Evaluation of Performance of Epoxy Based Coatings for Corrosion Inhibition in Reinforcing Bars

Abstract

Corrosion of reinforcing steel in concrete structures is a huge problem facing by the construction industry. Corrosion of reinforcing steel leads to a catastrophic failure of structures. Recently, to inhibit the corrosion of concrete structures either self-healing concrete or different epoxy coatings for reinforcing bars were used. In this study, three different types of epoxy based self-healing coatings: Nano-clay based, Tung-oil microcapsules based and hybrid of both epoxy coatings were proposed to inhibit the corrosion of reinforcing bars in concrete. Coatings were tested on plain mild steel rebar and rebar in concrete. Also coatings were initially damaged and tested to evaluate the self-healing performances of the coatings. Non-destructive testing used to evaluate the performances of all coatings and further destructive testing was done to quantify the non-destructive results. Pull-out strength testing was done to evaluate the effect of coatings on the bond strength between steel and concrete. Various tests revealed that, all the proposed coatings showed significant delay in corrosion as compared with conventional epoxy coatings whereas tung-oil based micro-encapsulated coatings were most promising out of all the coatings. In tung-oil micro-encapsulated epoxy coatings, self-healing effect was observed which was triggered by the damage of coatings either initially induced or due to corrosion initiation and achieved by the polymerization reaction of tung-oil. By introducing tung-oil microcapsules in epoxy, mass loss due to corrosion was 65% less and residual tensile strength was 63% more in comparison with conventional epoxy coatings. Pull-out strength barely affected by these coatings in comparison with conventional epoxy coatings.