Modified Epoxy Coatings for Corrosion Inhibition in Reinforcing Bars in Concrete

Abstract

Corrosion of reinforced concrete structures is one of the biggest problems faced by the construction industry with billions of dollars spent annually on corrosion control and mitigation. Epoxy Coated Rebars (ECRs) have been reported to effectively mitigate corrosion in concrete structures. However, their utilization is constrained by the presence of micro-pores and the inherent brittleness of epoxy coatings. This study delves into the mechanisms of corrosion inhibition through the application of nano-modified epoxy-based coatings. Three distinct formulations of modified epoxy-based coatings were precisely evaluated: nano-clay-modified epoxy coatings with polyaniline, graphene-derivatives modified epoxy coatings with carbon nanotubes and self-healing tung-oil microcapsules-based nano-modified epoxy coatings for plain bars directly and when they were further embedded in concrete and exposed to accelerated chloride corrosion. A multifaceted evaluation approach of Non-Destructive Testing (NDT) and Destructive testing techniques were employed to ascertain coating corrosion efficacy comprehensively. NDT monitoring comprises of visual inspection, corrosion current measurements and ultrasonic guided waves monitoring techniques whereas destructive testing techniques involved evaluation of loss in mass, tensile strength and pull-out strength vis-à-vis corrosion exposure. Nano-clay modified epoxy coatings examines the efficacy of nano-modified epoxy coatings using four different silane-treated nano-clays (Montmorillonite-MMT, Organic Montmorillonite-OMMT (Cloisite®15A and Cloisite®30B) and Halloysite-HNT) in a combination with polyaniline (PANI). PANI being good pigment material for anti-corrosion coatings is expected to provide enhanced corrosion resistance due to its unique ability to intercept electrons from the metal surface and transfer them to outside the coating. It was confirmed that nano-clay modified epoxy coatings showed superior performance in comparison with pure epoxy coatings, as a result of enhanced barrier