Natural dyes as eco-friendly corrosion inhibitors: A sustainable approach to metal protection

Natural dyes, historically celebrated for their capacity to enhance the visual appeal of textiles, foods, and artefacts, are now receiving increasing recognition for their functional applications, most significantly as eco-friendly corrosion inhibitors. Corrosion within aggressive industrial settings necessitates the formulation of an environmentally compatible inhibitor to replace conventional toxic systems. Natural dyes, extracted from botanical origins, are emerging as a sustainable alternative due to their abundant phytochemical constituents and biodegradability. Their efficacy in inhibition is primarily influenced by the presence of heteroatoms, π- electron density and molecular planarity, which enhance adsorption and the subsequent formation of protective films on metallic surfaces. Showing different adsorption behaviour like chemisorption, physisorption or mixed type inhibition behaviour. Comparative review reveals that dyes derived from tannins, flavonoids and quinonesexhibit superior efficacy,achieving their highest stability even though their efficiency is based on medium, temperature and substrate employed.A few obstacles, like limited mechanistic validation and a lack of standardization restrict their practical application. Hence,future research must emphasize on structure activity correlations, advanced surface analysis and hybrid or modified systems to validate the role of natural dyes as a reliable alternative for toxic inhibitors.