Enhancement of corrosion resistance and bond strength in rebars employing abrasives-infused soy-protein isolate coatings

While epoxy coatings effectively prevent rebar corrosion, they can sustain damage during transportation, making them susceptible to localized corrosion during service. Additionally, these coatings can reduce the bond strength with concrete by over 20%, necessitating an increase in development length. Although soy-protein coatings could potentially repair damaged epoxy coatings in the field, they may further reduce the bond strength. This study aims to enhance the corrosion resistance of soy-protein isolate (SPI) coatings without undermining their bond with concrete. To achieve this, five new coating formulations were prepared by blending chemically inert oxide abrasives into SPI coatings in varying proportions. These modified soy-protein coatings were then assessed through physical, chemical, mechanical, and electrochemical analyses to measure their improvements. Adding abrasives beyond a certain weight proportion increased the viscosity and thickness of the coatings, improving their mechanical properties, including abrasive resistance and lap shear strength. Potentiodynamic polarization tests and macrocell analyses revealed a 94% and 78% improvement in short-term and long-term corrosion performance respectively. Moreover, when compared to conventional SPI coatings, the bond strength of the modified soy-protein coatings improved by up to 90.41%. In conclusion, SPI coatings infused with abrasives outperform traditional SPI coatings and could serve as superior secondary coats. They could even be considered as stand-alone coatings for rebars.