buildings has spent billions of dollars for corrosion protection. Among the commercial technologies available today, migrating corrosion inhibitors (MCIs) show versatility in that they can be incorporated as admixtures, surface treatment, or used in rehabilitation programs. The effectiveness of Cortec’s MCI 2022, a mixture of amine carboxylates, amino alcohols and siloxane, on reinforced concrete using various application methods was evaluated. Bode and Nyquist plots showed high polarization resistance values for inhibitor treated concrete. XPS analysis verified the presence of inhibitor chemistry and chloride molecules on the steel rebar surfaces. Depth profiling revealed a 100 nm amine-rich layer of inhibitor along with chloride ions on the rebar, confirming that MCI had migrated through the concrete coverage to suppress chloride ion corrosiveness. Eight concrete specimens were prepared with reinforcement placed at 1 inch (2.5 cm) concrete coverage and tested for a period of 400 days. MCI 2022 was applied directly to the rebar, by surface impregnation and combined in a mortar coating. Electrochemical monitoring techniques were applied to samples immersed in 3.5% NaCl at ambient temperatures. The corrosion behavior of the steel rebar was monitored using AC electrochemical impedance spectroscopy (EIS). The changes in the polarization resistance and the corrosion potential of the rebar were compared with previous investigations conducted on several admixtures and stainless steel rebar. Click Here for more info.