Valorization of Tridax procumbens Biomass into Biochar–Epoxy Coatings for Sustainable Corrosion Protection of Steel

Steel corrosion in chloride-rich concrete environments causes major durability, economic, and environmental concerns, necessitating sustainable corrosion protection strategies. This study presents, for the first time, the utilization of Tridax procumbens-derived biochar as a functional filler in epoxy coatings for corrosion protection of construction steels. Biochar synthesized through pyrolysis was incorporated into an epoxy matrix and applied on mild steel, TMT bars, cold-formed steel, and structural steel exposed to simulated concrete pore solution containing chlorides. Electrochemical analyses revealed significant improvement in corrosion resistance, with a maximum inhibition efficiency of 91.58% for structural steel. SEM and XRD analyses indicated improved coating compactness and reduced surface degradation after prolonged exposure. Mechanical tests confirmed satisfactory adhesion and impact resistance. The enhanced protection is primarily attributed to the barrier effect of the biochar–epoxy composite, which restricts chloride ingress and electrolyte penetration. The developed coating demonstrates strong potential as a sustainable, low-cost, and environmentally friendly corrosion protection system for infrastructure applications.