Sustainable corrosion inhibition using leaf extract: a review of mechanistic aspects, and thermodynamic properties

Corrosion is the deterioration of metals and their alloys in different corrosive environments. Corrosion inhibitors (CIs) are one of the most widely accepted and economical remedies available to mitigate corrosion. Chemically synthesised CIs are often toxic, hazardous, and disruptive to ecological and human health by creating disturbance in various naturally occurring mechanisms. In response, the scientific community has devoted efforts to develop highly efficient, eco-friendly, sustainable CIs. Plant-based materials are interestingly used to solve corrosion damages, and this review article highlights the work conducted on leaves as a sustainable CI. Leaves are the primary site of phytochemical synthesis. Leaf extract contains alkaloids, flavonoids, terpenoids, saponins, phenolic compounds, and organic dyes, which are responsible for strong inhibition. This study is more precise in terms of the mechanisms of action and thermodynamic parameters. The physical nature of adsorption is predominant over chemical adsorption. The thermodynamic analysis indicated that the inhibition is spontaneous and exothermic, and the Langmuir, Freundlich, and Temkin models best fit the experimental data. However, leaf extracts are equivalent to chemical-based inhibitors with additional advantages, but the lack of industrial-scale production and the complex nature of the corrosion inhibition mechanism pose challenges and highlight directions for future research. The present investigation is restricted to the research articles published between 2008 and 2025.