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

Abstract

Corrosion of reinforcement in concrete is a critical durability challenge that undermines service life and increases maintenance costs of infrastructure. Conventional inorganic inhibitors such as zinc, although effective, are associated with high costs and environmental concerns, necessitating sustainable alternatives. This study investigates the potential of Azadirachta indica (Neem) powder as a green, bio-based corrosion inhibitor coating for reinforcing steel, with performance benchmarked against zinc coatings. Reinforced M30 grade concrete specimens were subjected to chloride-induced accelerated corrosion for 365 days and evaluated through half-cell potential, weight and diameter loss, pull-out bond strength, and surface morphology using SEM. Neem-coated specimens achieved a 47.5% reduction in half-cell potential and 25.3% reduction in weight loss, closely matching zinc-coated bars (45.0% and 25.7%). Bond strength improved significantly from 1.72 MPa (uncoated) to 2.66 MPa (Neem) and 2.95 MPa (Zinc), with SEM confirming compact protective layers on Neem-coated surfaces. Life cycle assessment revealed Neem coatings reduced carbon footprint by up to 43%, while 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 comparable performance to zinc, thereby supporting resilient and environmentally responsible construction practices.