IBA-modified gypsum-containing epoxy resin coating for rebar: corrosion performance and bonding characteristics

Abstract

In this study, epoxy resin-based coating was developed for concrete reinforcement mild steel bar (rebar), and the corrosion behaviors of the uncoated rebar, single-cured epoxy resin-coated rebar, and indole butyric acid (IBA)-modified gypsum-containing epoxy resin-coated rebar were investigated in NaCl, CaCl2, and NaOH solution. Triethylene tetramine was used as curing agent for the epoxy resin, and IBA along with gypsum or silica was used in the composition of epoxy coating as inhibitor. Gypsum or silica was used separately as carrier of the IBA. Assessment was carried out on the basis of the corrosion resistance performance and bonding characteristics of the coated rebar. Corrosion resistance performance of the coating was evaluated using polarization resistance test, cathodic disbonding test, and corrosion-induced cracking study. Electrochemical tests showed that incorporation of IBA significantly improved the corrosion protection capacity of the epoxy coating against rebar corrosion. This was related to its healing effect on surface passivation against attack by a corrosive environment. In addition to corrosion protection capacity, bond strength between concrete and rebar is determined through pullout test. It was found that the coating has no adverse effect on the bond strength between embedded rebar and concrete, and additionally, it contributes to the bond strength due to adhesion properties of the resin.