United States Department of Transportation
i
Mitigation of Chloride-Induced Corrosion through Chemisorption
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2023-07-01
[PDF-9.01 MB]
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Edition:Final Report 7/1/2020-6/30/2023
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Abstract:Salt brine deicing solution contains chloride ions that can penetrate the passive layer and cause corrosion in rebars. While epoxy coatings are effective, they can be easily damaged during transportation and construction. In addition, aggressive localized corrosion is observed in damaged epoxy coated rebars. To address this issue, this project aims to mitigate chloride-induced corrosion using two methods. First, migratory corrosion inhibitors, specifically polyols, are employed as they can adsorb onto the metal surface and block the chemical reactions responsible for corrosion. Second, a biobased coating is synthesized to act as a secondary coat to the epoxy coated rebars and improve the bond with concrete. In TR-754 project, polyols have been proven effective as corrosion inhibitors and their effect on cementitious materials is investigated in this project. Cement mortar samples are exposed to 90 wet-dry cycles of a salt brine solution containing the optimal amount of polyols. Surface scaling, mass loss, compression strength changes, ion penetration and chemical changes are monitored periodically. The addition of the optimal amount of polyol corrosion inhibitor (1% w/w) to the deicing solution did not lead to further deterioration in the properties of the hardened cement mortar compared to using the salt brine alone. Another aspect of this study involves synthesizing a new soy-based coating material for repairing damaged epoxy coated rebars. The soy-based coatings are made using denatured soy protein isolate (SPI) and corn-derived sorbitol plasticizer. Subsequently, chemically inert oxide abrasives are incorporated into the SPI coatings in varying proportions to improve the mechanical properties, including abrasive resistance and lap shear strength. Potentiodynamic polarization tests and macrocell analyses have revealed significant improvements in short-term and long-term corrosion performance, with reductions of 94% and 78% respectively, compared to SPI coatings without abrasives. Furthermore, an improvement in bond strength of up to 90.41% is observed justifying the incorporation of abrasives.
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