Corrosion Protection and Self-Healing Properties of Epoxy-Based Smart Coatings with Porous Silica, Sodium Phosphate, and Gum Arabic

Abstract

This study investigates the corrosion protection and self-healing properties of epoxy-based smart coatings incorporating porous silica, sodium phosphate, and Gum Arabic on carbon steel in a 3.5 wt% NaCl environment. Porous silica served as a carrier for controlled inhibitor release, leveraging its high surface area and porosity. Sodium phosphate acted as an anodic inhibitor, forming a protective iron phosphate layer, while Gum Arabic, a natural polysaccharide, enhanced self-healing through its barrier-forming and viscoelastic properties. Five coating formulations were evaluated: pure epoxy (EPOXY), epoxy with silica (EPOXY-Silica), epoxy with silica and sodium phosphate (EPOXY-Silica-SP), epoxy with silica and Gum Arabic (EPOXY-Silica-GA), and epoxy with all three components (EPOXY-Silica-SP-GA). Electrochemical impedance spectroscopy (EIS) and PDP revealed that EPOXY-Silica-GA exhibited the highest corrosion resistance (1049.4 ohm·cm⁻²) and a 93% reduction in corrosion rate, followed by EPOXY-Silica-SP-GA (92%) and EPOXY-Silica-SP (86%). Field-emission scanning electron microscopy (FE-SEM) and energy-dispersive X-ray spectroscopy (EDS) confirmed uniform particle distribution and reduced chloride/iron penetration in optimized coatings post-salt spray testing. Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) validated chemical interactions and structural changes. The superior performance of EPOXY-Silica-GA is attributed to Gum Arabic’s self-healing capability, while the multilayer system in EPOXY-Silica-SP-GA enhanced durability. This eco-friendly coating offers a sustainable solution for steel protection in harsh environments, with potential applications in marine and industrial settings.

Keywords: Smart coating, Corrosion protection, Self-healing, Porous silica, Sodium phosphate, Gum Arabic, Epoxy resin