Benzopyran derivatives as polydentate chelating corrosion inhibitors: Natural products-based σ-donors and π-acceptor ligands

Corrosion is a natural damaging process that costs the global economy approximately US $2.5 trillion annually, equivalent to 3.4% of the world's GDP. Corrosion poses high risks to infrastructure, economy, sustainability, and safety. The goal of corrosion engineers' and scientists' constant work is to reduce the direct and indirect expenses of corrosion. Organic inhibitors offer a practical and versatile approach to corrosion control, as they can be applied directly into corrosive media, forming self-assembled protective films, making them economical, adaptable, and environmentally sustainable. Because of their versatility and potent coordination ability, benzopyran derivatives have established themselves as promising environmentally benign substituents. This review focuses on the fundamental characteristics, sources, and usage of benzopyran derivatives, with a particular emphasis on their ability to prevent corrosion. The conjugated aromatic rings and heteroatoms contribute π-electrons and lone pairs of non-bonding electrons, allowing for strong adsorption onto metallic surfaces through coordination bonding. By directly taking part in coordination or generating inductive and resonance effects, the polar substituents are essential. The review also discusses the use of benzopyran-based ligands for creating long-lasting, effective corrosion inhibitors, highlighting their coordination, donation, retro-donation, and non-innocent ligand properties. The benzopyran derivatives exhibit reasonably high inhibition efficiency in basic, acidic, and neutral electrolytes. Going forward, the development of bio-derived synthetic routes, hybrid systems that combine organic inhibitors with nanomaterials or polymers, and computational screening can all contribute to the logical design of next-generation inhibitors for enhanced performance. • This article underscores the use of benzopyrene derivatives in Corrosion control. • Benzopyrane derivatives have emerged as sustainable alternatives for traditional corrosion inhibitors. • They exhibit excellent coordination due to their abundance of π-electrons and lone-pair electrons. • Their polar functional groups enhance efficiency and adsorption through inductive effects, resonance stabilization, and coordination bonding. • Their chemical structure facilitates strong donation and retro-donation bonding.