Eco-Friendly Neem-Based Corrosion Inhibitor Coatings for Reinforced Concrete: Performance, Sustainability and Cost Assessment

Corrosion of reinforcement in concrete is a critical durability challenge that undermines the service life and increases the maintenance costs of infrastructure. Although conventional inorganic inhibitors, such as zinc, are effective, they are associated with high costs and environmental concerns, necessitating the development of sustainable alternatives. This study investigated the potential of Azadirachta indica (Neem) powder as a green, bio-based corrosion inhibitor coating for reinforcing steel, with its performance benchmarked against zinc coatings. Reinforced M30 grade concrete specimens were subjected to chlorideinduced accelerated corrosion for 365 days and evaluated through half-cell potential, weight and diameter loss, pullout bond strength, and surface morphology using SEM. Neem-coated specimens demonstrated a 47.5% reduction in half-cell potential and a 54% improvement in bond strength relative to uncoated specimens, closely matching zinc-coated samples, whose performance differences were not statistically significant. Life cycle assessment revealed that Neem coatings reduced the carbon footprint by up to 43%, whereas cost analysis showed a 39.6% reduction in per-meter coating cost compared to zinc. The findings highlight neem-based coatings as a sustainable, cost-effective, and eco-friendly solution offering performance comparable to zinc, thereby supporting resilient and environmentally responsible construction practices.