Porous self-roughened epoxy coating constructed via induced phase separation technology to strengthen the steel–concrete interfacial bond

Epoxy coatings have shown great potential for protecting reinforcing steel because of their excellent chemical resistance, strong adhesion to steel substrates, and superior barrier performance. However, the inherently weak bonding at the epoxy–concrete interface remains a major limitation that restricts their broader application in reinforced concrete structures. To address this issue, epoxy coatings with controlled pore sizes were fabricated on reinforcing steel surfaces through a combined sol–gel and phase inversion method, aiming to strengthen the interfacial interaction between the epoxy coating and concrete and thus improve structural durability. The surface morphology, interfacial bonding performance, and corrosion resistance of the fabricated coatings were systematically characterized by laser scanning confocal microscopy, Fourier transform infrared spectroscopy, electrochemical measurements, and pull-out tests. The findings suggest that the spontaneously formed non-penetrating pores on the coating surface markedly improve the adhesion of epoxy-coated concrete interfaces by promoting interfacial friction and mechanical interlock. In particular, the tensile bond strength between the coating and mortar was improved by up to 3.6 times compared with that of the control group，and the pull-out shear strength between the coated rebar and concrete was enhanced by up to 1.5 times. In addition, the incorporation of pore-forming components promoted the crosslinking of the epoxy network, which further enhanced the corrosion resistance of the coating. These findings provide an effective strategy for simultaneously enhancing interfacial bonding and the corrosion resistance of epoxy-coated reinforcing steel embedded in reinforced concrete.