Influence of sol-gel film on fusion bonded epoxy coatings on carbon steel: Surface, adhesion, mechanical, and corrosion protection characteristics in a saline medium

Background: Utilizing sol-gel film as an intermediate layer is considered one of the most fascinating routes to improving the overall efficiency of protective coatings. The current study aims to expand the surface protective performance of the fusion bonded epoxy (FBE) coating using deposited sol-gel films at the interface between the FBE and steel surface. Methods: The structure, surface microstructure, and topography were characterized for prepared sol-gel films on carbon steel (CS). Also, contact angle measurements were performed to evaluate the surface free energy and wettability of the sol-gel coated CS substrates. Significant findings: The adhesion test results showed that the CS surface with silane films enhanced the interfacial adhesion with the FBE, providing high adhesive strength for FBE coatings. The corrosion test results showed the improved anticorrosion performance of sol-gel deposited CS surface coated with FBE by showing high impedance values after one-month exposure. The achieved results confirmed that the CS with the sol-gel films significantly enhanced the surface energy by 2.7 times and improved surface hardness by 30 % compared with the bare and interfacial adhesion bonding of the subsequent FBE coating, and provided the improvement on the anticorrosion performance of FBE films in the saline medium.